Nonwoven Scaffolds Research Articles

3D melt blowing of Elastollan thermoplastic polyurethane for tissue engineering applications: A pilot study

Scaffolds, in addition to being biocompatible, should possess structural and mechanical properties similar to the natural tissues they intend to replace. Many tissue engineering applications require porous 3D scaffolds characterized by unique microfibrous organization and mechanical anisotropy. Manufacturing process principles and process parameter-biomaterial interactions ultimately govern the properties that can be achieved in the scaffold. In this study, we investigate a recently developed nonwoven scaffold fabrication process, 3D melt blowing (3DMB), for processing Elastollan®, a thermoplastic polyurethane with basic mechanical properties suitable for musculoskeletal tissue engineering. The range of feasible processing parameters was screened and the effects of two sets of critical process parameters (fiber deposition offset and surface velocity of the collector) that produced contrasting scaffold morphologies were assessed. Results showed that scaffolds of Group B that were fabricated at the higher fiber deposition offset (90 %) and higher surface velocity of the collector (6 × 105 mm/min) possessed significantly smaller fiber diameter and higher porosity and degree of fiber alignment along the principal direction of collector rotation during 3DMB (all p < 0.05) compared to Group A scaffolds (fabricated at 50 % offset and 1 × 105 mm/min surface velocity). Although both groups possessed similar tensile stiffness, the elongation at failure was significantly different (p < 0.0001). The higher elongation at failure of Group B correlated with the higher degree of fiber alignment in these scaffolds. In contrast, the more isotropic fibrous organization of Group A contributed to their higher compressive stiffness (p = 0.004). The introduction of NaOH treatment to improve hydrophilicity of the scaffolds resulted in a significant reduction of tensile stiffness of Group A (p < 0.05) but not Group B. This treatment did not significantly affect the elongation at failure or compressive stiffness of both groups. With NaOH-treatment, both groups demonstrated good biocompatibility when seeded with fibroblast cells over 14 days. This study confirms the ability to fabricate via 3DMB, biocompatible, micro-fibrous, Elastollan scaffolds relevant for musculoskeletal tissue engineering.

Cell seeding dynamics in a porous scaffold material designed for meniscus tissue regeneration

AbstractWe study the dynamics of a seeding experiment where a fibrous scaffold material is colonized by two types of cell populations. The specific application that we have in mind is related to the idea of meniscus tissue regeneration. In order to support the development of a promising replacement material, we discuss certain rate equations for the densities of human mesenchymal stem cells and chondrocytes and for the production of collagen‐containing extracellular matrix. For qualitative studies, we start with a system of ordinary differential equations and refine then the model to include spatial effects of the underlying nonwoven scaffold structure. Numerical experiments as well as a complete set of parameters for future benchmarking are provided.

Controlling Mechanical Properties of Medical-Grade Scaffolds through Electrospinning Parameter Selection.

Electrospinning (ES) is a versatile process mode for creating fibrous materials with various structures that have broad applications ranging from regenerative medicine to tissue engineering and surgical mesh implants. The recent commercialization of this technology for implant use has driven the use of resorbable electrospun products. Resorbable electrospun meshes offer great promise as temporary implants that can utilize the layer upon layer method of additive manufacturing to incorporate porosity as a function of process parameters into a scaffold structure. The interconnected porosity and feature size known to ES have previously been observed to hold great potential for simulating the natural cellular environment of soft tissue. This microstructure, proper degradation kinetics, and mechanical properties combine to provide the design basis for artificial tissue structures that could aid in not only wound healing but also true tissue engineering and regenerative medicine. While current advancement in the field is understood to be limited by material properties, the importance of optimizing mechanical properties with currently available materials should not be overlooked. This work investigated the process parameter effects and interactions that control the structure-property relationship for a range of medical-grade aliphatic polyester materials with a range of intrinsic properties. An ε-caprolactone homopolymer (PCL), l-lactide homopolymer (PLLA), and Lactoflex, a copolymer with intermediate properties relative to the homopolymers, were characterized before, during, and after the additive manufacturing process. The interacting effects of process parameters, distance to collector, and dispensing rate were shown to produce variable-density, nonwoven scaffold structures. The resorbable mesh scaffolds of PLLA, PCL, and Lactoflex demonstrated a broad range of mechanical properties (approximately 1-10 MPa ultimate tensile strength and 5-390 MPa tensile modulus). Postprocessing of scaffolds demonstrated removal of solvents and preservation of micrometer-sized features. Resorbable polymers and electrospinning can produce scaffold materials with excellent features and offer tremendous potential in the field of implantable resorbable devices.

