pH-Responsive Electrospun Nanofibers and Their Applications

Abstract

Electrospun nanofibrous membranes offer superior properties over other polymeric membranes not only due to their high membrane porosity but also due to their high surface-to-volume ratio. A plethora of available polymers and post-modification methods allow the incorporation of "smart" responsiveness in fiber membranes. The pHresponsive property is achieved using polymers from the class of polyelectrolytes, which contain pH-dependent functional groups on their polymeric backbone. Electrospinning macroscopic membranes using polyelectrolytes earned considerable interest for biomedical and environmental applications due to the possibility to trigger chemical and physical changes of the membrane (swelling, wettability, degradation) in response to environmental pH-changes. Here, we review recent advancements in the field of electrospinning of pHresponsive nanofiber materials. Starting with the chemical background of pH-responsive polymers at the molecular level, we highlight the material-property transformation upon pH-change at the macroscopic membrane level and, finally, we provide an overview of recent applications of pH-responsive fiber membranes.

Tailoring Fibre Structure Enabled by X-ray Analytics for Targeted Biomedical Applications

“…Furthermore, steering the bulk and surface properties of fibrous constructs can help to obtain control over the release kinetics. [3] Several studies were done in our laboratories to elucidate fibre's structure to gain control over the release kinetics of fibrous materials for different applications. [25][26][27] In electrospinning, many process parameters can be tuned to specifically tailor the structure or the surface of fibres.…”

“…Due to these inherent properties, advanced fibrous materials have recently found applications as sensors, in biomedical and tissue engineering, filtration, energy harvesting and smart textiles. [1][2][3][4][5][6][7][8] Our emphasis and recent developments in X-ray-based analytical methods [9][10][11][12] and related structural findings, especially through small/wide-angle X-ray scattering (SAXS/WAXS) studies, enable us to tailor the fibre functions for advanced and smart applications. Non-destructive X-ray methods enable us to observe changes in the partially crystalline polymer structure depending on a change of experimental condition (temperature, mechanical load or humidity).…”

Fabrication of a Wearable Flexible Sweat pH Sensor Based on SERS-Active Au/TPU Electrospun Nanofibers

“…Additionally, electrospinning can produce mechanically durable and chemically resistant fibrous membranes allowing for postprocesses, such as metallization and chemisorption, to assemble SAMs of pH-responsive molecules, like 4-MBA or 4-MPy, on plasmonic materials coated on the fiber surface. Fields of research that have utilized electrospun fibers include drug delivery, energy harvesting, wound healing, and sensing. ,,, …”

“…Fields of research that have utilized electrospun fibers include drug delivery, 30 energy harvesting, 31 wound healing, 32 and sensing. 4,13,27,33 In this work, electrospun thermoplastic polyurethane (TPU) NFs, sputter coated with Au, are investigated as a pH-sensitive SERS substrate for the application of wearable, low-volume sweat analysis. TPU was chosen due to its high mechanical strength and elasticity as well as its chemical resistance and biocompatibility, which make it well-suited for wearable applications.…”

Light-Driven Polarity Switching of the Chromatographic Stationary Phase with Photoreversibility

“…Smart materials can be responsive to external stimuli, such as electric field, , light, − pH, − pressure, − and temperature, − to achieve predictable and reversible change in inherent structures and functions. Among these stimuli, light is highly advantageous to provide a superior spatial and temporal control in operation .…”