Platelet-derived growth factor bone graft putty formulation

Abstract

The present disclosure provides implant materials comprising platelet-derived growth factor and a biocompatible matrix that are useful for bone repair, including bone fusion procedures and fracture repair.

Description

[0001]SCD-01525 PLATELET-DERIVED GROWTH FACTOR BONE GRAFT PUTTY FORMULATION CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Application No. 63 / 533,444 filed on August 18, 2023, the contents of which are hereby incorporated by reference in their entirety. BACKGROUND Musculoskeletal problems are pervasive throughout the population in all age groups and in both sexes. Half of Americans will need services for fractures or bone fusions at some point in their lifetime according to a widely published article presented at the 2003 annual meeting of the American Academy of Orthopedic Surgeons (AAOS). Bone fusion is a common form of orthopedic surgery used to treat musculoskeletal problems associated with various joints of patients, particularly the spine or ankle. Bone fusion involves the artificial induction of joint ossification between two bones. Approximately 100,000 lumbar spine fusion surgeries are performed annually in the U.S. in patients with lower back pain due to degenerative disc disease, deformity, unstable spine trauma, or spondylolisthesis. Spine fusion failure rates currently are as high as 30%. The use of various orthopedic devices such as pedicle screws, plates and osteobiologics has led to an improvement in fusion rates, but failed spinal surgeries still remain a serious problem. Spinal fusions in people and animals are performed to relieve back pain and associated neurologic signs including neck, arm, and leg pain, and generally require fusion of the pathologic spine segment and decompression of the spinal cord at the same level. Bony fusion of adjacent vertebral bodies (VBs) of the spine is currently used as a solution to treat intervertebral disc disease. The diseased disc tissue is removed, the endplates of the adjacent vertebral bodies are debrided, and rigid fixation in the form of a cage to stabilize the two levels is implanted between the VBs. Healing progresses with the formation of new bone between the VBs throughout the cage hardware. In many cases, a bone graft of is used to ensure bony fusion across the cage gap and to stabilize the spine for the patient, alleviating pain and often returning the patient to some level of activity. In co-morbid - 1 - FoleyHoagUS12457270.1 SCD-01525 patients, it may be challenging to achieve boney fusion across the gap between the VBs, and an osteoconductive and osteoinductive graft is used to enhance the bone healing response. Both interbody and posterolateral spine fusions use a biological osteoinductive agent to generate the bone required for the spinal fusion. The current standard of care is to harvest bone from the iliac crest or other bony site to obtain an osteoinductive graft material. Accordingly, the patient must also undergo a procedure to harvest the graft, usually from the iliac crest, in addition to the spine fusion surgery itself. Harvesting bone graft from the iliac crest is associated with post-operative pain that can persist in up to 25% of patients. Other disadvantages associated with this treatment method are an increased risk of infection, availability and quality of bone autograft material, and the patient inconvenience that is caused due to donor site morbidity. Accordingly, there is a need for improved bone graft compositions that are useful in various bone fusion procedures. Furthermore, there is a need for a graft compositions that have good handling characteristics and can be easily shaped and provided at a site of bone fusion, such as a site of ankle arthrodesis or spine fusion. Additionally, a compositions that can remain at a site of bone fusion, or other orthopedic bone repair site, thereby reducing movement of the graft material into the tissue outside the fusion site so that the graft and any osteoconductive or osteoinductive agents remain localized at the fusion site. Finally, such grafting compositions should provide a suitable PDGF release profile in order to initiate the healing cascade at the site of fusion. The present disclosure addresses these needs. SUMMARY One aspect of the present disclosure provides an implant material comprising a growth factor, an acid, and a biocompatible matrix, the biocompatible matrix comprising a porous calcium phosphate, a fibrillar collagen, and an aqueous liquid. wherein the biocompatible matrix comprises about 70 to about 95% by weight of the porous calcium phosphate and about 5 to about 30% by weight of the fibrillar collagen wherein the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 2:1. - 2 - FoleyHoagUS12457270.1 SCD-01525 In some embodiments, the growth factor is selected from a bone morphogenic protein, platelet-derived growth factor (PDGF), fibroblast growth factor, insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β) and any combination thereof. In preferred embodiments, the growth factor is PDGF. In some embodiments, the aqueous liquid and the biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:1, and in more particular embodiments, the aqueous liquid and the biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) of about 0.5:1 about 0.75:1, or about 1:1. In some embodiments, the porous calcium phosphate is present in the biocompatible matrix in an amount ranging from about 70 weight percent to about 90 weight percent, about 80 weight percent to about 90 weight percent, about 85 weight percent to about 90 weight percent, about 80 weight percent to about 85 weight percent. In more particular embodiments, the porous calcium phosphate is present in the biocompatible matrix in an amount of about 90 weight percent, about 85 weight percent, or about 80 weight percent. In some embodiments, the porous calcium phosphate is selected from the group consisting of tricalcium phosphate, hydroxyapatite, poorly crystalline hydroxyapatite, amorphous calcium phosphate, calcium metaphosphate, dicalcium phosphate dihydrate, heptacalcium phosphate, calcium pyrophosphate dihydrate, calcium pyrophosphate, octacalcium phosphate, brushite, and mixtures thereof. In certain preferred embodiments, the porous calcium phosphate is β-tricalcium phosphate. In some embodiments, the calcium phosphate comprises particles having a size ranging from about 100 to about 1000 μm, preferably about 100 to about 500 μm, and more preferably from about 100 to about 300 μm. In some embodiments, the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 25 weight percent, about 10 weight percent to about 20 weight percent, about 10 weight percent to about 15 weight percent, or about 5 weight percent to about 10 weight percent. In other more particular embodiments, the fibrillar collagen is present in the biocompatible matrix in an amount of about 10 weight percent, about 15 weight percent, or about 20 weight percent. - 3 - FoleyHoagUS12457270.1 SCD-01525 In some embodiments, the fibrillar collagen comprises bovine collagen, preferably type I bovine collagen. In some embodiments, the fibrillar collagen comprises dermis collagen, while in other embodiments, the fibrillar collagen comprises tendon collagen. In some embodiments, the biocompatible matrix further comprises about 0.1 to about 10 weight % of soluble collagen about 0.1 to about 5 weight % of soluble collagen, about 0.1 to about 2 weight % of soluble collagen, or about 1 to about 10 weight % of soluble collagen. In some embodiments, the soluble collagen comprises bovine collagen, preferably type I bovine collagen. In some embodiments, the soluble collagen comprises bovine dermis collagen, while in other embodiments, the soluble collagen comprises tendon collagen. In some embodiments, the PDGF is present in the aqueous liquid at a concentration ranging from about 0.1 mg / ml to about 5.0 mg / ml, preferably about 0.1 mg / ml to about 1.0 mg / ml, more preferably, about 0.2 mg / ml to about 0.4 mg / ml, and most preferably about 0.3 mg / ml. In some embodiments, wherein the PDGF comprises PDGF-AA, PDGF-BB, PDGF- AB, PDGF-CC, PDGF-DD, or a mixture or a derivative thereof, preferably PDGF-BB. In some embodiments, the PDGF-BB comprises at least 65% intact PDGF-BB. In some embodiments, the PDGF-BB is recombinant human (rh)PDGF-BB. In some embodiments, the aqueous liquid comprises the growth factor in a buffer, preferably sodium acetate. In some embodiments, the putty retains its in vitro structural integrity at 37 ºC. In some embodiments, at least 20% of the PDGF is released after about 30 minutes in vitro. In some embodiments, at least 40% of the PDGF is released after about 1 hour in vitro. In some embodiments, at least 50% of the PDGF is released after about 1 hour in vitro. In some embodiments, at least 60% of the PDGF is released after about 1 hour in vitro. In some embodiments, at least 70% of the PDGF is released after 4 hours in vitro. In some embodiments, the acid is selected from acetic acid, citric acid, lactic acid, malic acid, succinic acid, formic acid, tartaric acid, and any combination thereof. Preferably, the acid is acetic acid. In some embodiments, the acid is an aqueous acid. In some embodiments, the acid has a concentration in a range of about 10 to about 50 mM in the aqueous liquid. - 4 - FoleyHoagUS12457270.1 SCD-01525 In some embodiments, biocompatible matrix comprises the acid. In some embodiments, the implant material has a pH of about 6.5 or less, preferably about 3 to about 6.5, and more preferably about 3 to about 6, and even more preferably about 3 to about 5.5. Another aspect of the invention provides a method for bone fusion in a subject in need thereof comprising administering the above-described composition to a desired site of bone fusion in the subject. The present disclosure further provides a method for fracture repair in a subject in need thereof comprising administering the above-described composition to a desired site of fracture repair in the subject. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1: Preparation of putty formulation by manual mixing technique. FIG.2: “Paste like” consistency of the AI formulation compared to the Moldable “putty like” consistency of the present formulation. FIG.3: Putty formulation A1 was dispensed from a syringe with a wide-bore opening. The putty formulation was back filled in to a 10 mL syringe and extruded through open bore (without a needle). FIG.4A: Structural integrity of various putty formulations at 37 ºC (body temperature). FIG.4B: A comparison of the structural integrity of the putty formulation and AI at37 ºC (body temperature). FIG.5: rhPDGF-BB Release kinetics from 80:20 β-TCP / collagen putty matrix. Under laboratory conditions, ~50% of the rhPDGF-BB combined with an 80:20 β- TCP / collagen putty matrix is cumulatively recoverable over a timeframe of 3 weeks at 37 ºC. FIG.6: The irrigation resistance of the putty formulation when exposed to a saline solution. FIG.7: A putty formulation A4 with 90:10 β-TCP / collagen and volume:mass ratio (rhPDGF-BB solution:β-TCP / collagen matrix) of 0.75:1 was applied inside and around a PEEK cage (slides 1-3). Slide 4 displays the AI in a PEEK cage. - 5 - FoleyHoagUS12457270.1 SCD-01525 FIG.8: The implant composition in shredded form is easier to mix and provides with homogeneous distribution of rhPDGF-BB. FIG.9 is a table describing the contents of samples 1 to 5. FIG.10 is a graph showing the PDGF elution results from samples 1 to 5, where sample 5 is Augment Injectable. FIG.11 is a table showing the isoelectric points of various growths factors. FIG.12 is a graph summarizing the ages of diabetes prone BB Wistar rats at the time of fracture. FIG.13 is a graph summarizing the amount of matrix applied to the fracture site. FIG.14 is a graph showing the blood glucose levels from each rat. FIG.15 is a graph showing the blood glucose levels by group. FIG.16 is a graph showing the starting weight of rats.at the time of fracture. FIG.17 is a graph showing the percent weight change of rats over the course of the study. FIG.18 is a graph showing the time from onset of diabetes to the fracture surgery. FIG.19 is a graph showing healing femur X-ray scores. FIG.20 is a graph showing μCT longitudinal section scores. FIG.21 are images showing μCT longitudinal section through the medial lateral plane for group A at 4 weeks and 8 weeks. FIG.22 are images showing μCT longitudinal section through the medial lateral plane for group B at 4 weeks and 8 weeks. FIG.23 are images showing μCT longitudinal section through the medial lateral plane for group C at 4 weeks and 8 