the invention discloses ph - controlling devices that comprise a biodegradable polymer and a ph - controlling substance , particularly an alkaline , acidic or buffering agent . by way of example , such alkaline agents include calcium carbonate and sodium bicarbonate . methods of preparing such devices are also described . methods for enhancing biocompatibility of an implantable device are also provided , as neutralizing alkaline materials are released at a rate that offsets changes in ph typically observed as polymers degrade to various acidic or alkaline by - products . by way of example , biodegradable polymers include pla , pga , polycaprolactone , copolymers thereof , or mixtures thereof . a new technique is also disclosed to increase the surface porosity of porous implants which have a tendency to form relatively impermeable coverings . this technique entails the use of mechanical means to remove at least part of said covering , thus increasing the implant &# 39 ; s surface porosity and permeability .