Wearable Sensing Systems for Monitoring Mental Health.

Wearable systems for monitoring biological signals have opened the door to personalized healthcare and have advanced a great deal over the past decade with the development of flexible electronics, efficient energy storage, wireless data transmission, and information processing technologies. As there are cumulative understanding of mechanisms underlying the mental processes and increasing desire for lifetime mental wellbeing, various wearable sensors have been devised to monitor the mental status from physiological activities, physical movements, and biochemical profiles in body fluids. This review summarizes the recent progress in wearable healthcare monitoring systems that can be utilized in mental healthcare, especially focusing on the biochemical sensors (i.e., biomarkers associated with mental status, sensing modalities, and device materials) and discussing their promises and challenges.

Highly enhanced Hg2+ detection using optimized DNA and a double coffee ring effect-based SERS map.

Hg2+ is a highly toxic heavy metal ion that poses serious risks to human health and the environment. Due to its tendency to accumulate, it can easily enter the human body through the food chain, making it crucial to develop detection sensors that mimic real environmental conditions. To achieve this, our study employed a surface-enhanced Raman scattering (SERS) sensor using two strategies. First, we designed a highly selective probe by optimizing the probe and reporter DNA strands to bind Hg2+ within a thymine-thymine mismatch. Second, we used the double coffee ring effect to concentrate the optimized probe DNA. These two strategies greatly enhanced the SERS signal, resulting in a sensor with exceptional sensitivity, a low detection limit of 208.71 fM, and superior selectivity for Hg2+. The practical application of the sensor was demonstrated by successfully detecting Hg2+ in drinking water, tap water, canned tuna, and tuna sashimi. Additionally, the experimental results were presented in a pizza-shaped SERS mapping image, allowing users to estimate Hg2+ concentrations through color, providing a user-friendly and intuitive method for data comprehension and analysis. Our study presents a promising approach for sensitive and reliable Hg2+ detection, with potential implications for environmental monitoring and food safety.

Asterias forbesi-Inspired SERS Substrates for Wide-Range Detection of Uric Acid.

Uric acid (UA), the final metabolite of purine, is primarily excreted through urine to maintain an appropriate concentration in the bloodstream. However, any malfunction in this process can lead to complications due to either deficiency or excess amount of UA. Hence, the development of a sensor platform with a wide-range detection is crucial. To realize this, we fabricated a surface-enhanced Raman spectroscopy (SERS) substrate inspired by a type of starfish with numerous protrusions, Asterias forbesi. The Asterias forbesi-inspired SERS (AF-SERS) substrate utilized an Au@Ag nanostructure and gold nanoparticles to mimic the leg and protrusion morphology of the starfish. This substrate exhibited excellent Raman performance due to numerous hotspots, demonstrating outstanding stability, reproducibility, and repeatability. In laboratory settings, we successfully detected UA down to a concentration of 1.16 nM (limit of detection) and demonstrated selectivity against various metabolites. In the experiments designed for real-world application, the AF-SERS substrate detected a broad range of UA concentrations, covering deficiencies and excesses, in both serum and urine samples. These results underscore the potential of the developed AF-SERS substrate as a practical detection platform for UA in real-world applications.

Revealing Redox Behavior of Molybdenum Disulfide and Its Application as Rechargeable Antioxidant Reservoir.

Molybdenum disulfide (MoS2) is a representative two-dimensional transition metal dichalcogenide and has a unique electronic structure and associated physicochemical properties. The redox property of MoS2 has recently attracted significant attention from various fields, such as biomedical applications. Intriguingly, MoS2 functions as an antioxidant in certain applications and as a pro-oxidant in others. We use the mediated electrochemical probing method to understand the redox behavior of MoS2. This method reveals that MoS2 (i) has a reversible and fast redox activity at a mild potential (between -0.20 and +0.25 V vs Ag/AgCl), (ii) functions as an antioxidant for molecules that have different redox mechanisms (electron or hydrogen atom transfer), and (iii) is electrochemically or molecularly rechargeable. Finally, we show that MoS2 reduces oxidized molecules more efficiently than the potent natural antioxidant, curcumin. This study enhances our understanding of MoS2 and shows its potential as an advanced antioxidant reservoir.