Developing Field Effect Transistor Sensors Based on DNA Probes to Detect Staphylococcus Lugdunensis Bacteria

Abstract

The goal of this research is to work with an Electrical Double Layer (EDL)-gated Field Effect Transistor (FET) to detect the bacteria Staphylococcus lugdunensis, which can cause a variety of illnesses, including infections of the skin and soft tissues. In rare cases, Staphylococcus lugdunensis can be successfully identified using the combination of a positive catalase test, a negative tube coagulase test, a positive PYR test, and a positive ornithine decarboxylase test. We are employing an Electrical DoubleLayer (EDL)-gated Field Effect Transistor (FET) to speed up the procedure because this test is time consuming and requires a highly competent individual to perform. An ssDNA probe was developed, and effectively immobilized on a gold surface electrode sensor with a square surface, and due to hybridization with the cDNA at different concentrations, electrical signals were generated in the form of current.Our sensor was fabricated using photolithography where the gold electrode surface having 500 μm x 500 μm gate sensing area consisting of each individually addressable sensor arranged in a 1 x 8 array which is the extent gate was expose for immobilization purpose. The sensor was then subjectedto O2 plasma & HCl solution for surface cleaning and fluorescence image of baregold were taken Figure1(b).The Single-Stranded DNA comprising of fluorescent dye (FAM) at 3’ and thiol modifier at 5’ was drop-casted on the gold surface and was incubated for 24 hours at 24°C. After, it went through a washing process in order to remove the unbound ssDNA and fluorescence images were taken. We observed that intensity was higher than that of baregold which indicates that our probe has successfully immobilized on the gold surface Figure 1(b).Figure 1(a) represents the device that we designed. The system works with N-Channel Enhancement-Mode DMOS FET (VN10LP) in which a continuous drain voltage (3.5 V) was applied and the drain current which is the signal, were measured at two distinct gate bias voltage (2V and 3V). cDNA having quencher (BHQ1) at 5’ was diluted in different concentration namely 1fM, 10fM, 100fM and 1000fM. These cDNA with different concentrations were drop-casted on our sensor with Tris-EDTA (TE) buffer as the baseline and starting with lower concentration to higher concentration every after 12 seconds periodically where we record the change in signal as shown in Figure 1(c).After the electrical measurement, fluorescence image was taken and we can observe that it quenched which indicates that the cDNA and the immobilized ssDNA has successfully hybridized which give the signal change. Figure 1: (a) Surface Immobilization Principal Display in Extended Gate EDL BioFETs. (b)Fluorescence value comparison. (c) Plot showing the change in drain current over time for aptamersensors exposed to various cDNA concentrations. Figure 1