weeks. FIG.24 shows graphs of μCT of callus bone by group and time points. FIG.25 shows graphs of μCT of callus bone by group only. FIG.26 shows histological images from fracture calluses of Group A at 4 and 8 weeks. FIG.27 shows histological images from fracture calluses of Group B at 4 and 8 weeks. FIG.28 shows histological images from fracture calluses of Group C at 4 and 8 - 6 - FoleyHoagUS12457270.1 SCD-01525 weeks. FIG.29 is a graph depicting the histomorphometric analysis of callus cartilage by group and time. FIG.30 is a graph depicting the histomorphometric analysis of callus cartilage by group only. DETAILED DESCRIPTION Augment™ Injectable (AI) consists of 2 components, Beta-tricalcium phosphate (β- TCP) / Bovine type I soluble collagen matrix and rhPDGF-BB (0.3 mg / ml solution of rhPDGF-BB in 20 mM sodium acetate solution, pH 6.0). AI is formulated for use by mixing the matrix and rhPDGF-BB solution in a volume to mass ratio of 3:1 (3 mL of rhPDGF-BB solution mixed with 1 gram of the matrix), as per the instructions for use (IFU) using the syringe provided as a part of the AI kit. The AI forms a paste-like formulation that is be applied to a site of fusion through a 14G cannula or blunt needle. The composition of the present disclosures pertains to an improved implant composition comprising where the collagen component is a mixture of non-fibrillar (soluble) and fibrillar (non-soluble collagen). The present composition comprises a β-TCP / Bovine type I Collagen matrix (fibrillar and a small proportion of non-fibrillar collagen), which when mixed with rhPDGF-BB solution manually or using a mixing instrument, results in an implant composition. The implant composition advantageously retains its shape after mixing and for a period of time after placement at a site of bone healing (e.g., when exposed to a tissue environment at 37 °C). The putty formulation is also moldable. Accordingly, the putty formulations provide excellent handling and manipulation characteristics during surgical procedures. Definitions As used herein, “promoting” or “facilitating” spinal fusion refers to a clinical intervention designed to desirably affect clinical progression of a spinal fusion procedure. Desirable effects of the clinical intervention include but are not limited to, for example, one or more of: increase in degree of bone density and / or acceleration of bone formation (e.g. acceleration of bone density) at the site of fusion, increase in degree of bony union or bone - 7 - FoleyHoagUS12457270.1 SCD-01525 bridging and / or acceleration of bony union or bony bridging at the site of fusion, improvement in composition and / or structure of bone at bone fusion site (for example, closer resemblance to natural bone at the bone fusion site). As used herein, the term “effective amount” refers to at least an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic result. An effective amount can be provided in one or more administrations. Reference to “about” a value or parameter herein also includes (and describes) embodiments that are directed to that value or parameter per se. As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly indicates otherwise. For example, reference to a “PDGF homodimer” is a reference to one or multiple PDGF homodimers, and includes equivalents thereof known to those skilled in the art, and so forth. It is understood that all aspects and embodiments of the invention described herein may include “comprising,” “consisting,” and “consisting essentially of” aspects and embodiments. It is to be understood that methods or compositions “consisting essentially of” the recited elements include only the specified steps or materials and those that do not materially affect the basic and novel characteristics of those methods and compositions. “As used herein, the term "fibrillar collagen" means a collagen of a type which can normally form collagen fibrils. The fibrillar collagens are collagen types I-III, V, and XI. The collagen monomers that make up the fibrillar collagens contain "telopeptide" regions at the amino (N) and carboxy (C) terminal ends of the monomers which are non-helical in the collagen trimer. These collagens self-assemble into fibrils with the C-terminal end of the helical domain and the C propeptide of one collagen triple helix overlapping with the N telopeptide and the N-terminal end of the triple helical domain of an adjacent collagen molecule. The monomers that make up the fibrillar collagens are made as preproproteins, including an N-terminal secretion signal sequence and N and C-terminal propeptide domains. The signal sequence is normally cleaved by signal peptidase, as with most secreted proteins, and the propeptides are removed by specific proteolytic processing enzymes after association, folding and secretion of trimeric procollagen. The term fibrillar collagen encompasses both native ( i.e., naturally occurring) and variant fibrillar collagens ( i.e., fibrillar collagens with - 8 - FoleyHoagUS12457270.1 SCD-01525 one or more alterations in the sequence of one or more of the fibrillar collagen monomers). Unless the context clearly indicates otherwise ( e.g., the term is modified by the word "monomer") "fibrillar collagen" refers to triple helical fibrillar collagen.” “Fibrillar collagen” also may be referred to herein as “insoluble collagen or polymeric collagen.” "Soluble collagen" refers to individual tropocollagen molecules that are soluble in acidic aqueous environments. Tropocollagen may be considered the monomeric unit of fibrillary collagen fibers. “Volume to mass ratio” as used herein refers to ratio of the volume of PDGF in milliliters (mL) to the mass of biocompatible matrix in grams (g). For example, the volume to mass ratio can range from about 0.5:1 to about 1.5:1, about 0.75:1 to about 1:1, about 0.5:1, about 0.75:1, or about 1:1. Exemplary embodiments may comprise, for example, about 0.1 mL of PDGF solution and about 1 g of biocompatible matrix, about 0.75 mL of PDGF and about 1 g of biocompatible matrix, or about 0.5 mL of PDGF solution and about 0.5 g of biocompatible matrix. The implant composition of the present disclosure includes a putty that is moldable, e.g. capable of being molded into a desired shape. In some embodiments, the putty is shape- retaining, e.g., tending to remain in the shape in which it is molded. The implant composition of the present disclosure also includes a putty that is malleable, i.e. capable of being permanently converted from a first shape to a second shape. The implant composition of the present disclosure also includes a putty that is cohesive, i.e. able to remain as a singular, connected mass upon stretching. Implant Materials The present disclosure provides an implant material comprising a growth factor, an acid, and a biocompatible matrix, the biocompatible matrix comprising a porous calcium phosphate, a fibrillar collagen, and an aqueous liquid. wherein the biocompatible matrix comprises about 70 to about 95% by weight of the porous calcium phosphate and about 5 to about 30% by weight of the fibrillar collagen wherein the aqueous liquid and the biocompatible matrix are present in the composition - 9 - FoleyHoagUS12457270.1 SCD-01525 in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 2:1. In some embodiments, the present disclosure provides an implant composition consisting essentially of a growth factor, an acid, and a biocompatible matrix, the biocompatible matrix comprising a porous calcium phosphate, a fibrillar collagen, and an aqueous liquid. wherein the biocompatible matrix comprises about 70 to about 95% by weight of the porous calcium phosphate and about 5 to about 30% by weight of the fibrillar collagen wherein the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 2:1. In other embodiments, the present disclosure provides an implant composition consisting of a growth factor, an acid, and a biocompatible matrix, the biocompatible matrix comprising a porous calcium phosphate, a fibrillar collagen, and an aqueous liquid. wherein the biocompatible matrix comprises about 70 to about 95% by weight of the porous calcium phosphate and about 5 to about 30% by weight of the fibrillar collagen wherein the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 2:1. In some embodiments, the growth factor is selected from a bone morphogenic protein, platelet-derived growth factor (PDGF), fibroblast growth factor, insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β) and any combination thereof. In particularly preferred embodiments, the growth is PDGF, such as PDGF-BB, and more particularly, rhPDGF-BB. In some embodiments, the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:1. In some preferred embodiments, the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) of about 0.5:1. In other preferred embodiments, the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) of about 0.75:1. Most preferably, the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) of about 1:1. In some embodiments, the porous calcium phosphate is present in the biocompatible - 10 - FoleyHoagUS12457270.1 SCD-01525 matrix in an amount ranging from about 70 weight percent to about 90 weight percent, about 80 weight percent to about 90 weight percent, about 85 weight percent to about 90 weight percent, about 80 weight percent to about 85 weight percent. In more particular embodiments, the porous calcium phosphate is present in the biocompatible matrix in an amount of about 90 weight percent, about 85 weight percent, or about 80 weight percent. In some embodiments, the porous calcium phosphate is selected from the group consisting of tricalcium phosphate, hydroxyapatite, poorly crystalline hydroxyapatite, amorphous calcium phosphate, calcium metaphosphate, dicalcium phosphate dihydrate, heptacalcium phosphate, calcium pyrophosphate dihydrate, calcium pyrophosphate, octacalcium phosphate, brushite, monetite and mixtures thereof. Most preferably, the porous calcium phosphate is β-tricalcium phosphate. In some embodiments, the calcium phosphate comprises particles having a size ranging from about 100 to about 1000 μm. In other embodiments, the calcium phosphate comprises particles having a size ranging from about 100 to about 500 μm. In particularly preferred embodiments, the calcium phosphate comprises particles having a size ranging from about 100 to about 300 μm. In some embodiments, the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 40 weight percent. In other embodiments, the collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 20 weight percent. In some embodiments, the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 25 weight percent, about 10 weight percent to about 20 weight percent, about 10 weight percent to about 15 weight percent, or about 5 weight percent to about 10 weight percent. In other more particular embodiments, the fibrillar collagen is present in the biocompatible matrix in an amount of about 10 weight percent, about 15 weight percent, or about 20 weight percent. In some embodiments, the fibrillar collagen comprises bovine collagen, preferably type I bovine collagen. In some embodiments, the fibrillar collagen comprises dermis collagen, while in other embodiments, the fibrillar collagen comprises tendon collagen. In some embodiments, the biocompatible matrix further comprises about 0.1 to about - 11 - FoleyHoagUS12457270.1 SCD-01525 10 weight % of soluble collagen about 0.1 to about 5 weight % of soluble collagen, about 0.1 to about 2 weight % of soluble collagen, or about 1 to about 10 weight % of soluble collagen. In some embodiments, the soluble collagen comprises bovine collagen, preferably type I bovine collagen. In some embodiments, the soluble collagen comprises bovine dermis collagen, while in other embodiments, the soluble collagen comprises tendon collagen. In some embodiments, the biocompatible matrix comprises about 80 to about 90% by weight of the porous calcium phosphate (preferably beta tricalcium phosphate), about 5 to about 15 by weight of the fibrillar collagen, and about 1 to about 10 % by weight of the soluble collagen. In some embodiments, the PDGF is present in the at a concentration ranging from about 0.1 mg / ml to about 5.0 mg / ml. More preferably, the PDGF is present in the aqueous liquid at a concentration ranging from about 0.1 mg / ml to about 1.0 mg / ml, and even more preferably, the PDGF is present in the aqueous liquid at a concentration from about 0.2 mg / ml to about 0.4 mg / ml. Most preferably, the PDGF is present in the aqueous liquid volume at a concentration of about 0.3 mg / ml. In some embodiments, the PDGF comprises PDGF-AA, PDGF-BB, PDGF-AB, PDGF- CC, PDGF-DD, or a mixture or a derivative thereof. Preferably, the PDGF comprises PDGF-BB. In some embodiments, the PDGF-BB comprises at least 65% intact PDGF-BB. Most preferably, the PDGF-BB is recombinant human (rh)PDGF-BB. In some embodiments, the PDGF is provided in a buffer, preferably sodium acetate. In some embodiments, the acid is selected from acetic acid, citric acid, lactic acid, malic acid, succinic acid, formic acid, tartaric acid, and any combination thereof. In certain preferred embodiments, the acid is acetic acid. In some embodiments, the implant material has a pH of less than 6.5. In other embodiments, the implant material has a pH of less than 6. In other embodiments, the implant material has a pH of less than 5.5. In still other embodiments, the total liquid volume has a pH of less than 5. In more particularly embodiments, the implant material has a pH of about 3 to about 6.5, about 3 to about 6, or about 3 to about 5.5. The pH of the implant material is determined, in some embodiments, by - 12 - FoleyHoagUS12457270.1 SCD-01525 Method 1: 1. Weigh 1g of putty matrix. 