Antibacterial Shape Memory Polymer

Abstract

One embodiment includes a system including a thermoset polyurethane shape memory polymer (SMP) foam containing at least one antimicrobial agent. The antimicrobial agent may include at least one phenolic acid that is a pendant group chemically bonded to the polyurethane polymer chain of the SMP foam. Other embodiments are described herein. [Selected figure] Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 430,620, filed December 6, 2016, and entitled "Antimicrobial Shape Memory Polymers," the contents of which are incorporated herein by reference.

[0002] Technical Field FIELD OF THE DISCLOSURE Embodiments of the present invention are in the field of shape memory polymer medical devices. [Background technology]

[0003] Background Hemorrhage is the leading cause of potentially preventable deaths on the battlefield. The current standard of field care is to utilize gauze in combination with a tourniquet. However, these treatments are insufficient for up to 80% of wounds. Furthermore, tourniquets only serve as a temporary measure against blood loss, as tourniquet use for more than approximately (~) 4-6 hours is associated with limb damage and loss. Improved hemostatic materials could allow for earlier tourniquet removal before the patient can receive treatment at a fixed facility.

[0004] The current standard of care in the battlefield involves the use of broad-spectrum antibiotic regimens combined with frequent dressing changes to prevent bacterial and fungal infections. However, growing concerns over antibiotic resistance require the use of alternative treatment methods, and dressing changes are not always feasible during combat.

[0005] BRIEF DESCRIPTION OF THE DRAWINGS Features and advantages of embodiments of the present invention will become apparent from the appended claims, the following detailed description of one or more exemplary embodiments, and the corresponding drawings, in which: Where considered appropriate, reference characters have been repeated among the figures to indicate corresponding or analogous elements. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1. Schematic of the incorporation of cinnamic acid (CA) into shape memory polymer (SMP) foam. Route A: In one embodiment, a prepolymer was prepared using CA, hydroxypropylethylenediamine (HPED), triethanolamine (TEA), and excess hexamethylene diisocyanate (HDI). The prepolymer was reacted with the remaining CA, HPED, and TEA with heating in the presence of a catalyst, surfactant, and blowing agent to form a CA-containing SMP foam. Route B: In one embodiment, the carboxylic acid group on the CA was esterified with the hydroxyl group on the HPED to form HCA. The CA-containing SMP foam was then formed using HCA instead of CA as the foamable monomer in the same manner as employed in Route A. [Diagram 2] Spectral confirmation of the synthesis of HCA / CA foams is shown in Figure 2. Figure 2(A) is the transmission Fourier transform infrared (FTIR) spectrum of HCA compared to HPED and CA, Figure 2(B) is the nuclear magnetic resonance (NMR) spectrum of HCA, and Figure 2(C) is the attenuated total reflectance (ATR)-FTIR spectrum for the control, CA, and HCA foams. [Diagram 3] Figure 3. Phenolic acid-containing foam composition. [Figure 4] Figure 4. Pore size and density of SMP foams synthesized with CA and CAOH monomers. [Diagram 5] Figure 5. Thermal and shape memory properties of CA- and CAOH-containing SMP foams. [Figure 6] Figure 6. E. coli colony forming units after exposure to control SMP, SMP containing CA or CAOH, and penicillin-streptomycin (antibiotic control). Both CA and CAOH containing SMPs reduced colony size and number compared to control SMP, and both reduced colony size compared to antibiotic control. [Figure 7]Figure 7 shows structural properties of SMP foams. Figure 7(A) is density, Figure 7(B) is pore size (axial and transverse foam directions) and isotropy (ratio between pore sizes in axial and transverse foam directions), and Figure 7(C) is a representative scanning electron micrograph in the axial and transverse foam directions. Scale bars apply to all images. [Figure 8] Figure 8 shows the thermal and shape memory properties of HCA / CA foams. Figure 8(A) shows the dry and wet glass transition temperatures (Tg), Figure 8(B) shows the volume recovery profile in water at 37°C, and Figure 8(C) shows the time to 100% volume recovery in water at 37°C. [Figure 9] Figure 9 shows representative bright field images of human dermal fibroblasts after 2 and 72 hours of contact with the SMP film. Scale bars apply to all images. [Figure 10] Figure 10: Colony forming unit (CFU) densities of E. coli (Figure 10(A)) and Staph. epidermidis (Figure 10(B)) after exposure to unmodified control, CA, HCA, and penicillin-streptomycin (P / S) soaked control SMP films. *p<0.05 vs. control. Dagger p<0.05 vs. 10% HCA and 20% HCA. ·p<0.05 vs. all other samples. [Figure 11] Figure 11. Colony forming unit (CFU) density of (A) Escherichia coli (E. coli) and (B) Staph. epidermidis (Staph. Epi.) after exposure to CA and HCA SMP films immersed in phosphate buffered saline for up to 30 days at 37°C. Red line - control CFU density. *p<0.05 vs. control. ·p<0.05 vs. all other time points within formulation, ■p<0.05 vs. 10 and 20 day samples within formulation, double dagger p<0.05 vs. 0 day samples within formulation. [Figure 12] Figure 12 is an antimicrobial SMP composition. NCO: isocyanate, OH: hydroxyl. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Detailed Description "An embodiment," "various embodiments," and the like indicate that the embodiment or embodiments so described include a particular feature, structure, or characteristic, but not necessarily all embodiments include the particular feature, structure, or characteristic. Some embodiments may have some, all, or none of the features described for other embodiments. "First," "second," "third," and the like describe a common object and indicate that different instances of a similar object are being referenced. Such adjectives do not imply that the objects so described must be in the given order, temporally, spatially, in ranking, or otherwise.

[0008] Various embodiments are addressed below. The embodiments are addressed first in a section entitled "Summary of the Embodiments". The embodiments are then further addressed in sections entitled "High Level Description of the Embodiments" and "More Detailed Description of the Embodiments". Summary of the Invention [Problem to be solved by the invention]

[0009] Overview of One or More Embodiments There is a great deal of concern in the medical community over antibiotic-resistant bacteria resulting in infections that are very difficult to treat. To address these concerns, one embodiment includes the incorporation of antimicrobial agents into shape memory polymers (SMPs). SMPs are very valuable materials that can be used in a variety of medical or other devices. One embodiment incorporates non-drug based antimicrobial agents (e.g., phenolic acids from honey, fluorescent dyes, silver, or peroxide generating compounds) into the SMP. The presence of these antimicrobial agents provides localized infection prevention around the SMP-based device. One embodiment provides that antimicrobial properties are introduced by incorporating small antimicrobial agents or agents in the polymer synthesis such that they are chemically or physically built into the polymer network.

[0010] Thus, embodiments include SMP-based medical devices that are infection resistant.Embodiments include antimicrobial SMPs utilized in a wide range of medical devices, including but not limited to intravascular medical devices, wound dressings, hemostatic materials, pulmonary puncture sealants, and / or bone grafts.In one embodiment, SMP medical devices with incorporated antimicrobial agents work in conjunction with oral antibiotics to reduce the risk of localized infection in damaged tissue.

[0011] Such embodiments are important for a variety of reasons. For example, these antimicrobial SMP-based medical devices fill a significant clinical need in the treatment and prevention of infection because infections acquired at the point of injury and / or in the hospital environment are a significant source of healthcare costs and contribute to patient morbidity and mortality. By delivering antimicrobial agents directly to the wound or implant source, these infections and their complications are reduced through the use of broad-spectrum antimicrobial agents that are particularly effective against drug-resistant bacterial strains. SMP medical devices can be easily delivered to small and / or irregularly shaped defect sites. Thus, antimicrobial SMPs offer a new treatment option with reduced risk of infection.

