Oligonucleotide Discrimination Enabled by Tannic Acid-Coordinated Film-Coated Solid-State Nanopores.

Discrimination of nucleotides serves as the basis for DNA sequencing using solid-state nanopores. However, the translocation of DNA is usually too fast to be detected, not to mention nucleotide discrimination. Here, we utilized polyphenolic TA and Fe3+, an attractive metal-organic thin film, and achieved a fast and robust surface coating for silicon nitride nanopores. The hydrophilic coating layer can greatly reduce the low-frequency noise of an original unstable nanopore, and the nanopore size can be finely tuned in situ at the nanoscale by simply adjusting the relative ratio of Fe3+ and TA monomers. Moreover, the hydrogen bonding interaction formed between the hydroxyl groups provided by TA and the phosphate groups of DNAs significantly increases the residence time of a short double-strand (100 bp) DNA. More importantly, we take advantage of the different strengths of hydrogen bonding interactions between the hydroxyl groups provided by TA and the analytes to discriminate between two oligonucleotide samples (oligodeoxycytidine and oligodeoxyadenosine) with similar sizes and lengths, of which the current signal patterns are significantly different using the coated nanopore. The results shed light on expanding the biochemical functionality of surface coatings on solid-state nanopores for future biomedical applications.

Visualization of Protein-Specific Glycation in Living Cells via Bioorthogonal Chemical Reporter.

Due to the lack of suitable chemical tools, probing the protein-specific glycation is highly challenging. Herein, we present a strategy based on glycation chemical reporter and proximity-induced FRET signal readout for visualizing protein-specific glycation in living cells. We first developed a bioorthogonal glucose analogue, 6-azido-6-deoxy-D-glucose (6AzGlc), as a novel glycation chemical reporter. Two types of DNA probes, glycation conversion probe and protein targeting probe, were designed to attach to glycation adducts and target proteins, respectively. After the protein was glycated by 6AzGlc, two DNA probes were sequentially applied to the target protein, triggering proximity-induced FRET signal readout. This strategy was successfully used to visualize glucose glycation of several proteins, including PD-L1 and integrin. More importantly, this strategy allowed us to analyze corresponding biological functions of glycated protein in the native environment.

DNA-Templated Glycan Labeling for Monitoring Receptor Spatial Distribution in Living Cells.

Tracking the spatial distribution of receptor tyrosine kinases in their native environment contributes to understanding the homeostatic or pathological states at a molecular level. Conjugation of DNA tags to a specific receptor is a powerful tool for monitoring receptor spatial distribution. However, long-term stable trafficking in live cells without interfering with the intrinsic receptor function remains a challenge. Here, we report a general DNA-templated glycan labeling strategy to track spatial distribution of a specific receptor in living cells. Different from existing target-selective covalent methods, the DNA tags were incorporated in glycan of a specific receptor via aptamer-assisted metabolic glycan labeling, thus resulting in minimal perturbation to the receptor's biological function. As proof of concept, covalent tagging of MET, HER2, and EGFR was achieved, and then the spatial distribution was successfully monitored, including homo-/heterodimerization and internalization. Overall, the proposed strategy will greatly aid in investigating receptor dynamics and is conducive to understanding their biological function in the native environment.

One-Step In Situ Self-Assembly of Biodegradable Films for Long-Term Intravesical Bladder Cancer Therapy.

Intravesical instillation therapy is increasingly recognized as one of the most common clinical treatment strategies for bladder cancer. However, the antitumor efficacy of chemotherapy drugs is still limited due to their rapid clearance by periodic urination. To circumvent this issue, a drug-loaded thin film comprising the self-assembly of tannic acid (TA) and ferric ions (Fe3+) was in situ fabricated on the bladder wall in vivo. As expected, the TA@Fe film with adjustable thickness could effectively prolong the residence time of anticancer drugs in the bladder and realize sustained release of anticancer drugs. Together with the antibacterial properties, the TA@Fe film enabled improved chemotherapeutic efficacy. Moreover, the TA@Fe film caused no adverse effects on bladder function, demonstrating the in vivo biocompatibility. In addition, the T2 contrast effect of Fe3+ was employed to real-time monitor the disassembly of the TA@Fe film and the ensuing drug release process by magnetic resonance imaging. We believe that the TA@Fe-based drug delivery platform with enhanced retention in the bladder would be of great potential for treating various bladder diseases.

Detection and Imaging of Hydrogen Sulfide in Lysosomes of Living Cells with Activatable Fluorescent Quantum Dots.

The simple, sensitive, and specific detection of hydrogen sulfide (H2S) is of great importance because of its crucial role in food safety, environmental pollution, and various pathological and physiological processes. Here, we reported activatable fluorescence nanoprobe-based quantum dots (QDs) for sensitive and selective monitoring of H2S in red wine, environmental water samples, and lysosome of live cancer cells. The nanoprobe was prepared through a strong electrostatic interaction between thioglycolic-acid-stabilized CdTe QDs and p-amino thiophenol capped silver nanoparticles (AgNPs) that resulted in the formation of the assembled nanostructure, called QD/AgNP nanocomplexes. The initial fluorescence of QDs was effectively quenched by the AgNPs because of the inner filter effect. Upon interaction with H2S, the strong etching ability of H2S to AgNPs could trigger the disassembly of QD/AgNP nanocomplexes and generate Ag2S on the surface of QDs, achieving a shell-core Ag2S/CdTe QDs with remarkable fluorescence as a result of the termination of inner filter effect. The aqueous solution studies displayed that the assembled QD/AgNP nanoprobe was sensitive to detect H2S, with a detection limit of 15 nM. In addition, this assembled QD/AgNP nanoprobe showed a high specificity toward H2S over other anions and biologically relevant species. The subsequent fluorescence imaging studies demonstrated that the assembled QD/AgNP nanoprobe exhibited high ability to enter into cellular lysosome and generated an enhancement fluorescence, which was used for endogenous H2S detection in lysosome of living cancer cells. This proposed nanoprobe revealed a more simple, rapid, time-saving, low-cost, sensitive, and selective process for monitoring of H2S in further environmental pollution, food safety, and clinical diagnosis of H2S-related diseases.