2. Add 1mL of appropriate pH-modifying solution to tubes with 1g of putty matrix. Note: For the final product where the acid incorporated within the matrix, 1 mL of 20mM sodium acetate buffer can be added as the hydration solution to formulate the putty. 3. Homogenize and incubate 2-5min at RT. 4. Add 4ml of pre-warmed DMEM and incubate at 37oC for 1hr. Note: DMEM used to monitor the color change. 5. Centrifuge at 1200rpm for 5min, collect the supernatant and measure the pH of each sample using a pH meter or pH test strips. In other embodiments, the pH of the putty is measured by Method 2: 1. Weigh 1g of putty matrix. 2. Add 1mL of appropriate pH-modifying solution to tubes with 1g of AP matrix. Note: For the final product where the acid incorporated within the matrix, 1 mL of 20mM sodium acetate buffer can be added as the hydration solution to formulate the putty. 3. Homogenize and incubate 2-5min at RT. 4. Add 4ml of pre-warmed DMEM and incubate at 37°C for 1hr. Note: DMEM used to monitor the color change. 5. Centrifuge at 1200rpm for 5min, Monitor the color change. In some embodiments, the implant material is a putty that retains its structural integrity at 37 ºC. In some embodiments, at least 20% of the PDGF is released after about 30 minutes in vitro. More preferably, at least 40% of the PDGF is released after about 1 hour in vitro, at least 50% of the PDGF is released after about 1 hour in vitro, or at least 60% of the PDGF is released after about 1 hour in vitro. In further preferred embodiments, at least 70% of the PDGF is released after 4 hours in vitro. Embodiments of the Methods The present disclosure provides a method for fusing bone in a subject comprising administering the implant material to a desired site of bone fusion in the subject. - 13 - FoleyHoagUS12457270.1 SCD-01525 In some embodiments, the site of bone fusion is in a foot, toe, ankle, knee, hip, spine, rib, sternum, clavicle, joint, shoulder, scapula, elbow, wrist, hand, or finger. In some embodiments, the site of bone fusion is a joint. In some embodiments, the site of bone fusion the spine. In some embodiments, the bone fusion is a spine fusion. In certain preferred embodiments, the bone fusion is an ankle fusion. In some embodiments, the bone fusion is a hindfoot fusion. In some embodiments, the method further comprises placing an intravertebral spacer between vertebral bodies. In some embodiments, the composition is disposed in the vertebral spacer prior to placing the vertebral spacer between the vertebral bodies. In some embodiments, further comprising disposing the composition in the spacer after placing the spacer between the vertebral bodies. In some embodiments, the spine fusion procedure is an interbody fusion procedure. In some embodiments, the spine fusion procedure is a lumbar fusion procedure. The present disclosure also provides a method for fracture repair in a subject comprising administering the composition to a desired site of fracture repair in the subject. In some embodiments, the site of fracture repair is an arm or a leg. In some embodiments, wherein the site of fracture repair is a tibia. In some embodiments, the composition is used in conjunction with a cage or intervertebral spacer. The composition may be deposited inside the lumen of the cage either prior to implantation of the cage between debrided vertebral bodies or after the cage has been placed between the vertebral bodies during a spine fusion surgical procedure. Interbody fusion places a bone graft (e.g. a composition of the invention) between the vertebrae in the area usually occupied by an intervertebral disc. In preparation for the spinal fusion, the disc may be removed entirely. A device may be placed between the vertebrae to maintain spine alignment and disc height. The intervertebral device may be, for example, a spacer. The intervertebral device may be made from, for example, plastic or titanium. The fusion then occurs between the endplates of the vertebrae. Types of interbody fusion include: - 14 - FoleyHoagUS12457270.1 SCD-01525 anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF). In some embodiments, the fusion is augmented by a process called fixation, meaning the placement of metallic screws (pedicle screws often made from titanium), rods or plates, spacers, or cages to stabilize the vertebrae to facilitate bone fusion. During the fusion process, external bracing (orthotics) may be used. Posterolateral fusion places the bone graft between the transverse processes in the back of the spine. These vertebrae may then be fixed in place with screws and / or wire through the pedicles of each vertebrae attaching to a metal rod on each side of the vertebrae. PDGF Solutions In some embodiments, the aqueous liquid comprises a solution comprising PDGF, and the solution is disposed or incorporated into the biocompatible matrix, for example by manual or mechanical mixing in order to form the desired consistency. In some embodiments, the PDGF is present in the solution in a concentration ranging from about 0.01 mg / ml to about 10 mg / ml, from about 0.05 mg / ml to about 5 mg / ml, or from about 0.1 mg / ml to about 1.0 mg / ml. PDGF may be present in the solution at any concentration within these stated ranges, including the upper limit and lower limit of each range. In other embodiments, PDGF is present in the solution at any one of the following concentrations: about 0.05 mg / ml; about 0.1 mg / ml; about 0.15 mg / ml; about 0.2 mg / ml; about 0.25 mg / ml; about 0.3 mg / ml; about 0.35 mg / ml; about 0.4 mg / ml; about 0.45 mg / ml; about 0.5 mg / ml; about 0.55 mg / ml; about 0.6 mg / ml; about 0.65 mg / ml; about 0.7 mg / ml; about 0.75 mg / ml; about 0.8 mg / ml; about 0.85 mg / ml; about 0.9 mg / ml; about 0.95 mg / ml; or about 1.0 mg / ml. It is to be understood that these concentrations are simply examples of particular embodiments, and that the concentration of PDGF may be within any of the concentration ranges stated above, including the upper limit and lower limit of each range. The concentration of PDGF or other growth factors in some embodiments of the present disclosure can be determined by using an enzyme-linked immunoassay as described in U.S. Pat. Nos.6,221,625, 5,747,273, and 5,290,708, incorporated herein by reference, or any other assay known in the art for determining PDGF concentration. When provided herein, the molar concentration of PDGF is determined based on the molecular weight (MW) - 15 - FoleyHoagUS12457270.1 SCD-01525 of PDGF dimer (e.g., PDGF-BB; MW about 25 kDa). PDGF may comprise PDGF homodimers and / or heterodimers, including PDGF-AA, PDGF-BB, PDGF-AB, PDGF-CC, PDGF-DD, and mixtures and derivatives thereof. In some embodiments, PDGF comprises PDGF-BB. In another embodiment PDGF comprises a recombinant human (rh) PDGF, such as rhPDGF-BB. PDGF, in some embodiments, can be obtained from natural sources. In other embodiments, PDGF can be produced by recombinant DNA techniques. In other embodiments, PDGF or fragments thereof may be produced using peptide synthesis techniques known to one of ordinary skill in the art, such as solid phase peptide synthesis. When obtained from natural sources, PDGF can be derived from biological fluids. Biological fluids, according to some embodiments, can comprise any treated or untreated fluid associated with living organisms including blood. Biological fluids, in another embodiment, can also comprise blood components including platelet concentrate (PC), apheresed platelets, platelet-rich plasma (PRP), plasma, serum, fresh frozen plasma (FFP), and buffy coat (BC). Biological fluids, in a further embodiment, can comprise platelets separated from plasma and resuspended in a physiological fluid. When PDGF is produced by recombinant DNA techniques, a DNA sequence encoding a single monomer (e.g., PDGF B-chain or A-chain), in some embodiments, can be inserted into cultured prokaryotic or eukaryotic cells for expression to subsequently produce the homodimer (e.g. PDGF-BB or PDGF-AA). In other embodiments, a PDGF heterodimer can be generated by inserting DNA sequences encoding for both monomeric units of the heterodimer into cultured prokaryotic or eukaryotic cells and allowing the translated monomeric units to be processed by the cells to produce the heterodimer (e.g. PDGF-AB). Research grade rhPDGF-BB can be obtained from multiple sources including R&D Systems, Inc. (Minneapolis, Minn.), BD Biosciences (San Jose, Calif.), Sigma Aldrich (Darmstadt, Germany), Invitrogen (Gibco – unknown location), and Chemicon, International (Temecula, Calif.). In some embodiments of the present invention, PDGF comprises PDGF fragments. In some embodiments rhPDGF-B comprises the following fragments: amino acid sequences 1- - 16 - FoleyHoagUS12457270.1 SCD-01525 31, 1-32, 33-108, 33-109, 1-108 and / or 1-109 of the entire B chain. The complete amino acid sequence (1-109) of the B chain of PDGF is provided in FIG.15 of U.S. Pat. No.5,516,896, the disclosure of which is hereby incorporated by reference in its entirety. It is to be understood that the rhPDGF-BB compositions of the present invention may comprise a combination of intact rhPDGF-B (1-109) and fragments thereof. Other fragments of PDGF may be employed such as those disclosed in U.S. Pat. No.5,516,896. In accordance with one embodiment, the rhPDGF-BB comprises at least 65% of intact rhPDGF-B (1-109). In another embodiment, the rhPDGF-BB comprises at least 75%, 80%, 85%, 90%, 95%, or 99% of intact rhPDGF-B (1-109). Methods of producing PDGF are described in US Publication No. 20140308332, the contents of which are hereby incorporated by reference in their entirety. In some embodiments, PDGF can be purified. Purified PDGF, as used herein, comprises compositions having greater than about 95% by weight PDGF prior to incorporation in solutions of the present invention. The solution may be any pharmaceutically acceptable solution. In other embodiments, the PDGF can be substantially purified. Substantially purified PDGF, as used herein, comprises compositions having about 5% to about 95% by weight PDGF prior to incorporation into solutions of the present invention. In some embodiments, substantially purified PDGF comprises compositions having about 65% to about 95% by weight PDGF prior to incorporation into solutions of the present invention. In other embodiments, substantially purified PDGF comprises compositions having about 70% to about 95%, about 75% to about 95%, about 80% to about 95%, about 85% to about 95%, or about 90% to about 95%, by weight PDGF, prior to incorporation into solutions of the present invention. In a further embodiment, PDGF can be partially purified. Partially purified PDGF, as used herein, comprises compositions having PDGF in the context of platelet rich plasma (PRP), fresh frozen plasma (FFP), or any other blood product that requires collection and separation to produce PDGF. Embodiments of the present invention contemplate that any of the PDGF isoforms provided herein, including homodimers and heterodimers, can be purified or partially purified. Compositions of the present invention containing PDGF mixtures may contain PDGF isoforms or PDGF fragments in partially purified proportions. Partially - 17 - FoleyHoagUS12457270.1 SCD-01525 purified and purified PDGF, in some embodiments, can be prepared as described in U.S. patent application Ser. No.11 / 159,533 (Publication No: 20060084602). In some embodiments, solutions comprising PDGF are formed by solubilizing PDGF in aqueous media or in one or more buffers. Buffers suitable for use in PDGF solutions of the present invention can comprise, but are not limited