Metabolites are the intermediatory products of metabolic processes catalyzed by numerous enzymes found inside the cells. Detecting clinically relevant metabolites is important to understand their physiological and biological functions along with the evolving medical diagnostics. Rapid advances in detecting the tiny metabolites such as biomarkers that signify disease hallmarks have an immense need for high-performance identifying techniques. Low concentrations are found in biological fluids because the metabolites are difficult to dissolve in an aqueous medium. Therefore, the selective and sensitive study of metabolites as biomarkers in biological fluids is problematic. The different non-electrochemical and conventional methods need a long time of analysis, long sampling, high maintenance costs, and costly instrumentation. Hence, employing electrochemical techniques in clinical examination could efficiently meet the requirements of fully automated, inexpensive, specific, and quick means of biomarker detection. The electrochemical methods are broadly utilized in several emerging and established technologies, and electrochemical biosensors are employed to detect different metabolites. This review describes the advancement in electrochemical sensors developed for clinically associated human metabolites, including glucose, lactose, uric acid, urea, cholesterol, etc., and gut metabolites such as TMAO, TMA, and indole derivatives. Different sensing techniques are evaluated for their potential to achieve relevant degrees of multiplexing, specificity, and sensitivity limits. Moreover, we have also focused on the opportunities and remaining challenges for integrating the electrochemical sensor into the point-of-care (POC) devices.

The pandemic of COVID-19 and its widespread transmission have made us realize the importance of early, quick diagnostic tests for facilitating effective cure and management. The primary obstacles encountered were accurately distinguishing COVID-19 from other illnesses including the flu, common cold, etc. While the polymerase chain reaction technique is a robust technique for the determination of SARS-CoV-2 in patients of COVID-19, there arises a high demand for affordable, quick, user-friendly, and precise point-of-care (POC) diagnostic in therapeutic settings. The necessity for available tests with rapid outcomes spurred the advancement of POC tests that are characterized by speed, automation, and high precision and accuracy. Paper-based POC devices have gained increasing interest in recent years because of rapid, low-cost detection without requiring external instruments. At present, microfluidic paper-based analysis devices have garnered public attention and accelerated the development of such POCT for efficient multistep assays. In the current review, our focus will be on the fabrication of detection modules for SARS-CoV-2. Here, we have included a discussion on various strategies for the detection of viral moieties. The compilation of these strategies would offer comprehensive insight into the detection of the causative agent preparedness for future pandemics. We also provide a descriptive outline for paper-based diagnostic platforms, involving the determination mechanisms, as well as a commercial kit for COVID-19 as well as their outlook.

Oral squamous cell carcinoma (OSCC) is a commonly known malignant tumor in the maxillofacial and oral region with a poor prognosis. Therefore, in the present letter, we have developed for the first-time screen-printed electrode (SPE) based affordable, simple, and ultrasensitive electrochemical immunosensor using a green synthesized hematite nanoparticles (α-Fe ₂ O ₃ NPs) supported on reduced graphene oxide (rGO) nanocomposite for determination of CYFRA-21-1 cancer biomarker. The α-Fe ₂ O ₃ NPs_rGO composite has been prepared using a green method employing the leaves extract of Cinnamomum tamala . The 3-aminopropyl triethoxysilane (APTES) helped in functionalization of α-Fe2O3NPs_rGO nanocomposite and was drop-casted to the working area of SPE, followed by immobilization with the anti-CYFRA-21-1 antibodies as well as bovine serum albumin (BSA) to form BSA/anti-CYFRA-21-1/APTES/α-Fe ₂ O ₃ NPs_rGO/SPE immunoplatform. The α-Fe ₂ O ₃ NPs_rGO nanocomposite were characterized utilizing the fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential pulse voltammetry (DPV) as well as cyclic voltammetry (CV) for investigating the crystal structure, as well as electrochemical properties. The developed immunosensor depicted remarkable electrochemical properties having broad linearity (0.5-20 ng/mL), limit of quantification (LOQ) of 0.048 ng/mL, low detection limit of 0.014 ng/mL, and high sensitivity of 90.42 μA (log (ng/mL) ^-1 cm ^-2 . In addition, it showed high reproducibility and good selectivity towards the CYFRA-21-1 biomarker. Thus, this letter unlocks innovative prospects for exploring the electrochemical behavior of green synthesized α-Fe ₂ O ₃ NPs_rGO and its efficacy for fabricating electrochemical biosensors as well as point of care (POC) sensing devices.