RNA interference (RNAi) is a biological mechanism wherein double-stranded RNAs (siRNAs) can be used to reduce expression of target proteins, and has emerged as a promising therapeutic strategy for the treatment of many diseases, including inflammatory diseases and malignancies. However, development of clinical applications of RNAi therapy has been hindered by the lack of clinically suitable, safe, and effective delivery vehicles. If such technology could be developed, a transformative advance in medicine would result. Macrophages are particularly attractive targets for RNA interference therapy because they promote pathogenic inflammatory responses in diseases such as rheumatoid arthritis, atherosclerosis, and diabetes. Thus, siRNA delivery systems capable of targeting immune cells present a promising therapeutic approach for the treatment of these and numerous other major human diseases. Despite significant recent progress in the delivery of small interfering RNA (siRNA) to immune cells, several major challenges to the clinical translation of siRNA as therapy remain. Thus, this proposal seeks to develop a platform for the delivery of small interfering RNA to immune cells (e.g., macrophages) and to demonstrate the utility of this technology in the treatment of inflammation-related diseases. Our laboratory has recently developed a novel siRNA delivery system based on glucan microparticles. We have demonstrated that these -1,3-D-glucan-encapsulated siRNA particles (GeRPs) can potently silence genes in mouse macrophages in vivo. A major advance would be to simplify this complex, multi-component system into a single component system that when mixed with siRNA forms a delivery vehicle. Aim 1 of this proposal will develop a technology that can efficiently deliver siRNA to immune cells. A small library of particles with tunable properties will be developed by the chemical modification of the glucan particles with a variety of functionalities. Aim 1 will also optimize the modified particles for delivery of siRNA to macrophages in vivo. Aim 2 will test the ability of chemically-conjugated glucan particles to mediate gene silencing in inflammatory macrophages and to ameliorate disease in mouse models of insulin resistance and type 2 diabetes. It will evaluate the in vivo biodistribution of the particles following administration to mice and quantify the ability of siRNA-loaded particles to silence inflammatory genes. Finally, it will demonstrate the therapeutic potential of the particles in the treatment of obesity-related diseases. The development of novel delivery technologies combined with evaluation of these systems in relevant disease models will be critical steps toward developing clinical therapies based on RNAi-mediated gene silencing.