Super-Absorbent Polymer Valves and Colorimetric Chemistries for Time-Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin-Mounted Soft Microfluidics.

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.

Fabrication of nitric oxide-releasing porous polyurethane membranes-coated needle-type implantable glucose biosensors.

The active release of pharmaceutical agents and the use of porous sensor membranes represent the two most promising strategies for addressing the poor tissue biocompatibility of implantable glucose biosensors. Herein, we describe the combination of these approaches to create nitric oxide (NO)-releasing porous fiber mat-modified sensor membranes. An electrospinning method was used to directly modify needle-type glucose biosensors with the NO donor-loaded fibers. The resulting NO-releasing fiber mat (540 ± 139 nm fiber diameter, 94.1 ± 3.7% porosity) released ~100 nmol of NO per mg of polyurethane over 6 h while maintaining a porous structure without leaching of the NO donor, even in serum. The porous fiber membrane did not influence the analytical performance of the biosensor when ≤50 µm thick.

Dietary Factors, Time of the Week, Physical Fitness and Saliva Cortisol: Their Modulatory Effect on Mental Distress and Mood.

Background: The purpose of the study was to assess the effect of diet quality and physical fitness on saliva cortisol, mood, and mental distress. These relationships were compared between a peak weekday (Wednesday) and a weekend day (Saturday) when mood may fluctuate. Methods: Forty-eight healthy college students participated in the study. Participants completed the Mood and Anxiety Symptom (MASQ) and Kessler Psychological Distress Scale 10 questionnaires on Wednesday and Saturday and recorded their diet for three days. Saliva was collected before and after a workout for cortisol extraction. Results: SA had significantly higher saliva cortisol levels post-workout but lower MASQ scores on Saturday (p < 0.05). There was a very significant association between MASQ scores on Wednesday (p = 0.005), which became less significant on Saturday. In addition, lower BMI values and high-fat consumption were associated with higher cortisol levels after exercise (p < 0.05). Conclusions: There is a strong link between dietary factors, cortisol levels, mood, and time of the week. In addition, our results suggest that saliva cortisol levels may not be directly linked to negative affect but are influenced by diet quality when mental distress exists. In addition, physical fitness may play a role in improving mood during weekends.

Sweat and saliva cortisol response to stress and nutrition factors.

Cortisol is a biomarker for stress monitoring; however, the biomedical and clinical relevance is still controversial due to the complexity of cortisol secretion mechanisms and their circadian cycles as well as environmental factors that affect physiological cortisol level, which include individual mood and dietary intake. To further investigate this multifaceted relationship, a human pilot study examined cortisol concentration in sweat and saliva samples collected from 48 college-aged participants during aerobic exercise sessions along with mental distress and nutrition surveys. Enzyme-linked immunosorbent assays determined highly significant differences between apocrine-dominant sweat (AP), saliva before exercise (SBE), and saliva after exercise (SAE) cortisol concentration (AP-SBE: p = 0.0017, AP-SAE: p = 0.0102). A significantly greater AP cortisol concentration was detected in males compared to females (p = 0.0559), and significant SAE cortisol concentration differences were also recorded between recreational athletes and non-athletes (p = 0.044). However, Kessler 10 Psychological Distress Scale (K10) scores, an examination administered to deduce overall wellness, provided no significant differences between males and females or athletes and non-athletes in distress levels, which statistically signifies a direct relationship to cortisol was not present. For further analysis, dietary intake from all participants was considered to investigate whether a multiplexed association was prevalent between nutrition, mood, and cortisol release. Significant positive correlations between AP cortisol, SAE cortisol, K10 scores, and fat intake among female participants and athletes were discovered. The various machine learning algorithms utilized the extensive connections between dietary intake, overall well-being, sex factors, athletic activity, and cortisol concentrations in various biofluids to predict K10 scores. Indeed, the understanding of physiochemical stress response and the associations between studied factors can advance algorithm developments for cortisol biosensing systems to mitigate stress-based illnesses and improve an individual's quality of life.

Skin-inspired, open mesh electrochemical sensors for lactate and oxygen monitoring.