to, carbonates, phosphates (e.g. phosphate buffered saline), histidine, acetates (e.g. sodium acetate), acidic buffers such as acetic acid and HCl, and organic buffers such as lysine, Tris buffers (e.g. tris(hydroxymethyl)aminoethane), N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), and 3-(N-morpholino) propanesulfonic acid (MOPS). Buffers can be selected based on biocompatibility with PDGF and the buffer's ability to impede undesirable protein modification. Buffers can additionally be selected based on compatibility with host tissues. In some embodiments, sodium acetate buffer is used. The buffers can be employed at different molarities, for example, about 0.1 mM to about 100 mM, about 1 mM to about 50 mM, about 5 mM to about 40 mM, about 10 mM to about 30 mM, or about 15 mM to about 25 mM, or any molarity within these ranges. In some embodiments, an acetate buffer is employed at a molarity of about 20 mM. In another embodiment, solutions comprising PDGF are formed by solubilizing lyophilized PDGF in water, wherein prior to solubilization the PDGF is lyophilized from an appropriate buffer. The pH of solutions comprising PDGF, in some embodiments, can be controlled by the buffers and pH modifiers recited herein. Various proteins demonstrate different pH ranges in which they are stable. Protein stabilities are primarily reflected by isoelectric points and charges on the proteins. The pH range can affect the conformational structure of a protein and the susceptibility of a protein to proteolytic degradation, hydrolysis, oxidation, and other processes that can result in modification to the structure and / or biological activity of the protein. In some embodiments, solutions comprising PDGF can further comprise additional components, such as other biologically active agents. In other embodiments, solutions comprising PDGF can further comprise cell culture media, other stabilizing proteins such as albumin, antibacterial agents, protease inhibitors [e.g., ethylenediaminetetraacetic acid - 18 - FoleyHoagUS12457270.1 SCD-01525 (EDTA), ethylene glycol-bis(beta-aminoethylether)-N, N,N′,N′-tetraacetic acid (EGTA), aprotinin, .epsilon.-aminocaproic acid (EACA), etc.] and / or other growth factors such as fibroblast growth factors (FGFs), epidermal growth factors (EGFs), transforming growth factors (TGFs), keratinocyte growth factors (KGFs), insulin-like growth factors (IGFs), bone morphogenetic proteins (BMPs), or other PDGFs including compositions of PDGF-AA, PDGF-BB, PDGF-AB, PDGF-CC and / or PDGF-DD. Biocompatible Matrix The implant material comprises a biocompatible matrix. In some embodiments, the biocompatible matrix comprises a porous calcium phosphate and fibrillar collagen. The calcium phosphate provides a framework or scaffold for new bone and tissue growth to occur. A calcium phosphate can be used to permanently or temporarily replace bone. Following implantation, the calcium phosphate can be retained by the body or it can be resorbed by the body and replaced with bone. Exemplary calcium phosphates include, e.g., a calcium phosphate (e.g., tricalcium phosphate, such as β-tricalcium phosphate (β-TCP), hydroxyapatite, poorly crystalline hydroxyapatite, amorphous calcium phosphate, calcium metaphosphate, dicalcium phosphate dihydrate, heptacalcium phosphate, calcium pyrophosphate dihydrate, calcium pyrophosphate, and octacalcium phosphate), calcium sulfate, and allograft (e.g. mineralized bone, mineralized deproteinized xenograft, or demineralized bone (e.g., demineralized freeze-dried cortical or cancellous bone), and any combination thereof. In some embodiments, the calcium phosphate comprises β-TCP. In other embodiments, the composition comprises a plurality of calcium phosphates. Calcium phosphates suitable for use have a calcium to phosphorus atomic ratio ranging from 0.5 to 2.0. In some embodiments, biocompatible matrices may include calcium phosphate particles with or without or bone allograft such as demineralized freeze dried bone allograft (DFDBA) or particulate demineralized bone matrix (DBM). In another embodiment, biocompatible matrices may include bone allograft such as DFDBA or DBM. In an - 19 - FoleyHoagUS12457270.1 SCD-01525 embodiment, the biocompatible matrix is bioresorbable. In some embodiment, a biocompatible matrix comprises an allograft such as DFDBA or particulate DBM. Non-limiting examples of suitable calcium phosphates suitable comprise amorphous calcium phosphate, monocalcium phosphate monohydrate (MCPM), monocalcium phosphate anhydrous (MCPA), dicalcium phosphate dihydrate (DCPD), dicalcium phosphate anhydrous (DCPA), octacalcium phosphate (OCP), α-tricalcium phosphate, β-TCP, hydroxyapatite (OHAp), poorly crystalline hydroxapatite, tetracalcium phosphate (TTCP), heptacalcium decaphosphate, calcium metaphosphate, calcium pyrophosphate dihydrate, calcium pyrophosphate, carbonated calcium phosphate, or any mixture thereof. In another embodiment, the calcium phosphate has a porous composition. Porosity is a desirable characteristic as it facilitates cell migration and infiltration into the implant material so that the infiltrating cells can secrete extracellular bone matrix. Porosity also provides access for vascularization. Porosity also provides a high surface area for enhanced resorption and release of active substances, as well as increased cell-matrix interaction. The composition can be provided in a shape suitable for implantation (e.g., a sphere, a cylinder, or a block) or it can be sized and shaped prior to use. In a preferred embodiment, the bone substituting agent is a calcium phosphate (e.g., (β-TCP). Porous calcium phosphates, according to some embodiments, can comprise pores having diameters ranging from about 1 μm to about 1 mm. In some embodiments, porous calcium phosphates comprises macropores having diameters ranging from about 100 μm to about 1 mm. In another embodiment, porous calcium phosphates comprises mesopores having diameters ranging from about 10 μm to about 100 μm. In a further embodiment, porous calcium phosphates comprises micropores having diameters less than about 10 μm. Embodiments of the present invention contemplate Porous calcium phosphates comprising macropores, mesopores, and micropores or any combination thereof. In some embodiments, the bone scaffolding material comprises interconnected pores. In some embodiments, the porous calcium phosphates comprise non- interconnected pores. In some embodiments, the porous calcium phosphates comprise interconnected and non-interconnected pores. The porous calcium phosphates, in some embodiments, has a porosity greater than about 25% or greater than about 40%. In another embodiment, porosity is greater than about - 20 - FoleyHoagUS12457270.1 SCD-01525 50%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 80%, or greater than about 85%. In a further embodiment, porosity greater than about 90%. In some embodiments, the porous calcium phosphate comprises a porosity that facilitates cell migration into the scaffolding material. In some embodiments, the porous calcium phosphates comprise a plurality of particles. Particles of the porous calcium phosphates, in some embodiments, can individually demonstrate any of the pore diameters and porosities provided herein. In other embodiments, particles of the porous calcium phosphates can form an association to produce a matrix having any of the pore diameters or porosities provided herein. Porous calcium phosphate particles may be mm, μm or submicron (nm) in size. Porous calcium phosphate particles, in some embodiments, have an average diameter ranging from about 1 μm to about 5 mm. In other embodiments, particles have an average diameter ranging from about 1 mm to about 2 mm, from about 1 mm to about 3 mm, or from about 250 μm to about 750 μm. In another embodiment, the particles have an average diameter ranging from about 100 μm to about 300 μm. In a further embodiment, the particles have an average diameter ranging from about 75 μm to about 300 μm. In additional embodiments, porous calcium phosphate particles have an average diameter less than about 25 μm, less than about 1 μm and, in some cases, less than about 1 mm. In some embodiments, porous calcium phosphate particles have an average diameter ranging from about 100 μm to about 5 mm or from about 100 μm to about 3 mm. In other embodiments, porous calcium phosphate particles have an average diameter ranging from about 250 μm to about 2 mm, from about 250 μm to about 1 mm, from about 200 μm to about 3 mm. Particles may also be in the range of about 1 nm to about 1000 nm, less than about 500 nm or less than about 250 nm. Porous calcium phosphate particles, in some embodiments, have a diameter ranging from about 1 μm to about 5 mm. In other embodiments, particles have a diameter ranging from about 1 mm to about 2 mm, from about 1 mm to about 3 mm, or from about 250 μm to about 750 μm. Porous calcium phosphate particles, in another embodiment, have a diameter ranging from about 100 μm to about 300 μm. In a further embodiment, the particles have a diameter ranging from about 75 μm to about 300 μm. In additional embodiments, porous calcium phosphate particles have a diameter less than about 25 μm, less than about 1 μm and, - 21 - FoleyHoagUS12457270.1 SCD-01525 in some cases, less than about 1 mm. In some embodiments, porous calcium phosphate particles have a diameter ranging from about 100 μm to about 5 mm or from about 100 μm to about 3 mm. In other embodiments, porous calcium phosphate particles have a diameter ranging from about 250 μm to about 2 mm, from about 250 μm to about 1 mm, from about 200 μm to about 3 mm. Particles may also be in the range of about 1 nm to about 1000 nm, less than about 500 nm or less than about 250 nm. In some embodiments, porous calcium phosphate materials are moldable, extrudable, and / or injectable. Moldable, extrudable, and / or injectable porous calcium phosphates can facilitate efficient placement of compositions of the present disclosure in and around target sites in bone and between bones at sites of desired bone fusion during spine fusion procedures. In some embodiments, moldable porous calcium phosphates can be applied to sites of bone fusion with a spatula or equivalent device. In some embodiments, porous calcium phosphates are flowable. Porous calcium phosphates, in some embodiments, can be applied to sites of bone fusion through a syringe with a needle or cannula. In some embodiments, porous calcium phosphates harden in vivo. In some embodiments, porous calcium phosphates are bioresorbable. In some embodiments, at least 30%, 40%, 50%, 60%, 70%, 75% or 90% resorbed within one year subsequent to in vivo implantation. In another embodiment, the material can be resorbed at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75% or 90% within 1, 3, 6, 9, 12, or 18 months of in vivo implantation. Bioresorbability will be dependent on: (1) the nature of the matrix material (i.e., its chemical make-up, physical structure and size); (2) the location within the body in which the matrix is placed; (3) the amount of matrix material that is used; (4) the metabolic state of the patient (diabetic / non-diabetic, osteoporotic, smoker, old age, steroid use, etc.); (5) the extent and / or type of injury treated; and (6) the use of other materials in addition to the matrix such as other bone anabolic, catabolic and anti-catabolic factors. The biocompatible matrix includes a fibrillar collagen, for example about 10 to about 40 percent by weight of fibrillar collagen. The biocompatible further comprises non-fibrillar (soluble) collagen) in an amount up to about 10% by weight. - 22 - FoleyHoagUS12457270.1 SCD-01525 Biocompatible matrices may be provided in block form or may be shredded. In preferred embodiments, the matrix is shredded, thus advantageously providing a putty consistency when combined with the aqueous liquid. Matrices containing collagen and calcium phosphate are available from several commercial suppliers, including DSM and CMI. β-Tricalcium Phosphate In some embodiments, the porous calcium phosphate is β-TCP. β-TCP, according to some embodiments, can comprise a porous structure having multidirectional and interconnected pores of varying diameters. In some embodiments, β-TCP comprises a plurality of pockets and non-interconnected pores of various diameters in addition to the interconnected pores. The porous structure of β-TCP, in some embodiments, comprises macropores having diameters ranging from about 100 μm to about 1 mm, mesopores having diameters ranging from about 10 μm to about 100 μm, and micropores having diameters less than about 10 μm. Macropores and micropores of the β-TCP can facilitate