Globally, heavy metal ion (HMI) contamination is on the rise, posing an ever-increasing risk to ecological and human health. In recent years, great research effort has been devoted to the sensitive detection and quantitative analysis of HMIs. Low cost, sensitive, selective, and rapid methods for HMI detection are of growing demand, and HMI biosensors have great potential in meeting this need due to their timeliness, cost-effectiveness and convenience in operation. Glutathione is known for its strong ability to bind with toxic heavy metal ions, in addition to its water solubility, stable activity and ready availability. As a result, glutathione is becoming a molecular probe of choice in the preparation of sensors for sensitive, affordable, and accessible HMI detection. This review summarizes the results from various glutathione-based HMI detection strategies reported in recent years, which are categorized according to their signal transduction methods. Their operation and implementation, along with figures of merit such as limit of detection, selectivity, and response time, are discussed and compared. Based on the review, both individual HMI detection and simultaneous detection of multiple HMIs can be realized under specific reaction conditions, showing the great potential of glutathione-based detection to realize various types of practical HMI detection.

Due to the friendly temperature for virus survival, SARS-CoV-2 is frequently found in cold-chain foods, posing a serious threat to public health. Utilizing an interdigitated microelectrode chip modified with an antibody probe and integrating dielectrophoresis enrichment with interfacial capacitance sensing, a strategy is presented for the detection of trace level spike-protein from SARS-CoV-2. It achieves a limit of detection as low as 2.29 × 10⁻⁶ ng/mL in 20 s, with a wide linear range of 10⁻⁵–10⁻¹ ng/mL and a selectivity of 234:1. The cost for a single test can be controlled to ~1 dollar. This strategy provides a competitive solution for real-time, sensitive, selective, and large-scale application in cold-chain food quarantine.

Nano/Pico farad scale AC micro-capacitance as an electronic signal has advantages on sensitivity and resolution for high-precision biosensors, while its compact test system for wearable applications has not been commercially available. A precise test system for micro-capacitance detection is designed and realized by combining direct digital synthesizer with impedance spectrum method. The system is of high integration, high portability, low cost, and can achieve data transmission with mobile terminals via wireless controlling. It has continuously variable frequency and amplitude modulations of 0~100 kHz and 0~1.98 V, respectively. A wide range of 0~100 nF and a precision as low as 1 pF are realized simultaneously. Combining a sweat collection patch and a capacitive biosensor, this system is employed for hepatitis B surface antibody detection in sweat, with the target concentration in the range of 10^-12~10^-16 g/mL, and a detection limit of 5.905×10^-17 g/mL. The application case verifies the system function with high precision, high reliability, stable data communication, as well as excellent field operability. This system provides an executable solution for constructing smart wearable platforms for point-of-care biosensing based on micocapacitance detection.