Antibacterial properties of electrospun Ti3C2T z (MXene)/chitosan nanofibers

Abstract

Electrospun natural polymeric bandages are highly desirable due to their low-cost, biodegradability, non-toxicity and antimicrobial properties. Functionalization of these nanofibrous mats with two-dimensional nanomaterials is an attractive strategy to enhance the antibacterial effects. Herein, we demonstrate an electrospinning process to produce encapsulated delaminated Ti₃C₂T _z (MXene) flakes within chitosan nanofibers for passive antibacterial wound dressing applications. In vitro antibacterial studies were performed on crosslinked Ti₃C₂T _z /chitosan composite fibers against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) - demonstrating a 95% and 62% reduction in colony forming units, respectively, following 4 h of treatment with the 0.75 wt% Ti₃C₂T _z - loaded nanofibers. Cytotoxicity studies to determine biocompatibility of the nanofibers indicated the antibacterial MXene/chitosan nanofibers are non-toxic. The incorporation of Ti₃C₂T _z single flakes on fiber morphology was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy equipped with an energy-dispersive detector (TEM-EDS). Our results suggest that the electrospun Ti₃C₂T _z /chitosan nanofibers are a promising candidate material in wound healing applications.

Fig. 1. (a) Schematic detailing the removal of the Al layers from the Ti₃AlC₂ to yield ML-Ti₃C₂T_z that washing, and sonication then separate into individual Ti₃C₂T_z flakes. (b) SEM micrographs of ML-Ti₃C₂T_z powder and, (c) Ti₃C₂T_z single and few-layer thick flakes on an anodized alumina membrane. (d) TEM micrograph of a Ti₃C₂T_z flake. (e) XRD diffractogram of the vacuum assisted filtered Ti₃C₂T_z film.

Fig. 2. SEM micrographs displaying the surface of the as-spun electrospun crosslinked Ti₃C₂T_z/CS mats for the five different MXene loadings: (a) 0, (b) 0.05, (c) 0.10, (d) 0.25, (e) 0.50, and (f) 0.75 wt%. Scale bars represent 5 μm.

Fig. 3. (a) FTIR spectra and (b) XRD patterns of the neat chitosan nanofibers and the 0.75 wt% Ti₃C₂T_z/CS nanofibers. Asterisks denote signal by the stage.

Fig. 4. (a) Schematic diagram illustrating the observed orientations of Ti₃C₂T_z flakes within the chitosan nanofibers. (b) TEM micrograph of the Ti₃C₂T_z/CS nanofibers and (c) elemental analysis (the presence of copper arises from the TEM grid).

Fig. 5. Antibacterial activity of, (a) E. coli and (b) S. aureus. B-X and GA-X indicate mats treated with NaOH and glutaraldehyde, respectively. SEM micrographs shows an, (c) intact and, (d) destroyed E. coli bacteria on the 0.75 wt% Ti₃C₂T_z/CS nanofiber mat. The star icon designates samples that are significantly different from the control, p ≤ 0.05.

Fig. 6. Biocompatibility of Ti₃C₂T_z/CS nanofibers.

Fig. 7. Comparison of the antibacterial properties with the previous literature of select polymeric nanofibers with incorporated metal oxides and 2D materials. The antibacterial effects of electrospun polymer blends were also compared. The stars denote the materials from this study. Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2016.