This book provides a critical overview of the advances being made towards overcoming biological barriers through the contribution of nanosciences and nanotechnologies. Overcoming these barriers is of importance for solving the problems of many current drugs and vaccines and it is also especially relevant for the commercial exploitation of new therapeutic strategies. Despite other books on nanomedicine, there is still a gap in the literature on the relationship between the chemical properties of nanobiomaterials and their interaction with the biological environment. This book focuses on the mechanistic issues related to the interaction between drug delivery systems and biological barriers and then on the analysis of the critical factors determining the efficacy of nanobiomaterials for specific applications.