Universal nanocomposite coating with antifouling and redox capabilities for electrochemical affinity biosensing in complex biological fluids.

Electrochemical affinity biosensors have the potential to facilitate the development of multiplexed point-of-care diagnostics in complex biological fluids. However, their commercial viability has been hindered by challenges such as electrode biofouling and the lack of inherent redox properties. To address this unmet need, we have developed a universal nanocomposite coating which is unique in its ability to not only allow oriented conjugation of the biorecognition element but also specific detection directly in complex biological fluids like serum and urine owing to its built-in antifouling and redox capabilities, thus improving suitability for point of care testing. This multifunctional coating comprises a 3D porous crosslinked bovine serum albumin matrix for oriented conjugation and antifouling properties with embedded graphene nanosheets modified with amino-ferrocene for enhanced conductivity and mediator-free biosensing. The coating showed minimal signal degradation despite prolonged exposure to 1% bovine serum albumin, artificial urine and untreated human serum for up to 30 days. To demonstrate its utility, we fabricated and tested proof-of-concept electrochemical immunosensors for bladder cancer protein biomarkers, specifically interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The practical feasibility was highlighted by the excellent sensitivity and specificity observed for IL-8 and VEGF with a limit of detection of 41 pg mL-1 and 67 pg mL-1, respectively. Consequently, this universal nanocomposite-based electrochemical biosensing platform can be extended to the point of care testing of a broad spectrum of biomarkers present in complex biological fluids, thus enabling reliable and early diagnostics.

Ultrasensitive Strain Sensor Utilizing a AgF-AgNW Hybrid Nanocomposite for Breath Monitoring and Pulmonary Function Analysis.

Breath monitoring and pulmonary function analysis have been the prime focus of wearable smart sensors owing to the COVID-19 outbreak. Currently used lung function meters in hospitals are prone to spread the virus and can result in the transmission of the disease. Herein, we have reported the first-ever wearable patch-type strain sensor for enabling real-time lung function measurements (such as forced volume capacity (FVC) and forced expiratory volume (FEV) along with breath monitoring), which can avoid the spread of the virus. The noninvasive and highly sensitive strain sensor utilizes the synergistic effect of two-dimensional (2D) silver flakes (AgFs) and one-dimensional (1D) silver nanowires (AgNWs), where AgFs create multiple electron transmission paths and AgNWs generate percolation networks in the nanocomposite. The nanocomposite-based strain sensor possesses a high optimized conductivity of 7721 Sm-1 (and a maximum conductivity of 83,836 Sm-1), excellent stretchability (>1000%), and ultrasensitivity (GFs of 35 and 87 when stretched 0-20 and 20-50%, respectively), thus enabling reliable detection of small strains produced by the body during breathing and other motions. The sensor patching site was optimized to accurately discriminate between normal breathing, quick breathing, and deep breathing and analyze numerous pulmonary functions, including the respiratory rate, peak flow, FVC, and FEV. Finally, the observed measurements for different pulmonary functions were compared with a commercial peak flow meter and a spirometer, and a high correlation was observed, which highlights the practical feasibility of continuous respiratory monitoring and pulmonary function analysis.

A review of recent advances in non-enzymatic electrochemical creatinine biosensing.

Creatinine biosensing is a rapidly developing field owing to the clinical relevance of creatinine as a vital biomarker for several diseases associated with renal, thyroidal, and muscular dysfunctions. Over the years, we have observed numerous creatinine biosensing strategies, including the most widely studied enzymatic creatinine biosensors. Though the enzymatic approach provides excellent selectivity and reliability, it has certain drawbacks, which include high fabrication cost and poor storage stability (that is inherent to every enzyme-based biosensors). This has led to the development of non-enzymatic creatinine biosensors, of which electrochemical sensors are the most promising for point-of-care applications. However, only a limited number of studies have been conducted and there is a lack of reviews addressing the recent advances in this research area. Herein, we present for the first time, a review with a prime focus on the various strategies implemented in non-enzymatic electrochemical creatinine biosensing. We aim to offer a comprehensive context on the achievements and limitations of currently available non-enzymatic electrochemical creatinine biosensors and address the underlying factors pertaining to the interplay of modification/fabrication techniques with the sensitivity, selectivity, interferences, and long-term storage stability of the biosensor. We hope that this work shall prove to be seminal in the conception and advancement of future non-enzymatic electrochemical creatinine biosensors.