[0012] Such embodiments are novel for a variety of reasons. For example, the incorporation of non-drug based antimicrobial agents directly into the SMP and the subsequent fabrication of devices with complex structures is novel. Points of novelty include the incorporation of non-drug small antimicrobial molecules (e.g., phenolic acids and fluorescent dyes) into the SM polymer foam system to enable delivery in medical devices.

[0013] Further regarding antimicrobial molecules, one embodiment encompasses phenolic acids (PAs). Honeybees produce plant-derived PAs in their honey to protect the hive from microbes and viruses. PAs exhibit broad antimicrobial properties and have been shown to be effective against multi-drug resistant organisms (MDROs). For example, antibiotic-resistant bacteria obtained from hospitals (Enterobacter aerogenes, Escherichia coli, and Staphylococcus aureus) were sensitive to PA cinnamic acid. Similarly, two other PSs (ferulic acid and gallic acid) reduced biofilm activity by >70% for four human pathogenic bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria monocytogenes).

[0014] As an alternative to PAs, embodiments use a number of fluorescent molecules that have antimicrobial activity and chemistries that allow for their incorporation into SMPs. A further embodiment incorporates monomers that spontaneously generate peroxides in the presence of water.

[0015] As an added benefit, the technique of utilizing antimicrobial agents as monomers allows for fine tuning of SMP properties using standard variables such as hydrophobicity and crosslink density. This property expands the potential applications of antimicrobial SMPs, as they can be engineered and tailored to different types of tissue.

[0016] Another embodiment uses antimicrobial SMPs that include the physical incorporation of antimicrobial particles, such as silver nanoparticles. The nanoparticle filler improves the mechanical properties of the SMP scaffold. Thus, the addition of silver nanoparticles enhances the mechanical integrity of the SMP and provides antimicrobial resistance.

[0017] There are still further advantages to the embodiment. Previous work (Landsman, et al. Acta Biomaterialia (2016)) has involved SMP foams integrated with iodine-containing hydrogels. While these iodine "sponges" also offer an option for antimicrobial SMP systems, the antimicrobial properties are entirely dependent on the hydrogel components, where the antimicrobial agent is not directly incorporated into the SMP. In contrast, one embodiment utilizes an SMP-only scaffold with various mechanisms for incorporating antimicrobial agents.

[0018] Various embodiments of the antimicrobial SMP foams are produced by several routes.

[0019] Route 1: Antimicrobial or peroxide generating monomers are functionalized with reactive hydroxyl or amine groups to allow their incorporation into polyurethanes. Briefly, the carboxylic acid of the phenolic acid is esterified with a foaming polyol (e.g., N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (HPED) or triethanolamine) in a suitable solvent using an esterification catalyst (e.g., dicyclohexylcarbodiimide (DCC) and dimethylaminopyridine (DMAP)). The reaction is filtered and washed to remove by-products and residual catalyst, and the final product is isolated by rotary evaporation. This method is suitable for use with any antimicrobial agent that has a carboxylic acid group. The final product is utilized as a polyol in SMP synthesis with other polyols (e.g., HPED and / or TEA) and diisocyanates (e.g., hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and / or isophorone diisocyanate).

[0020] Route 2: Direct Chemical Incorporation into SMP. Briefly, any antimicrobial or peroxide generating monomer having reactive groups (e.g., carboxylic acid, hydroxyl, or primary or secondary amine) is reacted with a polyol (e.g., HPED and / or TEA) and a diisocyanate (e.g., hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and / or isophorone diisocyanate) to form a polyurethane SMP.

[0021] Route 3: Direct physical incorporation into the SMP. Briefly, to yield an SMP network with a physically incorporated antimicrobial agent, any antimicrobial or peroxide generating monomer or particle (nanoscale or microscale) is mixed with the SMP monomer (e.g., polyol (e.g., HPED and / or TEA)) and diisocyanate (e.g., hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and / or isophorone diisocyanate) prior to the crosslinking reaction. Thus, the SMP foam is crosslinked around the antimicrobial or peroxide generating monomer or particle. In one embodiment, the iso or "B" side and the "poly" or "A" side of the polymer chain are crosslinked around the antimicrobial or peroxide generating monomer or particle.

[0022] In general, SMP networks include switch units or segments and net points or domains. The net points determine the permanent shape of the polymer network. In one embodiment, the antimicrobial agent is a physically crosslinked net point. With the antimicrobial agent, the SMP foam comprises a composite and thus becomes stronger in response to the inclusion of the antimicrobial agent.

[0023] Any of the above routes may be utilized with bulk or porous SMPs. After synthesis, the materials are cut, cleaned, processed, and incorporated into medical devices.

[0024] The embodiments include PA that was successfully modified with HPED and utilized in SMP foam and bulk film synthesis. The PA-containing SMP has similar thermal transition temperature as the control, demonstrating shape memory properties. The PA-containing SMP shows effective reduction in Escherichia coli growth compared to the control.

[0025] Various SMP foams have been discussed. Embodiments include polyurethane SMP foams synthesized by some combination of (a) and (b): (a) hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, triethanolamine, diethanolamine, butanediol, butynediol, N,N,N',N'-tetrakis(hydroxylpropylene)ethylenediamine, and (b) Antimicrobial agents, which may include, but are not limited to, phenolic acids (e.g., cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid), fluorescent dyes (e.g., phloxine B, toluidine blue O, indocyanine green), or metal particles or nanoparticles (e.g., colloidal silver). [Means for solving the problem]

[0026] High Level Description of the Embodiments Antimicrobial agents are incorporated into polyurethane shape memory polymers (SMPs) (Figure 1). In some embodiments, the incorporated antimicrobial agents work in conjunction with oral antibiotics to reduce the risk of infection in implanted SMP-based devices. There is much concern about antibiotic-resistant bacterial strains. To address this issue, antimicrobial phenolic acids (PAs) have been utilized in non-drug approaches. Honeybees produce plant-derived PAs in their honey to protect the hive from microbes and viruses. PAs exhibit broad antimicrobial properties and have been shown to be effective against multi-drug resistant organisms (MDROs). For example, antibiotic-resistant bacteria acquired from hospitals (Enterobacter aerogenes, Escherichia coli, Staphylococcus aureus) are susceptible to cinnamic acid. A recent review has covered the effectiveness of numerous PAs, including cinnamic acid, gentisic acid, and benzoic acid, against Candida infections (planktonic and biofilm, drug susceptible and drug resistant). Additionally, ferulic and gallic acids reduced biofilm activity by >70% for four human pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria monocytogenes). By taking a single component of honey (e.g., PA) and utilizing it as a foamable monomer, we harness the benefits of PA while maintaining a synthetic medical device system.

[0027] Study 1.1: Produce PA-containing SMP foams. PA (modified and unmodified) antimicrobial potency against MDROs is measured to down-select agents prior to foam production. For all agents with acceptable antimicrobial properties, SMP foams are synthesized with varying levels of cinnamic, gentisic, and benzoic acids by (a) pre-esterification with foaming polyol to produce PA-containing polyol (PAOH) and (b) direct compounding. In one embodiment, route (a) requires fewer modifications to the foam composition. Pre-esterification enhances the antimicrobial properties of the PA. In addition, route (a) eliminates / reduces foam generation from the reaction between the carboxylic acid on the PA and the isocyanate in the foam for better control of foam properties. Route (b) is simpler and less expensive. Thus, in some embodiments, foams synthesized via route (b) that meet all performance criteria and produce consistent and reliable foams are advantageous.

[0028] Method: PAOH synthesis. PAOH is synthesized from hydroxypropylethylenediamine (HPED). PAs (cinnamic acid, gentisic acid, and benzoic acid) are selected via esterification (catalyzed by dicyclohexylcarbodiimide (DCC) and dimethylaminopyridine (DMAP)) in chloroform at room temperature for 3 h (Figure 1). The reaction is filtered and washed to remove by-products and residual catalyst, and the final product is isolated by rotary evaporation. Successful synthesis of PAOH is confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy.

