Special focus on nanoscale regeneration

Printed microfluidic sweat sensing platform for cortisol and glucose detection

Wearable sweat biosensors offer compelling opportunities for improved personal health monitoring and non-invasive measurements of key biomarkers. Inexpensive device fabrication methods are necessary for scalable manufacturing of portable, disposable, and flexible sweat sensors. Furthermore, real-time sweat assessment must be analyzed to validate measurement reliability at various sweating rates. Here, we demonstrate a "smart bandage" microfluidic platform for cortisol detection and continuous glucose monitoring integrated with a synthetic skin. The low-cost, laser-cut microfluidic device is composed of an adhesive-based microchannel and solution-processed electrochemical sensors fabricated from inkjet-printed graphene and silver solutions. An antibody-derived cortisol sensor achieved a limit of detection of 10 pM and included a low-voltage electrowetting valve, validating the microfluidic sensor design under typical physiological conditions. To understand effects of perspiration rate on sensor performance, a synthetic skin was developed using soft lithography to mimic human sweat pores and sweating rates. The enzymatic glucose sensor exhibited a range of 0.2 to 1.0 mM, a limit of detection of 10 μM, and reproducible response curves at flow rates of 2.0 μL min^-1 and higher when integrated with the synthetic skin, validating its relevance for human health monitoring. These results demonstrate the potential of using printed microfluidic sweat sensors as a low-cost, real-time, multi-diagnostic device for human health monitoring.

Extended gate field-effect-transistor for sensing cortisol stress hormone

Cortisol is a hormone released in response to stress and is a major glucocorticoid produced by adrenal glands. Here, we report a wearable sensory electronic chip using label-free detection, based on a platinum/graphene aptamer extended gate field effect transistor (EG-FET) for the recognition of cortisol in biological buffers within the Debye screening length. The device shows promising experimental features for real-time monitoring of the circadian rhythm of cortisol in human sweat. We report a hysteresis-free EG-FET with a voltage sensitivity of the order of 14 mV/decade and current sensitivity up to 80% over the four decades of cortisol concentration. The detection limit is 0.2 nM over a wide range, between 1 nM and 10 µM, of cortisol concentrations in physiological fluid, with negligible drift over time and high selectivity. The dynamic range fully covers those in human sweat. We propose a comprehensive analysis and a unified, predictive analytical mapping of current sensitivity in all regimes of operation.

A new polymer lab-on-a-chip (LOC) based on a microfluidic capillary flow assay (MCFA) for detecting unbound cortisol in saliva

Unbound cortisol in saliva, which can be detected with non-invasive sampling, is now considered as one of the most effective biomarkers for the biochemical evaluation of common mental disorders. In this work, a new polymer lab-on-a-chip (LOC) based on a microfluidic capillary flow assay (MCFA) with on-chip dried reagents was newly developed and fully characterized for the detection of unbound cortisol in saliva. The new MCFA device consisted of serially connected microchannels for sample loading, dried detection antibodies, time delay for incubation time control, a spiral reaction chamber for testing, positive and negative controls, and a capillary pump for waste fluid collection. In addition, a portable fluorescence analyzer was also developed for the rapid quantitative measurement of salivary cortisol with high accuracy. A linear dynamic range of 7.0 pg mL-1-16.0 ng mL-1 was achieved from spiked artificial saliva samples with an inter-chip CV of around 4.0% using the developed LOC and fluorescence analyzer. The achieved results support the effective biochemical analysis of common mental disorders such as chronic stress, depression, anxiety and post traumatic stress disorder (PTSD). The new LOC based on a microfluidic capillary flow assay (MCFA) developed in this work can be one of the most promising LOC platforms for high-sensitivity and quantitative POCT with saliva and blood plasma/serum samples.

A hollow-nanosphere-based microfluidic biosensor for biomonitoring of cardiac troponin I

Cardiovascular diseases (CVDs) are the leading causes of death worldwide.

A sensitive electrochemical immunosensor for label-free detection of Zika-virus protein

This work, as a proof of principle, presents a sensitive and selective electrochemical immunosensor for Zika-virus (ZIKV)-protein detection using a functionalized interdigitated micro-electrode of gold (IDE-Au) array. A miniaturized IDE-Au immunosensing chip was prepared via immobilization of ZIKV specific envelop protein antibody (Zev-Abs) onto dithiobis(succinimidyl propionate) i.e., (DTSP) functionalized IDE-Au (electrode gap/width of 10 µm). Electrochemical impedance spectroscopy (EIS) was performed to measure the electrical response of developed sensing chip as a function of ZIKV-protein concentrations. The results of EIS studies confirmed that sensing chip detected ZIKV-protein selectively and exhibited a detection range from 10 pM to 1 nM and a detection limit of 10 pM along with a high sensitivity of 12 kΩM-1. Such developed ZIKV immune-sensing chip can be integrated with a miniaturized potentiostat (MP)-interfaced with a smartphone for rapid ZIKV-infection detection required for early stage diagnostics at point-of-care application.

Nano-biosensors to detect beta-amyloid for Alzheimer's disease management

Beta-amyloid (β-A) peptides are potential biomarkers to monitor Alzheimer's diseases (AD) for diagnostic purposes. Increased β-A level is neurotoxic and induces oxidative stress in brain resulting in neurodegeneration and causes dementia. As of now, no sensitive and inexpensive method is available for β-A detection under physiological and pathological conditions. Although, available methods such as neuroimaging, enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) detect β-A, but they are not yet extended at point-of-care (POC) due to sophisticated equipments, need of high expertize, complicated operations, and challenge of low detection limit. Recently, β-A antibody based electrochemical immuno-sensing approach has been explored to detect β-A at pM levels within 30-40 min compared to 6-8h of ELISA test. The introduction of nano-enabling electrochemical sensing technology could enable rapid detection of β-A at POC and may facilitate fast personalized health care delivery. This review explores recent advancements in nano-enabling electrochemical β-A sensing technologies towards POC application to AD management. These analytical tools can serve as an analytical tool for AD management program to obtain bio-informatics needed to optimize therapeutics for neurodegenerative diseases diagnosis management.

Antibody conjugated metal nanoparticle decorated graphene sheets for a mycotoxin sensor

The proposed rGO–Ni NPs based immunosensor utilized for aflatoxin B₁ detection indicates high sensitivity.

Robust and direct electrochemical sensing of arsenic using zirconia nanocubes

The presence of heavy metal ions in the environment and in food items can severely harm human health.