Cancer is one of the major public health issues in the world. It has become the second leading cause of death, with approximately 75% of cancer deaths transpiring in low- or middle-income countries. It causes a heavy global economic cost estimated at more than a trillion dollars per year. The most common cancers are breast, colon, rectum, prostate, and lung cancers. Many of these cancers can be treated effectively and cured if detected at the primary stage. Nowadays, around 50% of cancers are detected at late stages, leading to serious health complications and death. Early diagnosis of cancer diseases substantially increases the efficient treatment and high chances of survival. Biosensors are one of the potential screening methodologies useful in the early screening of cancer biomarkers. This review summarizes the recent findings about novel cancer biomarkers and their advantages over traditional biomarkers, and novel biosensing and diagnostic methods for them; thus, this review may be helpful in the early recognition and monitoring of treatment response of various human cancers.

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

A straightforward and disposable electrochemical sensor was developed by the direct electrodeposition of silver nanoparticles (AgNPs) on a conducting polymer and an acidfunctionalized carbon nanotube-modified screen-printed carbon electrode (f-CNT/SPCE) for the detection of the antiviral drug valganciclovir (VGC). A scaffold layer of the conducting polymer 2,6-diaminopyridine (p-DAP) was electrodeposited on an f-CNT/ SPCE surface via a potentiodynamic polarization method. Later, homogeneous deposition of AgNPs was carried out on the polymer-modified scaffold layers. The electrode activities related to the concentration of the polymer substrate and the AgNP precursor were systematically optimized. The electrochemical oxidation of VGC by SPCE/f-CNT/p-DAP-AgNPs was investigated by square-wave voltammetry. The modified sensor exhibited an attractive electroanalytical performance toward VGC with high sensitivity (nanomolar range), selectivity (in the presence of uric acid and dopamine), reproducibility, and long-term storage stability. Potential real-world applications of the modified screen-printed sensor were demonstrated using artificial urine/serum and industrial water samples. The straightforward design and attractive analytical performance of the conductive polymer-embedded AgNP -modified screen-printed sensor suggest considerable promise for use of this sensor in the point-of-care screening of antiviral drugs. The sensor strip would also be useful in the screening of antiviral drugs in industrial (quality control) and environmental (industry effluents) applications.