osteoinduction and osteoconduction while macropores, mesopores and micropores can permit fluid communication and nutrient transport to support bone regrowth throughout the β-TCP biocompatible matrix. In comprising a porous structure, β-TCP, in some embodiments, can have a porosity greater than 25% or greater than about 40%. In other embodiments, β-TCP can have a porosity greater than 50%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85%. In a further embodiment, β-TCP can have a porosity greater than about 90%. In some embodiments, (β-TCP can have a porosity that facilitates cell migration into the β-TCP. β-TCP particles, in some embodiments, can individually demonstrate any of the pore diameters and porosities provided herein for β-TCP. In other embodiments, β-TCP particles of a bone scaffolding material can form an association to produce a matrix having any of the pore diameters or porosities provided herein for the bone scaffolding material. Porosity may facilitate cell migration and infiltration into the matrix for subsequent bone formation. β-TCP particles, in some embodiments, have an average diameter ranging from about 1 μm to about - 23 - FoleyHoagUS12457270.1 SCD-01525 5 mm. In other embodiments, β-TCP particles have an average diameter ranging from about 1 mm to about 2 mm, from about 1 mm to about 3 mm, from about 250 μm to about 750 μm, from about 250 to about 1 mm, from about 250 μm to about 2 mm, or from about 200 μm to about 3 mm. In another embodiment, β-TCP particles have an average diameter ranging from about 100 μm to about 300 μm. In a further embodiment, β-TCP particles have an average diameter ranging from about 75 μm to about 300 μm. In additional embodiments, β-TCP particles have an average diameter less than about 25 μm, average diameter less than about 1 μm, or less than about 1 mm. In some embodiments, β-TCP particles have an average diameter ranging from about 100 μm to about 5 mm or from about 100 μm to about 3 mm. A biocompatible matrix comprising β-TCP particles, in some embodiments, can be provided in a shape suitable for implantation (e.g., a sphere, a cylinder, or a block). In other embodiments, a β-TCP bone scaffolding material can be moldable, extrudable, and / or injectable thereby facilitating placement of the matrix in and around target sites of desired bone fusion during spine fusion procedures. Flowable matrices may be applied through syringes, tubes, or spatulas or equivalent devices. Flowable β-TCP bone scaffolding materials, in some embodiments, can be applied to sites of bone fusion through a syringe and needle or cannula. In some embodiments, β-TCP bone scaffolding materials harden in vivo. β-TCP, according to some embodiments, is bioresorbable. In some embodiments, a β- TCP bone scaffolding material can be at least 30%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, or 85% resorbed one year subsequent to in vivo implantation. In another embodiment, a β- TCP bone scaffolding material can be greater than about 90% resorbed one year subsequent to in vivo implantation. Collagen While not being bound by theory, collagen can promote cohesion between combined substances. Collagen, for example, can promote adhesion between particles of calcium phosphate in the formation of a biocompatible matrix. In some embodiments, the fibrillar (non-soluble) collagen comprises Type I collagen comprises any type of collagen, including Type I, Type II, and Type III collagens. In some embodiments, a collagen comprises a mixture of collagens, such as a mixture of Type I and - 24 - FoleyHoagUS12457270.1 SCD-01525 Type II collagen. Other types of collagen present in bone or musculoskeletal tissues may be employed. Recombinant, synthetic and naturally occurring forms of collagen may be used in the present invention. In preferred embodiment, the implant material is free from or substantially free from soluble collagen. For example, collagen is substantially all fibrillary collagen. In some embodiments, the biocompatible matrix may include up to about 10%, up to about 5%, up to about 2%, up to about 1% or up to 0.5% of soluble collagen. While not being bound by theory, it is believed that the presence of a small amount of soluble collagen advantageously enhances matrix cohesivity and / or acts as blocking agent to prevent non-specific interactions of PDGF with the insoluble collagen component, while the fibrillar collagen helps maintain the putty structural integrity. β-TCP particles suitable for use with a collagen can comprise any of the β-TCP particles described herein. In some embodiments, β-TCP particles suitable for combination with a collagen have an average diameter ranging from about 1 μm to about 5 mm. In another embodiment, β-TCP particles suitable for combination with a collagen have an average diameter ranging from about 1 μm to about 1 mm, from about 1 mm to about 2 mm, from about 1 mm to about 3 mm, from about 250 μm to about 750 μm, from about 250 μm to about 1 mm, from about 250 μm to about 2 mm, from about 200 μm to about 1 mm, or from about 200 μm to about 3 mm. β-TCP particles, in other embodiments, have an average diameter ranging from about 100 μm to about 300 μm. In a further embodiment, β-TCP particles suitable for combination with a collagen have an average diameter ranging from about 75 μm to about 300 μm. In additional embodiments β-TCP particles suitable for combination with a collagen have an average diameter less than about 25 μm and, less than about 1 mm or less than about 1 μm. In some embodiments, β-TCP particles suitable for combination with a collagen have an average diameter ranging from about 100 μm to about 5 mm or from about 100 μm to about 3 mm. β-TCP particles, in some embodiments, can be adhered to one another by the collagen so as to produce a biocompatible matrix having a porous structure. In some embodiments, a biocompatible matrix comprising β-TCP particles and a collagen can comprise pores having diameters ranging from about 1 μm to about 1 mm. A biocompatible matrix comprising β-TCP particles and a collagen can comprise macropores having diameters - 25 - FoleyHoagUS12457270.1 SCD-01525 ranging from about 100 μm to about 1 mm, mesopores having diameters ranging from about 10 μm to 100 μm, and micropores having diameters less than about 10 μm. A biocompatible matrix comprising β-TCP particles collagen can have a porosity greater than about 25% or greater than 40%. In another embodiment, the biocompatible matrix can have a porosity greater than about 50%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 80%, or greater than about 85%. In a further embodiment, the biocompatible matrix can have a porosity greater than about 90%. Porosity facilitates cell migration and infiltration into the matrix for subsequent bone formation. A biocompatible matrix comprising β-TCP particles, in some embodiments, can comprise collagen in an amount ranging from about 10 weight percent to about 20 weight percent. In a further embodiment, a collagen can be present in an amount of about 20 weight percent of the biocompatible matrix. In a further embodiment, a collagen can be present in an amount of about 15 weight percent of the biocompatible matrix. In a further embodiment, a collagen can be present in an amount of about 10 weight percent of the biocompatible matrix. A biocompatible matrix comprising β-TCP particles and a collagen, according to some embodiments, can be moldable. In such embodiments, the biocompatible matrix can be in the form of a putty. A paste or putty can advantageously be molded into the desired implant shape or can be molded to the contours of the implantation site. A biocompatible matrix comprising β-TCP particles and a collagen, in some embodiments, can be provided in a predetermined shape such as a block, sphere, or cylinder. A biocompatible matrix comprising β-TCP particles and a collagen can be resorbable. In some embodiments, a biocompatible matrix comprising β-TCP particles and a collagen can be at least 30%, 40%, 50%, 60%, 70%, 75%, or 90% resorbed one year subsequent to in vivo implantation. In another embodiment, this matrix can be resorbed at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75% or 90% within 1, 3, 6, 9, 12, or 18 months subsequent to in vivo implantation. - 26 - FoleyHoagUS12457270.1 SCD-01525 pH modifier The biocompatible matrix advantageously includes a pH modifier. While not being bound theory, it is believed that growth factors, such as PDGF, may interact with fibrillary collagen such that its release rate after implantation is inhibited and / or slowed down. A “burst” release of PDGF is desired at the site of implantation in order to initiate the healing cascade. Accordingly, the present invention includes a pH modifier in order to lower the pH of the implant material. The lower pH may reduce the interaction of the growth factor with the fibrillar collagen, thereby improving its release. Suitable pH modifiers include acids, such as acetic acid, citric acid, lactic acid, malic acid, succinic acid, formic acid, tartaric acid, or any combination thereof. Preferably, the acid is acetic acid. The acid may be added to a fibrillar collagen / calcium phosphate matrix before, during, or after inclusion of the PDGF solution. Preferably, an acid solution is added to the collagen / calcium phosphate material before the addition of a PDGF solution. In other embodiments, a biocompatible matrix may be treated with aqueous acid and lyophylized, thus providing a dry matrix for use in the implant material. A growth factor (e,g., a PDGF solution) may then be incorporated into the acid-treated matrix. Incorporating PDGF Solution into a Biocompatible Matrix The present disclosure provides methods for producing compositions for use in bone fusion procedures. In some embodiments, a method for producing a composition for promoting the fusion of bone comprises providing a solution comprising PDGF, providing a biocompatible matrix, and incorporating the solution in the biocompatible matrix. PDGF solutions and biocompatible matrices suitable for combination are consistent with those described hereinabove. In some embodiments, a PDGF solution can be incorporated into the biocompatible matrix by soaking the biocompatible matrix in the PDGF solution. A PDGF solution, in another embodiment, can be incorporated in a biocompatible matrix by injecting the biocompatible matrix with the PDGF solution. In some embodiments, injecting a PDGF solution can comprise incorporating the PDGF solution in a syringe and expelling the PDGF solution into the biocompatible matrix to saturate the biocompatible matrix. The - 27 - FoleyHoagUS12457270.1 SCD-01525 biocompatible matrix may be incubated for a period of time and then worked with a spatula or stirring device to homogenize the implant material. Compositions Comprising Additional Biologically Active Agents The compositions described herein for promoting and / or facilitating bone fusion in procedures, according to some embodiments, can further comprise one or more biologically active agents in addition to PDGF. Biologically active agents that can be incorporated into compositions of the present invention in addition to PDGF can comprise organic molecules, inorganic materials, proteins, peptides, nucleic acids (e.g., genes, gene fragments, small insert ribonucleic acids [si-RNAs], gene regulatory sequences, nuclear transcriptional factors, and antisense molecules), nucleoproteins, polysaccharides (e.g., heparin), glycoproteins, and lipoproteins. Non-limiting examples of biologically active compounds that can be incorporated into compositions of the present invention, including, e.g., anti-cancer agents, antibiotics, analgesics, anti-inflammatory agents, immunosuppressants, enzyme inhibitors, antihistamines, hormones, muscle relaxants, prostaglandins, trophic factors, osteoinductive proteins, growth factors, and vaccines, are disclosed in U.S. patent application Ser. No. 11 / 159,533 (Publication No: 20060084602). In some embodiments, biologically active compounds that can be incorporated into compositions of the present invention include osteoinductive factors such as insulin-like growth factors, fibroblast growth factors, or other PDGFs. In accordance with other embodiments, biologically active compounds that can be incorporated into compositions of the present invention preferably include osteoinductive and osteostimulatory factors such as bone morphogenetic proteins (BMPs), BMP mimetics, calcitonin, calcitonin mimetics, statins, statin derivatives, or parathyroid hormone. Preferred factors also include protease inhibitors, as well as osteoporotic treatments that decrease bone resorption including bisphosphonates, and