Research in wearable electronics has paved the way for next-generation technology, sought to create point-of-care biosensors that combine chemical sensing on a biocompatible platform with a broad range of applications in human health monitoring. Despite significant progress, the microspatial mechanical mismatch and fluid-impermeable interface presented between skin and the electronics create adscititious problems in device lamination, conformality, and long-term monitoring. Herein, we engineered a skin-inspired, deterministically patterned, electrochemical biosensor that can be fully integrated with the curvilinear surface of the human body, while mechanically adapting to the natural stresses applied to the skin and allowing the mass transfer of gas and fluids. In particular, we developed mechanically-compliant lattice-structured biosensors for the continuous evaluation of lactate and oxygen. Systematic studies of the sensor performance were evaluated with variations in polymeric membranes and its ability to withstand commonplace harsh, multiaxial stresses.

Nitric oxide-releasing silica nanoparticle-doped polyurethane electrospun fibers.

Electrospun polyurethane fibers doped with nitric oxide (NO)-releasing silica particles are presented as novel macromolecular scaffolds with prolonged NO-release and high porosity. Fiber diameter (119-614 nm) and mechanical strength (1.7-34.5 MPa of modulus) were varied by altering polyurethane type and concentration, as well as the NO-releasing particle composition, size, and concentration. The resulting NO-releasing electrospun nanofibers exhibited ~83% porosity with flexible plastic or elastomeric behavior. The use of N-diazeniumdiolate- or S-nitrosothiol-modified particles yielded scaffolds exhibiting a wide range of NO release totals and durations (7.5 nmol mg(-1)-0.12 µmol mg(-1) and 7 h to 2 weeks, respectively). The application of NO-releasing porous materials as coatings for subcutaneous implants may improve tissue biocompatibility by mitigating the foreign body response and promoting cell integration.

The effect of nitric oxide surface flux on the foreign body response to subcutaneous implants.

Although the release of nitric oxide (NO) from biomaterials has been shown to reduce the foreign body response (FBR), the optimal NO release kinetics and doses remain unknown. Herein, polyurethane-coated wire substrates with varying NO release properties were implanted into porcine subcutaneous tissue for 3, 7, 21 and 42 d. Histological analysis revealed that materials with short NO release durations (i.e., 24 h) were insufficient to reduce the collagen capsule thickness at 3 and 6 weeks, whereas implants with longer release durations (i.e., 3 and 14 d) and greater NO payloads significantly reduced the collagen encapsulation at both 3 and 6 weeks. The acute inflammatory response was mitigated most notably by systems with the longest duration and greatest dose of NO release, supporting the notion that these properties are most critical in circumventing the FBR for subcutaneous biomedical applications (e.g., glucose sensors).

Glucose sensor membranes for mitigating the foreign body response.

Continuous glucose monitoring devices remain limited in their duration of use due to difficulties presented by the foreign body response (FBR), which impairs sensor functionality immediately following implantation via biofouling and leukocyte infiltration. The FBR persists through the life of the implant, culminating with fibrous encapsulation and isolation from normal tissue. These issues have led researchers to develop strategies to mitigate the FBR and improve tissue integration. Studies have often focused on abating the FBR using various outer coatings, thereby changing the chemical or physical characteristics of the sensor surface. While such strategies have led to some success, they have failed to fully integrate the sensor into surrounding tissue. To further address biocompatibility, researchers have designed coatings capable of actively releasing biological agents (e.g., vascular endothelial growth factor, dexamethasone, and nitric oxide) to direct the FBR to induce tissue integration. Active release approaches have proven promising and, when combined with biocompatible coating materials, may ultimately improve the in vivo lifetime of subcutaneous glucose biosensors. This article focuses on strategies currently under development for mitigating the FBR.

Fabrication of nitric oxide-releasing polyurethane glucose sensor membranes.

Despite clear evidence that polymeric nitric oxide (NO) release coatings reduce the foreign body response (FBR) and may thus improve the analytical performance of in vivo continuous glucose monitoring devices when used as sensor membranes, the compatibility of the NO release chemistry with that required for enzymatic glucose sensing remains unclear. Herein, we describe the fabrication and characterization of NO-releasing polyurethane sensor membranes using NO donor-modified silica vehicles embedded within the polymer. In addition to demonstrating tunable NO release as a function of the NO donor silica scaffold and polymer compositions and concentrations, we describe the impact of the NO release vehicle and its release kinetics on glucose sensor performance.