[0029] Results: Cinnamic acid-HPED (CAOH) was successfully synthesized as shown by the FTIR spectrum indicating the reduction of hydroxyl groups and the formation of ester bonds compared to HPED (Figure 2).

[0030] Form composition: Since PA and PAOH derivatives are effective antimicrobial agents, foams are synthesized with various amounts of PAOH in combination with HPED and hexamethylene diisocyanate (HDI) as previously described (Figure 1). Briefly, polyurethane prepolymers are synthesized with excess amounts of HDI, PAOH, and HPED. In some embodiments, the remaining PAOH and HPED are mixed together and added to the prepolymer in a final molar ratio of 1:1 (isocyanate (HDI):hydroxyl (PAOH and HPED)). Upon addition of the hydroxyl mix to the prepolymer, catalyst, surfactant, water (chemical blowing agent), and Enovate (physical blowing agent) are added, and the ingredients are mixed until homogeneous. In one embodiment, the resulting foam mixture is cured at 90°C for 20 minutes. In parallel, PA-containing foams are synthesized by directly incorporating phenolic acids into the polyurethane backbone (reaction of carboxylic acids on the PA with isocyanates in the foam) (Figure 3).

[0031] Study 1.2: Characterize the PA-containing foam structure; mechanical, thermal, and shape memory properties; and cytocompatibility. After the library of PA-containing foams are synthesized, they are characterized to ensure that the desired foam properties are retained. In particular, to enhance wound filling and clotting rates, as well as high cytocompatibility as an early indicator of their safety, PA-containing foam embodiments have thermal transitions at body temperature in aqueous conditions to allow for shape change upon application of the bleed, rapid shape recovery (<2 minutes). These properties are achieved by several compositions described herein.

[0032] Method: Structure: After the foams are formulated with PAOH and PA, the pore size and structure of the foams are quantified. Thin samples are cut transversely and longitudinally from each foam, sputter coated with gold, and imaged using a scanning electron microscope (SEM). Pore size and strut thickness are quantified from the SEM images using ImageJ software.

[0033] Results: CA and CAOH were successfully formulated into SMP foams, resulting in low density foams with retained pore size of about 1000 μm, Figure 3.

[0034] Thermal properties: The glass transition temperatures (Tg) of the control and modified foams are measured using differential scanning calorimetry (DSC) under wet and dry conditions. For the dry Tg, 3-8 mg samples are placed in aluminum pans at room temperature, cooled to -40°C using DSC, and then heated to 120°C. The samples are cooled and heated again, and the Tg is recorded from the second cycle as the inflection point of the thermal transition curve. For the wet Tg, 3-8 mg foam samples are immersed in 50°C reverse osmosis water for 5 minutes to fully plasticize, then pressed dry with laboratory wipes. The samples are weighed and placed in vented aluminum pans. DSC is used to cool the samples to -40°C and heat them to 80°C. The wet Tg (after water plasticization) is determined using the average inflection point of the thermal transition.

[0035] result: CA- and CAOH-containing SMP foams exhibited preserved dry thermal properties compared to the control (Figure 4). The wet glass transition temperature was decreased compared to the control but remained below body temperature to allow actuation upon implantation.

[0036] Shape memory properties: Cylindrical foam samples (2 mm diameter x 1 cm length) are cut and 203.20 μm diameter nickel titanium wire is threaded down the length of the sample to act as a stabilizer. The samples are crimped to their smallest possible diameter using a stent crimper while heated above the Tg. The initial foam diameter is measured using ImageJ software and the foams are placed in a 37°C water bath. Images are taken over 30 minutes and the foam diameter is calculated at each time point using ImageJ®. The measurements obtained are used to calculate the percent recovery to the original sample diameter and volume expansion.

[0037] result: CA- and CAOH-containing SMP foams exhibited retained shape memory properties with high volume recovery and volume expansion, FIG.

[0038] Study 1.3: Evaluate the antibacterial properties of PA-containing foams in comparison to clinically available silver-based antibacterial wound dressings. As an initial indication of the antimicrobial efficacy of PA-containing SMP foams, a series of in vitro studies were conducted with bacteria.Embodiments include formulations with antimicrobial properties comparable to those of clinically available antimicrobial oxidized regenerated cellulose hemostats.

[0039] Methods: E. coli (gram negative) and S. epidermidis (gram positive) colony forming units (CFU) were counted after exposure to control foam, PA and PAOH foams, and cellulose hemostat (Surgicel®, Ethicon).

[0040] result: CA and CAOH SMPs significantly inhibited E. coli growth (colony number and size) compared to the control SMP (Figure 6).

[0041] More detailed description of the embodiments The SMP foam embodiments described herein provide a biomaterial platform with numerous potential advantages for use as a hemostatic dressing. Polyurethane SMPs are manufactured as expanded, open-porous foams that can be compressed into a temporary secondary shape. The compressed shape is retained until the foam is exposed to water and heat, at which time the foam returns to its original expanded shape. The embodiments are designed to operate in aqueous conditions of 15-45°C (~40-70°C in dry conditions) with operation times adjusted between 30 seconds and 30 minutes. The SMP foams demonstrated excellent biocompatibility over 90 and 180 days after implantation in a porcine aneurysm model. Importantly, these foams induce rapid clotting due to their high surface area and thrombogenic material chemistry. In porcine hindlimb vessels, the SMP foams promoted arterial hemostasis within 90 seconds of device placement. The SMP foam embodiments have minimal particle generation, and no undesirable downstream clotting has been observed in prior in vivo occlusion studies. Embodiments allow application of a compressed device to deep, irregularly shaped bleeding sites, which rapidly expands when passively heated to body temperature to space-fill the wound volume and promote hemostasis.

[0042] One of the advantages of the embodiments of the SMP system described herein is the tunable material chemistry. Antimicrobial agents have been introduced into the polymer network to enhance the performance of the hemostatic device. In one embodiment, the incorporated antimicrobial agent works in conjunction with oral antibiotics to reduce the risk of infection and the need for frequent dressing changes. To address concerns regarding antibiotic-resistant bacterial strains, antimicrobial phenolic acids have been utilized to provide a non-drug approach. Honeybees produce plant-derived phenolic acids in their honey to protect the hive from microbes and viruses. Phenolic acids exhibit broad antimicrobial properties and have been shown to be effective against multi-drug resistant organisms (MDROs). For example, antibiotic-resistant bacteria obtained from hospitals (Enterobacter aerogenes, Escherichia coli, Staphylococcus aureus) are susceptible to cinnamic acid. A recent review has covered the effectiveness of a number of phenolic acids, including cinnamic acid, gentisic acid, and benzoic acid, against Candida infections (planktonic and biofilm, drug susceptible and drug resistant).

[0043] The embodiment incorporates native and modified cinnamic acids (CAs) into the SMP system (Figure 1). The resulting scaffolds were characterized to ensure the maintenance of desirable SMP properties including density, pore size and structure, thermal properties, shape recovery profile and cytocompatibility. Emphasis was placed on designing an SMP foam hemostat that can be stored under extreme battlefield conditions and activates immediately upon exposure to blood moisture at body temperature. To gain an understanding of the initial and sustained antibacterial effects, the antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (Staph. epi) were characterized after immersion of samples in saline at body temperature for up to 30 days.

[0044] Results and Discussion Synthesis of CA and HCA containing SMPs: To allow its incorporation without sacrificing the crosslink density of the polyurethane network, cinnamic acid (CA) was modified by esterification with N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (HPED) to form a CA-containing triol (HCA). The successful synthesis of HCA was confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. In the FTIR spectrum, a relative reduction in hydroxyl groups was observed at approximately 3350 cm. -1 The ester formation was observed at the carbonyl peak from about 1680 to about 1710 cm -1 (FIG. 2A). NMR showed the presence of esterified CA and HPED with approximately 90% functionalization (FIG. 2B).

