Use of additives in the design of poly(lactide-co-glycolide) microspheres for drug delivery

Poly(lactide-co-glycolide) (PLGA) microspheres can be generated making use of several techniques which feature partly competing, partly complementary characteristics. Besides PLGA polymeric platform, excipients are sometimes needed in order to optimize the final microsphere properties (size, internal/external morphology, encapsulation efficiency, distribution and release rate of the incorporated drug) as a function of the preparation technique. Thus, people working in this field face the crucial issue to select, for a specific microencapsulation technique, among a huge amount of excipients those chemicals that are the most suitable to obtain microspheres with the desired properties. The main aim of this chapter is to guide the reader with a specific microsphere design in mind through the selection of excipients that better fit the purpose and to clarify the effect one can expect after their incorporation in the formulation. A description is given of the main techniques employed to produce PLGA microspheres, highlighting the critical points where the addition of a specific excipient is needed. Then, the general properties of each class of excipients are reported and their application in microsphere manufacturing described.