Rapid and Sensitive Pathogen Detection in Serum for Early Sepsis Diagnostics Using an Electrical-Double-Layer Gated Field-Effect Transistor-Based Sensor Array

Abstract

Sepsis is a major medical inflammatory response to bloodstream infection caused bypathogens. Over 30 million infections occur due to sepsis in a year throughout the globe.With over 6 million deaths, sepsis treatment demands timely diagnosis and medicalinterventions to prevent large outspread of the infection. Rapid and sensitive detection ofinfectious bacteria plays an important role in disease control. However, fast and accuratediagnosis remains highly challenging for many hospitalized patients. Among variousbacterial diseases, Escherichia coli, (E. coli) a gram-negative bacterium, is the mostfrequently and extensively researched and has become a global concern of food safetyproblems. Traditional cell culture methods are considered as most accurate method forbacterial diagnosis. But some microorganisms like Bartonella spp, Treponema pallidum, etc.are difficult to grow on a culture plate, while some other virus species are unculturable, soeventually the traditional cell culture may take several days to a week for the diagnosticresults. Hence, over several years, different novel methods have been developed, such asoptical methods, electrochemical methods, molecular detection by PCR etc. Even thoughseveral techniques exist, concerns have been raised regarding their sensitivity, specificity etc.In addition, various fluorescence-based methods, and Surface Plasmon resonance (SPR)-based sensors have also been reported for bacterial detection. However, high cost, largeturnaround time, expensive instrumentation, and requirement of skilled personnel are some ofthe disadvantages of these existing techniques.FET biosensors have previously been used in different diagnosis areas. Nowadays, severalFET-based biosensors have been developed, which primarily concentrate on improving theoverall sensitivity of FET devices. However, the charge screening effect observed in aphysiological environment, and additional sample processing increase the complexity of thesensor platform. To overcome this hurdle, an electrical double layer (EDL) gated FETbiosensor has been proposed and explored in the detection of a variety of biological entities.Here, we proposed an EDL-FET sensor platform for the detection of Escherichia coliO157:H7 strain in blood serum. A single-step surface functionalization strategy was used forimmobilizing receptor probes as ssDNA. The probes were designed and immobilized over adisposable chip containing a pair of gold electrodes. A handheld reader which consists of anenhancement mode N-channel MOSFETs was connected to the laptop through a USB port tomeasure the sensor signals. Pulsed gate voltage was applied to the input electrode and whichmodulated the EDL capacitance and potential change eventually resulting in the drain currentof the MOSFET. The probe was immobilized on the gate electrode and tested with differentconcentrations of cDNA spiked in TE buffer. The probe-target binding was observed throughfluorescence change and electrically by measuring the change in drain current. In addition,surface potential change was also examined by performing KPFM test. Similarly, the BioFETdetections were validated for E. coli O157 variants by spiking with short and long DNAtarget sequences simultaneously in serum. The test results confirm selectivity by testingvarious non-complementary sequences, which ensures the potential of this BioFET as apoint-of-care sensing device. Figure 1