Smartphone based wearable sweat glucose sensing device correlated with machine learning for real-time diabetes screening.

BACKGROUND: Diabetes is a significant health threat, with its prevalence and burden increasing worldwide indicating its challenge for global healthcare management. To decrease the disease severity, the diabetic patients are recommended to regularly check their blood glucose levels. The conventional finger-pricking test possesses some drawbacks, including painfulness and infection risk. Nowadays, smartphone has become a part of our lives offering an important benefit in self-health monitoring. Thus, non-invasive wearable sweat glucose sensor connected with a smartphone readout is of interest for real-time glucose detection. RESULTS: Wearable sweat glucose sensing device is fabricated for self-monitoring of diabetes. This device is designed as a body strap consisting of a sensing strip and a portable potentiostat connected with a smartphone readout via Bluetooth. The sensing strip is modified by carbon nanotubes (CNTs)-cellulose nanofibers (CNFs), followed by electrodeposition of Prussian blue. To preserve the activity of glucose oxidase (GOx) immobilized on the modified sensing strip, chitosan is coated on the top layer of the electrode strip. Herein, machine learning is implemented to correlate between the electrochemical results and the nanomaterial content along with deposition cycle of prussian blue, which provide the highest current response signal. The optimized regression models provide an insight, establishing a robust framework for design of high-performance glucose sensor. SIGNIFICANCE: This wearable glucose sensing device connected with a smartphone readout offers a user-friendly platform for real-time sweat glucose monitoring. This device provides a linear range of 0.1-1.5 mM with a detection limit of 0.1 mM that is sufficient enough for distinguishing between normal and diabetes patient with a cut-off level of 0.3 mM. This platform might be an alternative tool for improving health management for diabetes patients.

Carbonization of self-reduced AuNPs on silk as wearable skin patches for non-invasive sweat urea detection.

Flexible conductive skin patches were readily fabricated on silk fabric by in situ deposition of gold nanoparticles (AuNPs) followed by carbonization. The carbonized AuNPs-silk with high flexibility was characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and Fourier transform Raman spectroscopy (FT-Raman) to verify the well arrangement surface and desired chemical binding. The conductivity of silk skin patch, measured by a four-point probe, was found to be 109.24 ± 13 S cm-1 × 10-3, verifying the potential application as a working electrode in electrochemical sensor and a sweat collection patch for direct detection by laser desorption/ionization mass spectrometry (LDI-MS). This silk skin patch offered a linear range of 0-100 mM with a detection limit (LOD) of 20 mM for electrochemical sensor and 8 mM for LDI-MS, respectively. Ultimately, this skin patch is successfully applied for the detection of sweat urea at its cut-off value (60 mM) for indicating chronic kidney disease (CKD) in artificial sweat with satisfactory results. By using dual-detection technique on single silk substrate, this platform might be an alternative approach for a non-invasive sweat urea detection with high precision.

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. We developed and validated a portable blood lactate detection kit for clinical screening that can measure early bedside lactate levels in intensive care unit (ICU) patients suspected of having sepsis. A TiO2 sol-G nanocomposite was prepared and coated on a screen-printed carbon electrode (SPCE) integrated with non-immobilized lactate oxidase (LOx) to produce a novel lactate biosensor with high sensitivity and high storage stability for human blood lactate measurement. The detection kit was based on an electrochemical technique and showed a wide linear range of 1-20 mM (R2 = 0.9937) with a low detection limit of 0.2 mM for lactate detection. This allowed for differentiating patient groups who may have sepsis using a cut-off level of 4 mM. The device was successfully implemented for blood lactate determination in critical patients, showing an accuracy range from 75% to 112%. This device provided high-precision and rapid quantitative information validated using a blood gas analyzer. Our detection kit might help to reduce the morbidity and mortality rates in severe sepsis and septic shock patients in community hospitals.

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.

Reduced Graphene Oxide/Carboxymethyl Cellulose Nanocomposites: Novel Conductive Films.

