Jun Kameoka

This study examines the use of uric acid (UA), a naturally occurring redox‐active molecule, as a reporter for aptamer‐mediated electrochemical signal transduction. Five graphite‐sheet electrode configurations were compared, with the multiwalled carbon nanotube/carbon paste‐modified graphite sheet electrode (MWCNT/CP/GSE) providing the strongest overall UA response. The measured linear UA range was 50–1000 μM, with a blank‐derived limit of detection of 0.26 μM and a calculated limit of quantification of 0.87 μM. Standard‐redox‐probe cyclic voltammetry (CV) and electrochemical impedance spectroscopy, together with a nanotube‐free CV‐treatment control, provided complementary evidence for changes caused by the modification sequence. Four consecutive UA measurements on the same MWCNT/CP/GSE electrode showed no progressive current loss, while the interdevice relative standard deviation was 9.2% across three independently fabricated electrodes. Using the T5 testosterone‐binding aptamer, the UA oxidation current decreased over the tested 100–700 nM testosterone interval. Additional cortisol, estradiol, and progesterone time‐course controls showed no comparable progressive attenuation under the tested conditions. At 400 nM testosterone, mean peak‐current retention was 78.83%–82.34% across 50, 100, and 200 μM UA backgrounds. These results support UA‐mediated signal transduction in a controlled model system and show normalized responses of similar magnitude across the tested UA backgrounds. The present study establishes a proof of concept in buffer; physiological testosterone sensitivity and quantitative performance in sweat remain to be established.

We developed an integrated device for plasma separation from whole blood and label-free protein detection using endogenous uric acid oxidation. Protein binding suppresses the uric acid oxidation current.

The advancement of wearable and point-of-care (POC) biosensing technologies has driven a growing demand for microfluidic substrates that are flexible, hydrophilic, and compatible with electrochemical sensing. In this study, a lyocell-based thread microfluidic platform was developed to overcome limitations of conventional microfluidic systems. The device employs polypropylene (PP) mesh as a structural substrate and is coupled with a modal absorption pad to sustain consistent and continuous liquid transport. Lyocell's inherent capillary-driven wicking, superior hydrophilicity, semicrystalline microstructure, and high wet modulus collectively provide excellent liquid transport efficiency, structural stability under wet conditions, and bubble-free flow. Experimental analysis revealed that unmodified lyocell achieved liquid transport velocities comparable to plasma-treated cotton, confirming its intrinsic capillary efficiency. When integrated with a microneedle-based electrochemical sensor, the device demonstrated rapid analyte delivery and stable signal generation for both ferrocyanide and lactate detection. The thread-integrated lactate sensor exhibited a strong log-linear correlation, with limits of detection (LoD) of 0.433 mM using chronoamperometry (CA) and 0.51 mM using differential pulse voltammetry (DPV). Human saliva testing was also conducted using saliva samples, and the results were compared with blood lactate concentrations. A strong correlation was observed between salivary and blood lactate levels (R = 0.94). Overall, the lyocell–modal hybrid microfluidic platform provides a sustainable, low-cost, and scalable strategy for electrochemical point-of-care testing (POCT), offering a promising route toward next-generation lab-on-fabric systems.

This review explores smart catheters as an emerging class of medical devices that combine embedded sensors, robotics, and communication systems with increasing functionality and complexity to enable real‐time health monitoring, diagnostics, and treatment. Evolving from traditional catheters used as drains or entry ports, smart systems are now able to track blood pressure, temperature, biochemical signals, and mechanical forces within the body with a high degree of accuracy. Advances in materials, wireless communication, and robotic navigation have helped reduce common risks like infection and catheter blockage while also improving precision catheter placement for minimally invasive procedures. This review highlights recent developments across a variety of different types of smart catheters, ranging from sensing and imaging tools to therapeutic and multimodal systems. Additionally, it discusses the challenges that remain, including biocompatibility, long‐term performance, and clinical translation. The incorporation of new capabilities is changing how catheters are used, and these new uses promise to enable more personalized and responsive healthcare.

