The targeted delivery of therapeutic agents to specific cells remains a challenge in drug delivery. Provided herein are nanoparticle-targeting agent conjugates that can be used for the targeted delivery of therapeutic agents to certain cells and target tissues. The conjugates comprise nanoparticles (e.g., metal nanoparticles such as gold nanoparticles) with organic outer shells capable of adsorbing large numbers of therapeutic agents (e.g., small molecule drugs). The nanoparticles are covalently linked to targeting agents (e.g., proteins such as antibodies). The present invention also provides formulations comprising the nanoparticle-targeting agent conjugates, and kits comprising the same. In another aspect, the present invention provides methods of using the conjugates for the delivery of therapeutic agents to cells, and the treatment and/or prevention of diseases (e.g., autoimmune diseases, infectious diseases, proliferative diseases such as cancer). In another aspect, the present invention provides methods of preparing the nanoparticle-targeting agent conjugates described herein.
