Sweat-Based Noninvasive Skin-Patchable Urea Biosensors with Photonic Interpenetrating Polymer Network Films Integrated into PDMS Chips

Abstract

A wearable noninvasive biosensor for in situ urea detection and quantification was developed using a ureaseimmobilized photonic interpenetrating polymer network (IPN urease ) film. The photonic IPN film was intertwined with solid-state cholesteric liquid crystals (CLC solid ) and a poly(acrylic acid) (PAA) network on a flexible poly(ethylene terephthalate) substrate adhered to a poly(dimethylsiloxane) (PDMS) chip that was fabricated using an aluminum mold. The presence of urea in the chemical matrix of human sweat red-shifted the reflected color of the photonic IPN urease film, and quantification was achieved by observing the wavelength at the photonic band gap (λ PBG ) with a limit of detection of 0.4 mM and a linear range of 0.9−50 mM. The color changes observed in the photonic IPN film were digitalized using the CIE 1931 xy coordinates on a cell phone image, thereby enabling fast, direct diagnosis via a downloadable app. This novel PDMS chip can be expanded for use with other biosensors.

Photonic Cholesteric Liquid-Crystal Elastomers with Reprogrammable Helical Pitch and Handedness

“…The change in the repeat length of the periodic structure alters the reflected color of the skin. Inspired by these stimulus responses, scientists have replicated these properties in synthetic materials using photonic colloidal crystals, , cellulose nanoparticles, , and cholesteric liquid crystals (CLCs). , These materials have a wide range of applications in various fields, such as biosensors, − data encryption, , anticounterfeiting, − communication, lasing applications, , and environmental sensors. − Other patterned and/or mechanochromic photonic elastomers were also reported with photonic cellulose films. − Among these synthetic photonic materials, CLCs have a self-organized supramolecular helical periodic structure that enables selective reflection of light. This is based on the Bragg relationship of λ = np cos δ, where λ, n , p , and δ are the wavelength at the photonic band gap, average refractive index, helical pitch, and angle between the incident beam and the helical axis, respectively.…”

Dissolvable Polymer Valves for Sweat Chrono-Sampling in Wearable Paper-Based Analytical Devices

“…The biosensors show a linear response in the concentration range between 5 and 30 mM, which fits well with physiological levels of this biomarker in sweat. 2 Figure 5B shows the results obtained by individual biosensors within the platform when these were queried with a solution of either 5 or 30 mM urea. All the biosensors performed similarly, with an intrasensor variability within the multisensor of 1.5 and 1.9% upon addition of 5 and 30 mM urea, respectively.…”

“…Analytical devices that can be worn and provide continuous information about our health status are revolutionizing health care by enabling the effortless monitoring of biomarker fluctuations over time. − Among these, wearable devices that measure sweat biomarkers are becoming increasingly popular in sports medicine thanks to the noninvasive nature of the measurements. − Filter paper is an excellent candidate material to manufacture these platforms because it can absorb sweat and transport it to sensing areas through capillarity. − Furthermore, paper can be patterned using hydrophobic inks or papercutting, which makes it possible to design microfluidic platforms that transport liquids to a downstream outlet through wicking. − Paper is also bendable, which makes it suitable for developing sensing patches attached to the skin with medical adhesive . Colorimetric signal generation mechanisms are the perfect match to these paper-based analytical devices because test outcomes can be recorded using the camera of a smartphone. , This type of readout is inherently wireless, which circumvents the need to implement antennae or any other type of circuity.…”

Chemically Triggered Changes in Mechanical Properties of Responsive Liquid Crystal Polymer Networks with Immobilized Urease

“…Polymers whose physical and chemical properties respond to external cues are of widespread interest in many areas, including sensing, − drug delivery, − actuation, − and tissue engineering. , Such materials also have sizable implications in the design of smart materials that readily adapt to their environment, catalyze reactions on demand, and repair and/or regenerate upon damage. Over the past two decades, there has been extensive work on integrating enzymes into polymeric supports to create biocatalytic materials; however, the polymers in such cases have generally been chosen solely for their ability to stabilize enzymes. − As a result, such materials have been composed of simple matricese.g., poly­(ethylene glycol), poly­(styrene), polyurethanes, and poly­(methyl methacrylate)that lack functional (e.g., shape-reconfigurable and adaptable/switchable) properties.…”