Hydrogen-Bonded, Mechanically Strong Nanofibers with Tunable Antioxidant Activity

Abstract

We report on mechanically strong, water-insoluble hydrogen-bonded nanofiber mats composed of a hydrophilic polymer and a natural polyphenol that exhibit prolonged antioxidant activity. The high performance of fibrous mats resulted from the formation of a network of hydrogen bonds between a low-molecular-weight polyphenol (tannic acid, TA) and a water-soluble polymer (polyvinylpyrrolidone, PVP) and could be precisely controlled by the TA-to-PVP ratio. Dramatic enhancement (5- to 10-fold) in tensile strength, toughness, and Young’s moduli of the PVP/TA fiber mats (as compared to those of pristine PVP fibers) was achieved at the maximum density of hydrogen bonds, which occurred at ∼0.2–0.4 molar fractions of TA. The formation of hydrogen bonds was confirmed by an increase in the glass-transition temperature of the polymer after binding with TA. When exposed to water, the fibers exhibited composition- and pH-dependent stabilities, with the TA-enriched fibers fully preserving their integrity in acidic and neutral media. Importantly, the fiber mats exhibited strong antioxidant activity with dual (burst and prolonged) activity profiles, which could be controlled via fiber composition, a feature useful for controlling radical-scavenging rates in environmental and biological applications.

Shape Memory Polymer Foams with Phenolic Acid-Based Antioxidant Properties

“…The ability to control the rate of oxidative degradation in biomaterials can extend potential applications to longer-term implants. The addition of PAs provides a new tool for tuning SMP foam degradation that could be extended to other oxidatively degradable polymers [ 55 ], such as polylactic acid (PLA) [ 56 ], polyvinyl alcohol (PVA) [ 57 , 58 ], polycaprolactone (PCL) [ 59 ], polyvinylpyrrolidone (PVP) [ 60 , 61 ], poly( N -vinylcaprolactam) (PVCL) [ 62 ], and polyethylene glycol (PEG) [ 63 , 64 ].…”

Integrating Antioxidant Functionality into Polymer Materials: Fundamentals, Strategies, and Applications

“…Also shown is a demonstration of (e, g, h, i) the ratio and (f) surface area dependence of PVP/TA NFs on stability in an aqueous solution (panel (e)), ABTS • + scavenging (panel (f)), proposed evolution of PVP/TA hydrogen bonding (panel (g)), NF tensile strength and toughness (panel (h)), and temporal TA release in an aqueous solution (panel (i)). [Adapted with permission from ref . Copyright 2020, American Chemical Society, Washington, DC.…”

“…Conversely, polyphenols that form strong, stoichiometric hydrogen-bonded complexes with the polymer matrix display controlled retention within the fiber, rather than diffusion-based release. In addition, hydrogen-bonded nanofibers can release polyphenols in response to pH changes if the ions infiltrate and destabilize the assemblies . For example, both polyvinylpyrrolidone (PVP, sometimes abbreviated as PVPON) and TA are soluble in water; however, PVP/TA fibers mixed at 1:0.5 and 1:0.67 stochiometric ratios maintained their structure after immersion in aqueous conditions (Figure e) .…”

“…In addition, hydrogen-bonded nanofibers can release polyphenols in response to pH changes if the ions infiltrate and destabilize the assemblies. 185 For example, both polyvinylpyrrolidone (PVP, sometimes abbreviated as PVPON) and TA are soluble in water; however, PVP/TA fibers mixed at 1:0.5 and 1:0.67 stochiometric ratios maintained their structure after immersion in aqueous conditions (Figure 7e). 185 The high-surface-area fiber mat demonstrated excellent antioxidant activity compared to a bulk complex (Figure 7f), attributed to both the TA held by hydrogen bonds with the fiber, proposed in Figure 7g, and the TA released into the surroundings (Figure 7i).…”

Augmenting Therapeutic Potential of Polyphenols by Hydrogen-Bonding Complexation for the Treatment of Acute Lung Inflammation

“…Polyphenols such as tannic acid (TA), procyanidin (PC), and epigallocatechin gallate (EGCG) are naturally occurring compounds that exist in vegetables, fruit peels, green tea, or medicinal plants. − They have been broadly used as food or drink additives and are generally recognized as safe by the U.S. Food and Drug Administration (FDA). , These natural polyphenols were confirmed to effectively eliminate ROS and show broad spectrum biological activities, such as anticancer, antibacterial, antioxidant, and anti-inflammatory effects. − Previous work described that catechin has beneficial effects for the treatment of ocular diseases through its anti-inflammatory and anti-oxidant properties . Whereas the therapeutic usefulness of polyphenolic drugs in clinical trials was very limited because they possessed poor stability, short half-life in plasma, and lower bioavailability .…”