[0045] Following successful synthesis of HCA, SMP foams were prepared using 10, 20, and 30% HCA (mol % of hydroxyl groups based off of 3 hydroxyl groups per mole of HCA). Foams were made with 10, 20 and 30% (mol % of hydroxyl groups, based off of one hydroxyl group (i.e., carboxylic acid) per mole of CA) CA. The 10% CA foam rose, but with 20 and 30% CA, a stable network could not be formed and the foam collapsed. This result was attributed to the termination of the polyurethane network due to the reaction between HDI and the monofunctional CA. Although the direct incorporation of CA is faster and simpler, its single functionality is a limitation to its effective use in this SMP system. This result also validates the additional HCA synthesis step, as it allows for more effective incorporation of higher concentrations of CA. In some embodiments, the relatively straightforward synthesis method of HCA can be utilized with a series of phenolic acids or other carboxylic acid-containing functional molecules (e.g., drugs, bioactive factors) to impart new properties to the SMP system.

[0046] ATR-FTIR spectra were obtained for CA and HCA containing foams, FIG. 2C. The peaks at ∼1615 cm in all CA and HCA foams were observed, which can be attributed to the C═C groups in the ring structure. -1 The relative absorbance of this peak increases with increasing HCA concentration (approximately 1680 cm -1の In the 10% CA spectrum, the peak at 1615 cm -1 The relative absorbance at the peaks is between that of 20-30% HCA, indicating a higher incorporation efficiency with unmodified CA. These spectra confirm that CA and HCA were successfully incorporated into the SMP network. Both routes are viable for the effective synthesis of phenolic acid-containing foams.

[0047] Structural characteristics: To verify the qualitative observation of good expansion of foams with CA and HCA, foam density and pore size were evaluated (Figure 3). In general, CA and HCA containing foams retained the ultra-low density characteristic of this SMP system, Figure 3A. The 10% HCA foams had higher density and tended to decrease in density with increasing HCA concentration. These results are consistent with the pore size measurements, where the pore size increases with increasing HCA concentration (Figure 3B). Qualitatively, the 10% and 20% HCA foams had less rounded pores, which further correlates with the density measurements (Figure 3C). Despite these slight differences, overall, the pore size of the CA and HCA foams was comparable to that of the control foam (Figures 3B-C). Improved isotropy (ratio between pore size in the axial and transverse expansion directions) was observed in the CA and HCA foams, indicating that the new monomer aided in the contraction of the foam rise process to provide more uniform pores, Figure 3B. Overall, these results indicate that CA and HCA can be incorporated into SMP foams with minimal protocol modifications to provide structurally similar materials and further suggest that this method may be effectively used with other functional monomers bearing similar reactive groups.

[0048] Thermal and shape memory properties: For effective field use, SMP foam-based hemostats need to retain their compressed shape under dry storage conditions, then rapidly at elevated temperatures reached in desert climates (e.g., up to about 45°C in Iraq), and then rapidly expand when exposed to body temperature blood water. As an initial indication of these capabilities, SMP foam glass transition temperatures (Tg) were measured under dry and wet conditions (Figure 8A). The 10% CA foam dry Tg was similar to that of the control, and both were below the 45°C required for field use. CA increases the hydrophobicity of the foam, which generally raises the Tg. However, the incorporation of monofunctional groups was expected to reduce the overall crosslink density, which had the opposite effect on the lower Tg. To increase the dry Tg of the CA foam to a useful level, the overall crosslink density could be increased by utilizing more HPED, or the hydrophobicity could be further increased by the introduction of a more hydrophobic monomer such as trimethylhexamethylene diisocyanate. The incorporation of HCA allowed for the retention of crosslink density while increasing hydrophobicity, resulting in an increase in dry Tg with increasing HCA content. All HCA-containing foams had a dry Tg above 45°C, indicating potential for battlefield use without premature expansion. Furthermore, the incorporation of HCA provides a new tool for tailoring the thermal properties of SMP foams. All CA and HCA foams had a wet Tg below 30°C. This allows for expansion following exposure to warm blood, even when the patient is in hypovolemic shock due to blood loss and / or exposed to hypothermia.

[0049] To further explore the functional capabilities of CA and HCA SMP foams, their volume expansion profiles were characterized in water at 37 °C (Figure 8B-C). CA foams showed more rapid expansion compared to the control. This is attributed to their theoretically reduced crosslink density due to the incorporation of monofunctional monomers. Increasing HCA content resulted in slower volume expansion, correlating with the increase in Tg measurements, and is attributed to the increase in foam hydrophobicity and skeletal rigidity with the introduction of ring structures in CA. The increase in the expansion rate of 10 and 20% HCA foams compared to the control is likely due to network incompatibility. Although a high average functionalization of HCA was achieved, the synthesized monomers are a mix of HPED and various numbers of tethered CA molecules. The resulting network heterogeneity may result in more rapid volume expansion despite the increase in hydrophobicity. This effect was more significant than the increase in HCA content in 30% HCA foams, where the increase in hydrophobicity likely had a greater effect on the deceleration of expansion than the network incompatibility. To address severe bleeding, SMP-based hemostats should achieve full expansion as soon as possible. Combined with their high dry Tg, the complete expansion of 10 and 20% HCA in less than 2 minutes is very promising for their potential use as hemostatic agents on the battlefield. The variation in volumetric expansion rate with increasing HCA content further validates the ability to use HCA incorporation as a tool to tailor SMP foam properties.

[0050] Cytocompatibility: As an early indicator of CA and HCA-containing SMP cytocompatibility, human dermal fibroblasts (HDFs) were indirectly exposed to SMP films and their morphology, initial attachment, and proliferation were qualitatively assessed, FIG. 9. Initial attachment between wells containing SMP films and the positive control, TCPS, was similar. HDFs attached uniformly across the well surface and spread well. The negative control, BSA-coated TCP, had rounded cells with less attachment. At 72 hours, HDFs had elongated and proliferated with some confluent areas in all SMP film-containing wells and TCPS controls. The BSA negative control wells still showed low binding numbers and low spreading after 72 hours. These studies indicate that the modifications did not adversely affect the cytocompatibility of the base SMP formulation, which is an advantage for their use as biomaterial scaffolds.

[0051] Antibacterial properties: To measure the antibacterial efficacy of CA and HCA after incorporation into SMP, colony forming unit (CFU) densities of E. coli (gram negative) and Staph. epidermidis (gram positive) were measured after exposure to SMP films. Compared to unmodified control SMP films, there was a large reduction in E. coli CFU after exposure to CA and HCA-containing films. The CFU densities were equal to or less than that of the drug-based (Penicillin Streptomycin, P / S) control (Figure 10A). The reduction in CFU compared to unmodified control SMP films was significant for 10% CA and 30% HCA films. The FTIR spectrum at 1615 cm -1The improved performance of CA at low concentrations is likely due to more effective incorporation, as seen by the increased C=C peak at 30% HCA (Figure 2C). The increased efficacy of 30% HCA illustrates how the antimicrobial properties increase with increasing CA concentration in the film. Similar results were observed for Staph.epi., which shows that the CFU density of 10% CA, 20% HCA, and 30% HCA films was significantly reduced to levels below the drug-based (P / S) control (Figure 10B). There was a trend for the CFU density to decrease with increasing HCA concentration. Some phenolic acids showed increased antimicrobial efficacy after esterification. This result has not been observed with CA. An embodiment encompasses the incorporation of phenolic acids that benefit from esterification. Overall, these results demonstrate that the antimicrobial properties of CA are retained after incorporation into SMPs, with or without prior modification. Efficacy comparable to P / S is very promising for the potential use of CA or HCA-containing SMPs against drug-resistant organisms.

