Fluorescent Features and Applicable Biosensing of a Core–Shell Ag Nanocluster Shielded by a DNA Tetrahedral Nanocage

Abstract

The DNA frame structure as a natural shell to stably shield the sequence-templated Ag nanocluster core (csAgNC) is intriguing yet challenging for applicable fluorescence biosensing, for which the elaborate programming of a cluster scaffold inside a DNA-based cage to guide csAgNC nucleation might be crucial. Herein, we report the first design of a symmetric tetrahedral DNA nanocage (TDC) that was self-assembled in a one-pot process using a C-rich csAgNC template strand and four single strands. Inside the as-constructed soft TDC architecture, the template sequence was logically bridged from one side to another, not in the same face, thereby guiding the in situ synthesis of emissive csAgNC. Because of the strong electron-repulsive capability of the negatively charged TDC, the as-formed csAgNC displayed significantly improved fluorescence stability and superb spectral behavior. By incorporating the recognizable modules of targeted microRNAs (miRNAs) in one vertex of the TDC, an updated TDC (uTDC) biosensing platform was established via the photoinduced electron transfer effect between the emissive csAgNC reporter and hemin/G-quadruplex (hG4) conjugate. Because of the target-interrupted csAgNC switching in three states with the spatial proximity and separation to hG4, an “on–off–on” fluorescing signal response was executed, thus achieving a wide linear range to miRNAs and a limit of detection down to picomoles. Without complicated chemical modifications, this simpler and more cost-effective strategy offered accurate cell imaging of miRNAs, further suggesting possible therapeutic applications.

Improved Catalytic Activity of Spherical Nucleic Acid Enzymes by Hybridization Chain Reaction and Its Application for Sensitive Analysis of Aflatoxin B1

“…Compared to other DNA sequences, G-quadruplex (G4) exhibits higher density of the nucleic acid layer after it is modified on the surface of AuNPs through the Au-S covalent band [6], showing good peroxidase-mimicking activity with the presence of the cofactor hemin [7][8][9][10]. However, G4 was formed via the Hoogsteen base pair instead of the traditional Watson-Crick base pair, which occupied more spaces on the limited surface of gold core [11][12][13], resulting in poor catalytic capacity due to the decreased local catalytic substrate concentrations [14][15][16]. Meanwhile, considering that its catalytic activity originated from the G4 DNAzyme layer rather than AuNPs core [17,18], an improvement regarding overcrowding G4 units on the limited AuNPs surface is urgently needed.…”

Upgraded and Light-Up Biosensing Platform: Entropy-Driven Catalysis Circuit Manipulates the Configuration Transformation of Novel DNA Silver Nanoclusters on the Graphene Oxide Surface

“…For example, an emissive core–shell Ag NC can be synthesized in the central cavity of a tetrahedral DNA nanocage (TDC). Due to the presence of the TDC, the resultant caged Ag clusters possess high stability and durability …”

Stimulus-Responsive Four-Stranded DNA Nanoring Assembly to Host Multiple Nanosilver Clusters for Cooperatively Enhanced Fluorescence Biosensing

“…Sequence-specific DNA-templated Ag clusters are formed through coordinating of silvers with short, single-stranded nucleobases. − The resulting DNA-cluster adducts, showing long-term stability, tunable spectral performance, and good biocompatibility, serve as increasingly attractive fluorophores for biosensing and imaging. ,− Building on these advantages, some interesting studies further explored the spectral and photophysical fluorescent profiles of Ag clusters that were synthesized in bifurcated parent scaffolds with two-split contiguous single-stranded oligonucleotides . When two split fragments were forced together on a short DNA duplex by a guided hybridization assembly, this DNA-Ag cluster complex was found to favor locally higher DNA concentrations and preferentially develop.…”