here , we present a photodegradable microparticle system that can be employed to entrap and deliver bioactive proteins to cells during culture . by using a photosensitive delivery system , experimenters can achieve a wide variety of spatiotemporally regulated release profiles with a single microparticle formulation , thereby enabling one to probe many questions as to how protein presentation can be manipulated to regulate cell function . photodegradable microparticles were synthesized via inverse suspension polymerization with a mean diameter of 22 μm , and degradation was demonstrated upon exposure to several irradiation conditions . the protein - loaded depots were incorporated into cell cultures and release of bioactive protein was quantified during the photodegradation process . this phototriggered release allowed for the delivery of tgf - β1 to stimulate pe25 cells and for the delivery of fluorescently labeled annexin v to assay apoptotic 3t3 fibroblasts during culture . by incorporating these photoresponsive protein delivery depots into cell culture , new types of experiments are now possible to test hypotheses about how individual or multiple soluble factors might affect cell function when presented in a uniform , temporally varying , or gradient manner .