Biologically based strategies for overcoming in vivo barriers with functional nano-delivery systems

Nanomedicine has been developed to reduce or eliminate the side effects and toxicity upon systemic therapy of chemotherapeutic agents and to improve their therapeutic efficacy. However, the translation of non-sized or nano-encapsulated drugs is hampered by the low penetration and accumulation of engineered nanoparticles (NPs) in sites of tumors as well as their poor pharmacokinetics. This may be due to the synthetic structure of NPs and also complicated and unknown characteristics of the solid tumor microenvironment (TME). As a result, the TME is being better identified, and the interactions between NPs and the TME or human body are being discovered or predicted. These findings have led to the development of more biocompatible, intelligent, and controllable bio-based nanoformulations that could overcome current barriers and provide sufficient drug delivery to the TME, as discussed in this paper. These formulations are designed to (i) modify the surface of NPs to improve blood circulation while reducing their off-target accumulation and side effects in vivo, (ii) pass through the tumor vasculature by modulating or targeting angiogenesis, (iii) promote NPs distribution in solid tumor regions by applying biological/physical stimuli or extracellular matrix remodeling, and (iv) overcome the cell membrane barrier and other compartments of the cell by specific cell targeting to release the payload drug into the cytoplasm or nucleoplasm.