Silk Fibroin Materials: Biomedical Applications and Perspectives.

The golden rule in tissue engineering is the creation of a synthetic device that simulates the native tissue, thus leading to the proper restoration of its anatomical and functional integrity, avoiding the limitations related to approaches based on autografts and allografts. The emergence of synthetic biocompatible materials has led to the production of innovative scaffolds that, if combined with cells and/or bioactive molecules, can improve tissue regeneration. In the last decade, silk fibroin (SF) has gained attention as a promising biomaterial in regenerative medicine due to its enhanced bio/cytocompatibility, chemical stability, and mechanical properties. Moreover, the possibility to produce advanced medical tools such as films, fibers, hydrogels, 3D porous scaffolds, non-woven scaffolds, particles or composite materials from a raw aqueous solution emphasizes the versatility of SF. Such devices are capable of meeting the most diverse tissue needs; hence, they represent an innovative clinical solution for the treatment of bone/cartilage, the cardiovascular system, neural, skin, and pancreatic tissue regeneration, as well as for many other biomedical applications. The present narrative review encompasses topics such as (i) the most interesting features of SF-based biomaterials, bare SF's biological nature and structural features, and comprehending the related chemo-physical properties and techniques used to produce the desired formulations of SF; (ii) the different applications of SF-based biomaterials and their related composite structures, discussing their biocompatibility and effectiveness in the medical field. Particularly, applications in regenerative medicine are also analyzed herein to highlight the different therapeutic strategies applied to various body sectors.

Fibroblasts and polymer composition are essential for bioengineering of airway epithelium on nonwoven scaffolds

To make tissue engineering a truly effective tool, it is necessary to understand how the patterns of specific tissue development are modulated by and depend on the artificial environment. Even the most advanced approaches still do not fully meet the requirements of practical engineering of tracheobronchial epithelium. This study aimed to test the ability of the synthetic and natural nonwoven scaffolds to support the formation of morphological sound airway epithelium including the basement membrane (BM). We also sought to identify the potential role of fibroblasts in this process. Our results showed that nonwoven scaffolds are generally suitable for producing well-differentiated tracheobronchial epithelium (with cilia and goblet cells), while the structure and functionality of the equivalents appeared to be highly dependent on the composition of the scaffolds. Unlike natural scaffolds, synthetic ones supported the formation of the epithelium only when epithelial cells were cocultured with fibroblasts. Fibroblasts also appeared to be obligatory for basal lamina formation, regardless of the type of the nonwoven material used. However, even in the presence of fibroblasts, the synthetic scaffolds were unable to support the formation of the epithelium and of the BM (in particular, basal lamina) as effectively as the natural scaffolds did.

Effect of PLGA Concentration in Electrospinning Solution on Biocompatibility, Morphology and Mechanical Properties of Nonwoven Scaffolds