antibodies to receptor activator of NF-kB ligand (RANK) ligand. Standard protocols and regimens for delivery of additional biologically active agents are known in the art. Additional biologically active agents can be introduced into compositions of the present invention in amounts that allow delivery of an appropriate dosage of the agent to the implant site. In most cases, dosages are determined using guidelines - 28 - FoleyHoagUS12457270.1 SCD-01525 known to practitioners and applicable to the particular agent in question. The amount of an additional biologically active agent to be included in a composition of the present invention can depend on such variables as the type and extent of the condition, the overall health status of the particular patient, the formulation of the biologically active agent, release kinetics, and the bioresorbability of the biocompatible matrix. Standard clinical trials may be used to optimize the dose and dosing frequency for any particular additional biologically active agent. Methods of Performing Fusion Procedures The present invention also provides methods of performing bone fusion procedures, such as spine fusion procedures. In some embodiments, a method of performing a spine fusion procedure comprises providing a composition comprising a PDGF solution incorporated in a biocompatible matrix and applying the composition to a site of desired spine fusion. A composition comprising a PDGF solution incorporated in a biocompatible matrix, for example, can be packed into a site of desired spine fusion. In some embodiments, the composition can be packed such that the composition is in contact with the entire surface area of the bones in the bone fusion site. The composition may additionally be applied to the vicinity of the bone fusion site to further strengthen the fused bones. In some embodiments, the method comprises using a cage. The composition may be applied into the space inside the cage prior to insertion in the desired site of fusion, or alternatively, the cage may be placed at the desired site of fusion, and the composition is then applied to the space inside the cage. Vertebral bones in any portion of the spine may be fused using the compositions and methods of the present invention, including the cervical, thoracic, lumbar, and sacral regions. In another embodiment, a method of the present invention comprises accelerating bony union in a spine fusion procedure wherein accelerating bony union comprises providing a composition comprising a PDGF solution disposed in a biocompatible matrix and applying the following examples will serve to further illustrate the present invention without, at the same time, however, constituting any limitation thereof. On the contrary, it is to be clearly understood that resort may be had to, various embodiments, modifications and equivalents - 29 - FoleyHoagUS12457270.1 SCD-01525 thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the invention. EXAMPLES Example 1: Preparation of a Putty Formulation without a pH modifer A putty formulation of 0.1 mg / ml up to 5 mg / ml recombinant human platelet-derived growth factor (rhPDGF-BB) in 20 mM sodium acetate solution, pH 6.0 solution combined with an 80% / 20%, 85% / 15%, or 90% / 10% w / w β-tricalcium phosphate / bovine type I collagen matrix FIG.1 details the mixing technique used to prepare the improved putty formulation as compared to the paste-like formulation of AI (see FIG.2). When mixed at a 0.5:1, 0.75:1 or 1:1 volume / mass ratio (mL / g), the putty formulation results in a putty that may be molded or be applied through a wide-bore syringe to the site requiring treatment (FIG.3). The test formulations (Table 1) were prepared using X g of matrix (β-TCP / collagen in a 90:10 w / w ratio (Formulation A), 85:15 w / w ratio (Formulation B), or 80:20 w / w ratio (Formulation C) and Y mL solution of rhPDGF-BB in 20 mM of sodium acetate, pH 6.0. A control article was similarly prepared with the 0.5 g matrix and 1.0 mL 20 mM of sodium acetate, pH 6.0. A 10 mL syringe equipped with an 18 gauge needle was used to draw 1.0 mL of the PDGF solution from a vial and into the barrel of the syringe. Table 1. - 30 - FoleyHoagUS12457270.1 SCD-01525 Example 2: Integrity of Putty Formulation Exemplary putty formulation of the present disclosure having a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:1, dos not dissolve and retains its structural integrity when incubated at 37 °C (body temperature). In particular, when incubated at 37 °C the collagen component of the putty matrix does not dissolve and retains its structural integrity. FIG.4 shows each formulation recited in Table 1 after exposure to 37 °C for 1.5 hours. Formulations that best resisted dissolution at 37 ºC included formulations A1, B1, B2, C1 and C2. FIG.4B shows a comparison of a representative putty formulation of the present disclosure to the formulation of AI. The putty formulation retains structural integrity and does not dissolve. However, the AI loses structural integrity by dissolving. Example 3: PDGF Release Kinetics The putty formulation of the present disclosure wherein the solution and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:1, is about 50% recoverable over a timeframe of 3 weeks at 37 ºC (FIG.5). The putty formulation releases in a sustained manner with approximately 20 to 25% of the rhPDGF released within the 1st one hour under in vitro conditions followed by release of remaining 20 to 25% of rhPDGF over the next 2 weeks. However, the AI formulation releases in bulk with 95% of the rhPDGF released within the 1st hour under in vitro conditions. - 31 - FoleyHoagUS12457270.1 SCD-01525 Example 4: Structural Integrity in Aqueous Environment The putty formulation of the present disclosure wherein the solution and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:1, retains its shape when irrigated with a saline solution and does not wash away (FIG.6). However, the AI formulation washes away when irrigated using a saline solution. Example 5: Fusion Cage It was demonstrated that the putty formulation of the present disclosure can be packed inside and around a PEEK spine cage (FIG.7). However, the AI formulation does not retain its shape when packed inside and around a PEEK spine cage. Example 6: pH modification of implant materials A shredded matrix was used in these preparations (see FIG. 8). Putty A contains 90% b- TCP (100-300 μm) and 10% insoluble (fibrillar) collagen, putty B contains 85% b-TCP (100- 300 μm) and 15% insoluble (fibrillary) collagen, and putty C contains 80% β-TCP (100-300 μm) and 20% insoluble (fibrillary) collagen and soluble collagen. The following protocol was implemented to prepare example implant materials. 1. Prepare a 5% (w / v) of bovine soluble collagen solution in 50mM Acetic Acid. Add 500mg of collagen to a total volume of 10 ml 50mM Acetic Acid. 2. Transfer appropriate amount of collagen solution to a pre-labeled protein lo-bind tube. 3. Weigh ~1g of shredded 20 / 80; 15 / 85; 10 / 90 Augment Graft material in 15 mL conical tubes. 4. Add appropriate amount of pre-wetting solution to a sample with pre-wetting condition and mix, then incubate for 10 min at 37oC. 5. Add appropriate amount of rhPDGF solution to each sample. 6. Incubate at RT for 2-5 min to allow adsorption of the drug into the matrix, then homogenize each sample with spatula. 7. Transfer appropriate amount of warm (37oC) elution buffers to each sample tube. 8. Incubate the tubes at 37oC on nutator. - 32 - FoleyHoagUS12457270.1 SCD-01525 9. After each pre-determined time points (30min, 1hr, 2hr, 4hrs, and 8hrs), collect 90% of the supernatant, then replace with same amount of pre-warmed elution buffer. 10. Perform ELISA on collected supernatants (Dilution 25000x; 12500x). A summary of each sample tube is shown in the table in FIG.9. Results of PDGF elution are depicted in FIG.10. As seen in Fig.10, pH modification increased the cumulative PDGF release in all samples. Example 7: Putty Formulation in a Diabetic Rat Fracture Model Group A: Control Matrix Augment® Injectable composed of rhPDGF-BB (0.3 mg / mL in 20 mM buffered sodium acetate) in a matrix of Bovine Type I Collagen and ß-TCB particles. Group B: Test Matrix-1 composed of rhPDGF-BB (0.4 mg / ml in 20 mM buffered sodium acetate) mixed in a test matrix of 90:10 β-TCP and fibrillar collagen without pH modifier at a ratio of 120 µg PDGF (300 µl of PDGF solution) with 300 mg test matrix. Group C: Test Matrix-2 composed of rhPDGF-BB (1.33 mg / ml in 20 mM buffered sodium acetate) mixed in a test matrix 90:10 β-TCP and fibrillar collagen with pH modifier (acetic acetic acid solution with soluble collagen) at a ratio of 120 µg PDGF (90 µl of PDGF solution), 210 µl of pH modifier, and 300 mg test matrix. Preparation of Test Samples Control Matrix: 1. The control matrix is prepared as described in MKS037-01-AUGMENT-Bone-Graft- Sales-Prep-Sheet-US-version-FINAL.pdf . Using the empty syringe and 18-gauge needle included in the kit, withdraw the total contents of the of 0.3 mg / mL -rhPDGF- BB solution. 2. Tap the syringe containing the Control Matrix against the edge of a solid surface 3-4 times or until the matrix is loosened and remove the cap on the needle hub of the syringe containing β-TCP / collagen matrix. 3. Insert the syringe with the 18-gauge needle containing 1 mL of rhPDGF-BB solution into the needle hub of the syringe containing the Control Matrix. 4. Transfer the rhPDGF-BB solution into the syringe containing the matrix. The reformulated rhPDGF-BB solution (0.3mg / mL) should be sufficient to treat multiple - 33 - FoleyHoagUS12457270.1 SCD-01525 fractures. While dispensing the rhPDGF-BB solution, gradually move the solution containing syringe out of the needle hub of the syringe containing the matrix, so that the rhPDGF-BB solution that is dispensed hydrates as much matrix as possible. After dispensing all of the rhPDGF-BB solution, remove the empty syringe and replace the cap back on the needle hub of the syringe containing the hydrated Control Matrix and then allow the mixture to be incubated for 2 min. 5. Connect the empty syringe (which previously contained the rhPDGF-BB solution with the needle removed) with the syringe containing the hydrated matrix using the female-to-female luer-lock connector provided with the kit. 6. Transfer the contents back and forth between the two syringes for twenty (20) cycles and the number of cycle mixing will be recorded. Note: A cycle is defined as passing the matrix into the empty syringe and then back into the original syringe. Upon completion, the matrix should form a homogeneous paste. 7. Transfer all of the matrix paste to one of the syringes, and relieve any pressure built up during the mixing process by gently pulling the plunger containing the matrix. Disconnect the empty syringe and female-to-female luer-lock connector. Connect the 14-gauge blunt cannula to the matrix filled syringe 8. Carefully apply appropriate amount (~100mg) of the hydrated matrix to the surgical site Test Matrix 1 Kit: 1. Aseptically filled rhPDGF-BB in a 20-mM sodium acetate buffer solution (concentration = 0.4 mg / mL concentration), 400µl. 2. 300 mg of sterile shredded Test Matrix (Note: A total 14 shredded matrix pouches sent. This kit component is similar for Test Matrix 1&2 preparation). 3. Mixing System: Sterile spatula; Sterile 5mL conical tube Mixing Instruction: 1. Unseal the sterile package containing 300mg of the shredded Test Matrix 1 and then transfer it to a Sterile 5mL conical tube. 2. Transfer 300µL of the 0.4 mg / mL rhPDGF-BB solution to a tube containing the shredded matrix. - 34 - FoleyHoagUS12457270.1 SCD-01525 3. Once the rhPDGF-BB solution is added, hydrate the sample at room temperature for 30 seconds. 4. Using the provided sterile spatula, mix for a minimum of 2 minutes until the mixture is homogenous. Note: the sample is homogenous when the putty is equally hydrated and there are no visible dry particles. There should be no solid areas when pressed with the sterile spatula. The mixing ratio will be 1:1 (Total liquid volume: Test Matrix 1). That is, for the mixing ratio of 1:1, the Test Matrix 1 mass will be 300 mg and the rhPDGF-BB solution will be 300 µL. The prepared putty should be enough for 3 animals. 5. Immediately prior to implantation, briefly mix the test article to ensure saturation of the β-TCP / collagen matrix. Weigh and document the values. 6. Transfer the hydrated Test Matrix mixture to the implant site as rapidly as possible. Weigh if there is any unused mixture from each test article (the weights of the putty may vary from animal to animal, so the actual weights will be recorded). 