Obtaining More Accurate Signals: Spatiotemporal Imaging of Cancer Sites Enabled by a Photoactivatable Aptamer-Based Strategy

Recent advances in optical aptasensor technology for amplification strategies in cancer diagnostics

Aptamers are chemically synthetic single-stranded DNA or RNA molecules selected by molecular evolution. They have been widely used as attractive tools in biosensing and bioimaging because they can bind to a large variety of targets with high sensitivity and high affinity and specificity. As recognition elements, aptamers contribute in particular to cancer diagnostics by recognizing different cancer biomarkers, while they can also facilitate ultrasensitive detection by further employing signal amplification elements. Optical techniques have been widely used for direct and real-time monitoring of cancer-related biomolecules and bioprocesses due to the high sensitivity, quick response, and simple operation, which has greatly benefited cancer diagnostics. In this review, we highlight recent advances in optical platform-based sensing strategies for cancer diagnostics aided by aptamers. Limitations and current challenges are also discussed.

Y-Shaped Backbone-Rigidified Triangular DNA Scaffold-Directed Stepwise Movement of a DNAzyme Walker for Sensitive MicroRNA Imaging within Living Cells

DNA as a programmable molecule shows great potential in a wide variety of applications, with the dynamic DNA nanodevices such as DNA motors and walkers holding the most promise in controlled functions for biosensing and nanomedicine. However, a motor or walker that consists of DNA exclusively has not been shown to function within cells because of its susceptibility to endogenous nuclease-mediated degradation. In this contribution, we demonstrate a Y-shaped backbone-rigidified triangular DNA scaffold (YTDS)-directed DNAzyme walker that functions inside living cells to detect microRNAs (miRNAs) with high sensitivity. A novel Y-shaped backbone offers access to geometrically well-defined configurations and increases the rigidity of DNA assemblies, providing a unique, circular, and rigid DNA track within living cells without non-nucleic acid auxiliary materials and enabling the stepwise movement of DNAzyme in an inchworm fashion. This strategy is extended to the construction of larger rigid planar geometric polygon-based DNA walkers, demonstrating unprecedented opportunities to build dynamic DNA nanostructures with precise geometry and versatile functionality.

Specific stabilization of DNA G-quadruplex structures with a chemically modified complementary probe

The DNA G-quadruplex is an important higher-order structure formed from guanine-rich DNA sequences. There are many molecules which can stabilize this structure. However, the selectivity of these ligands to different G-quadruplexes was not satisfactory. Herein, we designed and synthesized a chemically modified G-quadruplex probe, Razo-DNA, for the unique stabilization of the G-quadruplex. Razo-DNA consists of two fragments: The first is an organic molecular moiety which can stabilize G-quadruplex structures, and the second is a DNA molecule that is complementary with a sequence adjacent to the guanine-rich sequence of targeted DNA. Further studies showed that Razo-DNA could precisely stabilize the targeted DNA G-quadruplex structures in vitro.

A basic insight into aptamer-drug conjugates (ApDCs)

Aptamers are often compared with antibodies since both types of molecules function as targeting ligands for specific cancer cell recognition. However, aptamers offer several advantages, including small size, facile chemical modification, high chemical stability, low immunogenicity, rapid tissue penetration, and engineering simplicity. Despite these advantages, several crucial factors have delayed their clinical translation, such as concerns over inherent physicochemical stability and safety. Meanwhile, steps have been taken to make aptamer-drug conjugates, or ApDCs, a clinically practical tool. In this review, we highlight the development of ApDCs and discuss how researchers are solving some problems associated with their clinical application for targeted therapy.