[0052] To characterize the retention of antimicrobial properties, CA and HCA-containing films were immersed in saline for up to 30 days at 37°C, and E. coli and Staph. epi. CFU densities were measured after exposure to the immersed films. All 10% CA films retained significantly lower CFU densities compared to the unmodified control SMP for both bacterial types, Figure 11. The formation of urethane bonds between CA and HDI in the SMP network provides a biostable bond that is less susceptible to hydrolysis. In one embodiment, the majority of the CA was retained in the film throughout the immersion period, providing sustained antimicrobial efficacy. The 10% HCA films had comparable CFU densities up to 20 days of immersion, with increases for the 30-day samples approaching the control film values ​​(dashed red line) for both bacterial types. Because HCA is incorporated into the SMP network via ester bonds, hydrolysis likely caused a decrease in HCA concentration over time. A similar trend was observed for the 20% HCA samples, with an increase in CFU density after exposure to 20 and 30 days of immersion films. The increase in E. coli density was lower for 20% HCA at 30 days than that for 10% HCA. This indicates a higher retained HCA concentration along with an increased initial concentration. This trend was further confirmed for the 30% HCA films. Although an increase in CFU density was observed between 0 and 10 days of immersion samples, indicating an initial loss of HCA, the CFU density did not change dramatically beyond 10 days of immersion and did not approach that of the control film. Thus, even though it is a hydrolytically unstable bond, HCA provides sustained antimicrobial effects in SMPs when incorporated at higher concentrations. These results combined with the favorable thermal and shape memory properties of HCA-containing SMPs indicate their potential for use as antimicrobial hemostats.

[0053] Experimental Section material: DC 198, DC 5943, BL-22, T-131, and Enovate® were purchased from Evonik® (Essen, Germany) and used as received. All other chemicals were purchased from Sigma-Aldrich Inc. (St. Louis, MO) and used as received.

[0054] Phenolic acid monomer synthesis and characterization: N,N,N',N'-Tetrakis(2-hydroxypropyl)ethylenediamine (HPED)-cinnamic acid (HCA) was synthesized using an esterification procedure. Cinnamic acid (CA, 1 molar equivalent) was added to a round bottom flask and dissolved in chloroform. Then, 4-(dimethylamino)pyridine (DMAP, 0.1 molar equivalent) was added to the flask and allowed to dissolve. HPED (1 molar equivalent) was weighed into a separate vial, dissolved in chloroform, and added dropwise to the reaction flask. The flask was placed on ice and cooled for approximately 5 minutes. N,N'-Dicyclohexylcarbodiimide (DCC, 1.1 molar equivalent) was weighed into a separate vial, dissolved in chloroform, and added dropwise to the cooled reaction vessel. The reaction was stirred under nitrogen on ice for 5 minutes and then allowed to proceed at room temperature for 3 hours. After the reaction was complete, the flask was placed at 0°C for 30 minutes to precipitate the dicyclohexylurea, which was then removed by vacuum filtration. The reaction solution was washed twice with 1 molar equivalent of 0.1M HCl. It was then washed with saturated aqueous sodium bicarbonate. The organic phase was dried over magnesium sulfate and filtered. Rotary evaporation was then used to remove the chloroform, followed by drying under vacuum overnight. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were utilized to confirm the synthesis of HCA. 1H NMR (CdCl 3 ): 1.05 ppm (m, HOCHCH 3 , 9H), 1.2 ppm (m, -OCHCH 3 , 3H), 2.2-2.6 ppm (m, -CH 2 -, 12H), 3.6 ppm (m, HOCHCH 3 , 3H), 5.1 ppm (m, -OCHCH 3, 1H), 6.4 ppm (d, -CCH=, 1H), 7.3-7.6 ppm (m, -HC=CHC 6 H 5 , 6H).

[0055] Shape Memory Polymer (SMP) Foam and Film Compounds: An isocyanate (NCO) prepolymer was synthesized with appropriate molar ratios of HPED, triethanolamine (TEA), HCA or CA, and hexamethylene diisocyanate (HDI) with 42 mol% hydroxyl (OH) content. The remaining molar equivalents of HPED, TEA, and HCA or CA were used to prepare an OH mixture. To induce foam expansion, blowing agents (catalyst, surfactant, deionized water, and Enovate) were mixed with the NCO-prepolymer and OH mixture using a speed mixer (FlackTek, Inc., Landrum, SC).

[0056] The foams were then cured at 50°C for 5-10 min, cooled to room temperature, and washed in isopropyl alcohol (IPA) or reverse osmosis (RO) water for 15 min cycles. The purified foams were lyophilized until dry.

[0057] The SMP films were synthesized using the same monomer composition as the foams, but without the use of surfactant, deionized water, or Enovate®. Figure 12 shows the SMP compositions synthesized and characterized in these studies.

[0058] SMP Foam Density: SMP foam density (n=3) was determined on foam blocks cut from the top, middle, and bottom of the foam according to ASTM standard D-3574. Foam block mass was measured using a gravimeter, and length, width, and height values ​​were measured three times per sample using digital calipers. Density was calculated as mass divided by volume.

[0059] SMP foam pore size and structure: To assess pore size, thin slices (approximately 1 mm, n=3) were cut from each slice composition in the axial (parallel to foam rise) and transverse (perpendicular to foam rise) foaming directions. Samples were mounted on a sample holder with carbon black tape and sputter coated for 60 seconds at 20 mA (Cressington Sputter Coater®, Ted Pella, Inc. Redding, CA). Samples were imaged using a Jeol NeoScope JCM-5000 Scanning Electron Microscope (SEM)® (Nikon Instruments, Inc., Melviille, NY). A line was drawn through the center of each image. Pore size was measured for five randomly selected pores on the line using ImageJ software.

[0060] Thermal transition of SMP foam: Glass transition temperatures (Tg) were measured under wet and dry conditions (n=5). To measure the dry Tg, foam samples (3-8 mg) were cut and stored with a desiccant prior to testing. A Q-200 DSC® (TA Instruments, Inc., New Castle, Del.) was used to obtain a thermogram of each composition using the following program: (1) Keep the temperature at 10°C for 1 min. -1 The temperature was lowered to -40°C and kept isothermal for 2 minutes. (2)10℃・min -1 The temperature was increased to 120°C and held isothermally for 2 minutes. (3)10℃・min- 1 The temperature was reduced to -40°C and held isothermally for 2 minutes. (4)10℃・min- 1 The temperature was raised to 120°C by means of a kettle. The dry Tg was recorded from the second heating cycle using the inflection point of the thermal transition curve. The inflection point was determined using TA Instruments® software (TA Instruments, Inc., New Castle, Del.).

[0061] For wet Tg measurements, foam samples (3–8 mg) were immersed in 50 °C reverse osmosis (RO) water for 5 min to allow complete plasticization. The samples were removed from the water, pressed dry with laboratory wipes, weighed, and placed in an aluminum pan with a vented aluminum lid. The samples were then incubated at 10 °C min. -1 A Q-200 DSC was used to cool the samples to -40 °C at 10 °C min and hold them isothermal for 2 min. -1 The mixture was heated at 80° C. for 24 hours at 40° C. The TAInstruments software was used to generate thermograms and determine the wet Tg using the average inflection points of the thermal transitions.

[0062] Various examples at the end of this application deal with Tg, e.g., dry Tg and wet Tg, which terms should be interpreted in accordance with the immediately preceding two paragraphs (i.e., as used herein, dry and wet Tg should be determined using the methods described in the immediately preceding two paragraphs).

