Homogeneous bulk erosion

Polyesters, such as poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA), are examples of biomaterials that are degraded by homogeneous bulk erosion. 

Which one of the following polymers undergoes homogeneous bulk erosion (a) Poly(lactide-co-glycolide) (b) Poly[bis(p-carboxyphenoxy)propane sebacic acid) (c) Poly(ortho esters) and/or (d) Poly(ethylene-vinyl acetate). 

From the macroscopic viewpoint, degradation of aliphatic polyesters has been regarded as homogeneous (bulk erosion) until recently although surface erosion was claimed in a few cases. 

In bulk erosion, the entire area of polymer matrix is subject to chemical or enzymatic reactions, thus erosion occurs homogeneously throughout the entire matrix Accordingly, the degradation pattern is sometimes termed homogeneous erosion. 

Mechanism Homogeneous degradation (bulk) Heterogeneous degradation (surface-erosion)... 

Release pattern from slow-release polymers are generally divided into two major types homogeneous (bidk) and surface erosion. The glycolide-lactide copolymers display bulk degradation, i.e. diey exhibit significant degradation in the polymer matrix interior. Ideally, a polymer should exhibit only surface erosion as for the polyanhydrides and poly(ortho)esters. Unfortunately, due to their high pH sensitivity these materials cannot be used for all application. 

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