Abstract
Invasive pulmonary aspergillosis (IPA) is a dangerous fungal infection. At the initial stages, IPA has no characteristic clinical manifestations, therefore its early diagnosis is an essential problem. The important markers that allow fungal infection diagnostics are galactomannan (GM) and β-D-glucans (BDG), polysaccharide antigens that exists mainly in the cell wall of Aspergillus fungi. Currently, the main method for GM and BDG determination in biological fluids is enzyme-linked immunosorbent assay (ELISA) . The analysis can be carried out only under laboratory conditions since it requires the use of washers and large fluid flow. The development of biosensors opens new horizons in biomarker detection. Electrolyte-gated organic field-effect transistors (EGOFET) are a promising platform for ultrasensitive, fast and reliable detection of biological molecules by low cost, point-of-care electronic sensors . We used previously developed method of functionalization of the C8-BTBT/PS EGOFET surface with biotin receptors . The biosensor principle is based on biotin-streptavidin interaction on the EGOFET platform and it is well-proven for different analytes . The recognition elements in the sensor architecture are biotinylated oligosaccharides (GM and BDG), that form the biotin-streptavidin based sandwich on EGOFET surface, and specifically bind the monoclonal antibodies (7B8, 5H5 and 1D2). However, the EGOFET recognition layer composition was earlier optimized for influenza A virus detection, here the biorecognition surface was adapted. The 20% BTBT-biotin containing recognition layer provides the better accuracy of antibody detection. In order to improve the formation of recognition layer new BTBT-biotin compound designed and synthesized, containing ethoxy-groups in large spacer towards biotin fragment. Such chemical composition of functional compound provides better organization of the thin monolayer film of BTBT-dimer and BTBT-biotin (recognition layer similar to described in [3]) due to more hydrophilic fragment, connected to biotin in BTBT-biotin. The most relevant region of antibody concentration determination is below 50 ng/mL – in order to detect the disease IPA at the earliest stages. Here the region 1.69-50 ng/mL was investigated. The detection limits of 7B8, 5H5 and 1D2 by the corresponding oligosaccharides are equal 4 ng/mL.