The terahertz (THz) metamaterial biosensor has great potential for label-free and rapid specificity testing. Here, we designed two highly sensitive structures to detect the carcinoembryonic antigen (CEA) of the cancer biomarker in early stages. There was about 29 GHz (500 ng/ml) resonance shift for CEA with an insert grate metamaterial, which was consistent with simulation results. Moreover, the concentration of CEA was gained through the relationship between the cancer marker concentration and frequency shift (Δƒ). Our design and detection methods may provide a potential route for the early warning stages of cancer.
The high electron mobility transistor (HEMT)-based biosensors are highly competitive in the ultimate application of portable and point-of-care testing. Herein, we have demonstrated highly sensitive and real-time detection of cardiac troponin I (cTnI), a biomarker for the diagnosis of acute myocardial infarction (AMI) using AlGaAs/GaAs HEMT-based biosensors. The device has achieved a lower detection limit of 1 pg/ml in the buffer solution and less than 30 s response time, which demonstrated significant promise in the early diagnosis and screening of AMI. In addition, our results are consistent with the enzyme-linked immunosorbent assay according to the AMI patient’s blood test results. Furthermore, by comparing the two HEMT structures, we also calculated the equilibrium dissociation constant (KD) of the cTnI and cTnI antibody and analyzed the sensing mechanism. The results show that this method is very promising for early diagnosis of AMI.
Separative extended-gate AlGaAs/GaAs high electron mobility transistor (HEMT) biosensors based on the capacitance change strategy are proposed and fabricated. The working mechanism underlying this strategy is clearly clarified via examining the capacitance evolution on biorecognition and the capacitance matching issue between the HEMT and the sensing pad. The fabricated biosensors demonstrate a good linear current/voltage response to a label-free prostate-specific antigen (PSA) target over a broad concentration range of 100 fg/ml to 10 ng/ml in both 0.1Â and 1Â phosphate buffered saline solutions. Specifically, the sensitivity variation approaches 8.7% dec À1 at the critical concentration level of 2-8 ng/ml that enters the normal PSA region in the human body. The advantages of high sensitivity, low-cost, and convenience of usage make the proposed HEMT biosensors potential candidates for prostate cancer diagnosis.
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