New biorecognition molecules in biosensors for the detection of toxins.

Biological and synthetic recognition elements are at the heart of the majority of modern bioreceptor assays. Traditionally, enzymes and antibodies have been integrated in the biosensor designs as a popular choice for the detection of toxin molecules. But since 1970s, alternative biological and synthetic binders have been emerged as a promising alternative to conventional biorecognition elements in detection systems for laboratory and field-based applications.

Microfabricated biosensor for the simultaneous amperometric and luminescence detection and monitoring of Ochratoxin A.

The low molecular weight hapten, Ochratoxin A (OTA), is a natural carcinogenic mycotoxin produced by Aspergillus and Penicillium fungi and so it commonly appears in wines, other foods, and in the environment. An amperometric biosensor has been developed that uses the immobilized synthetic peptide, NFO4; which possesses a high binding affinity and thus provides for molecular recognition of OTA; simulating the mycotoxin-specific antibody. Biotransducers were produced from a microlithographically fabricated electrochemical cell-on-a-chip that uses the microdisc electrode array working electrode format augmented with microporous graphitized carbon (MGC) that was electrodeposited within a poly(aniline-co-meta-aminoaniline) electroconductive polymer layer.

Sorption of his-tagged Protein G and Protein G onto chitosan/divalent metal ion sorbent used for detection of microcystin-LR.

A highly sensitive, specific, simple, and rapid chemiluminescence enzyme immunoassay (CLEIA) was developed for the determination of microcystin-LR (MC-LR) by using strategies for oriented immobilization of functionally intact polyclonal antibodies on chitosan surface. Several physicochemical parameters such as metal ion adsorption, hexahistidine-tagged Protein G sorption, the dilution ratio polyclonal antibody concentration, and peroxidase-labeled MC-LR concentration were studied and optimized. The sorption in batch system of G-histidine and G-proteins was studied on a novel sorbent consisting of chitosan/divalent metal ions.

Sensing of barrier tissue disruption with an organic electrochemical transistor.

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the passage of necessary ions and molecules. A breach in this barrier can be caused by a reduction in the extracellular calcium concentration. This reduction in calcium concentration causes a conformational change in proteins involved in the sealing of the barrier, leading to an increase of the paracellular flux.

Dynamic monitoring of Salmonella typhimurium infection of polarized epithelia using organic transistors.

Ion flow across polarized epithelia is a tightly regulated process. Measurement of the transepithelial resistance is a highly relevant parameter for assessing the function or health of the tissue. Dynamic, electrical measurements of transepithelial ion flow are preferred as they provide the most accurate snapshot of effects of external stimuli.

Validation of the organic electrochemical transistor for in vitro toxicology.

Background: The gastrointestinal epithelium provides a physical and biochemical barrier to the passage of ions and small molecules; however this barrier may be breached by pathogens and toxins. The effect of individual pathogens/toxins on the intestinal epithelium has been well characterized: they disrupt barrier tissue in a variety of ways, such as by targeting tight junction proteins, or other elements of the junctions between adjacent cells. A variety of methods have been used to characterize disruption in barrier tissue, such as immunofluorescence, permeability assays and electrical measurements of epithelia resistance, but these methods remain time consuming, costly and ill-suited to diagnostics or high throughput toxicology.

Measurement of barrier tissue integrity with an organic electrochemical transistor.

The integration of an organic electrochemical transistor with human barrier tissue cells provides a novel method for assessing toxicology of compounds in vitro. Minute variations in paracellular ionic flux induced by toxic compounds are measured in real time, with unprecedented temporal resolution and extreme sensitivity.