An MXene-supported cobalt-MOF nanocomposite-printed electrochemical sensor with high sensitivity for blood creatinine detection in point-of-care settings.

2D MXenes have been used as electrochemical sensor materials, but their output current signal remains weak in point of care (PoC) settings. To address this issue, here we report a novel MXene-supported cobalt-MOF-based nanocomposite, which is used with a carbon black (CB) ink and 3-D printed as the CoMOF-MXene@CB layered electrode structure for the development of a sensor electrode and a PoC chip for electrochemical detection of blood creatinine with an enhanced current range, specificity, and sensitivity. The limit of detection (LOD) and sensitivity of the fabricated sensor were found to be 0.005 µM and 1.1 µA µM-1 cm-2, which are 44 times lower and 32 times enhanced, respectively, as compared to the existing literature report (LOD 0.22 µM and sensitivity 0.034 µA µM-1) for creatinine sensing in PoC settings. The sensor exhibited an excellent linear sensor response ranging from 10 to 800 µM and good reproducibility, stability, and selectivity with significant accuracy. These characteristics helped the sensor to accurately determine the creatinine levels in real human serum samples.

Risk assessment of diabetes using the Indian Diabetes Risk Score among older adults: Secondary analysis from the Longitudinal Ageing Study in India.

BACKGROUND: The Indian Diabetes Risk Score (IDRS) is a simple tool to assess the probability of an individual having type 2 diabetes (T2DM) but its applicability in community-dwelling older adults is lacking. This study aimed to estimate the risk of T2DM and its determinants among older adults without prior diabetes (DM) using the IDRS, while also assessing its sensitivity and specificity in individuals with a history of diabetes. METHODS: We analyzed cross-sectional data from the Longitudinal Ageing Study in India (LASI) wave-1 (2017-18). IDRS was calculated amongst individuals aged ≥45 years considering waist circumference, physical activity, age and family history of DM. Risk was categorized as high (≥60), moderate (30-50), and low (<30). RESULTS: Among 64541 individuals, 7.27 % (95 % CI: 6.78, 7.80) were at low risk, 61.80 % (95 % CI: 60.99, 62.61) at moderate risk, and 30.93 % (95 % CI: 30.19, 31.67) at high risk for T2DM. Adjusted analysis showed higher risk of T2DM among men, widowed/divorced, urban residents, minority religions, overweight, obese, and individuals with hypertension. ROC curve yielded an AUC of 0.67 (95 % CI: 0.66, 0.67, P < 0.001). The IDRS cutoff ≥50 had 73.69 % sensitivity and 51.40 % specificity for T2DM detection. CONCLUSION: More than 9 in 10 older adults in India without history of DM have high-moderate risk of T2DM when assessed with the IDRS risk-prediction tool. However, the low specificity and moderate sensitivity of IDRS in existing DM cases constraints its practical utility as a decision tool for screening.

Efficient Point-of-Care Detection of Uric Acid in the Human Blood Sample with an Enhanced Electrocatalytic Response Using Nanocomposites of Cobalt and Mixed-Valent Molybdenum Sulfide.

This work efficiently detects uric acid (UA) in a human blood sample using cobalt nanoparticle-immobilized mixed-valent molybdenum sulfide on the copper substrate in a point-of-care (PoC) device. The sensor electrode was fabricated by micromachining of Cu clad boards employing an engraver to generate a three-electrode system consisting of working electrode (WE), reference electrode (RE), and counter electrode (CE). The WE was subjected to physical vapor deposition of mixed-valent MoSx layers by a reaction between Mo(CO)6 and H2S at ∼200 °C using a simple setup following which CoNPs were electrochemically deposited. The RE and CE were covered with Ag/AgCl and Ag paste, respectively. A plasma separation membrane acted as the medium of UA/blood serum delivery to the electrodes. The material and electrochemical characterization confirmed that CoNPs over MoSx provided an enlarged electroactive surface for the direct electron transfer to achieve an enhanced electrocatalytic response. The binary combination of CoNPs and MoSx layers over the Cu electrode reduced the charge-transfer resistance by two times, enhanced the surface adsorption by more than two times, and yielded a high diffusion coefficient of 3.46 × 10-3 cm2/s. These interfacial effects facilitated the UA oxidation, leading to unprecedented mA range current density for UA sensing for the PoC device. The electrochemical detection tests in the PoC device revealed a sensitivity of 64.7 µA/µM cm-2, which is ∼50 times higher compared to the latest reported value (1.23 µA/µM cm-2), a high limit of detection of 5 nM, and shelf life of 6 months, confirming the synergistic effect-mediated high sensitivity under PoC settings. Interference tests confirmed no intervention of similar analytes. Tests on blood samples demonstrated a recovery percentage close to 100% in human serum UA, signifying the suitability of the nanocomposite-based sensor and the PoC device for clinical sensing applications.

