ACS Sensors最新文献

Adenosine 5′-triphosphate (ATP) plays an essential role in regulating many metabolic activities. Therefore, developing tools to directly measure ATP in real time will help us understand its underlying functions. Here, we report an optimized genetically encoded ATP sensor (OAS1.0) with a high specificity for ATP detection. OAS1.0 can be genetically targeted to specific cell types and subcellular compartments to monitor ATP production and consumption. We also used OAS1.0 to visualize metabolic-activity-dependent changes in ATP in normal and tumor cell lines and ATP consumption during the virus–host interaction process. OAS1.0 also worked well with a Ca²⁺ sensor to concurrently monitor ATP and Ca²⁺ dynamics in living cells. Thus, OAS1.0 represents a promising tool for ATP imaging under both physiological and pathophysiological conditions.

In this study, we report on the fabrication and evaluation of gas sensing performance for 3 × 3 graphene pixel array sensors coated with polymers of intrinsic microporosity (PIM-1 and PIM-EA-TB) and Matrimid, a commercial polyimide, for the detection of nitrogen dioxide (NO₂). The polymer films, with thicknesses of only 9–11 nm, significantly enhanced the gas sensing performance, demonstrating responses as high as −25.7% compared to a bare graphene response of −10.8%. The gas sensing performance was evaluated in real-time by exposing the sensors to NO₂ concentrations from 1 to 50 ppm, along with selectivity tests using ammonia (NH₃), nitric oxide (NO), methane (CH₄), and carbon dioxide (CO₂). In addition to their high sensitivity, the sensors exhibited reduced response times by 56 s. They also demonstrated high selectivity for NO₂, with minimal cross-sensitivity to other gases. Furthermore, the polymer membranes exhibited rapid recovery times (114–153 s) and limits of detection in the low parts per billion range, with PIM-EA-TB achieving a detection limit of 0.7 ppb. These features highlight their potential as promising candidates for real-time environmental monitoring of toxic gases, showcasing the potential use of PIMs to enhance the sensitivity and selectivity of graphene-based gas sensors and providing a foundation for further development of cost-effective and reliable NO₂ detection systems.

Cysteine cathepsins are important proteases that are highly upregulated in cancers and other diseases. While their reported location is mostly endolysosomal, some evidence shows their nuclear localization and involvement in the cell cycle. We aim to generate tools to investigate the involvement of cathepsins in the cell cycle progression. To investigate nuclear cathepsin activity, we designed nucleus-directed quenched activity-based probes (qABPs) by attaching cell-penetrating peptides (CPPs). qABPs are active-site-directed compounds that enable direct real-time monitoring of enzyme activity by the covalent linkage between the probe and the enzyme’s active site. Biochemical evaluation of the CPP-qABPs showed potent and selective probes; cell fractionation, multimodal flow cytometry-imaging, and time-lapse movies demonstrated nuclear cathepsin activity in living cells. Interestingly, these probes reveal a spatiotemporal pattern, a surge of nuclear cathepsin just before mitosis, suggesting yet unrevealed roles of cathepsin in cell division. In summary, these nuclear-directed qABPs serve as unique scientific tools to unlock the hidden features of cysteine proteases and to understand their involvement in cell division and cancer.

Near-infrared (NIR)-to-NIR upconversion nanoparticles (UCNPs) are promising materials for biomedical imaging and sensing applications. However, UCNPs with long lifetimes continue to face the limitation that they are usually accompanied by weak luminescence intensity, resulting in difficulties in achieving high-resolution and sensitive time-gated imaging. To overcome this limitation, we have developed NIR long-lifetime luminescent nanoparticles (NLL NPs) with strong 800 nm emission by adding a photosensitizing shell and with a prolonged lifetime by lowering the activator concentration. NLL NP-based time-gated imaging overcomes the inherent limitations of steady-state imaging by providing higher signal-to-noise ratios and more robust signal intensities. When integrated into a lateral flow immunoassay (LFA) for the detection of avian influenza viruses, NLL NP-based time-gated imaging demonstrates a 32-fold lower limit of detection compared to conventional optimal 800 nm emitting nanoparticles. Furthermore, the high accuracy of the NLL NP-based LFA is confirmed through clinical validations using 65 samples, achieving a sensitivity and specificity of 100% and an area under the curve of 1.000. These results demonstrate the potential of NLL NP-based time-gated imaging as a powerful tool for the highly sensitive and accurate detection of avian influenza viruses in complex clinical samples.