In this work, the effects of weight concentration on the properties of poly(lactide-co-glycolide) polymeric scaffolds prepared by electrospinning are investigated, using four different weight concentrations of poly(lactide-co-glycolide) for the electrospinning solutions (2, 3, 4, 5 wt.%). With increasing concentration of poly(lactide-co-glycolide) in the electrospinning solutions, their viscosity increases significantly. The average fiber diameter of the scaffolds also increases with increasing concentration. Moreover, the tensile strength and maximum elongation at break of the scaffold increase with increasing electrospinning concentration. The prepared scaffolds have hydrophobic properties and their wetting angle does not change with the concentration of the electrospinning solution. All poly(lactide-co-glycolide) scaffolds are non-toxic toward fibroblasts of the cell line 3T3-L1, with the highest numbers of cells observed on the surface of scaffolds prepared from the 2-, 3- and 4-wt.% electrospinning solutions. The results of the analysis of mechanical and biological properties indicate that the poly(lactide-co-glycolide) scaffolds prepared from the 4 wt.% electrospinning solution have optimal properties for future applications in skin tissue engineering. This is due to the fact that the poly(lactide-co-glycolide) scaffolds prepared from the 2 wt.% and 3 wt.% electrospinning solution exhibit low mechanical properties, and 5 wt.% have the lowest porosity values, which might be the cause of their lowest biological properties.

Cell culture design for homogeneous proliferation of cells in three-dimensional nonwoven polymer scaffolds

The objective of this study is to establish strategies to uniformly proliferate cells in a three-dimensional nonwoven polyethylene terephthalate (PET)/ethylene vinyl alcohol (EVOH) scaffold by simple adjustments in seeding and culture methods and the scaffold design. The combined dynamic and static seeding (intermittent agitations at 300 rpm with 1 h interval) resulted in the highest seeding efficiency (71%) comparing to the static and continuous agitating seeding methods. Cell-attached scaffolds were cultivated under different conditions. The stirring culture permitted cells to proliferate to a significantly greater extent than the static or agitating cultures, although faster cell proliferation in the outer region of the scaffold was observed. Next, based on this observation, scaffolds were opened with holes to alleviate the cell aggregation. The effect of hole size and number of scaffolds on the distribution of cells proliferated in the scaffold was evaluated. Two of 1-mm holes showed to be an optimal adjustment to allow cells to proliferate in a homogeneous manner. After 14 days culture, both of the holes were filled by cells proliferated with a fourfold increase in the cell number. The cell viability in the scaffolds was also high upon evaluating the live/dead and 3[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) staining examinations. Different cell types of 3T3-L1, C3H/10T1/2, and KUM6 cells showed similar behavior of cell proliferation and distribution in the scaffold, indicating the applicability of the established procedure. It is concluded that the nonwoven PET/EVOH scaffold serves as a potential cell culture substrate for an efficient cell proliferation.

Влияние мультипотентных мезенхимальных стромальных клеток на физико-химические и механические свойства полиэфирных матриксов различной архитектоники

The biocompatibility of polylactic-co-glycolic acid (PLGA) scaffolds for tissue engineering constructions can be significantly improved by autologous mesenchymal stem cells (MSCs) colonization. However, the features of the cell colonization procedure can generally affect the changes in the physical and mechanical properties of these scaffolds, which are mostly determined by their architectonics. To study this issue, in this work, we have formed and investigated three types of experimental PLGA samples: 1). molded monolithic blocks; 2). porous scaffolds formed by plasticization in supercritical CO2 followed by foaming; and 3). electrospun fibrous non-woven scaffolds. The quantitative XTT test showed the nontoxicity of all studied samples, as well as the greater efficiency of the dynamic cell colonization method compared to the static one. After 48 hours of samples incubation with cell cultures, their physical and mechanical properties were noted to change both at macro- and microlevels. These changes, in our opinion, occur due to the processes of hydrolytic and enzymatic PLGA hydrolysis, as well as the effect of adhered MSCs on the scaffold internal structure and surface morphology. Similar transformations of certain physical, mechanical and structural properties of scaffolds based on other biodegradable polymers or their compositions can also occur as a result of their colonization with various cell cultures, which should be taken into account when applying the scaffolds to develop tissue engineering constructions.

Surface Modification of Electrospun Bioresorbable and Biostable Scaffolds by Pulsed DC Magnetron Sputtering of Titanium for Gingival Tissue Regeneration.

