New Surface-Enhanced Raman Sensing Chip Designed for On-Site Detection of Active Ricin in Complex Matrices Based on Specific Depurination.

Quick and accurate on-site detection of active ricin has very important realistic significance in view of national security and defense. In this paper, optimized single-stranded oligodeoxynucleotides named poly(21dA), which function as a depurination substrate of active ricin, were screened and chemically attached on gold nanoparticles (AuNPs, ∼100 nm) via the Au-S bond [poly(21dA)-AuNPs]. Subsequently, poly(21dA)-AuNPs were assembled on a dihydrogen lipoic-acid-modified Si wafer (SH-Si), thus forming the specific surface-enhanced Raman spectroscopy (SERS) chip [poly(21dA)-AuNPs@SH-Si] for depurination of active ricin. Under optimized conditions, active ricin could specifically hydrolyze multiple adenines from poly(21dA) on the chip. This depurination-induced composition change could be conveniently monitored by measuring the distinct attenuation of the SERS signature corresponding to adenine. To improve sensitivity of this method, a silver nanoshell was deposited on post-reacted poly(21dA)-AuNPs, which lowered the limit of detection to 8.9 ng mL(-1). The utility of this well-controlled SERS chip was successfully demonstrated in food and biological matrices spiked with different concentrations of active ricin, thus showing to be very promising assay for reliable and rapid on-site detection of active ricin.

Galactose-functionalized magnetic iron-oxide nanoparticles for enrichment and detection of ricin toxin.

To generate a new specific recognition module for the enrichment and detection of ricin, galactose-functionalized silanized magnetic iron-oxide nanoparticles (Gal-SiMNPs) were assembled by amino-silanized MNPs (amino-SiMNPs) and a galactose linker. Amino-SiMNPs were produced by a coprecipitation method, and were coated with double layers of silica and aminosilane by hydrolysis of tetraethoxysilane and 3-aminopropyltriethoxysilane, respectively. A galactose with an amido-acid linker was synthesized by four steps of chemical modification from O-acetyl protected galactose. The diameters of Gal-SiMNPs were characterized as being 60 ± 20 nm. The average amount of galactose-loading and ricin-binding on Gal-SiMNPs was 30 ± 2 µg galactose and 29 ± 2 µg ricin toxin on the surface of 1 mg of Gal-SiMNPs, respectively. Furthermore, a rapid, simple and efficient colorimetric assay was established for the detection of ricin based on the Gal-SiMNPs, and the limits of detection (LODs) of 2 and 4 ng/mL for ricin in physiological buffer and serum were obtained, respectively.

A photoluminescent nanocrystal-based signaling protocol highly sensitive to nerve agents and highly toxic organophosphate pesticides.

A photoluminescent II-VI group semiconductor nanocrystal (NC)-based signaling platform composed of thioglycolic acid capped CdS NCs and acetylcholinesterase-acetylthiocholine enzyme catalytic reaction system was developed that was shown to be highly sensitive to nerve agents and toxic organophosphate pesticides with detection limits down to sub-nM levels. This new sensing protocol does not require troublesome conjugation of biomacromolecules onto the surface of NCs.