7. Once and it will be administered as an implant. The unused mixtures will be discarded as regular wastes. Test Matrix 2 Kit: 1. Aseptically prepared rhPDGF-BB in a 20-mM sodium acetate buffer solution (concentration = 1.33 mg / mL concentration), 120µl. 2. Sterile pH modifier solution, 400µL. Note: Warm the pH modifier at 37°C (2 -3min) before use. 3. 300 mg of sterile shredded Test Matrix (Note: A total 14 shredded matrix pouches sent. This kit component is similar for Test Matrix 1&2 preparation) 4. Mixing System: Sterile spatula; Sterile 5mL conical tube Mixing Instruction: 1. Unseal the sterile package containing 300mg of the shredded Test Matrix 1 and then transfer it to a Sterile 5mL conical tube. - 35 - FoleyHoagUS12457270.1 SCD-01525 2. Add 210µL of pH modifier solution per 300mg of Test Matrix 2 to adjust the pH of Test Matrix 2 microenvironment, then using a sterile small spatula, mix for a minimum of 1-2 minutes until the mixture is homogenous. 3. Once the Test Matrix 2 pH adjusted, add 90 µL of the 1.33mg / ml rhPDGF-BB solution to the mixture from step 2, then allow to hydrate at room temperature for 30 seconds. 4. Using a sterile small spatula, mix for a minimum of 2 minutes until the mixture is homogenous. Note: the sample is homogenous when the putty is equally hydrated and there are no visible dry particles. There should be no solid areas when pressed with the sterile spatula. The mixing ratio will be 1:1 (Total liquid volume: Test Matrix 2). That is, for the mixing ratio of 1:1, the Test Matrix 1 mass will be 300 mg, and the total volume of pH modifier solution and rhPDGF-BB solution will be 300 µL. The prepared putty should be enough for 3 animals. 5. Immediately prior to implantation, briefly mix the test article to ensure saturation of the β-TCP / collagen matrix. Weigh and document the values. 6. Transfer the hydrated Test Matrix mixture to the implant site as rapidly as possible. Weigh if there is any unused mixture from each test article (the weights of the putty may vary from animal to animal, so the actual weights will be recorded). 7. Once and it will be administered as an implant. The unused mixtures will be discarded as regular wastes. Animal Model: The experiments were performed using diabetic BB Wistar rats obtained from a diabetes-prone BB Wistar rat colony established at the New Jersey Medical School (Colle et al.1981). Prior research performed at this laboratory established that fracture healing is significantly impaired in hyperglycemic, diabetic BB Wistar rats (Beam et al.2002). The diabetic prone BB Wistar rats generally become diabetic between 70 and 100 days old. Male rats that had spontaneously developed Type I diabetes were identified and 26 were removed from the colony for this experiment. The rats were treated with subcutaneous, controlled- release insulin implants (LinShin Canada, Inc.) to maintain the rats in a state of poorly - 36 - FoleyHoagUS12457270.1 SCD-01525 controlled diabetes (target blood glucose level greater than 300 mg / dL). Rats had an average age of 201 days (range 114 to 306 days) at time of fracture surgery. No difference in age at time of surgery was detected (Figure 12). Diabetes was monitored using commercial blood glucose meters using blood (a drop) obtained from each rats’ tail. Blood glucose was monitored at least once per week. Closed femur fractures were made to the right femur of each rat using methods adapted from Bonnarens and Einhorn (Bergenstock et al. 2005, Bonnarens and Einhorn 1984). Briefly, an incision was made at the right knee to expose the patella, which was reflected medially to expose the distal femoral condyles. An 18, 19, or 20 g needle was used to hand drill a hole into the femoral canal between the femoral condyles and the femur was reamed with the needle. A 0.4-inch diameter stainless steel rod was inserted retrograde into the femoral canal to support the femur following the impending fracture. The rod was trimmed at the condyles, the patella reduced, and the wound closed with interrupted sutures. A mid-diaphyseal fracture was produced using a 3-point impact device (Cottrell et al. 2009). Following fracture, a lateral incision was made at the fracture site. Soft tissue was bluntly separated to exposure the femur fracture. Approximately 0.1g of PDGF-Matrix was then applied directly to the site as previously described (Al-Zube et al. 2009). The amount of matrix applied to each fracture site is shown in Figure 13 and summarized in Table 2. Table 2: Matrix amounts applied and rats used. X-ray Examination: Rat health and fracture healing progression were monitored by X-ray examination using a Kubtec Xpert-80 digital radiography cabinet. After either ketamine-xylazine or isoflurane anesthetization, X-rays were generally collected from each rat in the ventral-dorsal plane and the lateral- medial planes at 2, 4, 6, and 8 weeks after fracture. Following femur resection at the experimental endpoints, excised femurs were imaged using DV and LM views. Endpoint X-rays were scored using a 0 to 4-point scoring system for each planar view - 37 - FoleyHoagUS12457270.1 SCD-01525 to yield a score range from 0-8 (Bergenstock et al.2005). X-rays were scored based on apparent bony bridging of the callus at the left and at the right periphery of the callus and at the left and right femur cortical fracture site. µCT Imaging and Analysis: Following euthanization, femurs were resected, fixed in formalin, and then stored in 70% ethanol. Stainless steel rods were removed and then the resected femurs underwent µCT imaging using a Bruker Skyscan 1275 using the following scan parameters: 71kV, 133 µA, 24 µm resolution, 0.4o rotation step, with 4X frame averaging. Following reconstruction of the µCT images into a 3D volume, a longitudinal section through the medial-lateral plane was obtained from each specimen and scored for healing using the 0-4-point scoring system described above. The reconstructed 3D volume of each specimen was also analyzed to determine callus volume (TV), callus bone volume (BV), and normalized callus bone volume (BV / TV). Histology & Histomorphometry: Following µCT scanning, the femurs were embedded in polymethylmethacrylate. A longitudinal section through the medial-lateral plane was obtained using diamond wafering saw blades, polished, and applied to a plexiglass slide using methacrylate glue. The slide was stained with Stevenel’s blue to identify cartilage (deep blue) and other soft tissues (lighter shades of blue) and van Gieson’s picrofuchsin to identify bone (red) and calcified cartilage (yellow-orange). The specimens were visualized using an Olympus BH53 microscope and callus, callus bone area, and callus cartilage area were determined using the Osteometrics Osteomeasure system. Statistics: Continuously variable data were compared between groups by ANOVA and Tukey corrected post-hoc tests. Non-continuous data (X-ray scores and µCT longitudinal section scores) were compared between groups using ANOVA on Ranks and post-hoc Kruskal-Walis tests. Analyses were performed using Prism Graphpad software (v10.2.2). Means and standard deviations are shown as well as individual value. - 38 - FoleyHoagUS12457270.1 SCD-01525 RESULTS Animal Health: Five animals were excluded from the study as detailed in Table 3. Table 3. Animal Disposition Blood glucose values from each rat varied over the study course as shown in Figure 14. No difference was found between the treatment groups (Figure 15, ANOVA p=0.82). Rat body weights were measured at time of fracture (Figure 16) and at endpoint (Figure 17). Average starting body weight for all rats was 377g (± 54g), for Group A was 355g (± 67g), for Group B was 364g (± 45g), and for Group C was 410g (± 36g). The variation between groups approached significance (p=0.07) with an apparent trend to heavy Figure 6. Time with Diabetes(larger) rats in Group C. Body weights decreased by an overall average of 7.2% (± 7.4%). No difference in the percent body weight change was detected (p=0.17). The time from onset of diabetes to fracture surgery was also compared between groups as shown in Figure 18. The mean value for Group B was the lowest at 61 days (± 30 days) but was not significantly different (p=0.29) from Group A (98 ± 76 days) or Group C (101 ± 63 days). X-ray Healing Outcomes: Radiograph digital images are available in supplemental files. Healing femurs were resected at either 4 or 8 weeks after fracture. The femurs were examined by medial-lateral and dorsal-ventral X- rays which were scored for apparent bony bridging. Scores were summed between the two X- rays views and are shown in Figure 19. Between group comparisons were performed using Kruskal-Walis tests. No significant difference was detected. µCT Imaging and Analysis: All fractured femurs were scanned by µCT. Select images (longitudinal section through the medial-lateral plane) are shown in Figures 21-23. Additional images, including - 39 - FoleyHoagUS12457270.1 SCD-01525 3D rendering for 1 specimen in each cohort can be found in the supplemental files. Note that un- resorbed matrix is clearly visible in many of the specimens. The longitudinal µCT sections were scored for healing except only 1 view was scored (0-4 points, Figure 20). While no differences in µCT image scores were detected, we noted that 4 of 7 in Group A showed no bridging while only 4 of 14 in Groups B and C showed no bridging. The µCT image data was analyzed to determine callus total volume (TV), bone volume (BV), a normalized bone volume (BV / TV). Whether when analyzed by time points or by group only, no significant difference was detected (Figures 24 and 25). When comparing between 4 and 8 weeks Histology and Histomorphometry: Following µCT examination, each specimen was embedded in PMMA for calcified histological examination. Slides were stained with van Gieson’s picrofuchsin and Stevenel’s blue. Representative images from each treatment group and time point are shown in Figures 26-28. Each panel shows one quadrant from the callus of the designated animal. Each image is oriented so that the fracture site is to the left edge while the intramedullary (bone marrow) space is on the bottom. At 4 weeks, the external callus was well-developed in all groups. By 8 weeks, all external fracture calluses had been reduced in size, consistent with callus remodeling. Evidence of bony union was evident in some specimens by 8 weeks. Histomorphometric analysis of the histological specimens found very low levels of callus cartilage by 4 weeks after fracture (<1% by callus area) (Figures 29 and 30). Percent callus bone area significantly increased from 24% at 4 weeks to 50% at 8 weeks (p=0.02) for the Group A specimens. However, no difference in callus percent bone was detected from 4 to 8 weeks in either the Group B (mean 41%) or C specimens (mean 34%). REFERENCES Al-Zube, L., Breitbart, E.A., O'Connor, J.P., Parsons, J.R., Bradica, G., Hart, C.E. and Lin, S.S., 2009. Recombinant human platelet-derived growth factor BB (rhPDGF-BB) and beta- tricalcium phosphate / collagen matrix enhance fracture healing in a diabetic rat model. J Orthop Res.27(8): 1074-1081. Beam, H.A., Parsons, J.R. and Lin, S.S., 2002. The effects of blood glucose control upon fracture healing in the BB Wistar rat with diabetes mellitus. J Orthop Res.20(6): 1210-1216. - 40 - FoleyHoagUS12457270.1 SCD-01525 Bergenstock, M., Min, W., Simon, A.M., Sabatino, C. and O'Connor, J.P., 2005. A comparison between the effects of acetaminophen and celecoxib on bone fracture healing in rats. J Orthop Trauma.19(10): 717-723. Bonnarens, F. and Einhorn, T.A., 1984. Production of a standard closed fracture in laboratory animal bone. J Orthop Res.2(1): 97-101. Colle, E., Guttmann, R.D. and Seemayer, T., 1981. Spontaneous diabetes mellitus syndrome in the rat. I. Association with the major histocompatibility complex. J Exp Med.154(4): 1237-1242. Cottrell, J.A., Meyenhofer, M., Medicherla, S., Higgins, L. and O'Connor, J.P., 2009. Analgesic effects of p38 kinase inhibitor treatment on bone fracture healing. Pain.142(1-2): 116-126. INCORPORATION BY REFERENCE All of the U.S. patents and U.S. and PCT published patent applications cited herein are hereby incorporated by reference. EQUIVALENTS The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the invention. The present invention is not to be limited in scope by examples provided, since the examples are intended as a single illustration of one aspect of the invention and other functionally equivalent embodiments are within the scope of the invention. Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims. The advantages and objects of the invention are not necessarily encompassed by each embodiment of the invention. - 41 - FoleyHoagUS12457270.1

