Transforming layered 2D mats into multiphasic 3D nanofiber scaffolds with tailored gradient features for tissue regeneration

Multiphasic scaffolds with tailored gradient features hold significant promise for tissue regeneration applications. Herein, this work reports the transformation of two-dimensional (2D) layered fiber mats into three dimensional (3D) multiphasic scaffolds using a 'solids-of-revolution' inspired gas-foaming expansion technology. These scaffolds feature precise control over fiber alignment, pore size, and regional structure. Manipulating nanofiber mat layers and Pluronic F127 concentrations allows further customization of pore size and fiber alignment within different scaffold regions. The cellular response to multiphasic scaffolds demonstrates the number of cells migrated and proliferated onto the scaffolds are mainly dependent on the pore size rather than fiber alignment. In vivo subcutaneous implantation of multiphasic scaffolds to rats reveals substantial cell infiltration, neo tissue formation, collagen deposition, and new vessel formation within scaffolds, greatly surpassing the capabilities of traditional nanofiber mats. Histological examination indicates the importance of optimizing pore size and fiber alignment for promotion of cell infiltration and tissue regeneration. Overall, these scaffolds have potential applications in tissue modeling, studying tissue-tissue interactions, interface tissue engineering, and high-throughput screening for optimized tissue regeneration.

The Possibility of Reuse of Nanofiber Mats by Machine Washing at Different Temperatures

The worldwide spread of coronavirus COVID-19 infections demonstrates the great need for personal protective equipment and, in particular, hygiene masks. These masks are essential for the primary protection of the respiratory tract against pathogens such as viruses and bacteria that are infectious and transmitted through the air as large droplets or via small airborne particles. The use of protective masks will continue to accompany humans for an indefinite period of time, and therefore there is an urgent need for a safe method to extend their usability by reusing them under perspective with minimal loss of protective properties. Nanofiber mats are widely used in masks and in this study the reusability of nanofiber mats is investigated by washing them at different temperatures. This paper shows the first measurements of the washability of nanofiber mats. Furthermore, the air permeability is measured, and the evaporation resistance is evaluated. According to the results of this study, the air permeability performance of nanofiber mats does not change significantly after washing, confirming the possibility of reuse.

Simultaneous Delivery of Multiple Antimicrobial Agents by Biphasic Scaffolds for Effective Treatment of Wound Biofilms

Biofilms pose a major challenge to control wound-associated infections. Due to biofilm impenetrability, traditional antimicrobial agents are often ineffective in combating biofilms. Herein, a biphasic scaffold is reported as an antimicrobial delivery system by integrating nanofiber mats with dissolvable microneedle arrays for the effective treatment of bacterial biofilms. Different combinations of antimicrobial agents, including AgNO3 , Ga(NO3 )3 , and vancomycin, are incorporated into nanofiber mats by coaxial electrospinning, which enables sustained delivery of these drugs. The antimicrobial agents-incorporated dissolvable microneedle arrays allow direct penetration of drugs into biofilms. By optimizing the administration strategies, drug combinations, and microneedle densities, biphasic scaffolds are able to eradicate both methicillin-resistant Staphylococcus aureus (MRSA) and MRSA/Pseudomonas aeruginosa blend biofilms in an ex vivo human skin wound infection model without necessitating surgical debridement. Taken together, the combinatorial system comprises of nanofiber mats and microneedle arrays can provide an efficacious delivery of multiple antimicrobial agents for the treatment of bacterial biofilms in wounds.

Fabrication of an Inverse Size-Selective Membrane Using an Electrospun Nanofiber Mat as a Template

Size-selective membranes have applications in water purification and other areas. Although many methods have been developed for the fabrication of nanoporous membranes, each method has its limitations. For example, thin films containing uniform nanochannels can be prepared from block copolymer precursors. However, block copolymers are expensive. The electrospinning of a polymer solution can yield long nanofibers that fold into mats and the diameters of these fibers can be tuned from nanometers to micrometers. Infusing another polymer into the voids between these fibers and subsequently removing the nanofiber template should yield an inverse porous membrane, complementary in pore structure to the original nanofiber mat membrane. In this paper, we report on the fabrication of these membranes. We discovered that the flux across such membranes increased by thermally annealing the nanofiber mats under pressure before the infusion of the second polymer and by etching the surfaces of the final membrane with plasma to expose the encapsulated nanochannels. We further discovered that the size of the pores formed at the junction of the fused nanofibers and, eventually, the nanotubes governed the size selectivity of the final membrane. The pore size at the junctions increased by increasing the thermal annealing temperature and, thus, the extent of fiber fusion. The developed methodology is general and should be useful for the fabrication of nanoporous membranes from different materials possessing pore diameters that are governed by the diameter of the templating nanofibers and the extent of their fusion.

Effect of Saponification Condition on the Morphology and Diameter of the Electrospun Poly(vinyl acetate) Nanofibers for the Fabrication of Poly(vinyl alcohol) Nanofiber Mats

Novel poly(vinyl alcohol) (PVA) nanofiber mats were prepared for the first time through heterogeneous saponification of electrospun poly(vinyl acetate) (PVAc) nanofibers. The effect of varying the saponification conditions, including temperature, time, and concentration of the alkaline solution, on the morphology of the saponified PVA fibers were evaluated by field-emission scanning electron microscopy. At 25 °C, the saponified PVA fibers exhibited a broad diameter distribution. The average fiber diameter, however, was found to decrease with increasing saponification temperature. When the saponification time was increased from 6 to 30 h, the average fiber diameter decreased gradually from 1540 to 1060 nm. In addition, the fiber diameter and morphology were also affected by the concentration of the alkaline saponification solution. The most optimal conditions for fabrication of thin, uniform, and smooth PVA nanofibers corresponded to an alkaline solution containing 10 g each of NaOH, Na₂SO₄, and methanol per 100 g of water, a temperature of 25 °C, and a saponification time of 24 h.