RNA Aptamer-functionalized Polymeric Nanoparticles in Targeted Delivery and Cancer Therapy: An up-to-date Review

Cancer nanotechnology takes advantage of nanoparticles to diagnose and treat cancer. The use of natural and synthetic polymers for drug delivery has become increasingly popular. Polymeric nanoparticles (PNPs) can be loaded with chemotherapeutics, small chemicals, and/or biological therapeutics. Major problems in delivering such therapeutics to the desired targets are associated with the lack of specificity and the low capacity of PNPs to cross cell membranes, which seems to be even more difficult to overcome in multidrugresistant cancer cells with rigid lipid bilayers. Despite the progress of these nanocarrier delivery systems (NDSs), active targeting approaches to complement the enhanced permeability and retention (EPR) effect are necessary to improve their therapeutic efficiency and reduce systemic toxicity. For this, a targeting moiety is required to deliver the nanocarrier systems to a specific location. A strategy to overcome these limitations and raise the uptake of PNPs is the conjugation with RNA aptamers (RNApt) with specificity for cancer cells. The site-directed delivery of drugs is made by the functionalization of these specific ligands on the NDSs surface, thereby creating specificity for features of cancer cell membranes or an overexpressed target/receptor exposed to those cells. Despite the advances in the field, NDSs development and functionalization are still in their early stages and numerous challenges are expected to impact the technology. Thus, RNApt supplies a promising reply to the common problem related to drug delivery by NDSs. This review summarizes the current knowledge on the use of RNApt to generate functionalized PNPs for cancer therapy, discussing the most relevant studies in the area.