Polyamide substrates

Polyamide substrates with a pore size of 200 nm and a thickness of 60 µm were obtained from GE Healthcare Life Sciences (Piscataway, NJ, USA). The linker molecule dithiobis succinimidyl propionate (DSP), dimethyl sulfoxide (DMSO), and 1X phosphate buffered saline (PBS) were procured from Thermo Fisher Scientific Inc. (Waltham, MA, USA). Salt-free streptavidin from Streptomyces avidiini (≥13 units/mg protein), alcohol oxidase enzyme from Pichia pastoris (10–40 units/mg protein), glucose oxidase from Asperigillus niger (100,000–250,000 units/g), D-(+)-glucose, sodium L-lactate (~98% purity), absolute ethyl alcohol (≥99.5%), and sodium bicarbonate (≥99.7%) were procured from Sigma-Aldrich (St. Louis, MO, USA). NHS-biotin was purchased from Vector laboratories (Burlingame, CA, USA). Glucose oxidase antibody was purchased from Abcam (Cambridge, MA, USA). Lactate oxidase (80 U/mg) was purchased from Toyobo USA. Synthetic sweat was prepared from the recipe described in M.T. Mathew et al. [20 (link)]. The pH range was varied by varying the concentrations of the constituents. Single donor human sweat of pH~6 was purchased from Lee Biosolutions Inc. (Maryland Heights, MO, USA). No preservatives were added to this product and it was stored at −20 °C. All alcohol, glucose, and lactate dilutions were made in synthetic sweat pH 6, 8, and in human sweat buffers.

Polyamide substrates (pore size, 200 nm; thickness, 60 µm) were obtained from GE Healthcare Life Sciences (Piscataway, NJ, USA). The crosslinking molecule dithiobis succinimidyl propionate (DSP) and its solvent, dimethyl sulfoxide (DMSO), were purchased from Thermo Fisher Scientific Inc. (Waltham, MA, USA). The chloride ionophore, 4,5-Bis-[N′-(butyl) thioureido]-2,7-di-tert-butyl-9,9-dimethylxanthene (synonym: Chloride Ionophore IV Selectophore™), was purchased from Sigma-Aldrich (St. Louis, MO, USA). Ionophore solution was prepared by dissolving it in DMSO and vortexing it for 30 min at 1000 rpm. Perspired human sweat of pH 5.98 from a single donor was obtained from Lee Biosolutions Inc. (Maryland Heights, MO, USA) and was stored at −20 °C, without the addition of any preservatives. Potassium chloride, which was used to spike the human sweat samples with the desired chloride levels for sensor calibration, was ordered from Thermo Fisher Scientific Inc. Synthetic sweat (pH 2, 4, 6, and 8) was used as a buffer for zeta potential studies, which was prepared as per the recipe described by Mathew et al., minus the NaCl and KCl dissolution [26 (link)]. Buffer pH was varied using lactic acid (85%) and urea, which were obtained from Sigma-Aldrich (St. Louis, MO, USA) and Thermo Fisher Scientific Inc. (Waltham, MA, USA), respectively.

Polyamide substrates were ordered from GE Healthcare Life Sciences (Piscataway, NJ, USA) with 0.2 μm pore size. The linker molecule Dithiobis [Succinimidyl Propionate] (DSP) and its solvent Dimethyl Sulfoxide (DMSO) is ordered from Thermo Fisher Scientific Inc. (Waltham, MA, USA). The α-cortisol antibody and cortisol hormone (Hydrocortisone) was ordered from Abcam (Cambridge, MA, USA). IL-1β antigen was bought from Thermo Fisher Scientific Inc. (Waltham, MA, USA). The antibody was diluted in 1X phosphate buffered saline (PBS, Thermo Fisher Scientific Inc., Waltham, MA, USA). Both cortisol hormone and IL-1β are diluted using synthetic sweat. The synthetic sweat was prepared as per the recipe stated in Table 2 of M.T. Mathew et al.26 . The pH range is varied by varying the concentration of the components. Human sweat was purchased from Lee biosolutions Inc. (St. Louis, MO, USA), where it was collected from single human donor with pH ~ 4–5. No preservatives have been added to this product and it was stored unfiltered at below −20 °C.