Dual detection of human motion and glucose in sweat with polydopamine and glucose oxidase doped self-healing nanocomposite hydrogels

Design of self-healing nanocomposite hydrogels and the application to the detection of human exercise and ascorbic acid in sweat

Hydrogels, as flexible materials, have been widely used in the field of flexible sensors. Human sweat contains a variety of biomarkers that can reflect the physiological state of the human body. Therefore, it is of great practical significance and application value to realize the detection of sweat composition and combine it with human motion sensing through a hydrogel. Based on mussel-inspired chemistry, polydopamine (PDA) and gold nanoparticles (AuNPs) were coated on the surface of cellulose nanocrystals (CNCs) to obtain CNC-based nanocomposites (CNCs@PDA-Au), which could simultaneously enhance the mechanical, electrochemical, and self-healing properties of hydrogels. The CNCs@PDA-Au was composited with poly(vinyl alcohol) (PVA) hydrogel to obtain the nanocomposite hydrogel (PVA/CNCs@PDA-Au) by freeze-thaw cycles. The PVA/CNCs@PDA-Au has excellent mechanical strength (7.2 MPa) and self-healing properties (88.3%). The motion sensors designed with PVA/CNCs@PDA-Au exhibited a fast response time (122.9 ms), wide strain sensing range (0-600.0%), excellent stability, and fatigue resistance. With the unique electrochemical redox properties of uric acid, the designed hydrogel sensor successfully realized the detection of uric acid in sweat with a wide detection range (1.0-100.0 μmol/L) and low detection limit (0.42 μmol/L). In this study, the dual detection of human motion and uric acid in sweat was successfully realized by the designed PVA/CNCs@PDA-Au nanocomposite hydrogel.

A sample-to-answer, wearable cloth-based electrochemical sensor (WCECS) for point-of-care detection of glucose in sweat

Lancet-free and label-free diagnostics of glucose in sweat using Zinc Oxide based flexible bioelectronics

Self-healing hydrogels with excellent toughness and mechanical strength are particularly desirable for practical application. In this paper, green and environmentally friendly cellulose nanocrystals (CNCs) were successfully modified on the surface via metal-free photoinduced electron transfer atom transfer radical polymerization (PET-ATRP). Surface-initiated PET-ATRP was achieved by using 4-vinylpyridine (4VP) as functional monomer, 10-phenylphenothiazine (Ph-PTZ) as photocatalyst and ultraviolet light (365 nm) as light source, respectively. The prepared P4VP-CNCs hybrid materials (CNCs@P4VP) were used as green reinforcement to obtain self-healing nanocomposite hydrogels by electrostatic interactions. As a result, the nanocomposite hydrogels displayed outstanding mechanical (6.6 MPa at a strain of 921.6%) and self-healing (85.9% after repairing 6 h) properties. This work provides a promising green method for designing novel self-healing nanocomposite hydrogels with high strength.

Realizing high-performance glucose sensing in sweat: Synergistic use of nickel oxide nanosheets as photoelectrodes and the masking effect of Mo-POM for photoelectrochemical detection

For deposition of two-dimensional materials (e.g., graphene) on a substrate, self-aggregation and poor anchor strength are still issues. Herein, the GaN nanowire (NW) substrate was employed for electrochemical deposition of reduced graphene oxide (rGO) with satisfying dispersion uniformity and anchor strength. The deposited rGO exhibited flake morphology without agglomeration. Moreover, PtAu and rGO can be simultaneously and uniformly deposited on the GaN NW substrate to realize a PtAu–rGO/GaN electrochemical sensor for glucose detection. In comparison with deposition of PtAu–rGO on a stainless steel (SS) substrate (i.e., PtAu–rGO/SS), PtAu–rGO/GaN demonstrated much higher sensitivity and long-term stability, owing to better dispersion and anchor strength on GaN NW. In addition, with decoration of glucose oxidase (GOx), the GOx/PtAu–rGO/GaN sensor can be used for detecting glucose in human sweat with a low limit of detection of 5 μM, a wide linear detection range of 5 μM–12 mM, and high long-term stability, which indicates that GOx/PtAu–rGO/GaN sensor is promising for noninvasive glucose detection.

