The scientists at the NJCBM are a highly interdisciplinary group consisting of polymer chemists, material scientists, cell and stem cell biologists, biomedical engineers and industrial scientists with expertise in product development. In conducting their research, the faculty and students at the NJCBM combine excellence in basic science with highly focused application-driven research.
Poly(amino acid)s are conventional polymers made of natural amino acids that are usually intractable materials with limited practical applications. However, by modifying the way the amino acids are incorporated into the polymer backbone, Joachim Kohn and his students developed an entirely new class of polymers that combine the non-toxicity of natural amino acids with the favorable materials properties of common engineering plastics. In this way, tyrosine-derived poly(carbonate-amide)s, polyarylates, and most recently new poly(carbonate- ester)s were identified and further optimized for use in a wide range of medical implants. Not only are these degradable polymers strong enough to do the job, but also they can be rendered visible under x-ray during implantation.
Radio-opaque Polymer Biomaterials
Synthetic degradable polymers are used as medical implants in a wide range of applications, such as orthopedic bone fixation devices, drug delivery systems, cardiovascular implants, and scaffolds for the regeneration/engineering of tissue. Such polymers, when used as implants are non-traceable without invasive procedures. A radio-opaque polymer offers the unique advantage of being traceable via routine X-ray imaging. The fate of such an implant through various stages of its use can be followed without requiring invasive surgery. Such a radio-opaque polymer was developed at the NJCBM and has since been licensed by REVA Medical.
Polymers are needed that have high modulus (> 10 GPa) and high strength (> 200 MPa) for applications such as bone repair, and ligament and meniscus replacement. NJCBM has led development of polymer compositions to fulfill this need. One composition, a polyarylate, has been successfully tested for ligament and meniscus application. Improving this composition, by controlling the degradability is being achieved by expanding the current library of polyarylates to include other polymer chemistries, and by exploring a new library of polyesters and aromatic-aliphatic poly(tyrosol carbonate)s. These compositions are expected to achieve modulus and strength higher than that of polymers currently available for biomedical applications.
Highly elastic materials that are biocompatible and match the characteristics of the tissue at the implantation site are being developed as scaffolds for regenerating injured or diseased blood vessels and muscles. A key requirement for such application is high degree of elasticity and shape-memory, i.e., the material has to recover its shape completely after significant elongation of ~100%. Such materials are needed in devices used for vascular stents, and in mimicking muscles. Our laboratory has developed candidate polymers for these applications. These are based on the highly elastic poly(trimethylene carbonate) and tyrosine-derived polycarbonates. These polymers have a strain to break ~ 1000%, and have very good recovery after 100% strain. These materials possess an added advantage over competing materials in that they can be designed to degrade at a desired rate for a specific application.
Ultrafast degradable Polymers
Materials that can be resorbed within hours, ultrafast degradable polymers, are being sought for application such as cortical neural prosthesis. We have recently developed one such polymer based on our library of tyrosine-derived terpolymers. These polymers contain either poly(ethylene glycol) (PEG) or poly(trimethylene carbonate) (PTMC), as the non-tyrosine segments. The in vivo tissue response to both polymers used as intraparenchymal cortical devices was compared to poly(lactic-co-glycolic acid) (PLGA). The fast degrading tyrosine-derived terpolymer that is also fast resorbing, significantly reduced both the glial response in the implantation site and the neuronal exclusion zone. Such polymers allow for brain tissue recovery, thus render them suitable for neural interfacing applications.