Aptamer--nanoparticle-based chemiluminescence for p53 protein.

A simple colorimetric biosensing technique based on the interaction of gold nanoparticles (AuNPs) with the aptamer was developed for detection of p53, a tumor suppressor protein, in the current study. Aggregation of AuNPs was induced by desorption of the p53 binding RNA aptamer from the surface of AuNPs as a result of the aptamer target interaction leading to the color change of AuNPs from red to purple. The detection limit of p53 protein by the colorimetric approach was 0.1 ng/ml after successful optimization of the amount of aptamer, AuNPs, salts, and incubation time. Furthermore, the catalytic activity of the aggregated AuNPs was greatly enhanced by chemiluminescence (CL) reaction, where the detection limit was enhanced to 10 pg/ml with a regression coefficient of R2 = 0.9907. Here the sensitivity was increased by 10-fold compared with the AuNP-based colorimetric method. Hence, the sensitivity of detection was increased by employing CL, by using the catalytic activity of aggregated AuNPs, on the luminol-hydrogen peroxide reaction. Thus, the combination of colorimetric and CL-based aptasensor can be of great advantage in increasing the sensitivity of detection for any target analyte.

Functionalized aptamers as nano-bioprobes for ultrasensitive detection of bisphenol-A.

A novel functionalized aptamer based 'turn-off' fluorescent biosensor for ultra-sensitive detection of small molecules like bisphenol-A in water samples.

Nano RNA aptamer wire for analysis of vitamin B12.

A simple and stable RNA aptamer-based colorimetric sensor for the detection of vitamin B12 using gold nanoparticles (AuNPs) has been proposed. Vitamin B12 belongs to the B vitamin group and prevents pernicious anemia, which is caused by vitamin B12 deficiency. A highly stable RNA aptamer that binds to vitamin B12 was employed by structural modification of 2'-hydroxyl group of ribose to 2'-flouro in all pyrimidines indicated in lowercase in 35-mer aptamer (5' GGA Acc GGu GcG cAu AAc cAc cuc AGu GcG AGc AA 3'). Aggregation of AuNPs was specifically induced by desorption of the vitamin B12 binding RNA aptamer from the surface of AuNPs as a result of the aptamer-target interaction, leading to the color change from red to purple. The level of detection of vitamin B12 was 0.1 µg/ml by successful optimization of the amount of the aptamer, AuNPs, salts, and stability of the aptamer. Analysis of vitamin B12 was carried out, and the observed recovery was 92 to 95.3% with a relative standard deviation in the range of 2.08 to 8.27%. The results obtained were compared with those of the ultraviolet-visible (UV-vis) spectrometry method. This colorimetric aptasensor is advantageous for on-site detection with the naked eye.

Dipstick based immunochemiluminescence biosensor for the analysis of vitamin B12 in energy drinks: a novel approach.

In this article, we describe a dipstick based immunochemiluminescence (immuno-CL) biosensor for the detection of vitamin B(12) in energy drinks. The method is a direct competitive type format involving the immobilization of vitamin B(12) antibody on nitrocellulose membrane (NC) followed by treatment with vitamin B(12) and vitamin B(12)-alkaline phosphatase conjugate to facilitate the competitive binding. The dipstick was further treated with substrate disodium 2-chloro-5-(4-methoxyspiro {1,2-dioxetane-3,2¢-(5¢-chloro)tricyclo[3.3.1.13,7]decan}-4-yl)-1-phenyl phosphate (CDP-Star) to generate chemiluminescence (CL). The number of photons generated was inversely proportional to the vitamin B(12) concentration. After systematic optimization, the limit of detection was 1 ng mL(-1). The coefficient of variation was below 0.2% for both intra- and inter-assay precision. Vitamin B(12) was extracted from energy drinks with recovery ranged from 90 to 99.4%. Two different energy drinks samples were analyzed, and a good correlation was observed when the data were compared with a reference enzyme linked immuno sorbent assay (ELISA) method. The developed method is suitable for an accurate, sensitive, and high-throughput screening of vitamin B(12) in energy drinks samples. The dipstick technique based on immuno-CL is suitable for the detection of several analyte in food and environmental samples.