In this study, a flexible and wearable chemiresistive biosensor (FWCB) is developed for the real‐time analysis of glucose in sweat on the human skin surface based on a novel detection strategy of p‐type reduced graphene oxide (rGO) sensing film, which met the requirements of rapid, nondestructive testing. The proposed FWCB is fabricated in the form of interdigital electrodes (IEs) made of laser‐induced graphene (LIG) synthesized by the laser inducing of a polyimide (PI) film. Additionally, a semiconducting rGO sensing film modified on the surface of IEs is synthesized by thermal reduction of graphene oxide (GO), which is functionalized with glucose oxidase (GOx) by chemical cross‐linking to obtain GOx/FWCB. Moreover, the key parameters for FWCB fabrication are optimized, and the sensing strategy of the proposed GOx/FWCB is also investigated. The results show that the proposed GOx/FWCB can be used for the detection of glucose in the range of 0.01–3.0 mM with satisfactory selectivity, and the limit of detection (LOD) is calculated to be as low as 0.8 µM (S/N = 3). These dramatic advantages endow the proposed FWCB with broad application prospects in the field of portable, wearable, and real‐time detection of glucose in human sweat for health monitoring.

Biocompatible, self-healing, highly stretchable polyacrylic acid/reduced graphene oxide nanocomposite hydrogel sensors via mussel-inspired chemistry

Infrared-light-driven self-healing MoS2/polyvinyl alcohol hydrogel with simultaneous enhancement of strength and ductility

Stretchable, rapid self-healing guar gum-poly(acrylic acid) hydrogels as wearable strain sensors for human motion detection based on Janus graphene oxide

Surface-initiated PET-ATRP and mussel-inspired chemistry for surface engineering of MWCNTs and application in self-healing nanocomposite hydrogels.

Fabrication of Janus graphene oxide hybrid nanosheets by Pickering emulsion template for self-healing nanocomposite hydrogels

Continuous painless glucose monitoring is the greatest desire of more than 422 million diabetics worldwide. Therefore, new non-invasive and convenient approaches to glucose monitoring are more in demand than other tests for microanalytical diagnostic tools. Besides, blood glucose detection can be replaced by continuous glucose monitoring of other human biological fluids (e.g. sweat) collected non-invasively. In this study, a skin-attachable and stretchable electrochemical enzymatic sensor based on ZnO tetrapods (TPs) and a new class of 2D materials - transition metal carbides, known as MXene, was developed and their electroanalytical behavior was tailored for continuous detection glucose in sweat. The high specific area of ZnO TPs and superior electrical conductivity of MXene (Ti3C2Tx) nanoflakes enabled to produce enzymatic electrochemical glucose biosensor with enhanced sensitivity in sweat sample (29 μA mM−1 cm−2), low limit of detection (LOD ≈ 17 μM), broad linear detection range (LDR = 0.05–0.7 mM) that satisfices glucose detection application in human sweat, and advanced mechanical stability (up to 30% stretching) of the template. The developed skin-attachable stretchable electrochemical electrodes allowed to monitor the level of glucose in sweat while sugar uptake and during physical activity. Continuous in vivo monitoring of glucose in sweat obtained during 60 min correlated well with data collected by a conventional amperometric blood glucometer in vitro mode. Our findings demonstrate the high potential of developed ZnO/MXene skin-attachable stretchable sensors for biomedical applications on a daily basis.

Achieving quantification of biomarkers in body fluids is crucial to the indication of the state of a person’s body and health. Wearable sensors could offer a convenient, fast and painless sensing strategy. In this work, we fabricated a wearable electrochemical patch sensor for simultaneous detection of dopamine and glucose in sweat. The sensor was printed on a flexible PDMS substrate with a simple screen-printed method. This prepared four-electrode sensor integrated two working electrodes for dopamine and glucose electrochemical sensing, one Ag/AgCl reference electrode and one carbon counter electrode, respectively. Cyclic voltammetry, differential pulse voltammetry and chronoamperometry were used for the evaluation of the wearable electrochemical patch sensor. It exhibits good sensitivity, wide linear range, low limit of detection, good anti-interference and reproducibility toward dopamine and glucose sensing in PBS and sweat.