Antifouling Electrospun Nanofiber Mats Functionalized with Polymer Zwitterions.
ABSTRACT: 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.
Project description:Hydration is central to mitigating surface fouling by oil and microorganisms. Immobilization of hydrophilic polymers on surfaces promotes retention of water and a reduction of direct interactions with potential foulants. While conventional surface modification techniques are surface-specific, mussel-inspired adhesives based on dopamine effectively coat many types of surfaces and thus hold potential as a universal solution to surface modification. Here, we describe a facile, one-step surface modification strategy that affords hydrophilic, and underwater superoleophobic, coatings by the simultaneous deposition of polydopamine (PDA) with poly(methacryloyloxyethyl phosphorylcholine) (polyMPC). The resultant composite coating features enhanced hydrophilicity (i.e., water contact angle of ~10° in air) and antifouling performance relative to PDA coatings. PolyMPC affords control over coating thickness and surface roughness, and results in a nearly 10 fold reduction in Escherichia coli adhesion relative to unmodified glass. The substrate-independent nature of PDA coatings further promotes facile surface modification without tedious surface pretreatment, and offers a robust template for codepositing polyMPC to enhance biocompatibility, hydrophilicity and fouling resistance.
Project description:Biofilm-associated infections stemming from medical devices are increasingly challenging to treat due to the spread of antibiotic resistance. In this study, we present a simple strategy that significantly enhances the antifouling performance of covalently crosslinked poly(ethylene glycol) (PEG) and physically crosslinked agar hydrogels by incorporation of the fouling-resistant polymer zwitterion, poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC). Dopamine polymerization was initiated during swelling of the hydrogels, which provided dopamine and pMPC an osmotic driving force into the hydrogel interior. Both PEG and agar hydrogels were synthesized over a broad range of storage moduli (1.7,1300 kPa), which remained statistically equivalent after being functionalized with pMPC and polydopamine (PDA). When challenged with fibrinogen, a model blood-clotting protein, the pMPC/PDA-functionalized PEG and agar hydrogels displayed a >90% reduction in protein adsorption compared to hydrogel controls. Further, greater than an order-of-magnitude reduction in Escherichia coli and Staphylococcus aureus adherence was observed. This study demonstrates a versatile materials platform to enhance the fouling resistance of hydrogels through a pMPC/PDA incorporation strategy that is independent of the chemical composition and network structure of the original hydrogel.
Project description:We demonstrate antifouling ultrafiltration membranes with retained selectivity and pure water flux through the controlled deposition of zwitterionic polymers and poly(ethylene glycol) (PEG). Molecules for polymerization were immobilized on the membrane's surface yet prevented from attaching to the membrane's pores due to a backflow of nitrogen (N2) gas achieved using an in-house constructed apparatus that we named the polymer prevention apparatus, or "PolyPrev". First, the operating parameters of the PolyPrev were optimized by investigating the polymerization of dopamine, which was selected due to its versatility in enabling further chemical reactions, published metrics for comparison, and its oxidative self-polymerization. Membrane characterization revealed that the polydopamine-modified membranes exhibited enhanced hydrophilicity; moreover, their size selectivity and pure water flux were statistically the same as those of the unmodified membranes. Because it is well documented that polydopamine coatings do not provide a long-lasting antifouling activity, poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC, Mn = 30 kDa) and succinimidyl-carboxymethyl-ester-terminated PEG ( Mn = 40 kDa) were codeposited while dopamine was polymerizing to generate antifouling membranes. Statistically, the molecular-weight cutoff of the polyMPC- and PEG-functionalized membranes synthesized in the PolyPrev was equivalent to that of the unmodified membranes, and the pure water flux of the PEG membranes was equivalent to that of the unmodified membranes. Notably, membranes prepared in the PolyPrev with polyMPC and PEG decreased bovine serum albumin fouling and Escherichia coli attachment. This study demonstrates that by restricting antifouling chemistries from attaching within the pores of membranes, we can generate high-performance, antifouling membranes appropriate for a wide range of water treatment applications without compromising intrinsic transport properties.
Project description: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.
Project description:The combination of natural active antifouling composition and intelligent coatings has been regarded as a prospective approach to avoid marine biofouling. However, the relatively complex coating structure and the excessive rapid release of antifoulants maintain unresolved issues in their practical application. In this work, a novel environmentally friendly natural antifoulant (Stellera chamaejasme, SC) encapsulated in the polydopamine (PDA) microcapsule (SC@PDA) is prepared by emulsion interfacial polymerization and blended with the acrylate polymer to prepare a sustainable antifouling coating. Herein, the PDA shell acting as an "intelligent capsule" ensures the controlled release of the antifoulant SC, and the corresponding SC loading amount could be high up to 75.40%. As a model antifoulant, the impact of SC on the adsorption activity of the protein bovine serum albumin (BSA) is studied, as well as the settlement of presentative fouling communities (diatom Navicula sp. and red algae Porphyridium sp.) on the constructed coating. The experimental results demonstrate that the natural product SC integrated eco-friendly antifouling coating occupies the superior capacity of impeding the adsorption of both protein BSA and algae. Such antifoulant (SC) integrating with controlled release character is a great advance in terms of marine antifouling applications. It is, therefore, expected that this innovation will provide guiding significance for developing the next generation of antifouling techniques, especially in the field of marine antifouling.
