Graphene oxide-alginate hydrogel-based indicator displacement assay integrated with diaper for non-invasive Alzheimer's disease screening

Pyrocatechol violet/copper ion-graphene oxide/alginate (PV/Cu2+-GO/Alg) hydrogel was fabricated and applied as a colorimetric sensor for monitoring urinary cysteine via an indicator-displacement assay (IDA) and Cu2+-cysteine affinity pair. The hydrogel-based sensor was formed by Ca2+ cations cross-linked PV/Cu2+-GO/Alg. The morphologies of hydrogel were characterized by field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and Fourier-transform Raman spectroscopy. Incorporating GO into the hydrogel improved its uniformity of porosity, large surface area, and compressive strength, leading to amplified colorimetric signals of the hydrogel sensor. Under optimal conditions, this sensor offered a linear range of 0.0-0.5 g/L with a detection limit of 0.05 g/L for cysteine without interfering effects in urine. Furthermore, this hydrogel-based sensor was applied for urinary cysteine detection and validated with laser desorption ionization mass spectrometry. This platform could be used to determine cysteine at its cutoff (0.25 g/L) in human urine, which was distinguishable between normal and abnormal individuals, to evaluate an early stage of Alzheimer's disease. Eventually, this system was integrated with diapers for a wearable cysteine sensor.

A portable blood lactate sensor with a non-immobilized enzyme for early sepsis diagnosis

Early determination of blood lactate levels may accelerate the detection of sepsis, one of the most time-sensitive illnesses.

TiO2/MXene-PVA/GO hydrogel-based electrochemical sensor for neurological disorder screening via urinary norepinephrine detection

A hydrogel based on titanium dioxide/MXene with polyvinyl alcohol/graphene oxide (TiO₂/MXene-PVA/GO) composite was successfully formulated and applied to modify a screen-printed carbon electrode (SPCE) for urinary norepinephrine (NE) detection. The characterization confirmed that a nanocomposite hydrogel structure of TiO₂/MXene-PVA/GO was formed. The as-prepared hydrogel substantially enhanced the sensor performances due to electrocatalytic activity of TiO₂, high conductivity of MXene, and auto-sample preconcentration via PVA/GO hydrogel. The electrochemical behavior of NE was investigated by cyclic voltammetry and amperometry. Under optimized conditions, the TiO₂/MXene-PVA/GO hydrogel/SPCE response due to the oxidation of NE at +0.4 V (vs. Ag|AgCl) is proportional to the concentration of NE over 0.01 to 1.00 μM (R² = 0.9968) and 1.00 to 60.0 μM (R² = 0.9936) ranges with a detection limit (3σ) of 6 nM without interferent effect from common interferences in urine. Furthermore, this sensor was employed for urinary NE determination and validated by high performance liquid chromatography (HPLC) with a UV detector at 280 nm; the average recovery was found to be 97.6 to 102%, with a relative standard deviation (RSD) less than 4.9%. This device was sensitive enough to evaluate an early stage of neurological disorder via detecting clinically relevant NE level. Eventually, it was integrated with pantyliners which could be a potential wearable sensor in the near future.

Recent Advances in Microfluidic Paper-Based Analytical Devices toward High-Throughput Screening

Microfluidic paper-based analytical devices (µPADs) have become promising tools offering various analytical applications for chemical and biological assays at the point-of-care (POC). Compared to traditional microfluidic devices, µPADs offer notable advantages; they are cost-effective, easily fabricated, disposable, and portable. Because of our better understanding and advanced engineering of µPADs, multistep assays, high detection sensitivity, and rapid result readout have become possible, and recently developed µPADs have gained extensive interest in parallel analyses to detect biomarkers of interest. In this review, we focus on recent developments in order to achieve µPADs with high-throughput capability. We discuss existing fabrication techniques and designs, and we introduce and discuss current detection methods and their applications to multiplexed detection assays in relation to clinical diagnosis, drug analysis and screening, environmental monitoring, and food and beverage quality control. A summary with future perspectives for µPADs is also presented.