Degradation behavior of novel poly(α-hydroxy acid)-derived polyesters

Due to their bioresorbable characteristics biodegradable polyesters are attractive materials for sutures, fracture fixation devices, and drug delivery systems. These polymers degrade primarily through a bulk erosion mechanism. In many instances including drug delivery and fabrication of orthopaedic devices, surface erosion is desired as it confers linearity with respect to degradation and changes in modulus. We hypothesized that surface erosion could be achieved in poly(α,ω-hydroxy acids) by tuning the lipophilicity of the system and hence the water uptake. Toward this end, we used a modular design strategy to manipulate the hydrophilic-lipophilic balance (HLB) of a polymer chain at various stages by judicious choice of building blocks. Using this novel synthetic strategy we have synthesized a library of degradable polyesters derived from poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) that exhibit surface erosion behavior. Surface erosion was further verified by ultrastructure analysis of degraded polymer pellets and thin films by Scanning Electron Microscopy and tapping mode Atomic Force Microscopy respectively.