Macrophages, phagocytic cells of the innate immune system, are the body's first line of defense against pathogens and are responsible for tissue maintenance. Macrophages are capable of sensing and internalizing external stimuli, and in response change their morphology and phenotype accordingly. Because macrophages are integral to immune function and tissue maintenance, dysregulation of macrophage behavior is associated with a range of diseases including infections, cancer, autoimmune disorders, atherosclerosis, and more. Because of the implications of macrophage failure, there is interest in creating new materials to manipulate macrophage behavior for a therapeutic effect. In this thesis, I describe the application of several new nanomaterials and chemical methods for the therapeutic manipulation of macrophages. Initially, I generated a gold nanoparticle-stabilized nanocapsule (NPSC) for delivering siRNA directly to the cytosol of cells. After demonstrating effective siRNA delivery in vitro, I utilized NPSCs to deliver TNF-α targeted siRNA into macrophages in vivo to reduce over-inflammation in a LPS challenge model. In a related system, I worked with a gold nanoparticle-based nanocomposite delivery system for delivery of engineered proteins. Specifically, this system was used to deliver glutamate tagged Cas9 into macrophages to alter macrophage DNA. This system was used to knockout SIRP-α in macrophages to increase macrophage killing of cancer cells. I also chemically modified macrophage cell surfaces through biorthogonal reactions to attach fluorescent molecules. Once modified, the natural tumor homing ability of macrophages turned the modified macrophages into tumor imaging agents. I then again took advantage of macrophage tumor homing ability by loading nanoparticle embedded bioorthogonal catalysts, "nanozymes," into macrophages for delivery to tumor sites. The nanozymes activate pro-chemotherapeutics into active drugs that specifically kill surrounding tumor cells. I also produced a mannose-functionalized macrophage-targeted nanozyme to generate antibiotics to specifically kill macrophage-invading bacteria. Additionally, I generated and characterized a small molecule TLR4 agonist to activate macrophages into a pro-inflammatory state, with increased anti-cancer activity. Finally, I utilized an array-based polymer sensor to detect macrophages in different activation states in a high-throughput manner. In summary, this thesis provides evidence of the utility of next generation chemical and nanomaterial tools in macrophage-based applications.