Antifouling Electrospun Nanofiber Mats Functionalized with Polymer Zwitterions.

In this study, we exploit the excellent fouling resistance of polymer zwitterions and present electrospun nanofiber mats surface functionalized with poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC). This zwitterionic polymer coating maximizes the accessibility of the zwitterion to effectively limit biofouling on nanofiber membranes. Two facile, scalable methods yielded a coating on cellulose nanofibers: (i) a two-step sequential deposition featuring dopamine polymerization followed by the physioadsorption of polyMPC, and (ii) a one-step codeposition of polydopamine (PDA) with polyMPC. While the sequential and codeposited nanofiber mat assemblies have an equivalent average fiber diameter, hydrophilic contact angle, surface chemistry, and stability, the topography of nanofibers prepared by codeposition were smoother. Protein and microbial antifouling performance of the zwitterion modified nanofiber mats along with two controls, cellulose (unmodified) and PDA coated nanofiber mats were evaluated by dynamic protein fouling and prolonged bacterial exposure. Following 21 days of exposure to bovine serum albumin, the sequential nanofiber mats significantly resisted protein fouling, as indicated by their 95% flux recovery ratio in a water flux experiment, a 300% improvement over the cellulose nanofiber mats. When challenged with two model microbes Escherichia coli and Staphylococcus aureus for 24 h, both zwitterion modifications demonstrated superior fouling resistance by statistically reducing microbial attachment over the two controls. This study demonstrates that, by decorating the surfaces of chemically and mechanically robust cellulose nanofiber mats with polyMPC, we can generate high performance, free-standing nanofiber mats that hold potential in applications where antifouling materials are imperative, such as tissue engineering scaffolds and water purification technologies.

Electrospinning chitosan/poly(ethylene oxide) solutions with essential oils: Correlating solution rheology to nanofiber formation.

Electrospinning hydrophilic nanofiber mats that deliver hydrophobic agents would enable the development of new therapeutic wound dressings. However, the correlation between precursor solution properties and nanofiber morphology for polymer solutions electrospun with or without hydrophobic oils has not yet been demonstrated. Here, cinnamaldehyde (CIN) and hydrocinnamic alcohol (H-CIN) were electrospun in chitosan (CS)/poly(ethylene oxide) (PEO) nanofiber mats as a function of CS molecular weight and degree of acetylation (DA). Viscosity stress sweeps determined how the oils affected solution viscosity and chain entanglement (Ce) concentration. Experimentally, the maximum polymer:oil mass ratio electrospun was 1:3 and 1:6 for CS/PEO:CIN and:H-CIN, respectively; a higher chitosan DA increased the incorporation of H-CIN only. The correlations determined for electrospinning plant-derived oils could potentially be applied to other hydrophobic molecules, thus broadening the delivery of therapeutics from electrospun nanofiber mats.

Antimicrobial Activity of Silver Ions Released from Zeolites Immobilized on Cellulose Nanofiber Mats.

In this study, we exploit the high silver ion exchange capability of Linde Type A (LTA) zeolites and present, for the first time, electrospun nanofiber mats decorated with in-house synthesized silver (Ag(+)) ion exchanged zeolites that function as molecular delivery vehicles. LTA-Large zeolites with a particle size of 6.0 µm were grown on the surface of the cellulose nanofiber mats, whereas LTA-Small zeolites (0.2 µm) and three-dimensionally ordered mesoporous-imprinted (LTA-Meso) zeolites (0.5 µm) were attached to the surface of the cellulose nanofiber mats postsynthesis. After the three zeolite/nanofiber mat assemblies were ion-exchanged with Ag(+) ions, their ion release profiles and ability to inactivate Escherichia coli (E. coli) K12 were evaluated as a function of time. LTA-Large zeolites immobilized on the nanofiber mats displayed more than an 11 times greater E. coli K12 inactivation than the Ag-LTA-Large zeolites that were not immobilized on the nanofiber mats. This study demonstrates that by decorating nanometer to micrometer scale Ag(+) ion-exchanged zeolites on the surface of high porosity, hydrophilic cellulose nanofiber mats, we can achieve a tunable release of Ag(+) ions that inactivate bacteria faster and are more practical to use in applications over powder zeolites.

Polyelectrolyte-Functionalized Nanofiber Mats Control the Collection and Inactivation of Escherichia coli.

Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: poly (acrylic acid) (PAA), chitosan (CS), and polydiallyldimethylammonium chloride (pDADMAC). The polyelectrolyte functionalized nanofiber mats retained the cylindrical morphology and average fiber diameter (~0.84 µm) of the underlying cellulose nanofibers. X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed the presence of polycations or polyanions on the surface of the nanofiber mats. Both the control cellulose and pDADMAC-functionalized nanofiber mats exhibited a high collection of E. coli K12, which suggests that mat hydrophilicity may play a larger role than surface charge on cell collection. While the minimum concentration of polycations needed to inhibit E. coli K12 was 800 µg/mL for both CS and pDADMAC, once immobilized, pDADMAC-functionalized nanofiber mats exhibited a higher inactivation of E. coli K12, (~97%). Here, we demonstrate that the collection and inactivation of microorganisms by electrospun cellulose nanofiber mats can be tailored through a facile polyelectrolyte functionalization process.

Electrospinning an essential oil: cinnamaldehyde enhances the antimicrobial efficacy of chitosan/poly(ethylene oxide) nanofibers.

Due to the persistent spread of antibiotic resistance, commercial antibiotic treatments are proving ineffective. Cinnamaldehyde (CA), a volatile essential oil, eradicates pathogens non-specifically. However, the ability to incorporate essential oils into nanofiber mats has not yet been demonstrated, and, only six studies have electrospun two immiscible phases. Here, CA (0.5 and 5.0%) was incorporated into chitosan/poly(ethylene oxide) (PEO) solutions that were successfully electrospun into mats with ∼ 50 nm fiber diameters. Solid-state NMR results corroborated with release studies wherein the 5.0% CA mats released a statistically higher amount of CA-liquid (545% more) and CA-vapor (279% more) than the 0.5% CA mats. In time dependent cytotoxicity studies, the intrinsic antibacterial activity of chitosan along with the quick release of CA enabled high inactivation rates against Escherichia coli and Pseudomonas aeruginosa. For the first time we have demonstrated chitosan/CA/PEO nanofiber mats can serve as CA delivery vehicles that potentially eradicate pseudomonas infections.

Designing electrospun nanofiber mats to promote wound healing - a review.

Current strategies to treat chronic wounds offer limited relief to the 7.75 million patients who suffer from burns or chronic skin ulcers. Thus, as long as chronic wounds remain a global healthcare problem, the development of alternate treatments remain desperately needed. This review explores the recent strategies employed to tailor electrospun nanofiber mats towards accelerating the wound healing process. Porous nanofiber mats readily produced by the electrospinning process offer a promising solution to the management of wounds. The matrix chemistry, surface functionality, and mat degradation rate all can be fine-tuned to govern the interactions that occur at the materials-biology interface. In this review, first we briefly discuss the wound healing process and then highlight recent advances in drug release, biologics encapsulation, and antibacterial activity that have been demonstrated via electrospinning. While this versatile biomaterial has shown much progress, commercializing nanofiber mats that fully address the needs of an individual patient remains an ambitious challenge.