More Symmetrical “Hot Spots” Ensure Stronger Plasmon-Enhanced Fluorescence: From Au Nanorods to Nanostars

Abstract

Plasmon-enhanced fluorescence (PEF) is considered to be a powerful signal amplification technology to overcome intrinsic shortcomings of photobleaching and brightness of the traditional fluorescent dyes. Nevertheless, exploitation of PEFbased probes for bioimaging application is still at a very early stage. In this work, a simple but powerful gold nanostar (Au NST)@ SiO 2 -based PEF probe with 20 symmetric "hot spots" was developed for highly sensitive "lighting up" in situ imaging of intracellular microRNAs (miRNAs). By regulating the thickness of the silica shell, the distance between Au NSTs and fluorescent dyes was controlled, and the optimum fluorescence enhancement (21fold) was obtained with the silica shell thickness of approximately 22 nm. Thanks to the 20 more powerful "hot spots" that can produce stronger localized electric fields, the Au NST-based PEF probe exhibits stronger PEF effects than the traditional plasmonic nanostructures such as gold nanorods (Au NRs), gold nanobipyramids (Au NBPs), and triangular gold nanoprisms (Au NPRs), resulting in high sensitivity and improved detection limit (LOD) of 0.21 pM for miRNA-21 analysis. Moreover, not only cancer cells (MCF-7 and Hela) and normal cells (L02) with distinct miRNA-21 expression levels can be discriminated but also tumor cells in cocultured mixtures can be recognized, indicating its promising potential in clinical diagnosis.

Metal-Mediated Polydopamine Nanoparticles–DNA Nanomachine Coupling Electrochemical Conversion of Metal–Organic Frameworks for Ultrasensitive MicroRNA Sensing

“…The proposed biosensor was compared with the reported methods for miRNA-21 detection, and it was found that this strategy had higher sensitivity and possessed a lower detection limit (Table S2). − …”

From Passive Signal Output to Intelligent Response: “On-Demand” Precise Imaging Controlled by Near-Infrared Light

“…Furthermore, the capability of the NIR light-activatable UTDS to dynamically monitor the fluctuation of intracellular miRNA contents was evaluated. Here, miRNA-21 mimics were used to upregulate and an miRNA-21 inhibitor was used to downregulate miRNA-21 expression levels in HeLa cells, according to a previous work . Compared with untreated HeLa cells, mimic-treated HeLa cells showed obviously enhanced green fluorescence, while inhibitor-treated HeLa cells showed obviously decreased green fluorescence (Figure S13), confirming that the fluctuation of intracellular miRNA contents can be dynamically monitored using UTDS, which is of high significance for disease diagnosis and evaluation of therapeutic effect.…”

Plasmonic gold nanostructures for biosensing and bioimaging

“…The localization of fluorophores near metal nanoparticle will lead to dramatic fluorescent signal enhancement on the nanometer scale and allows for an even lower LOD for early disease detection and clinical diagnosis applications. Gao et al constructed a versatile AuNSs@SiO 2 -based plasmon-enhanced fluorescence probe together with 20 symmetric “hot spots” for in situ “lighting up” imaging of intracellular miRNAs [ 55 ]. By regulating the thickness of the silica shell, the distance between AuNSs and fluorescent dyes was controlled, and an optimum fluorescence enhancement (21-fold) was obtained when the silica shell was of approximately 22 nm thickness.…”

“…Reprinted with permission from ref. [ 55 ], Copyright 2021 American Chemical Society. B Schematic representation of the nanogap antennas assembly for target miRNA detection.…”