Claims

SCD-01525 CLAIMS We claim:

1. An implant material comprising a growth factor, an acid, and a biocompatible matrix, the biocompatible matrix comprising a porous calcium phosphate, a fibrillar collagen, and an aqueous liquid, wherein the biocompatible matrix comprises about 70 to about 95% by weight of the porous calcium phosphate and about 5 to about 30% by weight of the fibrillar collagen, and wherein the aqueous liquid and the biocompatible matrix are present in the composition in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 2:

1.

2. The implant material of claim 1, wherein the growth factor is selected from a bone morphogenic protein, platelet-derived growth factor (PDGF), fibroblast growth factor, insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β) and any combination thereof.

3. The implant material of claim 1 or 2, wherein the growth factor is PDGF.

4. The implant material of any one of claims 1 to 3, wherein the aqueous liquid and the biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) ranging from about 0.5:1 to about 1.5:

1.

5. The implant material of claim 4, wherein the aqueous liquid and the biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) of about 0.5:

1.

6. The implant material of claim 4, wherein the aqueous liquid and the biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) of about 0.75:

1.

7. The implant material of claim 4, wherein the aqueous liquid and the - 42 - FoleyHoagUS12457270.1SCD-01525 biocompatible matrix are present in the implant material in a volume to mass ratio (mL / g) of about 1:

1.

8. The implant material of any one of claims 1-7, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount ranging from about 70 weight percent to about 90 weight percent.

9. The implant material of 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount ranging from about 80 weight percent to about 90 weight percent.

10. The implant material of 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount ranging from about 85 weight percent to about 90 weight percent.

11. The implant material of 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount ranging from about 80 weight percent to about 85 weight percent.

12. The implant material of claim 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount of about 90 weight percent.

13. The implant material of claim 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount of about 85 weight percent.

14. The implant material of claim 8, wherein the porous calcium phosphate is present in the biocompatible matrix in an amount of about 80 weight percent.

15. The implant material of any one of claims 1-14, wherein the porous calcium phosphate is selected from the group consisting of tricalcium phosphate, hydroxyapatite, poorly crystalline hydroxyapatite, amorphous calcium phosphate, calcium metaphosphate, dicalcium phosphate dihydrate, heptacalcium phosphate, calcium pyrophosphate dihydrate, - 43 - FoleyHoagUS12457270.1SCD-01525 calcium pyrophosphate, octacalcium phosphate, brushite, and mixtures thereof.

16. The implant material of claim 14, wherein the porous calcium phosphate is β- tricalcium phosphate.

17. The implant material of any one of claims 1 to 16, wherein the calcium phosphate comprises particles having a size ranging from about 100 to about 1000 μm.

18. The implant material of claim 17, wherein the calcium phosphate comprises particles having a size ranging from about 100 to about 500 μm.

19. The implant material of claim 17, wherein the calcium phosphate comprises particles having a size ranging from about 100 to about 300 μm.

20. The implant material of any one of claims 1-19, wherein the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 25 weight percent.

21. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 20 weight percent.

22. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 10 weight percent to about 15 weight percent.

23. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount ranging from about 5 weight percent to about 10 weight percent. - 44 - FoleyHoagUS12457270.1SCD-01525 24. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount of about 10 weight percent.

25. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount of about 15 weight percent.

26. The implant material of claim 20, wherein the fibrillar collagen is present in the biocompatible matrix in an amount of about 20 weight percent.

27. The implant material of any one of claims 1-26, wherein the fibrillar collagen comprises bovine collagen.

28. The implant material of any one of claims 1 to 27, wherein the fibrillar collagen comprises type I bovine collagen.

29. The implant material of any one of claims 1 to 28, wherein the fibrillar collagen comprises dermis collagen.

30. The implant material of any one of claims 1 to 29, wherein the fibrillar collagen comprises tendon collagen.

31. The implant material of any one of claims 1-30, wherein biocompatible matrix further comprises about 0.1 to about 10 weight % of soluble collagen.

32. The implant material of claim 31, wherein the biocompatible matrix comprises about 0.1 to about 5 weight % of soluble collagen.

33. The implant material of claim 31, wherein the biocompatible matrix comprises about 0.1 to about 2 weight % of soluble collagen. - 45 - FoleyHoagUS12457270.1SCD-01525 34. The implant material of claim 31, wherein the biocompatible matrix comprises about 1 to about 10 weight % of soluble collagen.

35. The implant material of any one of claims 31 to 34, wherein the soluble collagen comprises bovine collagen.

36. The implant material of any one of claims 31 to 34, wherein the soluble collagen comprises type I bovine collagen.

37. The implant material of any one of claims 31 to 34, wherein the soluble collagen comprises bovine dermis collagen.

38. The implant material of any one of claims 3 to 31, wherein the PDGF is present in the aqueous liquid at a concentration ranging from about 0.1 mg / ml to about 5.0 mg / ml.

39. The implant material of claim 38, wherein the PDGF is present in the aqueous liquid at a concentration ranging from about 0.1 mg / ml to about 1.0 mg / ml.

40. The implant material of claim 39, wherein the PDGF is present in the aqueous liquid at a concentration from about 0.2 mg / ml to about 0.4 mg / ml.

41. The implant material of claim 40, wherein the PDGF is present in the aqueous liquid at a concentration of about 0.3 mg / ml.

42. The implant material of any one of claims 3 to 41, wherein the PDGF comprises PDGF-AA, PDGF-BB, PDGF-AB, PDGF-CC, PDGF-DD, or a mixture or a derivative thereof.

43. The implant material of claim 42, wherein the PDGF comprises PDGF-BB.

44. The implant material of claim 43, wherein the PDGF-BB comprises at least 65% - 46 - FoleyHoagUS12457270.1SCD-01525 intact PDGF-BB.

45. The implant material of claim 42 to 44, wherein the PDGF-BB is recombinant human (rh)PDGF-BB.

46. The implant material of any one of claims 1-45, wherein the aqueous liquid comprises the growth factor in a buffer.

47. The implant material of claim 46, wherein the buffer comprises sodium acetate.

48. The implant material of any one of claims 1 to 47, wherein the putty retains its in vitro structural integrity at 37 ºC.

49. The implant material of any one of claims 3 to 48, wherein at least 20% of the PDGF is released after about 30 minutes in vitro.

50. The implant material of any one of claims 3 to 48, wherein at least 40% of the PDGF is released after about 1 hour in vitro.

51. The implant material of any one of claims 3 to 48, wherein at least 50% of the PDGF is released after about 1 hour in vitro.

52. The implant material of any one of claims 3 to 48, wherein at least 60% of the PDGF is released after about 1 hour in vitro.

53. The implant material of any one of claims 3 to 48, wherein at least 70% of the PDGF is released after 4 hours in vitro.

54. The implant material of any one of claims 1 to 53, wherein the acid is selected from acetic acid, citric acid, lactic acid, malic acid, succinic acid, formic acid, tartaric acid, and - 47 - FoleyHoagUS12457270.1SCD-01525 any combination thereof.

55. The implant material of claim 54, wherein the acid is acetic acid.

56. The implant material of any one of claims 1 to 55, wherein the acid is an aqueous acid.

57. The implant material of claim 56, wherein the acid has a concentration in a range of about 10 to about 50 mM in the aqueous liquid.

58. The implant material of any one of claims 1 to 55, wherein the biocompatible matrix comprises the acid.

59. The implant material of any one of claims 1 to 58, wherein the implant material has a pH of about 6.5 or less.

60. The implant material of claim 59, wherein the implant material has a pH of about 3 to about 6.

5.

61. The implant material of claim 59, wherein the implant material has a pH of about 3 to about 6.

62. The implant material of claim 59, wherein the implant material has a pH of about 3 to about 5.

5.

63. A method for bone fusion in a subject comprising administering the implant material of any one of claims 1 to 62 to a desired site of bone fusion in the subject.

64. The method of claim 63, wherein the site of bone fusion is in a foot, toe, ankle, knee, hip, spine, rib, sternum, clavicle, joint, shoulder, scapula, elbow, wrist, hand, or finger. - 48 - FoleyHoagUS12457270.1SCD-01525 65. The method of claim 64, wherein the site of bone fusion is a joint.

66. The method of claim 65, wherein site of bone fusion is an ankle.

67. The method of claim 65, wherein site of bone fusion is a spine.

68. The method of claim 67, wherein the method further comprises placing an intravertebral spacer between vertebral bodies.

69. The method of claim 68, wherein the implant material is disposed in the vertebral spacer prior to placing the vertebral spacer between the vertebral bodies.

70. The method of claim 69, further comprising disposing the implant material in the spacer after placing the spacer between the vertebral bodies.

71. The method of any one of claims 67 to 70, wherein the spine fusion procedure is an interbody fusion procedure.

72. The method of any one of claims 67 to 70, wherein the spine fusion procedure is a lumbar fusion procedure.

73. A method for fracture repair in a subject comprising administering the implant material of any one of claims 1 to 62 a desired site of fracture repair in the subject.

74. The method of claim 73, wherein the site of fracture repair is an arm or a leg.

75. The method of claim 74, wherein the site of fracture repair is a tibia.

76. The method of any one of claims 63 to 75, wherein the method accelerates bony union. - 49 - FoleyHoagUS12457270.1

Images