Multivalent Conjugates of Sonic Hedgehog Accelerate Diabetic Wound Healing.

Despite their preclinical promise, few recombinant growth factors have been fully developed into effective therapies, in part, due to the short interval of therapeutic activity after administration. To address this problem, we developed nanoscale polymer conjugates for multivalent presentation of therapeutic proteins that enhance the activation of targeted cellular responses. As an example of this technology, we conjugated multiple Sonic hedgehog (Shh) proteins onto individual hyaluronic acid biopolymers to generate multivalent protein clusters at defined ratios (i.e., valencies) that yield enhanced Shh pathway activation at equivalent concentrations relative to unconjugated Shh. In this study, we investigated whether these multivalent conjugates (mvShh) could be used to improve the therapeutic function of Shh. We found that a single treatment with mvShh significantly accelerated the closure of full-thickness wounds in diabetic (db/db) mice compared to either an equivalent dose of unconjugated Shh or the vehicle control. Furthermore, we identified specific indicators of wound healing in fibroblasts and endothelial cells (i.e., transcriptional activation and cell migration) that were activated by mvShh in vitro and at concentrations approximately an order of magnitude lower than the unconjugated Shh. Taken together, our findings suggest that mvShh conjugates exhibit greater potency to activate the Shh pathway, and this multivalency advantage improves its therapeutic effect to accelerate wound closure in a diabetic animal model. Our strategy of multivalent protein presentation using nanoscale polymer conjugates has the potential to make a significant impact on the development of protein-based therapies by improving their in vivo performance.

Student award for outstanding research winner in the Ph.D. category for the 9th World Biomaterials Congress, Chengdu, China, June 1-5, 2012: synthesis and application of photodegradable microspheres for spatiotemporal control of protein delivery.

In this study, the authors present a photodegradable microparticle system that can be used 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-ß1 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.