Electronic anabolic steroid recognition with carbon nanotube field-effect transistors.

A proof of concept of the electronic detection of two anabolic steroids, stanozolol (Stz) and methylboldenone (MB), was carried out using two specific antibodies and arrays of carbon nanotube field-effect transistors (CNTFETs). Antibodies specific for Stz and MB were prepared and immobilized on the carbon nanotubes (CNTs) using two different approaches: direct noncovalent bonding of antibodies to the devices and bonding the antibodies covalently to a polymer previously attached to the CNTFETs. The results indicated that CNTFETs bonded to specific antibodies covalently or noncovalently are able to detect the presence of steroids. Statistically significant changes in the threshold voltage and drain current were registered in the transistors, allowing the steroids to be recognized. On the other hand, it was determined that the specific antibodies do not detect other steroids other than Stz and MB, such as nandrolone (ND) because, in this case, statistically significant changes in the transistors were not detected. The polymer prevents the aggregation of antibodies on the electrodes and decreases the transistor hysteresis. Nevertheless, it is not able to avoid the nonspecific adsorption of streptavidin, meaning that nonspecific adsorption on CNTs remains a problem and that this methodology is only useful for purified samples. Regarding the detection mechanism, in addition to charge transfer, Schottky barrier, SB, modification, and scattering potential reported by other authors, an electron/hole trapping mechanism leading to hysteresis modification has been determined. The presence of polymer seems to hinder the modulation of the electrode-CNT contact.

A high-throughput screening (HTS) immunochemical method for the analysis of stanozolol metabolites in cattle urine samples.

A high-throughput immunosorbent solid-phase extraction (HTS-IS-SPE) procedure coupled to enzyme-linked immunosorbent assay (ELISA) has been established for the analysis of stanozolol (St) and its main metabolite in cattle, 16beta-hydroxy-stanozolol (16betaOH-St), in cow urine samples. The chemical structure of the immunizing hapten 2'H-androst-2-eno[3,2-c]-pyrazol-17-hemiglutarate 5 (hapten A) has been designed to accomplish simultaneous detection of St and 16betaOH-St. The antibodies obtained have been used to establish a microplate ELISA method able to detect these metabolites with IC(50) values of 0.57microgL(-1) and 1.46microgL(-1), respectively in PBST. Immunosorbents prepared by covalently attaching the antibodies to Sepharose, efficiently removed the matrix interferences caused by the cattle urine samples. Moreover, St and 16betaOH-St were efficiently extracted from urine samples as demonstrated by LC-MS/MS analysis. The immunosorbents are filled on small mini-columns arranges on a 96-SPE-setup compatible with the microplate based ELISA methods. Samples and standards can be run in parallel which increment considerably the speed of the screening method. The recovery values of the whole HTS-IS-SPE-ELISA procedure has found to be 112+/-10% and St can be detected in hydrolyzed urine samples with LOD of 1.26+/-0.46microgL(-1) using just 1mL of sample. As proof-of-concept the urinary excretion profile of St treated animals has been investigated by analyzing individual sampling points. Results from pooled urine samples have also been compared with the results obtained by GC-MS analysis demonstrating the StIR equiv. measured with the HTS-IS-SPE-ELISA protocol are in accordance with the St and 16betaOH-St levels found with the chromatographic method. The analytical procedure is rapid, effective and the detectability achieved is below the MPRL (minimum performance required levels) recommended by CRL (Community Reference Laboratory) to the European Community.

Quantitative detection of doping substances by a localised surface plasmon sensor.

Within this communication, consistent evidence of a quantitative biosensing principle for steroidal residue analysis is presented. Our approach uses a simple method for the quantitative determination of an anabolic agent called stanozolol (Sz). Sz (Mw 328) is widely used in sports, horse racing and as a growth promoter in animals for human consumption. Through the use of localised surface plasmons (LSPs), sustained by three-dimensional noble metal nanostructures, we have developed a highly specific, label-less immunosensor for the detection of this small organic molecule to low levels (nM range). A main practical advantage over conventional flat extended film surface plasmon resonance (SPR) systems is the simplicity of the optical configuration, since there is no need for cumbersome total internal reflection illumination, thus making integration easier. In addition, the active area of the LSP-based sensor is smaller, decreasing the minimum detectable number of molecules involved in the binding event. Assay times are short and the set-up is comprised of relatively cheap instrumentation. Detection levels found here are comparable with SPR, even at this early stage of development and with further modifications, we envisage sensing down to pM (10(-12)) levels.

[Characteristics of blastolysin preparations in their ability to inhibit hemagglutination caused by bacteria of the genus Lactobacillus]. / Kharakteristika preparatov blastolizina po sposobnosti tormozit' gemaggliutinatsiiu, vyzyvaemuiu bakteriiami roda Lactobacillus.

Anabol and blastolysin preparations obtained from L. bulgaricus may contain surface structural components of the initial strain with adhesion activity; of these, one is similar in specificity to L. casei adhesin and the other, to L. plantarum adhesin. The antigenic activity of anabol and blastolysin, evaluated in the immunodiffusion test, does not correlate with their capacity for binding the receptors of susceptible bacterial cells, determined in the Lactobacillus-induced hemagglutination inhibition test.