A new method of label free sensing approach with superior selectivity and sensitivity towards virlabel-freeon is presented here, employing the localized surface plasmon resonance (LSPR) behavior of gold nanoparticles (AuNPs) and fluorescent CdSeTeS quantum dots (QDs). Inorganic quaternary alloyed CdSeTeS QDs were capped with -cysteine via a ligand exchange reaction. Alternatively, citrate stabilized AuNPs were functionalized with 11-mercaptoundecanoic acid to generate carboxylic group on the gold surface. The carboxylic group on the AuNPs was subjected to bind covalently with the amine group of-cysteine capped CdSeTeS QDs to form CdSeTeS QDs/AuNPs nanocomposites. The fluorescence of CdSeTeS QDs/AuNPs nanocomposite shows quenched spectrum of CdSeTeS QDs at 640 nm due to the close interaction with AuNPs. However, after successive addition of norovirus-like particles (NoV-LPs), steric hindrance-induced LSPR signal from the adjacent AuNPs triggered the fluorescence enhancement of QDs in proportion to the concentration of the target NoV-LPs. A linear range of 10 to 10 g mL NoV-LPs with a detection limit of 12.1 × 10 g mL was obtained. This method was further applied on clinically isolated norovirus detection, in the range of 10-10 copies mL with a detection limit of 95.0 copies mL, which is 100-fold higher than commercial ELISA kit. The superiority of the proposed sensor over other conventional sensors is found in its ultrasensitive detectability at low virus concentration even in clinically isolated samples. This proposed detection method can pave an avenue for the development of high performance and robust sensing probes for detection of virus in biomedical applications.
The detection and identifi cation of dengue virus serotypes with quantum dot and AuNP regulated localized surface plasmon resonanceThe detection of dengue virus (DENV) serotypes has been described here, based on the distance dependent localized surface plasmon resonance (LSPR) between CdSeTeS QDs and AuNPs, which generates an altered fl uorescence signal for each serotype of DENV. In the reaction mixture of hairpin nanoprobes and functionalized AuNPs, the addition of analyte oligos of DENV can open the hairpin structure of the nanoprobe to form various structures depending on the serotypes initiating the LSPR enhancement or the quenching eff ect on the QD fl uorescence.Registered charity number: 207890
rsc.li/nanoscale-advancesThe detection and identification of dengue virus serotypes with quantum dot and AuNP regulated localized surface plasmon resonance † The dengue hemorrhagic fever or dengue shock syndrome has become a severe human fatal disease caused by infection with one of the four closely related but serologically distinct dengue viruses (DENVs).All four dengue serotypes are currently co-circulating throughout the subtropics and tropics. Since the fatality rate increases severely when a secondary infection occurs by a virus serotype different from that of the initial infection, serotype identification is equally important as virus detection. In this study, the development and validation of a rapid and quantitative DENV serotype-specific (serotypes 1-4) biosensor are reported by optimizing the stable system between cadmium selenide tellurium sulphide fluorescent quantum dots (CdSeTeS QDs) and gold nanoparticles (AuNPs). Four different nanoprobes are designed using each primer-probe serotype-specific hairpin single-stranded DNA covalently bound at different positions to CdSeTeS QDs, which generates an altered fluorescence signal for each serotype of DENV. In fourplex reactions with free functionalized AuNPs and the four nanoprobes, the standard dilutions of the target virus DNA from 10 À15 to 10 À10 M were successfully detected. The limit of detection was found to be in the femtomolar range for all four serotypes, where the serotype detection ability was undoubtedly established. To confirm the applicability of this sensing performance in long chained complex RNAs, the sensor was also applied successfully to RNAs extracted from DENV culture fluids for serotype identification as well as quantification, which can lead to a potential diagnostic probe for point-of-care detection. Fig. 6 (A-D) Concentration-dependent fluorescence changes of the CdSeTeS-dsDNA-AuNP nanocomposites in the presence of the target analyte DENV ssDNA of all four serotypes in the concentration range of 10 À15 to 10 À9 M. (E) Calibration curves for all four DENV serotypes.This journal is
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