Pure versions of PLGA/PLA polymers will generally have a delayed onset of acidity due to removal of lactide/glycolide monomers. Impure versions have fairly rapid onset due to monomers degrading quickly. In all cases however, PLGA will always acidify and this can create inflamation issues if acid is formed faster than it can be removed.
For polyvivo polymers we utilize purification to remove any excess monomers so as to avoid this problem. Prior customers have utilized AK12 (which is a 50:50 LA:GA ratio PLGA-PEG-PLGA thermogel) in animals and in their research (see: http://www-leland.stanford.
edu/group/Zarelab/publinks/ zarepub853.pdf, notably P. 231.) they reported no notable inflamation relative to control.