i-Motif in Cancer Diagnosis and Treatment: Fabrication and Functionalization

Abstract

As a four-stranded DNA structure which forms within cytosine(C)-rich sequences, i-Motif, introduces a state-of-the-art pH-responsive targeting agent having remarkable ability in drug delivery systems (DDSs). Upon exposing to the slightly acidic environment, these sequences present significant tendency to fold into the intramolecular i-motif structure, normally with three loop style, supplying potent drug carriers. The conformational flexibility, easy modification, symmetrical architecture, and intrinsic biocompatibility of C-rich sequences, powerfully support their usage in drug delivery applications. Particularly, conjugation of C-rich with different inorganic nanoparticles or organic fragments improves their efficacy as nanocarriers by providing increased biocompatibility, reduced cytotoxicity, and enhanced stability. The i-motif-based systems are hired for both their cancer detection and therapeutic interventions. Despite the fact that utilizing the i-motifs has opened a shining topic in the usage of pH-responsivity, there is still a lack of thorough review which specifically analyzes the progresses of this materials in constituting targeted/non-targeted DDSs and biosensors. In this timely update we aim to supply an in-depth analysis of these progresses, with the goal of inspiring innovative strategies for designing targeting/non-targeting systems that benefitted from i-motifs as pH-responsive agents in combination with different types of nanocarriers for enhanced cancer diagnosis and treatment.