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Poly (diol co-citrate) hydroxyapatite composite for tissue engineering and orthopaedic fixation devices

Inactive Publication Date: 2007-09-27
NORTHWESTERN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0004] The present invention provides a composition comprising a composite of a citric acid polyester having the generic formula (A-B-C)n, wherein A is a linear aliphatic dihydroxy monomer; B is citric acid, C is a linear aliphatic dihydroxy monomer, and n is an integer greater than 1; and a bioceramic used for implantable tissue devices, wherein less than 75 wt. % weight ratio of said composition comprises said bio

Problems solved by technology

Although biodegradable devices can have significant advantages over their metal counterparts, there are concerns with their use.
These include slow degradation, which can be as long as 5 years, and their inability to fully integrate with bone, which can be a problem for revision surgeries [8,9].
Also, PLLA bone screws can fracture during the fixation procedure.
Although HA is very brittle and hard to process into fixation devices of sufficient strength and fatigue resistance, it can impart osteoconductivity to polymers [10, 11].
Nevertheless, there remains a significant problem in that the PLLA continues to slowly degrade over a period of time.
% of HA into any such composite leads to a material that is too brittle for use in implantable devices.

Method used

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  • Poly (diol co-citrate) hydroxyapatite composite for tissue engineering and orthopaedic fixation devices
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  • Poly (diol co-citrate) hydroxyapatite composite for tissue engineering and orthopaedic fixation devices

Examples

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example 1

Biodegradable Elastomeric Polymers

[0068] The compositions of the invention are based on biodegradable elastomeric polymers of poly(diol) citrate molecules. Such molecules typically comprising a polyester network of citric acid copolymerized with a linear aliphatic di-OH monomer in which the number of carbon atoms ranges from 2 to 20. Polymer synthesis conditions for the preparation of these molecules vary from mild conditions, even at low temperature (less than 100° C.) and no vacuum, to tough conditions (high temperature and high vacuum) according the requirements for the materials properties. By changing the synthesis conditions (including, but not limited to, post-polymerization temperature, time, vacuum, the initial monomer molar ratio, and the di-OH monomer chain length) the mechanical properties of the polymer can be modulated over a wide range. This series of polymers exhibit a soft, tough, biodegradable, hydrophilic properties and excellent biocompatibility in vitro.

[0069]...

example 2

Materials and Methods used in Preparing and Characterizing Biodegradable Elastomeric Composites made from POC and Bioceramics

[0083] Example 1 describes the production of PDC as well as a number of other poly(diol)citrate polymers. In the present Example, there are provided teachings of how to further strengthen and stiffen is the poly(diol)citrate polymers by incorporating ceramics into the elastomeric polymer matrix.

[0084] Materials and Methods

[0085] Materials: Hydroxyapatite [Mw: 502.32, Assay>90 (as Ca3 (PO4)2), 0.5%>75 um, 1.4% between 45-75 um, 98.1%<45 um] was purchased from Fluka (St. Louis, Mo., USA). 1,8-octanediol (98%) and citric acid (99.5%) were purchased from Sigma-Aldrich (St. Louis, Mo., USA). These materials were used as received. PTFE tubes were purchased from McMaster-CARR, Chicago, USA.

[0086] Sample preparation: POC pre-polymer was synthesized according to published methods [1,5]. Briefly, 0.05 mol of 1,8-octandiol and 0.05 mol of citric acid were added to a ...

example 3

Preparation and Analysis of Bone Screws made from Composites of POC and Bioceramics

[0094] POC-HA composites having HA fraction of 40 wt. %, 50 wt. %, 60 wt. %, 65 wt. % HA were investigated for bone screws. Using compression molding method, POC-HA composites with HA from 40-65 wt. % were compressed into molds of rods and screws. The POC-HA rods obtained were strong enough to be further machined into screws. The POC-HA screws from compression molding and machining methods were shown in FIG. 1.

[0095] Characterization of the mechanical properties of composites. The mechanical property measurements (bending, compression, shear, tension and torsion) are summarized in Table 1.

TABLE 1Effect of HA fraction on mechanical properties of POC-HA compositesPOC-HAρSbEbScEcStEtSsTsComposite(Wt %)(g / cm3)(MPa)(MPa)(MPa)(MPa)(MPa)(MPa)(MPa)(N · m)HA 4040 / 601.60933.927532.01897.821.423.322.9(±0.016)(±5.7)(±80)(±13.0)(±21)(±0.5)(±1.8)(±1.6)(±1.6)HA 5050 / 501.65337.732364.02647.130.225.124.2(±0.014)(±...

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Abstract

The present invention is directed to a novel poly (diol citrates)-based bioceramic composite materials created using completely biodegradable and a bioceramic material polymers that may be used in implantable devices. More specifically, the specification describes methods and compositions for making and using bioceramic composites comprised of citric acid copolymers and a bioceramic material.

Description

[0001] The present application claims benefit of U.S. Provisional Application No. 60 / 771,241 filed Feb. 8, 2006. The entire text of the aforementioned application is incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention describes new composites for use in orthopedic devices. BACKGROUND [0003] Orthopaedic, cranio-facial, and oral-maxillofacial surgeons often use tissue fixation devices such as pins, plates, and screws that are made from poly-1-lactide (PLLA),a biodegradable polymer[1-7]. Although biodegradable devices can have significant advantages over their metal counterparts, there are concerns with their use. These include slow degradation, which can be as long as 5 years, and their inability to fully integrate with bone, which can be a problem for revision surgeries [8,9]. Also, PLLA bone screws can fracture during the fixation procedure. A strategy to improve the osteointegration capacity of PLLA has been to blend it with hydroxyapatite (HA), a b...

Claims

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Application Information

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IPC IPC(8): A61F2/44C08F20/00
CPCA61L27/12A61L27/427A61L27/46A61L27/58A61L31/06A61L31/121A61L31/127A61L31/148A61L31/026A61L27/18A61L27/425A61L31/123A61L2430/02
Inventor AMEER, GUILLERMOQIU, HONGJINYANG, JIAN
Owner NORTHWESTERN UNIV
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