Adopting Back Reduction Current as an Additional Output Signal for Achieving Photoelectrochemical Differentiated Detection

An immunosensor for the near real-time and site of inflammation detections of multiple proinflammatory cytokines

Diseases mediated by cytokine storms are often characterized by an overexuberant pace of pathogenesis accompanied by significant morbidity and mortality. Thus, near real-time (NRT) detections via a site-of-inflammation (SOI) sampling of proinflammatory cytokines are essential to ensure a timely and effective treatment of acute inflammations, which up to now, has not been fully possible. In this work, we proposed a novel NRT and SOI immunosensor using ZIF-8 signal amplification together with an off-on strategy. To achieve NRT detections via a SOI sampling, the body fluid of choice is the dermal interstitial fluid (ISF). The significant merits of ISF over blood are the quality, quantity and diversity of ISF-based biomarkers; the fluid is non-coagulating, making it feasible to perform multiple or continuous samplings and the sampling is minimally invasive. Our immunosensor requires only 5 μL of ISF to achieve a simultaneous detection of five highly potent proinflammatory cytokines: IL-6, IFN-γ, IL-1β, TNF-α, IP-10. We employed a microneedle array patch (MAP) together with a trifurcated nozzle pump to extract a mean volume of between 30 and 60 μL of ISF in 20 min. Under optimal conditions, the biosensor is capable of high-quality performance that exhibits a lower limit of detection (LOD) of 5.761 pg/mL over a wide linear range of 5.761-3 ‒ 20.00 ng/mL. We believe our immunosensor for NRT detections via a SOI sampling of ISF-biomarkers offers new theranostic opportunities that may not be possible with blood-based biomarkers.

Carbon Nitride-Based Heterojunction Photoelectrodes with Modulable Charge-Transfer Pathways toward Selective Biosensing

Photoelectrochemical (PEC) sensing enables the rapid, accurate, and highly sensitive detection of biologically important chemicals. However, achieving high selectivity without external biological elements remains a challenge because the PEC reactions inherently have poor selectivity. Herein, we report a strategy to address this problem by regulating the charge-transfer pathways using polymeric carbon nitride (pCN)-based heterojunction photoelectrodes. Interestingly, because of redox reactions at different semiconductor/electrolyte interfaces with specific charge-transfer pathways, each analyte demonstrated a unique combination of photocurrent-change polarity. Based on this principle, a pCN-based PEC sensor for the highly selective sensing of ascorbic acid in serum against typical interferences, such as dopamine, glutathione, epinephrine, and citric acid was successfully developed. This study sheds light on a general PEC sensing strategy with high selectivity without biorecognition units by engineering charge-transfer pathways in heterojunctions on photoelectrodes.

Molecular Imprinted Poly(2,5-benzimidazole)-Modified VO2-CuWO4 Homotype Heterojunction for Photoelectrochemical Dopamine Sensing

A photoactive molecularly imprinted poly(2,5-benzimidazole)-modified vanadium dioxide-cupric tungstate (VO₂-CuWO₄) as an efficient photosensitive n-n type-II heterojunction thin film was electrochemically deposited on Ti substrate for the selective and robust photoelectrochemical (PEC) bioanalysis of dopamine (DA). The optical absorption of n-VO₂/n-CuWO₄ type-II heterojunction was capably broadened toward the visible region, which permitted superior light-harvesting and robust carriers generation, separation, and transfer processes significantly enhancing the anodic photocurrent, as confirmed by a series of PEC analyses. Findings revealed that the as-prepared label-free MIP-PEC sensor can quantitatively monitor DA in a linear range of 1 nM to 200 μM with a detection limit of 0.15 nM. This MIP-PEC sensor showed robust selectivity under conditions with high concentrations of interfering substances, which can be recovered in the real samples of urine, cocoa chocolate, and diluted yogurt, indicating its promising potential applications in biological and food samples. This work not only featured the use of photoelectrically active MIP/VO₂-CuWO₄ for PEC detection of DA, but also provided a new horizon for the design and implementation of functional polymers/metal oxides heterojunction materials in the field of PEC sensors and biosensors.