SkinAid: A Wirelessly Powered Smart Dressing Solution for Continuous Wound-Tracking Using Textile-Based Frequency Modulation.

In this article, SkinAid, a battery-free, low-cost, robust, and user-friendly smart bandage for electrochemical monitoring and sensing of chronic wounds is proposed. The working principle of the bandage is based on direct frequency modulation of a tri-electrode electrochemical sensing of wound data. The electronics and biotelemetry links were realized using low-cost manufacturing process of textile embroidery onto fabric substrate. The transmitter was represented by a bedsheet with novel corrugated crossed-dipole made of Elektrisola-7 embroidered onto gauze fabric. An input RF signal of 1 W was transmitted at 462 MHz from the bedsheet to the all-textile bandage featuring a rectifying circuit, a voltage-controlled oscillator (VCO), an electrochemical sensor, and a 915-MHz dipole for re-transmission of the modulated wound data. We demonstrate that for wound fluid emulated by various uric acid concentrations from 0.2 mM to 1.2 mM, corresponding modulated frequency varies from 1090 MHz to 1145 MHz for signals captured at 25 cm away from the bandage. For pH modulation ranging from 2 to 10, the corresponding modulated frequency was between 800 MHz and 830 MHz for signals received at more than 6 feet away from the bandage. For quick and reliable assessment, two empirical models were developed for the direct frequency modulation as a function of uric acid and pH. To the best of our knowledge, this is the first time an all-textile (fabric-integrated), battery-free and wirelessly powered smart bandage have been proposed for wound monitoring. This result can be used as a first step in developing RFID-type, battery-free, and low-cost 5G/6G smart bandages using millimeterwave and terahertz frequencies where the bedsheet can be host to a MIMO-aided beamforming.

Bio-acceptability of wearable sensors: a mechanistic study towards evaluating ionic leaching induced cellular inflammation.

The recent need for remote health wellness monitoring has led to the extensive use of wearable sensors. Owing to their increased use, these sensors are required to exhibit both functionality and safety to the user. A major component in the fabrication of these sensors and their associated circuitry is the use of metallic/organic conductive inks. However, very less is known about the interfacial and molecular interactions of these inks with biological matter as they can result in an inflammatory reaction to the user. Significant efforts are thus needed to explore and improve the bio-acceptability of such conductive ink-based wearable sensors. The present study investigates the biocompatibility of encapsulated and non-encapsulated wearable electrochemical sensors used for sensing uric acid as a biomarker for wound healing fabricated using screen-printing technique. Ionic release of metallic ions was investigated first to understand the susceptibility of the conductive inks towards ionic leaching when in contact with a fluid. Time-lapse investigation using ICPS (inductive couple plasma spectroscopy) shows a high concentration (607.31 ppb) of leached silver (Ag+) ions from the non-encapsulated sensors. The cell viability data suggests a 2.5-fold improvement in the sensor biocompatibility for an encapsulated sensor. While the carbon ink shows negligible effect on cell viability, the silver ink elicits significant decrease (< 50%) in cell viability at concentrations higher than 2 mg ml-1. The toxicity pathway of these sensors was further determined to be through the generation of reactive oxygen species resulting in over 20% apoptotic cell death. Our results show that the lower biocompatibility of the non-encapsulated sensor attributes to the higher leaching of Ag+ ions from the printed inks which elicits several different inflammatory pathways. This work highlights the importance biocompatibility evaluation of the material used in sensor fabrication to develop safe and sustainable sensors for long-term applications.

Toxicity assessment of wearable wound sensor constituents on keratinocytes.

This research reports on the cytotoxicity of materials present in a wound biosensor on human keratinocytes (HaCaT) to evaluate the biocompatibility of the sensor for continuous wound monitoring applications. Individual and collective effects of the sensor materials, gold (Au) and silver (Ag) nanoparticles (NPs), uricase enzyme (UOx), ferrocene carboxylic acid (FCA), multi-walled carbon nanotubes (MWCNTs) and poly vinyl alcohol-based polymer (PVA-SbQ) on HaCaT were studied. The toxicology profiles of these materials were derived from cell viability, mitochondrial activity retention and apoptotic behavior studies. At the concentrations present in the sensor, the cell viability studies showed minimal toxicity for Au and Ag NPs, UOx and FCA (cell viability >75%), while MWCNTs and PVA-SbQ exhibited excellent biocompatibility towards keratinocytes (cell viability >90%). Resazurin assay confirmed minimal impairment of mitochondrial activity at lower concentrations for all the materials (mitochondrial activity >0.7). The caspase-3/7 apoptotic assay showed no pronounced apoptotic behavior caused by the materials. The material mixtures studied were Au/UOx/FCA/PVA-SbQ, Ag/UOx/FCA/PVA-SbQ, and MWCNTs/UOx/FCA/PVA-SbQ. A higher toxicity profile was observed for the heterogeneous material mixtures as a result of the cumulative effect of the individual materials. However, the biosensor itself was seen to exhibit lower toxicity (~5%) compared to the material mixtures, due to the protective PVA-SbQ capping over the biosensor. This work establishes the biocompatibility of the reported wound sensor for human measurements with minimal toxic effects on human keratinocytes.

Tapered lateral flow immunoassay based point-of-care diagnostic device for ultrasensitive colorimetric detection of dengue NS1.

Dengue virus, a Flaviviridae family member, has emerged as a major worldwide health concern, making its early diagnosis imperative. Lateral flow immunoassays have been widely employed for point-of-care diagnosis of dengue because of their rapid naked eye readouts, ease of use, and cost-effectiveness. However, they entail a drawback of low sensitivity, limiting their usage in clinical applications. Herein, we report a novel lateral flow immunoassay for detection of dengue leveraging on the benefits of gold decorated graphene oxide sheets as detection labels and a tapered nitrocellulose membrane. The developed assay allows for rapid (10 min) and sensitive detection of dengue NS1 with a detection limit of 4.9 ng mL-1, ∼11-fold improvement over the previously reported values. Additionally, the clinical application of the developed assay has been demonstrated by testing it for dengue virus spiked in human serum. The reported lateral flow immunoassay shows significant promise for early and rapid detection of several target diseases.