Project description:Polydiacetylenes (PDAs) are conjugative polymers that demonstrate color changes as a response to an external stimulus. In this study, 10,12-pentacosadiynoic acid (PCDA) was mixed with a supporting polymer including poly(ethylene oxide) (PEO) and polyurethane (PU), and the mixture solution was electrospun to construct fiber composites. The electrospun fibers were then photopolymerized using UV irradiation to produce PEO-PDA and PU-PDA nanofiber mats with a fiber diameter ranging from 130 nm to 2.5 ?m. The morphologies of both PEO-PDA and PU-PDA nanofibers were dependent on electrospinning parameters such as the ratio of PCDA to PEO or PCDA to PU and the total polymer concentrations. Scanning electron microscopy images showed beaded fibers of PEO-PDA and PU-PDA at 2 and 18 w/v % concentrations, respectively. Smooth fibers were found when the solvent concentration was increased to 3.75 w/v % in PEO-PDA and 25 w/v % in PU-PDA fibers. Both PEO-PDA and PU-PDA nanofiber composites demonstrated excellent colorimetric responses to the presence of Escherichia coli ATCC25922 bacterial cells and the changes in pH as external stimuli. The nanofibers underwent a rapid colorimetric response when exposed directly to E. coli ATCC25922 grown on Luria-Bertani agar. The comparison between the PEO-PDA and PU-PDA suggested that the combination of PEO and PDA is favorable because it provides a sensitive response to the presence of E. coli. The results were compared with samples of a PDA polymer in the absence of a matrix polymer. The colorimetric response was similar when the PDA polymer and the PDA nanofiber composites were exposed to pH changes, and the color change was found to occur at pH 10 and enhanced at pH 11-13. The PDA-containing nanofiber composites showed stronger colorimetric responses than those of the PDA polymer only, suggesting their potential as biosensors and chemosensors.
Project description:In this study, we have improved membrane performance by enhancing ultrafiltration membranes with electrospun nanofibers. The high-porosity nanofiber layer provides a tailorable platform that does not affect the base membrane structure. To decouple the effects that nanofiber chemistry and morphology have on membrane performance, two polymers commonly used in the membrane industry, cellulose and polysulfone, were electrospun into a layer that was 50 ?m thick and consisted of randomly accumulated 1-?m-diameter fibers. Fouling resistance was improved and selectivity was retained by ultrafiltration membranes enhanced with a layer of either cellulose or polysulfone nanofibers. Potentially because of their better mechanical integrity, the polysulfone nanofiber-membranes demonstrated a higher pure-water permeance across a greater range of transmembrane pressures than the cellulose nanofiber-membranes and control membranes. This work demonstrates that nanofiber-enhanced membranes hold potential as versatile materials platforms for improving the performance of ultrafiltration membranes.
Project description:A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl(-)/SO4(2-) separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl(-)/SO4(2-) permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90?minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08??cm(2) 30?minutes later.
Project description:Electrospinning can be used to create nanofiber mats for diverse applications, from wound dressings and tissue engineering to filters for medical and biotechnological applications. In most of these applications, it is necessary to fix the nanofiber mat on a macroscopic textile fabric, on another nanofiber mat or within a frame to keep it at the desired position. Due to their extremely low thickness and areal mass, however, nanofiber mats are easily destroyed by sewing, and in several situations glued bonds are too thick and not flexible enough. Here we report on ultrasonic welding of polyacrylonitrile nanofiber mats, suggesting this method as a joining process without destruction of the mat morphology for thermoplastic nanofiber mats. A variety of welding patterns results in different adhesion forces between both joined nanofiber mats and different failure mechanisms, with some welding patterns enabling bonding stronger than the mats themselves. Our findings show that ultrasonic welding is a possible joining method for polyacrylonitrile nanofiber mats.
Project description:A facile fabrication strategy of transparent and upconversion photoluminescent nylon 6 (PA6) nanofiber mats was developed based on PA6 nanofiber mats, carboxylic acid-functionalized upconversion nanoparticles (UCNP-COOH), and poly(methyl methacrylate) (PMMA) solution. UCNP-COOH were prepared by a solvothermal method, followed by the ligand exchange process. The electrospinning method and the spin-coating process were employed to combine PA6 nanofiber mats with UCNP-COOH and PMMA to introduce upconversion photoluminescent properties and transparency into the nanocomposite mats, respectively. The prepared UCNP-COOH/PA6/PMMA nanofiber mats are transparent and exhibit green emission, which are similar to UCNP-COOH when they were excited under 980 nm laser. The upconversion luminescent intensity of the functional nanofiber mats can be tailored by adjusting the weight fraction of UCNP-COOH as fillers. This facile strategy can be readily used to other types of intriguing nanocomposites for diverse applications.