3-D printed electrode integrated sensing chip and a PoC device for enzyme free electrochemical detection of blood urea.

Herein we report a novel electrochemical sensing chip and a point-of-care device (PoC) for enzyme-free electrochemical detection of urea in human blood. The electrochemical sensing chip was developed by 3-D printing of conductive Ag ink and subsequent electrodeposition of AuNP-rGO nanocomposite. Material characterization of the sensing chip was conducted to find a plausible mechanism for the electrochemical reaction with urea. Subsequently, the response with varying concentrations of urea in solution and human blood samples was tested. High peak response current (~5 times than that of the highest reported value), low impedance, rapid sensor fabrication procedure, high selectivity towards urea, excellent linear response (R2 = 0.99), high sensitivity of 183 µA mM-1 cm-2, the fast response indicated by high diffusion coefficient, the limit of detection of 0.1 µM, tested shelf life of more than 6 months and recovery rate of >99% ensured the application of the developed sensor chip towards PoC urea detection test kit. A PoC device housing an electronic circuitry following the principles of linear sweep voltammetry and compatible with a sensing chip was developed. A maximum percentage error of 4.86% and maximum RSD of 3.63% confirmed the use of the PoC device for rapid urea measurements in human blood.

Facile Detection of Blood Creatinine Using Binary Copper-Iron Oxide and rGO-Based Nanocomposite on 3D Printed Ag-Electrode under POC Settings.

Metal nanoparticles have been helpful in creatinine sensing technology under point-of-care (POC) settings because of their excellent electrocatalyst properties. However, the behavior of monometallic nanoparticles as electrochemical creatinine sensors showed limitations concerning the current density in the mA/cm2 range and wide detection window, which are essential parameters for the development of a sensor for POC applications. Herein, we report a new sensor, a reduced graphene oxide stabilized binary copper-iron oxide-based nanocomposite on a 3D printed Ag-electrode (Fe-Cu-rGO@Ag) for detecting a wide range of blood creatinine (0.01 to 1000 µM; detection limit 10 nM) in an electrochemical chip with a current density ranging between 0.185 and 1.371 mA/cm2 and sensitivity limit of 1.1 µA µM-1 cm-2 at physiological pH. Interference studies confirmed that the sensor exhibited no interference from analytes like uric acid, urea, dopamine, and glutathione. The sensor response was also evaluated to detect creatinine in human blood samples with high accuracy in less than a minute. The sensing mechanism suggested that the synergistic effects of Cu and iron oxide nanoparticles played an essential role in the efficient sensing where Fe atoms act as active sites for creatinine oxidation through the secondary amine nitrogen, and Cu nanoparticles acted as an excellent electron-transfer mediator through rGO. The rapid sensor fabrication procedure, mA/cm2 peak current density, a wide range of detection limits, low contact resistance including high selectivity, excellent linear response (R2 = 0.991), and reusability ensured the application of advanced electrochemical sensor toward the POC creatinine detection.

Printed oxygen gas sensor using copper-DTDTPA solid electrolyte.

We present a new method for the rapid and cost-effective fabrication of solid electrolyte-based printed potentiometric oxygen sensors working at ambient temperature using Cu-dithiolated diethylene triamine pentaacetic acid complex molecules (Cu-DTDTPA) adsorbed on Grade-1 laboratory filter paper and subsequent 3-D printing of interdigitated electrodes employing silver/silver chloride ink. The decrease in conductivity with time and frequency-dependent impedance response confirms the filter paper adsorbed Cu-DTDTPA as a solid electrolyte. A plausible structure of the Cu-DTDTPA solid electrolyte and its mechanism of reaction with oxygen are presented. A maximum sensitivity of 0.052 mV per %O2, the maximum response time of 1.15 s per %O2, a wide measurement output ranging from 14.55 mV to 17.25 mV for 20%-90% of O2 concentration, a maximum standard deviation of 0.12 mV in output voltage, almost similar trends of the response on temperature, humidity variations and ageing and high selectivity establish the sensor for use in medical ventilator applications, specifically in the COVID19 pandemic.