Search

Development of rapid, sensitive, and selective method for pathogenic bacteria detection is of great importance for food safety, medical diagnostic, and environmental monitoring. Currently, most techniques for low numbers of bacteria detection require advanced instrumentation or skilled operators. Herein, we present a facile colorimetric detection platform for bacterial detection using Ag nanoplates as chromogenic substrate, which takes advantages of the high specificity and affinity of aptamer and the ability of catalase to hydrolyze H 2 O 2 that can etch Ag nanoplates. By introducing catalase to the sandwich structure composed by dual-aptamer recognition strategy, bacteria detection signal is converted to the peak shift of LSPR and colorimetric change. This proposed method allows a fast naked-eye detection of S. aureus at the concentration of 60 CFU/mL based on the combination of streptavidin-biotin system and inherent sensitivity of plasmonic Ag nanoplates. Owing to the high selectivity and sensitivity, as well as the low-cost and good adaptability, this plasmonic assay is expected to be suitable for pathogenic bacteria detection in resource-limited settings. Dual aptamer-based plasmonic detection platform for S. aureus was fabricated using silver nanoplates as the signal transducer. [Display omitted] • Silver nanoplates are outstanding chromogenic substrates for the construction of plasmonic assay. • Dual-aptamer recognition strategy can achieve highly sensitive and selective detection of S. aureus. • RGB approach proposed could potentially be adapted for the development of low-cost, portable detection devices. [ABSTRACT FROM AUTHOR]

Combining the unique optical properties of metal nanoparticles and the specific recognition of aptamer, aptamer-nanoparticle conjugates have been extensively used in a wide range of applications, particularly multifunctional nanoparticles for cell detection and molecular imaging. Conventional conjugates prepared by chemisorption of monothiol-modified oligonucleotides onto nanoparticle surfaces suffer from a lack of stability when exposed to a variety of small molecules. If silver is used in place of gold, then this lack of stability is even more pronounced. In this study, we reported here the effective and facile strategy of preparing stable silver nanoparticle-aptamer conjugates by in situ generation of strong metal affinity capping ligands, dithiocarbamates modified anti-prion protein aptamer. The conjugates produced are stable and can withstand NaCl concentration at 0.25 mol/L. Meanwhile, they could be applied in the cellular prion protein imaging successfully. [ABSTRACT FROM AUTHOR]

A new spectrofluorometric method for cellular prion protein (PrPC) was developed based on the regulation of N,N′-bis[3,3′-(dimethylamino)propylamine]-3,4,9,10-perylenetetracarboxylic diimide (DAPER) fluorescence. As a perylene derivative, DAPER emits strong fluorescence in the form of free monomer in aqueous medium, but not in the form of aggregates. In this contribution, we found that the aptamer of PrPC could induce the aggregation of DAPER, and the bright fluorescence of DAPER was completely quenched. The quenched fluorescence, however, was recovered if PrPC was further added, which was ascribed to the specific binding of PrPC to its aptamer and the releasing of free DAPER monomers. This signalling mechanism makes it possible to detect PrPC by fluorescence spectroscopy. The assay allows the selective determination of PrPC in aqueous solution with high sensitivity and exhibits a good linear range from 0.4 to 1.6 nmol L−1. Moreover, this probe can be applied to monitor the level of PrPC in human urine samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) spectra, which can provide large information about trace amount of chemical and biological species have been widely performed as a well-established tool in complex biological system. In this work, coomassie brilliant blue (R-250) with high affinity to proteins and high Raman activity was employed as a Raman reporter to probe prion protein (PrP) through a dual-aptamer mechanism, and thus an original strategy for PrP determination was proposed, which showed great potential to turn on the SERS response through specific recognition of anti-prion aptamers towards the target protein. Aptamers (Apt1 and Apt 2) recognizing distinct epitopes of PrP with high affinity were first conjugated to Ag@Si NPs, and Ag@Si-PrP/R-250-Ag@Si conjugates were obtained in the presence of PrP/R-250, inducing dramatically enhanced Raman signal. SERS responses enhanced with increasing amount of PrP and a linear equation of I SERS =6729.7+3091.2 c PrP was obtained in the range of 3.0–12.0×10 −9 M with the determination coefficient of 0.988. The proposed strategy is simple, rapid, and high specificity to probe protein–aptamer recognition in the solution. [ABSTRACT FROM AUTHOR]

A new type of highly selective aptamer-labeled fluorescent silica nanoparticles [Apt-tris(2,2′-bipyridyl)ruthenium(II)@SiO NPs] were prepared through the reverse microemulsion method by using prolonged fluorescence lifetime ruthenium complexes of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)) as the source of the fluorescence for cellular prion protein imaging. Investigations showed that the newly prepared Ru(bpy)@SiO NPs possessed superior advantages of strong fluorescence, low toxicity, and easy surface modification for bioconjugation. Cell imaging experiments indicated that Apt-Ru(bpy)@SiO NPs had great tendency to human bone marrow neuroblastoma cells (SK-N-SH cells), since they can express large amount of prion protein on the surface of the cell, while in HeLa cells this phenomenon disappeared for the reason that HeLa cells cannot express prion proteins. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report a solution-based MEF sensing platform. [•] Metallic surface-dye distance is controlled by changing the thickness of silica shell. [•] Dual-aptamer was involved to recognize distinct binding epitopes of the same target. [•] Ag@Si NPs was used as an excellent probe for darkfield light scattering imaging. [ABSTRACT FROM AUTHOR]