Abstract
Successful commercialization of wearable diagnostic sensors necessitates stability in detection of analytes over prolonged and continuous exposure to sweat. Challenges are primarily in ensuring target disease specific small analytes (i.e. metabolites, proteins, etc.) stability in complex sweat buffer with varying pH levels and composition over time. We present a facile approach to address these challenges using RTILs with antibody functionalized sensors on nanoporous, flexible polymer membranes. Temporal studies were performed using both infrared spectroscopic, dynamic light scattering, and impedimetric spectroscopy to demonstrate stability in detection of analytes, Interleukin-6 (IL-6) and Cortisol, from human sweat in RTILs. Temporal stability in sensor performance was performed as follows: (a) detection of target analytes after 0, 24, 48, 96, and 168 hours post-antibody sensor functionalization; and (b) continuous detection of target analytes post-antibody sensor functionalization. Limit of detection of IL-6 in human sweat was 0.2 pg/mL for 0–24 hours and 2 pg/mL for 24–48 hours post-antibody sensor functionalization. Continuous detection of IL-6 over 0.2–200 pg/mL in human sweat was demonstrated for a period of 10 hours post-antibody sensor functionalization. Furthermore, combinatorial detection of IL-6 and Cortisol in human sweat was established with minimal cross-talk for 0–48 hours post-antibody sensor functionalization.
Highlights
This work is the first report to date, based on our assessments of other similar works in the published domain, of the combinatorial detection of IL-6 and Cortisol in Human Sweat
The primary reason is due to the difficulty in ensuring the biomolecules stability in the complex buffer media such as sweat with widely varying pH levels
It can be concluded that the sensor stability is sustained until 96 hours in the presence of RTIL after immobilization of the antibody and can be utilized for detection of IL-6 from human sweat
Summary
This section is organized as follows: (1) Structural characterization of functionalized ZnO sensor arrays fabricated on nanoporous polyamide substrates; (2) ATR-IR spectroscopy analysis of efficacy and stability of biomolecule binding in RTIL; (3) DLS analysis of protein stability in RTIL using hydrodynamic radius and zeta potential; and (4) Sensor analytical performance and cross-reactivity studies using EIS. C-N stretch of aliphatic amines[40] is observed at 1064 cm−1 These results conclude the diffusion of protein through the nanoporous polyamide membrane without any hindrance in presence of RTIL. The binding between DSP linker and antibody is indicated by the breaking of C-O bond of NHS ester and binding of primary amine of the antibody in that position depicting aminolysis as shown in inset of Fig. 5 This process is verified through: 1) decreasing peak height of 1780 cm−1 and increasing peak height at 1665 cm−1 from DSP only spectra to DSP-antibody spectra at T0, T24 and T48 hours respectively; and 2) breaking of C-O vibrations that is indicated by decreasing peak at 1150 cm−1 over time. Expected Peak position 3000–2640 cm−1 1465 cm−1 1375 cm−1 720 cm−1 1020–1250 cm−1 3225–3280 cm−1 1600–1700 cm−1 1510–1580 cm−1
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