The present disclosure provides a delivery system for controlled protein release without encapsulation. Identical, burst-free, extended release profiles for three different protein therapeutics were obtained with and without encapsulation in PLGA nanoparticles embedded within a hydrogel. Using both positively and negatively charged proteins, it was shown that short-range electrostatic interactions between the proteins and the PLGA nanoparticles are the underlying mechanism for controlled release. Moreover, tunable release was demonstrated by modifying nanoparticle concentration, nanoparticle size, or environmental pH. Additionally, the utility of this system was demonstrated in vivo for BDNF delivery in a rat model of stroke. These new insights obviate the need for encapsulation and offer promising, translatable strategies for more effective delivery of therapeutic biomolecules.