Development of a portable, high throughput biosensor system for rapid plant virus detection.

Biosensors based on living cells are characterized by high sensitivity, selectivity and rapid response times. A novel portable cell biosensor system for the detection of plant viruses, based on immobilized 'Vero' cells carrying on their membrane virus specific antibodies was developed and was designated as High Throughput Bioelectric Recognition Assay (BERA-HTP). BERA-HTP was tested for the detection of purified Potato virus Y (PVY), Cucumber mosaic virus (CMV) and Tobacco rattle virus (TRV) and of CMV and TRV in single, as well as in mixed infections in two different plant host species. The sensor was based on live, mammalian cells, the membrane of which has been artificially saturated with antibodies specific to different plant viruses. The attachment of PVY, CMV or TRV viral particles to the homologous electroinserted antibodies caused a virus-specific change of the cell membrane electric potential that was not observed with virus-free samples or with heterologous viruses. Fluorescence microscopy observations showed that attachment of virus particles to the cell membrane bearing the homologous antibody, was associated with a decrease of [Ca(2+)]cyt. The perspective for the development of BERA-HTP as a portable, reliable and rapid (duration of assay for 96 samples: ∼70 min) detection method of plant viruses in the field is discussed.

Evaluation of the antioxidants activities of four Slovene medicinal plant species by traditional and novel biosensory assays.

We investigated the antioxidant activity of methanolic and water extracts of Slovene accessions of four medicinal plant species (Salvia officinalis, Achillea millefolium, Origanum vulgare subsp. vulgare and Gentiana lutea). Their free radical-scavenging activity against the DPPH. free radical was studied with a spectrophotometric assay, while their biological activity with the help of a laboratory-made biosensor based on immobilized fibroblast cells (assay duration: 3 min). The observed antioxidant activity of the extracts from the four investigated medicinal plant species was dependent on both the solvent used for extraction and the assay method (conventional or biosensor-based). Independently from the assay method and the solvent used for extraction, the lowest scavenging activity was observed in root extracts of G. lutea. Treatment of the immobilized cells with the plant extracts resulted in an increase of the cell membrane potential (membrane hyperpolarization), possibly due to the reduction of membrane damage due to oxidation. The novel cell biosensor could be utilized as a rapid, high throughput tool for screening the antioxidant properties of plant-derived compounds.