(653b) Carefully Controlled Photo-Crosslinkable PLA Networks

Poly(lactic acid) (PLA) has become one the most widely used biomedical polymers. Its bio-absorbability, bio-compatibility, and hydrophobicity has made it ideal for degradable implants, tissue engineering scaffolds, and time released drug delivery. Further, its enzymatic and hydro-catalyzed pathways for non-toxic degradation makes it a similarly priced, environmentally friendly plastic alternative to polystyrene and other non-degradable household plastics. However, despite its many advantages, certain issues have slowed its progress into these applications. First, PLA is mechanically weak. Its poor fracture toughness and elastic modulus has prevented its use as bone implants and screws. Additionally, its limited range of degradation rates has prevented it from replacing many household plastics used every day. Consistent and limited degradation profiles also remains a challenge in the field of drug delivery. This paper outlines a procedure to produce bis alpha, omega–ene functionalized PLA oligomers for use with near clickable thiolene chemistry. PLA oligomers are synthesized with dispersities around 1.3 using a ring opening polymerization and organic catalysts. These oligomers are then bis functionalized at the ends with vinyl groups. A multi-arm thiol is then introduced and a highly ordered network is formed using cell safe 365 nm UV light. Two millimeter diameter crosslinked samples prepared with the same oligomer consistently show almost identical characterization parameters as analyzed by differential scanning calorimetry, nuclear magnetic resonance, fourier transform infrared spectroscopy, and nano-indentation. Crosslink density scaled with crystallization rate, hardness and elastic modulus in a repeatable and consistent manner.