Nanoparticles for colorectal cancer targeted drug delivery and mr imaging: Current situation and perspectives

The application of nanoparticles (NPs) offers new prospects for the early detection and effective therapy of colorectal cancer (CRC). Various NPs have been designed and explored as diagnostic and/or therapeutic drug delivery vehicles. To achieve selective treatment and to reduce toxicity, these nanoparticles are usually endowed with targeting abilities. Passive targeting is based on the extravasation and enhanced permeability and retention effect of tumors, while active targeting always involves binding to specific ligands that are recognizable by CRC tissues, such as vascular endothelial growth factor, folate, monoclonal antibodies (mAbs), aptamers, and membrane penetrating peptides. In addition, contrast agents, such as gadolinium complexes and iron oxide particles, can be introduced into the delivery system to enable MR imaging and lesion detection. Furthermore, smart carriers have been gradually applied to the delivery system. These carriers are designed to respond to certain changes in the bio-environment and release encapsulated contents on demand, thus achieving effective drug concentrations at tumor sites. This review focuses on recent advances of NP technology for the targeted diagnosis and treatment of CRC and aims to unveil the emerging possibilities of using nanocarriers to enhance therapeutic applications.