Metal-enhanced fluorescence-based core-shell Ag@SiO₂ nanoflares for affinity biosensing via target-induced structure switching of aptamer.
One of the great challenges in metal-enhanced fluorescence (MEF) technology is the achievement of distance modulation with nanometer accuracy between the fluorophore and metal surface to obtain maximum enhancement. We propose an MEF-based core-shell Ag@SiO2 nanoflare for distance control via the thickness of silica shell with cooperation of DNA hybridization. The nanoflare contains a 50 nm spherical silver nanoparticle (Ag NP) core, a 8 nm silica shell, and cyanine (Cy5)-labeled aptamer hybridized with a complementary DNA (cDNA) immobilized onto the shell surface. The formation of the Cy5-labeled aptamer/cDNA duplex on the Ag@SiO2 NP surface results in the confinement of Cy5 to the shell surface and an increase in the fluorescence of Cy5 with a 32-fold enhancement factor in bulk solution (signal-on). In the presence of affinity-binding targets, the Cy5-labeled aptamers confined onto the Ag@SiO2 NP surface dissociate from their cDNA into the solution because of structure switching. The target-induced release of aptamer leads to a reduction in the enhanced fluorescence signal of the labeled Cy5 moiety (signal-off). Thus, the nanoflare can be used as a sensor for target recognition. Using adenosine-5'-triphosphate (ATP) aptamer, detection of ATP has a linear response from 0 to 0.5 mM and a detection limit of 8 μM. With various types of DNA probes immobilized onto the core-shell Ag@SiO2 NPs, the MEF-based nanoflare has provided an effective platform for the detection and quantification of a broad range of analytes, such as mRNA regulation and detection, cell sorting, and gene profiling.
Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education and ‡Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University , Xi'an 710062, China.
Lu
L
Lu
Yunxia
Y
Qian
Lihui
L
Wang
Keke
K
Ma
Yaodong
Y
Zhang
D000255:Adenosine Triphosphate / Q000097:blood; D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods; D002942:Circular Dichroism; D005260:Female; D005453:Fluorescence; D006801:Humans; D008297:Male; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D012822:Silicon Dioxide / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence
D052157:Aptamers, Nucleotide; D012996:Solutions; D012834:Silver; D012822:Silicon Dioxide; D000255:Adenosine Triphosphate