Nano-engineered paper-based electrochemical biosensors: Versatile diagnostic tools for biomarker detection

After the COVID-19 pandemic, the demand for highly sensitive, miniaturized, non-destructive sensing of disease biomarkers has received significant attention. Nanomaterial-coated paper-based electrochemical biosensors were utilized to diagnose various disease biomarkers. Nanomaterials have contributed significantly to electrochemical biosensors advancements because they improve biosensing properties such as specificity, sensitivity, robustness, and reproducibility. Moreover, the viability of environmentally friendly paper-based electrochemical biosensors for the highly sensitive detection of target analytes in complicated samples has improved. Paper-based electrode (PE) substrates are desirable for lab-scale and large-scale manufacturing applications because they are inexpensive, do not require microfluidic pumps because electrolyte migration can be achieved through capillary action, can be stacked with reagents for reagent-less applications, and can achieve multiphase detection via origami-based approaches. Therefore, this review considers the properties of functional nanomaterials, such as the active surface area available for interactions, attachment of biorecognition species to the electrode via microporous capillary action, cellulose conductivity, and photochemical functional properties, and electrochemical properties of carbon-based conductive pastes that are widely used to print sensors onto paper substrates. The conclusions can be used to improve PE biosensors for biomedical research. Recent paper-based electrodes modified with different nanomaterials for detecting various biomarkers are discussed.