[0063] Volume Recovery: Cylindrical foam samples (n=3, diameter=4 mm, length=10 mm) were prepared and a stabilizing 203.20 μm diameter nickel-titanium wire (NDC, Fremont, CA) was threaded through the center of each sample along its length. The foam samples were radially crimped to their smallest possible diameter using an ST150-42 stent crimper (Machine Solutions, Flagstaff, AZ). The samples were programmed into the crimped form by heating to 100° C., holding isothermally for 15 minutes, and cooling to room temperature. The initial foam diameter was measured for each sample using ImageJ® software (NIH, Bethesda, MD). The crimped foams were placed in a 37° C. water bath and images were taken every 30 seconds up to 7 minutes. Foam diameters were measured at each time point at five equally spaced locations along the length of the foam using ImageJ®. Percent volume recovery was calculated using Equation 1.

number

[0064] Cell interactions: Human dermal fibroblasts (HDFs, Invitrogen, Inc., San Diego, CA) were used to assess cell attachment and spreading. They were cultured at 37°C / 5% CO in Medium 105 (Invitrogen) supplemented with low serum growth supplement (Invitrogen) and 1% penicillin-streptomycin (P / S, Gibco). 2 The cells were cultured in vitro at passage 3.

[0065] SMP films were cut into 6 mm diameter cylinders and sterilized by overnight incubation in 70% ethanol followed by washing with sterile phosphate-buffered saline (PBS, 3 washes). As a negative cell attachment control, wells in a 96-well tissue culture polystyrene (TCPS) plate were blocked with sterile 5% bovine serum albumin (BSA) in PBS. Unmodified TCPS wells served as positive cell attachment controls. HDFs were seeded at 5,000 cells cm into wells containing SMP films. -1 The seeded cells were incubated at 37°C / 5% CO 2 The specimens were cultured at 4°C for up to 72 hours. Medium was changed at 2 and 36 hours. Brightfield images were obtained after 2 and 72 hours to qualitatively assess cell attachment and proliferation. Representative images were obtained using a Nikon Eclipse TE2000-S® with 4 fields per specimen and 3 specimens per sample type.

[0066] Antibacterial properties: To obtain initial measurements of antimicrobial properties, SMP films were cut into 6 mm diameter cylinders. To characterize antimicrobial properties over time, samples were incubated in PBS at 37°C for 0, 10, 20, or 30 days. The films were then sterilized as described in the cellular interactions section. Escherichia coli (E. coli) and Staphylococcus epidermidis (Staph.epi.) were grown overnight at 37°C in 5 ml of LB medium lysogeny broth (LB). 500 μL was then removed from each overnight culture and grown in 10 mL of fresh LB to an optical density (OD) of 0.6 (i.e., until the bacteria entered logarithmic growth phase). OD was measured using a Tecan plate reader. Samples were placed in a sterile 96-well plate and 100 μL of bacterial solution was pipetted onto the surface of each sample. To provide a drug-based antimicrobial control, control SMP films were immersed in P / S overnight. Samples were incubated with bacteria at 37°C for 1 hour and then vortexed to remove adherent bacteria. The bacterial solution was diluted 106-fold in fresh LB and plated on LB agar plates overnight at 37°C. Images of each specimen plating area were obtained. Colony forming unit (CFU) density was measured by counting the number of colonies and dividing by the plating area.

[0067] statistics: Data are reported as mean ± standard deviation. Student's t-test was used to determine statistical significance, accepted at p<0.05.

[0068] The embodiments demonstrate the successful incorporation of CA, a honey-based phenolic acid, into SMP foams via two routes. The resulting foams retain the desirable porous structure of the control SMP while providing tunable thermal transition and shape recovery properties that are ideal for their use in hemostatic agents for bleeding control. That is, the CA-based SMPs are designed with a high dry Tg to enable their storage under extreme battlefield conditions, and a low wet Tg to enable their rapid shape recovery when exposed to blood at body temperature. Furthermore, the CA-based SMPs are highly cytocompatible while effectively reducing bacterial growth to levels comparable to penicillin / streptomycin-based treatments, even after 30 days of storage in saline at body temperature. Overall, the embodiments provide a hemostatic device that is easy to use, biocompatible, and antibacterial. An additional benefit of phenolic acids is their antioxidant properties. Phenolic acids contain hydrogen donor groups that scavenge free radicals and reduce oxidation. This is ideal for SMP foams that are susceptible to oxidative degradation. In other words, the pendant phenolic acids can be used in biodurable implants, for example, occlusive foams (e.g., aneurysm occlusive foams) that are biodurable to help prevent recanalization, a problem experienced with hydrogel and coil-based aneurysm treatments.

[0069] Example embodiments are described below.

[0070] Example 1 includes a shape memory polymer composition having an incorporated antimicrobial agent.

[0071]

[89] Example 2 includes the device of example 1, wherein the antimicrobial agent is chemically incorporated into the polymer backbone via at least one of (a) and (b): (a) a direct reaction of a hydroxyl, carboxylic acid, or amine on the antimicrobial agent with the backbone; and (b) reacting a polyurethane monomer or macromer with said antimicrobial agent prior to polymerization to produce a pendant antimicrobial species.

[0072] Example 3 includes the device of Example 1, where the antimicrobial agent is physically incorporated into the polymer.

[0073] Example 4 includes the device of Example 1, where the antimicrobial agent is utilized to surface treat the polymer.

[0074] For example, rather than modifying the bulk of the polymer, one embodiment functionalizes the surface with an antimicrobial agent, which maintains the bulk physical / mechanical properties of the polymer but allows for the incorporation of the antimicrobial agent at the surface of the foam.

[0075] Example 5 includes the polymer composition of Example 1, where the monomer for the SMP foam is selected from the group consisting of hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), isophorone diisocyanate (IPDI), triethanolamine (TEA), diethanolamine, butanediol, butynediol, N,N,N',N' tetrakis(hydroxylpropylene)ethylenediamine (HPED), and the antimicrobial agent is selected from the group consisting of phenolic acids, fluorescent dyes, and silver.

[0076] An exemplary network involves the reaction between HPED and an antimicrobial agent with carboxylic acid groups to produce a triol with pendant antimicrobial groups. The antimicrobial triol is incorporated into a polyurethane network with HDI, TEA, and HPED to produce a polyurethane with pendant antimicrobial groups throughout the bulk.

[0077] Example 6 includes a method of rendering the polymer foam from Example 1 into a porous structure or foam by one or a combination of processes including, but not limited to, freeze drying, phase separation, emulsion foaming / templating, or physical blowing.

[0078] Example 7 includes polymers of Examples 1 and 6 that can be used in the manufacture of medical devices and as medical materials, including, but not limited to, subdermal implants, aneurysm filling devices, peripheral filling devices, wound dressings, bone grafts, and the like.

[0079] Example 1a involves a system comprising a thermoset polyurethane shape memory polymer (SMP) foam that includes at least one antimicrobial agent.

[0080] Example 2a encompasses the system of claim 1a, in which the SMP foam is chemically bonded to at least one antimicrobial agent.

[0081] Example 3a encompasses the system of claim 2a, wherein the at least one antimicrobial agent comprises a phenolic acid.

[0082] Example 4a includes the system of claim 3a, where the at least one phenolic acid includes at least one of cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, and caffeic acid.

[0083] Example 5a encompasses the system of claim 4a, where at least one phenolic acid is a pendant group that is chemically bonded to the polyurethane polymer chains of the SMP foam.

[0084] A pendant group (sometimes spelled pendent) or side group, as used herein, is a molecule or group of molecules attached to the backbone of a longer chain molecule. Usually, this "long chain molecule" will be a polymer. Pendant groups differ from pendant chains because they are not oligomers or polymers. For example, phenyl groups are pendant groups on a polystyrene chain.

