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Chronic non-healing wounds show delayed and incomplete healing processes and in turn expose patients to a high risk of infection. Treatment currently focuses on dressings that prevent microbial infiltration and keep a balanced moisture and gas exchange environment. Antibacterial delivery from dressings has existed for some time, with responsive systems now aiming to trigger release only if infection occurs. Simultaneously, approaches that stimulate cell proliferation in the wound and encourage healing have been developed. Interestingly, few dressings appear capable of simultaneously impairing or treating infection and encouraging cell proliferation/wound healing. Electrospinning is a simple, cost-effective, and reproducible process that can utilize both synthetic and natural polymers to address these specific wound challenges. Electrospun meshes provide high-surface area, micro-porosity, and the ability to load drugs or other biomolecules into the fibers. Electrospun materials have been used as scaffolds for tissue engineering for a number of years, but there is surprisingly little literature on the interactions of fibers with bacteria and co-cultures of cells and bacteria. This Review examines the literature and data available on electrospun wound dressings and the research that is required to develop smart multifunctional wound dressings capable of treating infection and healing chronic wounds.

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The effects of different poly(ethylene glycol) (PEG) attachment strategies upon the adhesion of a Gramnegative bacteria (Pseudomonas sp.) was tested. PEG was covalently immobilized, at the lower critical solution temperature of PEG, to a layer of branched poly(ethylenimine) (PEI). PEI was both physically adsorbed to a stainless-steel (SS) substrate and covalently immobilized to a carboxylated poly(ethylene terephthalate) (PET-COOH) surface. On both substrates, the PEI and PEG grafting conditions were optimized so that the levels of surface coverage after each step were maximized and were the same on both substrates, as judged by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, ToF-SIMS imaging showed that both substrates were chemically uniform after each surface modification step. Thus, the two surfaces differ only in the mode of attachment of PEI to the substrate. In bacterial adhesion experiments, the optimal SS-PEG surface was not capable of reducing the number of adherent Pseudomonas sp. when compared to the controls. However, the PET-PEG surface reduced the level of adhesion by between 2 and 4 orders of magnitude for up to 5 h. ToF-SIMS analysis showed that both PEG surfaces adsorbed low but comparable levels of proteinaceous growth medium components (tryptic soy broth), as indicated by the addition of unique amino acid fragment ions in the spectra, most likely small peptides. Thus, bacterial adhesion was strongly dependent on the PEG immobilization strategy and not on the extent of peptide/protein adsorption. However, for the best PEG surfaces the residual bacterial adhesion is most likely from recognition of the small amount of adsorbed peptides. This highlights the necessity for preventing the adsorption of small biological species that can even penetrate PEG layers of high graft density, in the quest for the ultimate "nonfouling" surface.

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