DNA-Based Fluorescent Nanoprobe for Cancer Cell Membrane Imaging.

As an important barrier between the cytoplasm and the microenvironment of the cell, the cell membrane is essential for the maintenance of normal cellular physiological activities. An abnormal cell membrane is a crucial symbol of body dysfunction and the occurrence of variant diseases; therefore, the visualization and monitoring of biomolecules associated with cell membranes and disease markers are of utmost importance in revealing the biological functions of cell membranes. Due to their biocompatibility, programmability, and modifiability, DNA nanomaterials have become increasingly popular in cell fluorescence imaging in recent years. In addition, DNA nanomaterials can be combined with the cell membrane in a specific manner to enable the real-time imaging of signal molecules on the cell membrane, allowing for the real-time monitoring of disease occurrence and progression. This article examines the recent application of DNA nanomaterials for fluorescence imaging on cell membranes. First, we present the conditions for imaging DNA nanomaterials in the cell membrane microenvironment, such as the ATP, pH, etc. Second, we summarize the imaging applications of cell membrane receptors and other molecules. Finally, some difficulties and challenges associated with DNA nanomaterials in the imaging of cell membranes are presented.

Endogenous Adenosine Triphosphate-Assisted Three-Dimensional DNA Walker Assembled on Soft Nanoparticles for Intracellular MicroRNA Imaging.

DNA walkers, a sophisticated type of nanomachines, exhibit intelligent application in biosensing with high programmability and flexibility but usually need additional auxiliary driving force, particularly when walking on hard surfaces. Herein, we construct a three-dimensional (3D) DNA walker on the soft surface of DNA nanospheres (DSs) by using a single-stranded DNA (ssDNA), which is powered by endogenous adenosine triphosphate (ATP) of live cells, so as to sensitively image microRNA (miRNA) in the tumor microenvironment. When the DS walker enters into live cells, miR-21, a general overexpressed biomarker in cancer cells, binds with the blocking strand (B), releasing the walking strand (W) and triggering an ATP-propelled walking reaction. The walking of the DS walker then generates an increasing Cy3 fluorescence signal that indicates the content of miR-21 with about 2.73-fold increase in sensitivity and about 157-fold decrease in the detection limit. Notably, the assembly of the DS walker on soft nanoparticles needs just an easy hybridization process, which facilitates the operation. Meanwhile, this endogenous ATP-powered 3D DNA walker walking on the soft surface performs real-time in situ imaging of miR-21 in live cells, which not only avoids the complex cell treatment and signal error induced by additional auxiliary factors, but also shows high promise of designing programmable DNA nanomachines.

MicroRNA Imaging Encounters Rolling Circle Amplification: Intracellular Na+-Fueled Linear Programmable DNAzyme Nanostructure.

DNAzyme motors are widely used for the sensitive detection of intracellular miRNAs due to their excellent signal response. Generally, the addition of exogenous mental ions to DNAzyme motors is crucial for the efficient operation of the system. Moreover, the position of the DNAzyme relative to the substrate has a significant impact on the cleavage rate during the reaction. Herein, we proposed a highly loaded Na+-fueled linear programmable DNAzyme nanostructure (LPDN) composed of long, single-strand DNA produced by rolling circle amplification reactions that served as binding partners for Na+-specific DNAyme and substrate. In the meantime, the long, programmable scaffolds can precisely control the position of the DNAzyme and substrate for the optimal effect. During the assay, miR-21 and endogenous Na+ can specifically trigger multiple adjacent substrate-cleaving reactions, resulting in a significant recovery of the Cy3 fluorescence signal in living cells. This method could enable in situ real-time imaging and biocompatibility-enhancing evaluation of intracellular miR-21-level changes. Furthermore, LPDN's ability to distinguish normal cells from cancer cells makes it a promising candidate for early cancer diagnosis and imaging analysis of cancer.

Multi-Catcher Polymers Regulate the Nucleolin Cluster on the Cell Surface for Cancer Therapy.

Cell signal transduction mediated by cell surface ligand-receptor is crucial for regulating cell behavior. The oligomerization or hetero-aggregation of the membrane receptor driven by the ligand realizes the rearrangement of apoptotic signals, providing a new ideal tool for tumor therapy. However, the construction of a stable model of cytomembrane receptor aggregation and the development of a universal anti-tumor therapy model on the cellular surface remain challenging. This work describes the construction of a "multi-catcher" flexible structure GC-chol-apt-cDNA with a suitable integration of the oligonucleotide aptamer (apt) and cholesterol (chol) on a polymer skeleton glycol chitosan (GC), for the regulation of the nucleolin cluster through strong polyvalent binding and hydrophobic membrane anchoring on the cell surface. This oligonucleotide aptamer shows nearly 100-fold higher affinity than that of the monovalent aptamer and achieves stable anchoring to the plasma membrane for up to 6 h. Moreover, it exerts a high tumor inhibition both in vitro and in vivo by activating endogenous mitochondrial apoptosis pathway through the cluster of nucleolins on the cell membrane. This multi-catcher nano-platform combines the spatial location regulation of cytomembrane receptors with the intracellular apoptotic signaling cascade and represents a promising strategy for antitumor therapy.