[0085] Another version of Example 5a includes the system of claim 4a, where the at least one phenolic acid is chemically bonded pendant to the polyurethane polymer chain of the SMP foam (one or more molecules that may or may not be in a chain).

[0086] Example 6a encompasses the system of claim 5a, where the pendant groups are chemically bonded to the polyurethane polymer chain via an ester.

[0087] For example, FIG. 2(B) shows an example of a pendant group (CA) chemically attached to the polyurethane chain via an ester bond.

[0088] Example 7a encompasses the system of claim 6a, where the SMP foam has a dry glass transition (Tg) greater than 40°C and a wet Tg less than 30°C.

[0089] Other embodiments may have a dry Tg of greater than 35, 37, 39, 42, 45, 47 or 50°C and a wet Tg of less than 34, 32, 28, or 26°C.

[0090] Example 8a includes the system of claim 2a, where the at least one antimicrobial agent includes a carboxylic acid group.

[0091] Another version of Example 8a includes the system of claim 2a, where the at least one antimicrobial agent includes an amine group.

[0092] Another version of example 8a includes the system of claim 2a, where the at least one antimicrobial agent is selected from the group consisting of: (a) a first antimicrobial agent that includes an amine group, and (b) a second antimicrobial agent that includes a carboxylic acid group; Includes

[0093] Example 9a encompasses the system of claim 1a, where the SMP foam is physically crosslinked around the at least one antimicrobial agent.

[0094] For example, the agent may not be chemically bound to the polyurethane chains, but may crosslink the chains to give the foam shape-memory properties and to physically retain the agent that is not chemically bound to the chains.As the foam regains its programmed primary shape (from its compressed secondary shape), the agent may be released.

[0095] The embodiment also provides that the SMP is both (a) physically crosslinked around some of the antimicrobial agent and (b) contains chemically bonded pendant antimicrobial groups.

[0096] Example 10a is a second SMP foam of a thermoset polyurethane including phenolic acid groups pendant thereto chemically bonded to the polyurethane polymer chains of the second SMP foam; a third SMP foam of a thermoset polyurethane including phenolic acid groups pendant thereto chemically bonded to the polyurethane polymer chains of the third SMP foam; The present invention also encompasses a system according to claim 1a, comprising: (a) the SMP form comprises a first form; (b) the first, second, and third SMP forms are all enclosed in a sealed kit;

[0097] The embodiments are provided in many different form factors. Some embodiments include one or more pieces of SMP foam that can be applied independently of each other to the bleeding site. Other embodiments may have multiple foam pieces tied together to help facilitate their removal. For example, one embodiment includes a first and a second SMP foam, each arranged along a single backbone. The backbone may be metal, fabric, string, suture, or polymer filament. The sponge may have fabric, Dacron, or PTFE pledgets on either side of the SMP foam to help secure the foam to the backbone and help control any slippage of the foam along the backbone. The pledgets may be secured by simply tying a knot to the backbone adjacent to the pledget. This may also help the practitioner (e.g., a surgeon in an operating room) to quickly remove a series of foams that have been rapidly placed in a wound in a traumatic / emergency situation (e.g., a medic treating a soldier in the field, or an emergency medical technician treating a gunshot wound in the field). The foam may be combined with gauze. The gauze may be a strip of gauze with foam bonded to it. However, the gauze may be a gauze pouch containing multiple foams, with the entire pouch being placed into the wound (and then easily retrieved later considering all foams are kept in a single pouch). The foam pieces themselves may be organized as pellets (regular or irregular shaped, one or more, cylindrical, conical, and / or planar sheets). Pellets may be placed into the wound, which may or may not be bonded to each other. Other embodiments may bond one or more foams to a backbone such as a Nitinol coil, which may then be deployed into an aneurysm, a peripheral blood vessel desired to be occluded, a void in a septal wall, etc. Other embodiments include simply placing free foam from a catheter into the site of internal bleeding. Other embodiments include a single large foam that can be placed independently at any bleeding site or any site containing liquid that the user wishes to control (e.g., remove).

[0098] Example 11a is the following: reacting the first polyol portion with an antimicrobial agent to form a first reaction product; reacting a first portion of the first reaction product with a second polyol portion and an isocyanate to form a second reaction product; reacting the second reaction product with a second portion of the first reaction product and a third polyol portion to form a third reaction product; mixing the third reaction product with a blowing agent to form a shape memory polymer (SMP) foam; A method comprising: The method includes the steps of: (a) providing a thermoset polyurethane SMP foam;

[0099] For example, see Figure 1 (Route B). Figure 1 (Route B) shows that reacting the first polyol portion (HPED from line 1 of route B) with an antimicrobial agent (CA) to form a first reaction product (HCA from line B); reacting a first portion of said first reaction product (HCA from line 2, route B) with a second polyol portion (HPED and / or TEA from line 2, route B) and an isocyanate (HDI from line 2, route B) to form a second reaction product (prepolymer from line 2, route B); reacting the second reaction product (prepolymer) with a second portion of the first reaction product (HCA from line 3 of route B) and a third polyol portion (HPED and / or TEA from line 3 of route B) to form a third reaction product; mixing the third reaction product with a blowing agent to form a shape memory polymer (SMP) foam; wherein the SMP is a thermoset polyurethane SMP foam.

[0100] Another version of Example 11a is reacting a first polyol portion (HPED or some other polyol) with an antimicrobial agent (CA or some other agent) to form an antimicrobial monomer as the first reaction product; reacting a first portion of the first reaction product with a second polyol portion (HPED and / or TEA and / or some other polyol) and an isocyanate (HDI or some other isocyanate) to form a second reaction product (prepolymer); reacting the second reaction product (prepolymer) with a second portion of the first reaction product and a third polyol portion (HPED and / or TEA or some other polyol); and in response thereto, forming a shape memory polymer (SMP) foam; wherein the SMP is a thermoset polyurethane SMP foam.

[0101] In one embodiment, the "side A" portion of the reaction includes hydroxyl components such as HPED, TEA, HCA, CA, and water as well as combinations thereof. The "side B" portion of the reaction includes the prepolymer described above (containing unreacted isocyanate). Sides A and B are mixed and the foam blowing reaction occurs.

[0102] By referring above to a first polyol portion and a second polyol portion, these portions may be two portions of a single polyol or may include two (or more) polyols that are different from one another.

[0103] Example 12a includes the method of claim 11a, where the at least one antimicrobial agent includes a phenolic acid.

[0104] Example 13a includes the method of claim 12a, wherein the phenolic acid includes at least one of cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, and caffeic acid.

[0105] Example 14a, wherein reacting the first polyol moiety with an antimicrobial agent to form a first reaction product includes esterifying the antimicrobial agent.

[0106] For example, line 1 of route B in FIG. 1 depicts one embodiment of an esterification.

[0107] Example 15a includes the method of claim 11a, where the first reaction product comprises a triol.

[0108] Example 16a includes the method of claim 16a, wherein at least one of the first, second, and third polyol portions includes at least one of triethanolamine (TEA), diethanolamine, butanediol, butynediol, and N,N,N',N' tetrakis(hydroxylpropylene)ethylenediamine (HPED); The isocyanate includes at least one of hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), and isophorone diisocyanate (IPDI).

[0109] Example 17a includes the method of claim 16a, where the antimicrobial agent includes at least one of a phenolic acid, a fluorescent dye, and silver.

[0110] Example 18a includes the method of claim 17a, where the antimicrobial agent includes a carboxylic acid group.

[0111] Example 19a includes the method of claim 18a, where the antimicrobial agent includes at least one phenolic acid that is a pendant group chemically bonded to the polyurethane polymer chains of the SMP foam.