Herein, carboxymethyl cellulose nanocomposite films incorporated with graphene oxide and reduced graphene oxide were successfully prepared by a novel approach for the first time, and their alternative properties compared with the original carboxymethyl cellulose films were disclosed. For carboxymethyl cellulose/reduced graphene oxide film preparation, sodium borohydride was used as a chemical reducing agent. The carboxymethyl cellulose films were prepared by using a solvent casting method, followed by an acid treatment to decrease the water solubility (98%) while enhancing the tensile strength (15%) and elastic modulus (32%) of the original carboxymethyl cellulose films. Overall, the addition of 1.0 wt% graphene oxide and reduced graphene oxide to the treated films increased the water solubility, water absorption, tensile properties and electrical conductivity. Particularly, the electrical conductivity was predominantly enhanced 1.3×105 times with graphene oxide and 2.2×105 times with reduced graphene oxide compared to the treated carboxymethyl cellulose film. The electrical conductivity of the treated carboxymethyl cellulose film also increased with an increase in reduced graphene oxide. The effects of reduced graphene oxide on the water solubility, water absorption, tensile properties and electrical conductivity of the treated carboxymethyl cellulose film were more pronounced than those of graphene oxide, especially for the electrical conductivity. In conclusion, graphene oxide and reduced graphene oxide might be alternative nanofillers for improving the carboxymethyl cellulose film properties. For the future applications, carboxymethyl cellulose/reduced graphene oxide films prepared by using this approach might be employed as alternative materials in electronic packagings and electrochemical biosensors.

Non-invasive textile based colorimetric sensor for the simultaneous detection of sweat pH and lactate.

A non-invasive textile-based colorimetric sensor for the simultaneous detection of sweat pH and lactate was created by depositing of three different layers onto a cotton fabric: 1.) chitosan, 2.) sodium carboxymethyl cellulose, and 3.) indicator dye or lactate assay. This sensor was characterized using field emission scanning electron microscopy and fourier transform infrared spectroscopy. Then, this sensor was used to measure pH and lactate concentration using the same sweat sample. The sensing element for sweat pH was composed of a mixture of methyl orange and bromocresol green while a lactate enzymatic assay was chosen for the lactate sensor. The pH indicator gradually shifted from red to blue as the pH increased, whereas the purple color intensity increased with the concentration of lactate in the sweat. By comparing these colors with a standard calibration, this platform can be used to estimate the sweat pH (1-14) and the lactate level (0-25 mM). Fading of the colors of this sensor was prevented by using cetyltrimethylammonium bromide (CTAB). The flexibility of this textile based sensor allows it to be incorporated into sport apparels and accessories hence potentially enabling real-time and continuous monitoring of sweat pH and lactate. This non-invasive sensing platform might open a new avenue for personal health monitoring and medical diagnosis as well as for determining of the physiological conditions of endurance athletes.

Hydrophilic graphene surface prepared by electrochemically reduced micellar graphene oxide as a platform for electrochemical sensor.

Graphene is one of the promising hydrophobic carbon-based nanomaterials used for electrode modification in electrochemical sensor. However, hydrophobicity of graphene makes it incompatible with aqueous electrolyte solution, leading to significant impediment to the electron transfer process. Here, we aim to alter graphene property to be hydrophilicity by using an electrochemically reduced micellar graphene oxide for electrode surface modification. Then, this system was applied for the simultaneous determination of toxic pesticides (e.g. carbofuran and carbendazim). Interestingly, the modified electrode offers an improved electrochemical sensitivity, verified by a drastic increase in current signal of carbofuran (4 times) and carbendazim (12 times) compared to an unmodified electrode. Under the optimal conditions, low detection limits of carbofuran and carbendazim were found to be 10µgL-1 and 5µgL-1, respectively. Ultimately, this system was successfully applied for the sensitive and simultaneous determination of carbofuran and carbendazim residues in various agricultural products.