Plasmonic Gold Nanostar-Based Probes with Distance-Dependent Plasmon-Enhanced Fluorescence for Ultrasensitive DNA Methyltransferase Assay.

The ultrasensitive DNA methyltransferase (Dam MTase) assay is of high significance for biomedical research and clinical diagnosis because of its profound effect on gene regulation. However, detection sensitivity is still limited by shortcomings, including photobleaching and weak signal intensities of conventional fluorophores at low concentrations. Plasmonic nanostructures with ultrastrong electromagnetic fields and fluorescence enhancement capability that can overcome these intrinsic defects hold great potential for ultrasensitive bioanalysis. Herein, a silica-coated gold nanostars (Au NSTs@SiO2)-based plasmon-enhanced fluorescence (PEF) probe with 20 "hot spots" was developed for ultrasensitive detection of Dam MTase. Here, the Dam Mtase assay was achieved by detecting the byproduct PPi of the rolling circle amplification reaction. It is worth noting that, benefiting from the excellent fluorescence enhancement capability of Au NSTs originating from their 20 "hot spots", the detection limit of Dam Mtase was reduced by nearly 105 times. Moreover, the proposed Au NST-based PEF probe enabled versatile evaluation of Dam MTase inhibitors as well as endogenous Dam MTase detection in GW5100 and JM110 Escherichia coli cell lysates, demonstrating its potential in biomedical analysis.

Light and endogenous enzyme triggered plasmonic antennas for accurate subcellular molecular imaging with enhanced spatial resolution.

Developing accurate tumor-specific molecular imaging approaches holds great potential for evaluating cancer progression. However, traditional molecular imaging approaches still suffer from restricted tumor specificity due to the "off-tumor" signal leakage. In this work, we proposed light and endogenous APE1-triggered plasmonic antennas for accurate tumor-specific subcellular molecular imaging with enhanced spatial resolution. Light activation ensures subcellular molecular imaging and endogenous enzyme activation ensures tumor-specific molecular imaging. In addition, combined with the introduction of plasmon enhanced fluorescence (PEF), off-tumor signal leakage at the subcellular level was effectively reduced, resulting in the significantly enhanced discrimination ratio of tumor/normal cells (∼11.57-fold) which is better than in previous reports, demonstrating great prospects of these plasmonic antennas triggered by light and endogenous enzymes for tumor-specific molecular imaging at the subcellular level.