Credit: Jian Yang, Penn State
When biology and materials science converge, the results can be new materials that can be used to deliver targeted drugs, repair damaged arteries or rebuild failing tissues, such as the anterior cruciate ligament, the ACL injury that can end sports careers. Penn State bioengineer Jian Yang is developing polymers designed to target all three.
Finding the right balance between mechanical strength and elasticity in artificial tissue scaffolding has been problematic, as has been the need to add in the desirable traits of biocompatibility and controlled biodegradability. In a recent article in Advanced Materials, Yang and his colleagues in Penn State’s Department of Biomedical Engineering and the Academy of Orthopedics of Guangdong Province in China report on the use of thermal click chemistry to make crosslinked citrate-based biodegradable elastomers with high mechanical strength (up to 40 MPa of tensile stress) with easy surface biofunctionalization. In comparison, the ACL has a tensile strength of 38 MPa and most biodegradable elastomers have a dry tensile strength below 10MPa. Click chemistry is a relatively new technique used primarily in drug discovery that uses a few reliable reactions to lock or “click” together small units of biomaterials in simple processes. Yang believes that this is the first reported use of click chemistry to design versatile biodegradable elastomers for tissue engineering.
Beyond superior mechanical strength, Yang’s click polymers provide user-friendly and site-specific functionalization with bioactive molecules to, for instance, promote cell growth. In addition the click polymers show a desirable type of biodegradability he calls “first slow then fast.” In many tissue engineering applications the preservation of mechanical strength of the artificial scaffolding during the early period of tissue regeneration is important. Yet many elastomeric polymers begin to degrade at a steady rate after implantation. The click polymer in this study, called POC-click-3, had low degradation for a sustained period compared to other polymers, but then rapidly degraded.
Yang and colleagues believe that their clickable biodegradable elastomer design will greatly expand the application of biodegradable polymers in areas such as drug delivery, orthopedic fixation devices, tissue engineering and other types of medical implants. The paper, “Click Chemistry Plays a Dual Role in Biodegradable Polymer Design,” was coauthored by Jinshan Guo, Zhiwei Xie, Richard T. Tran and Jian Yang of Penn State, and Denghui Xie, Dadi Jin, and Xiaochun Bai of the Academy of Orthopedics of Guangdong Province.