[0112] Example 20a includes the method of claim 19a, where the pendant groups are chemically bonded to the polyurethane polymer chain via an ester.

[0113] Example 21a encompasses the method of claim 11a, where the second reaction product is a prepolymer formed prior to polymerization of the SMP foam.

[0114] As used herein, the term "prepolymer" refers to a monomer or system of monomers that has been reacted to an intermediate molecular weight state. This material can be further polymerized to a fully cured, high molecular weight state through reactive groups. Thus, a mixture of reactive polymer and unreacted monomer can also be referred to as a prepolymer. The terms "prepolymer" and "polymer precursor" are interchangeable.

[0115] In one embodiment, the prepolymer includes unreacted isocyanate.

[0116] Example 22 is the following: reacting a first polyol portion with a first antimicrobial portion and an isocyanate to form a first reaction product; reacting the first reaction product with a second polyol portion and a second antimicrobial portion to form a second reaction product; mixing the second reaction product with a blowing agent to form a shape memory polymer (SMP) foam; A method comprising: the SMP being a thermoset polyurethane SMP foam; The first reaction product is a prepolymer formed prior to polymerization of the SMP foam.

[0117] For example, route A in Figure 1 is reacting a first polyol portion (e.g., HPED and / or TEA, line 1, route A) with a first antimicrobial portion (e.g., CA, line 1, route A) and an isocyanate (e.g., HDI, line 1, route A) to form a first reaction product (e.g., prepolymer, line 1, route A); reacting the first reaction product with a second polyol portion (HPED and / or TEA, line 2 of route A) and a second antimicrobial portion (e.g. CA, line 2 of route A) to form a second reaction product; mixing the second reaction product with a blowing agent to form a shape memory polymer (SMP) foam; A method comprising: the SMP being a thermoset polyurethane SMP foam; The first reaction product is a prepolymer formed prior to polymerization of the SMP foam.

[0118] Another version of Example 22 is, for example, Route A in FIG. reacting a first polyol portion (HPED and / or TEA or some other polyol) with a first antimicrobial portion (e.g., CA or some other antimicrobial) and an isocyanate (e.g., HDI or some other isocyanate) to form a first reaction product (e.g., a prepolymer); reacting the first reaction product with a second polyol portion (HPED and / or TEA or some other polyol) and a second antimicrobial portion (e.g., CA or some other antimicrobial) to form a second reaction product; in response thereto, forming a shape memory polymer (SMP) foam; A method comprising: the SMP being a thermoset polyurethane SMP foam; The first reaction product is a prepolymer formed prior to polymerization of the SMP foam.

[0119] Example 23 includes the method of claim 22a, wherein the antimicrobial agent includes at least one phenolic acid that forms a pendant group chemically bonded to the polyurethane polymer chains of the SMP foam.

[0120] Thus, despite many clinically available hemostatic agents, uncontrolled bleeding remains the leading cause of trauma-related mortality. Shape memory polymer (SMP) foams have several desirable properties for use as hemostatic agents, including shape recovery to enable delivery to the bleeding site, biocompatibility, and rapid blood clotting. To further elaborate on this material system, the current study aims to incorporate phenolic acid, a honey-based antimicrobial agent, into SMP foams. Applicants have shown that cinnamic acid (CA) can be utilized as a monomer in SMP synthesis to provide foams with comparable pore structure and retained cytocompatibility. The addition of CA allowed for tuning the thermal and shape memory properties within a clinically relevant range. Furthermore, the modified foams exhibited initial and sustained antibacterial activity against Gram-positive and Gram-negative bacteria. These multifunctional scaffolds demonstrate the potential for use as hemostatic agents to improve current bleeding treatments and provide new tools in tailoring the biological and material properties of SMP foams.

[0121] The foregoing description of embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Those skilled in the relevant art will recognize that numerous modifications and variations are possible in light of the above teachings. Those skilled in the art will recognize various equivalent combinations and substitutions for the various components illustrated in the figures. It is therefore intended that the scope of the present invention be limited not by this detailed description, but rather by the appended claims.

Claims

1. A system comprising a polyurethane shape memory polymer (SMP) foam synthesized by thermosetting and containing at least one phenolic acid, wherein the SMP foam is chemically bonded to the at least one phenolic acid, and the phenolic acid is cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid, and a system comprising at least one of combinations thereof.

2. The system according to claim 1, wherein the phenolic acid is a pendant group chemically bonded to the polyurethane polymer chain of the SMP foam.

3. The system according to claim 2, wherein the pendant group is chemically bonded to the polyurethane polymer chain via an ester.

4. The system according to any one of claims 1 to 3, wherein the SMP foam has a glass transition temperature (Tg) in the dry state exceeding 40 °C and a glass transition temperature (Tg) in the wet state below 30 °C.

5. Comprising the polyurethane shape memory polymer (SMP) foam synthesized by thermosetting according to claim 1 as a first SMP foam, and further the following A second SMP foam of polyurethane synthesized by thermosetting, wherein the second SMP foam is chemically bonded to at least one phenolic acid, and the at least one phenolic acid is cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid, and comprising at least one of combinations thereof, and A third SMP foam of polyurethane synthesized by thermosetting, wherein the third SMP foam is chemically bonded to at least one phenolic acid, and the at least one phenolic acid is cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid, and comprising at least one of combinations thereof, Comprising a sealed kit, wherein At least one of the phenolic acids of the first, second, and third SMP forms is different from each other. The system according to any one of claims 1 to 4. **Claim 6** The following: Reacting a first polyol moiety with a phenolic acid to form a first reaction product; Reacting a first portion of the first reaction product with a second polyol moiety and an isocyanate to form a second reaction product; Reacting the second reaction product with a second portion of the first reaction product and a third polyol moiety to form a third reaction product; Mixing the third reaction product with a blowing agent to form an SMP form; A method comprising: The SMP form is a polyurethane SMP form synthesized by thermosetting, and the phenolic acid includes at least one of cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid, and combinations thereof. **Claim 7** The step of reacting a first polyol moiety with a phenolic acid to form a first reaction product includes esterification of the phenolic acid, and / or The first reaction product includes a triol, and / or At least one of the first, second, and third polyol moieties further includes at least one of triethanolamine (TEA), diethanolamine, butanediol, butynediol, N,N,N',N'-tetrakis(hydroxypropyl)ethylenediamine (HPED), and combinations thereof. The isocyanate includes at least one of hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), isophorone diisocyanate (IPDI), and combinations thereof, and / or The phenolic acid includes at least one phenolic acid that is a pendant group chemically bonded to the polyurethane polymer chain of the SMP form, and / or The pendant group is chemically bonded to the polyurethane polymer chain via an ester, and / or The second reaction product is a prepolymer formed prior to polymerization of the SMP form, the method according to claim 6. **Claim 8** The pendant group is chemically bonded to the polyurethane polymer chain via an ester. The method according to claim 7.

9. The following: Reacting a first polyol moiety with a first phenolic acid moiety and an isocyanate to form a first reaction product; Reacting the first reaction product with a second polyol moiety and a second phenolic acid moiety to form a second reaction product; Mixing the second reaction product with a blowing agent to form an SMP form; A method comprising: The SMP form is a polyurethane SMP form synthesized by thermosetting, The first reaction product is a prepolymer formed prior to polymerization of the SMP form, and the phenolic acid of the phenolic acid moiety includes at least one of cinnamic acid, benzoic acid, gentisic acid, 4-hydroxybenzoic acid, p-coumaric acid, vanillic acid, syringic acid, protocatechuic acid, gallic acid, ferulic acid, sinapic acid, caffeic acid, and combinations thereof.

10. The method according to claim 9, wherein the phenolic acid of the phenolic acid moiety includes at least one phenolic acid that forms a pendant group chemically bonded to the polyurethane polymer chain of the SMP form.

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