Strategies for combination of aptamer and targeted drug delivery

Cell-specific delivery of active agents for treatment of human disease is a long cherished object for scientific researchers. Nanoscience generated nanosized carriers, such as liposome, micelle and nanoparticle, provides potential to realize such purpose based on the nanometer size effect (< 1000 nm), however, the sole nanocarrier with no specific ligands are not sufficient to deliver drugs to target sites. Aptamers are single-stranded oligonucleotides which can specifically recognize and bind to target cells by distinct secondary and tertiary structures even without knowledge of characteristic protein profiles on cell surface. Thus, aptamer, as a target moiety, provides a potential approach to realize pathological site-specific delivery of active agents. This review highlighted the strategies for combination of aptamer and targeted drug delivery, further summarized their preparation methods, strengths and weaknesses to facilitate the development of targeted drug delivery system.