Biopharmaceuticals are a class of therapeutics including recombinant therapeutic proteins, engineered antibodies and genetic material. They are attractive from a medical point of view, but technologically they face major challenges. The delivery of biopharmaceuticals still prevents them from reaching their maximum pharmacodynamic potential, owing to their physicochemical properties, poor stability, permeability and biodistribution. In our research group we have been involved with inter-related projects that intend to optimize strategies to improve the bioavailability of biopharmaceutical drugs after administration. One of the most employed drugs has been insulin, the oldest therapeutic protein, as well as siRNA and gene silencing genetic material. We are interested in formulating such drugs in polymeric nanoparticles, because they encompass an array of advantages compared with classical dosage forms. We also look for tools to correlate in vitro and in vivo absorption rates of biopharmaceuticals, in a rational chronologic sequence of manufacturing parameters, preclinical assessments and requirements for marketing approval.