This paper reports on the development of a wearable biosensor for high-sensitivity uric acid detection, utilizing graphite ink and multi-walled carbon nanotubes (GP/MWCNT). This microneedle biosensor achieves high sensitivity (1200 μAcm ^- ²mM ^-1 ) and a broad linear detection range (0–1500 μM), thereby covering both healthy individuals and gout patients. An exceptionally low detection limit was achieved, with 0.053 μM measured by DPV and 18.34 μM measured by continuous amperometry using a microfluidic system. This microneedle biosensor’s structure incorporates three medical-grade ultrafine stainless-steel needles designated as the reference electrode (RE), counter electrode (CE), and working electrode (WE), ensuring safe skin penetration and biocompatibility. Selectivity studies in a microfluidic system have shown that common interfering substances such as glucose do not affect the biosensor’s response, enhancing the specificity of uric acid detection. During the development process, MWCNTs were electrochemically deposited onto a layer of graphite ink formed on the ultrafine stainless-steel needles. This technique ensures a robust and stable microneedle-type biosensor that minimizes manufacturing processes and is unaffected by external disturbances such as friction. While carbon ink has been commonly used in uric acid detection sensors, this study found that graphite ink with MWCNTs on the electrodes significantly enhances the sensitivity for uric acid. This improvement is believed to be due to the smooth electron transfer through the multiple layered structures at the working electrode. This discovery and the high detection capability have the potential to enhance the performance of biosensors in medical fields where accurate monitoring of uric acid levels is crucial.

Multianalyte biosensors have been of interest in various applications, especially in healthcare areas that target a broad range of biomarkers related to various pathological diseases. However, successful examples of such sensors generally utilize electrochemical transducers, a fact which limits their use as implants due to the presence of interferents in vivo, the difficulty of transdermal signal transduction, and the difficulty of miniaturizing the electronics into an integrated biocompatible form factor suitable for implantation. In this study, we demonstrate an attractive alternative for multiplexed sensing platform based on oxidoreductase enzymes coupled with optically distinct oxygen-sensitive metalloporphyrin phosphors which are immobilized within nanofilm-coated alginate microparticles; these are embedded in discrete compartments of a single miniature biocompatible hydrogel to achieve a “barcode” sensor device. Continuous multiplex oxygen and glucose monitoring were demonstrated through the measurement of phosphorescence lifetime changes of the metalloporphyrin phosphors when exposed to different environmental conditions. The phosphorescence lifetime exhibited a negative correlation with increases in oxygen concentration for all compartments. In contrast, the oxygen-responsive assays maintained a constant phosphorescence lifetime and the glucose-responsive assays showed increased phosphorescence lifetime when the glucose concentration increased from 0 to 400 mg/dL. This observation confirmed the desired behavior without any apparent crosstalk between the adjacent oxygen- and glucose-responsive compartments. Furthermore, the sensors demonstrated high stability during repeated glucose challenges over 10 cycles. These findings suggest that the hydrogel barcode optical sensing platform has potential for use in various situations requiring multiplexed chemical analysis such as in continuous medical monitoring.

This study investigated carbon-based electrode materials for the application of wearable biosensors measuring uric acid concentration

Serotonin plays a crucial role in regulating a broad range of physiological and psychological functions, and an imbalance in serotonin levels can trigger the pathogenesis of various diseases. Thus, monitoring serotonin levels is vital for the early detection of multiple diseases. We have developed a cost-effective and efficient wearable biosensor using graphite and carbon nanotube as working electrode materials for detecting low concentrations of serotonin solutions. The graphite electrode modified with MWCNT(multi-walled carbon nanotube) exhibited excellent electrochemical sensing performance in serotonin detection, compared to commonly used carbon paste(CP) electrodes coated with MWCNT. Quantitative detection of serotonin with the GSE/GI/MWCNT(graphite sheet electrode/graphite ink/MWCNT) is performed using Differential Pulse Voltammetry, and a linear range of 100nM-900nM with a minimum detection limit of 45nM was achieved.

The coronavirus disease (COVID-19) pandemic has increased pressure to develop low-cost, compact, user-friendly, and ubiquitous virus sensors for monitoring infection outbreaks in communities and preventing economic damage resulting from city lockdowns. As proof of concept, we developed a wearable paper-based virus sensor based on a molecular imprinting technique, using a conductive polyaniline (PANI) polymer to detect the lentivirus as a test sample. This sensor detected the lentivirus with a 4181 TU/mL detection limit in liquid and 0.33% to 2.90% detection efficiency in aerosols at distances ranging from 30 cm to 60 cm. For fabrication, a mixture of a PANI monomer solution and virus were polymerized together to form a conductive PANI sensing element on a polyethylene terephthalate (PET) paper substrate. The sensing element exhibited formation of virus recognition sites after the removal of the virus via ultrasound sonication. A dry measurement technique was established that showed aerosol virus detection by the molecularly imprinted sensors within 1.5 h of virus spraying. This was based on the mechanism via which dispensing virus droplets on the PANI sensing element induced hybridization of the virus and molecularly imprinted virus recognition templates in PANI, influencing the conductivity of the PANI film upon drying. Interestingly, the paper-based virus sensor was easily integrated with a wearable face mask for the detection of viruses in aerosols. Since the paper sensor with molecular imprinting of virus recognition sites showed excellent stability in dry conditions for long periods of time, unlike biological reagents, this wearable biosensor will offer an alternative approach to monitoring virus infections in communities.