Electrospun polyamide (PA) nanofibers have great potential for
medical applications (in dermatology as antimicrobial compound carriers
or surgical sutures). However, little is known about microbial colonization
on these materials. Suitable methods need to be chosen and optimized
for the analysis of biofilms formed on nanofibers and the influence
of their morphology on biofilm formation. We analyzed 11 PA nanomaterials,
both nonfunctionalized and functionalized with AgNO3, and
tested the formation of a biofilm by clinically relevant bacteria
(Escherichia coli CCM 4517, Staphylococcus aureus CCM 3953, and Staphylococcus epidermidis CCM 4418). By four different
methods, it was confirmed that all of these bacteria attached to the
PAs and formed biofilms; however, it was found that the selected method
can influence the outcomes. For studying biofilms formed by the selected
bacteria, scanning electron microscopy, resazurin staining, and colony-forming
unit enumeration provided appropriate and comparable results. The
values obtained by crystal violet (CV) staining were misleading due
to the binding of the CV dye to the PA structure. In addition, the
effect of nanofiber morphology parameters (fiber diameter and air
permeability) and AgNO3 functionalization significantly
influenced biofilm maturation. Furthermore, the correlations between
air permeability and surface density and fiber diameter were revealed.
Based on the statistical analysis, fiber diameter was confirmed as
a crucial factor influencing biofilm formation (p ≤ 0.01). The functionalization of PAs with AgNO3 (from 0.1 wt %) effectively suppressed biofilm formation. The PA
functionalized with a concentration of 0.1 wt % AgNO3 influenced
the biofilm equally as nonfunctionalized PA 8% 2 g/m2.
Therefore, biofilm formation could be affected by the above-mentioned
morphology parameters, and ultimately, the risk of infections from
contaminated medical devices could be reduced.
Background:
Repairs to deep skin wounds continue to be a difficult issue in clinical practice. A promising approach is to fabricate full-thickness skin substitutes with functions closely similar to those of the natural tissue. For many years, a three-dimensional (3D) collagen hydrogel has been considered to provide a physiological 3D environment for co-cultivation of skin fibroblasts and keratinocytes. This collagen hydrogel is frequently used for fabricating tissue-engineered skin analogues with fibroblasts embedded inside the hydrogel and keratinocytes cultivated on its surface. Despite its unique biological properties, the collagen hydrogel has insufficient stiffness, with a tendency to collapse under the traction forces generated by the embedded cells.
Methods:
The aim of our study was to develop a two-layer skin construct consisting of a collagen hydrogel reinforced by a nanofibrous poly-L-lactide (PLLA) membrane pre-seeded with fibroblasts. The attractiveness of the membrane for dermal fibroblasts was enhanced by coating it with a thin nanofibrous fibrin mesh.
Results:
The fibrin mesh promoted the adhesion, proliferation and migration of the fibroblasts upwards into the collagen hydrogel. Moreover, the fibroblasts spontaneously migrating into the collagen hydrogel showed a lower tendency to contract and shrink the hydrogel by their traction forces. The surface of the collagen was seeded with human dermal keratinocytes. The keratinocytes were able to form a basal layer of highly mitotically-active cells, and a suprabasal layer.
Conclusion:
The two-layer skin construct based on collagen hydrogel with spontaneously immigrated fibroblasts and reinforced by a fibrin-coated nanofibrous membrane seems to be promising for the construction of full-thickness skin substitute.
Although nanomaterials are used in many fields, little is known about the fundamental interactions between nanomaterials and microorganisms. To test antimicrobial properties and retention ability, 13 electrospun polyamide (PA) nanomaterials with different morphology and functionalization with various concentrations of AgNO3 and chlorhexidine (CHX) were analyzed. Staphylococcus aureus CCM 4516 was used to verify the designed nanomaterials’ inhibition and permeability assays. All functionalized PAs suppressed bacterial growth, and the most effective antimicrobial nanomaterial was evaluated to be PA 12% with 4.0 wt% CHX (inhibition zones: 2.9 ± 0.2 mm; log10 suppression: 8.9 ± 0.0; inhibitory rate: 100.0%). Furthermore, the long-term stability of all functionalized PAs was tested. These nanomaterials can be stored at least nine months after their preparation without losing their antibacterial effect. A filtration apparatus was constructed for testing the retention of PAs. All of the PAs effectively retained the filtered bacteria with log10 removal of 3.3–6.8 and a retention rate of 96.7–100.0%. Surface density significantly influenced the retention efficiency of PAs (p ≤ 0.01), while the effect of fiber diameter was not confirmed (p ≥ 0.05). Due to their stability, retention, and antimicrobial properties, they can serve as a model for medical or filtration applications.
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