Rapid and Sensitive Pathogen Detection in Serum for Early Sepsis Diagnostics Using an Electrical-Double-Layer Gated Field-Effect Transistor-Based Sensor Array
Authors: Paulose Akhil K , Hou Yueh-Ju , Kalaimani Vishal Mani , Wang Yu-Lin 
Published: September 2023

Sepsis is a major medical inflammatory response to bloodstream infection caused by

pathogens. 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 medical

interventions to prevent large outspread of the infection. Rapid and sensitive detection of

infectious bacteria plays an important role in disease control. However, fast and accurate

diagnosis remains highly challenging for many hospitalized patients. Among various

bacterial diseases, Escherichia coli, (E. coli) a gram-negative bacterium, is the most

frequently and extensively researched and has become a global concern of food safety

problems. Traditional cell culture methods are considered as most accurate method for

bacterial 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, so

eventually the traditional cell culture may take several days to a week for the diagnostic

results. Hence, over several years, different novel methods have been developed, such as

optical methods, electrochemical methods, molecular detection by PCR etc. Even though

several 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, large

turnaround time, expensive instrumentation, and requirement of skilled personnel are some of

the disadvantages of these existing techniques.

FET biosensors have previously been used in different diagnosis areas. Nowadays, several

FET-based biosensors have been developed, which primarily concentrate on improving the

overall sensitivity of FET devices. However, the charge screening effect observed in a

physiological environment, and additional sample processing increase the complexity of the

sensor platform. To overcome this hurdle, an electrical double layer (EDL) gated FET

biosensor 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 coli

O157:H7 strain in blood serum. A single-step surface functionalization strategy was used for

immobilizing receptor probes as ssDNA. The probes were designed and immobilized over a

disposable chip containing a pair of gold electrodes. A handheld reader which consists of an

enhancement mode N-channel MOSFETs was connected to the laptop through a USB port to

measure the sensor signals. Pulsed gate voltage was applied to the input electrode and which

modulated the EDL capacitance and potential change eventually resulting in the drain current

of the MOSFET. The probe was immobilized on the gate electrode and tested with different

concentrations of cDNA spiked in TE buffer. The probe-target binding was observed through

fluorescence change and electrically by measuring the change in drain current. In addition,

surface potential change was also examined by performing KPFM test. Similarly, the BioFET

detections were validated for E. coli O157 variants by spiking with short and long DNA

target sequences simultaneously in serum. The test results confirm selectivity by testing

various non-complementary sequences, which ensures the potential of this BioFET as a

point-of-care sensing device.

Figure 1