Nanofiber diameter as a critical parameter affecting skin cell response.

Electrospun polymer nanofibers have opened new opportunities in the rapidly evolving field of tissue engineering, particularly due to their topography and variability of available biomaterials. In order to better understand nanofiber influence on cell growth, the impact of their diameter was systematically examined. In this study homogenous, randomly oriented poly(vinyl alcohol) nanofibers with five different average diameters, ranging from 70nm to 1120nm, were produced, characterized and their impact on morphology, proliferation and mobility of keratinocytes and skin fibroblasts was evaluated. The results have shown that nanofiber diameter affects cell response and that this response is cell line specific. Nanofiber thickness affected size, morphology and actine organization of keratinocytes much more than fibroblasts. Specifically, the keratinocyte grown on nanofibers were more spherical and smaller compared to the control cells, while the fibroblasts were much less affect. They stayed almost unchanged and spread across growth surface. The cell proliferation determined based on their metabolic activity was the highest, when keratinocytes were grown on 305nm thick nanofibers, whereas proliferation of fibroblasts grown similar nanofibers was decreased. Finally, fibroblasts exerted higher mobility than keratinocytes. Both tested cell lines on nanofiber diameters of 300nm resulted in decreased cell mobility. These findings suggest that the control over nanofiber diameter offers promising possibility to better design the tissue scaffolds, since cells distinguish between differently sized nanofibers and respond accordingly.

Development and bioevaluation of nanofibers with blood-derived growth factors for dermal wound healing.

The aim of our work was to produce a modern nanomaterial with incorporated blood-derived growth factors, produced by electrospinning, applicable in treatment of chronic wounds. Platelet-rich plasma was chosen as a natural source of growth factors. Results showed that platelet-rich plasma stimulates keratinocyte and fibroblast cell growth in vitro. Its optimal concentration in growth medium was 2% (v/v) for both types of skin cells, while higher concentrations caused alterations in cell morphology, with reduced cell mobility and proliferation. In the next step hydrophilic nanofibers loaded with platelet-rich plasma were produced from chitosan and poly(ethylene oxide), using electrospinning. The morphology of nanofibers was stable in aqueous conditions for 72 h. It was shown that electrospinning does not adversely affect the biological activity of platelet-rich plasma. The effects of nanofibers with incorporated platelet-rich plasma on cell proliferation, survival, morphology and mobility were examined. Nanofibers limited cell mobility, changed morphology and stimulated cell proliferation. Despite of the small amount of blood-derived growth factors introduced in cell culture via platelet-rich plasma-loaded nanofibers, such nanofibrillar support significantly induced cell proliferation, indicating synergistic effect of nanotopography and incorporated growth factors. The overall results confirm favorable in vitro properties of produced nanofibers, indicating their high potential as a nanomaterial suitable for delivery of platelet-rich plasma in wound healing applications.

Nanofibers and their biomedical use.

The idea of creating replacement for damaged or diseased tissue, which will mimic the physiological conditions and simultaneously promote regeneration by patients' own cells, has been a major challenge in the biomedicine for more than a decade. Therefore, nanofibers are a promising solution to address these challenges. These are solid polymer fibers with nanosized diameter, which show improved properties compared to the materials of larger dimensions or forms and therefore cause different biological responses. On the nanometric level, nanofibers provide a biomimetic environment, on the micrometric scale three-dimensional architecture with the desired surface properties regarding the intended application within the body, while on the macrometric scale mechanical strength and physiological acceptability. In the review, the development of nanofibers as tissue scaffolds, modern wound dressings for chronic wound therapy and drug delivery systems is highlighted. Research substantiates the effectiveness of nanofibers for enhanced tissue regeneration, but ascertains that evidences from clinical studies are currently lacking. Nevertheless, due to the development of nano- and bio-sciences, products on the market can be expected in the near future.

The impact of relative humidity during electrospinning on the morphology and mechanical properties of nanofibers.

Electrospinning is an efficient and flexible method for nanofiber production, but it is influenced by many systemic, process, and environmental parameters that govern the electrospun product morphology. This study systematically investigates the influence of relative humidity (RH) on the electrospinning process. The results showed that the morphology of the electrospun product (shape and diameter) can be manipulated with precise regulation of RH during electrospinning. Because the diameter of nanofibers correlates with their rigidity, it was shown that RH control can lead to manipulation of material mechanical properties. Finally, based on the solution's rheological parameter-namely, phase shift angle-we were able to predict the loss of homogenous nanofiber structure in correlation with RH conditions during electrospinning. This research addresses the mechanism of RH impact on the electrospinning process and offers the background to exploit it in order to better control nanomaterial properties and alter its applicability.

The design trend in tissue-engineering scaffolds based on nanomechanical properties of individual electrospun nanofibers.

This paper especially highlights the finding that the mechanical properties of polymeric nanofibers can be tuned by changing the fiber size as well as the composition. For this purpose, the bending Young's modulus was determined using atomic force microscope by involving single-material (polyvinyl alcohol (PVA), polyethylene oxide (PEO 400K)) and composite nanofibers (polyvinyl alcohol/hyaluronic acid (PVA/HA), polyethylene oxide/chitosan (PEO 400K/CS)). The mechanical property, namely the bending Young's modulus, increases as the diameter of the fibers decreases from the bulk down to the nanometer regime (less than 200 nm). The ranking of increasing stiffness according to the AFM measurements of the three-point beam bending test are in agreement, and can be ranked: PEO 400K

Interfacial rheology: an overview of measuring techniques and its role in dispersions and electrospinning.

Interfacial rheological properties have yet to be thoroughly explored. Only recently, methods have been introduced that provide sufficient sensitivity to reliably determine viscoelastic interfacial properties. In general, interfacial rheology describes the relationship between the deformation of an interface and the stresses exerted on it. Due to the variety in deformations of the interfacial layer (shear and expansions or compressions), the field of interfacial rheology is divided into the subcategories of shear and dilatational rheology. While shear rheology is primarily linked to the long-term stability of dispersions, dilatational rheology provides information regarding short-term stability. Interfacial rheological characteristics become relevant in systems with large interfacial areas, such as emulsions and foams, and in processes that lead to a large increase in the interfacial area, such as electrospinning of nanofibers.