Targeting of nanoparticles in cancer: drug delivery and diagnostics

Anticancer agents continue to be a preferred therapeutic option for several malignancies. Despite their effectiveness, oncologists are continually looking for tumor-specific anticancer agents to prevent adverse effects in patients. Targeting of imaging agents to cancerous tissue is another area that is enthusiastically explored to circumvent some of the drawbacks that current imaging agents possess, including the inability to target small tumor cells, inadequate imaging period, and the risk of renal damage. Formulation scientists have explored nanotechnology-based delivery systems for targeting anticancer agents and tumor-imaging agents to cancer tissue. Targeting with nanotechnology-based delivery systems has been investigated by both passive and active mechanisms with significant clinical success. This review presents a discussion on targeting strategies used for the delivery of nanoparticles by passive and active mechanisms, focusing more specifically on active targeting of nanoparticles using albumin, folic acid, transferrin, and aptamers as targeting ligands.