In this study, polymer scaffolds were fabricated from biodegradable poly(lactide-co-glycolide) (PLGA) and from non-biodegradable vinylidene fluoride-tetrafluoroethylene (VDF-TeFE) by electrospinning. These polymer scaffolds were subsequently surface-modified by sputtering titanium targets in an argon atmosphere. Direct current pulsed magnetron sputtering was applied to prevent a significant influence of discharge plasma on the morphology and mechanical properties of the nonwoven polymer scaffolds. The scaffolds with initially hydrophobic properties show higher hydrophilicity and absorbing properties after surface modification with titanium. The surface modification by titanium significantly increases the cell adhesion of both the biodegradable and the non-biodegradable scaffolds. Immunocytochemistry investigations of human gingival fibroblast cells on the surface-modified scaffolds indicate that a PLGA scaffold exhibits higher cell adhesion than a VDF-TeFE scaffold.

Green Chemistry for Biomimetic Materials: Synthesis and Electrospinning of High-Molecular-Weight Polycarbonate-Based Nonisocyanate Polyurethanes.

Conventional synthesis routes for thermoplastic polyurethanes (TPUs) still require the use of isocyanates and tin-based catalysts, which pose considerable safety and environmental hazards. To reduce both the ecological footprint and human health dangers for nonwoven TPU scaffolds, it is key to establish a green synthesis route, which eliminates the use of these toxic compounds and results in biocompatible TPUs with facile processability. In this study, we developed high-molecular-weight nonisocyanate polyurethanes (NIPUs) through transurethanization of 1,6-hexanedicarbamate with polycarbonate diols (PCDLs). Various molecular weights of PCDL were employed to maximize the molecular weight of NIPUs and consequently facilitate their electrospinnability. The synthesized NIPUs were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The highest achieved molecular weight (M w) was 58,600 g/mol. The NIPUs were consecutively electrospun into fibrous scaffolds with fiber diameters in the submicron range, as shown by scanning electron microscopy (SEM). To assess the suitability of electrospun NIPU mats as a possible biomimetic load-bearing pericardial substitute in cardiac tissue engineering, their cytotoxicity was investigated in vitro using primary human fibroblasts and a human epithelial cell line. The bare NIPU mats did not need further biofunctionalization to enhance cell adhesion, as it was not outperformed by collagen-functionalized NIPU mats and hence showed that the NIPU mats possess a great potential for use in biomimetic scaffolds.

The Performance of Nonwoven PLLA Scaffolds of Different Thickness for Stem Cells Seeding and Implantation.

The 3D reconstruction of 100 μm- and 600 μm-thick fibrous poly-L/L-lactide scaffolds was performed by confocal laser scanning microscopy and supported by scanning electron microscopy and showed that the density of the fibers on the side adjacent to the electrode is higher, which can affect cell diffusion, while the pore size is generally the same. Bone marrow mesenchymal stem cells cultured in a 600 μm-thick scaffold formed colonies and produced conditions for cell differentiation. An in vitro study of stem cells after 7 days revealed that cell proliferation and hepatocyte growth factor release in the 600 μm-thick scaffold were higher than in the 100 μm-thick scaffold. An in vivo study of scaffolds with and without stem cells implanted subcutaneously onto the backs of recipient mice was carried out to test their biodegradation and biocompatibility over a 0–3-week period. The cells seeded onto the 600 μm-thick scaffold promoted significant neovascularization in vivo. After 3 weeks, a significant number of donor cells persisted only on the inside of the 600 μm-thick scaffold. Thus, the use of bulkier matrices allows to prolong the effect of secretion of growth factors by stem cells during implantation. These 600 μm-thick scaffolds could potentially be utilized to repair and regenerate injuries with stem cell co-culture for vascularization of implant.

How the Nonwoven Polymer Volume Microstructure Is Transformed under Tension in an Aqueous Environment.

The fibrous porous structure of polymers can mimic the extracellular matrix of the native tissue, therefore such polymers have a good potential for use in regenerative medicine. Organs and tissues within the body exhibit different mechanical properties depending on their functionality, thus artificial scaffolds should have mechanical behaviors similar to the extracellular matrix in conditions like living organisms, primarily in aqueous media. Several methods have been investigated in aquatic environments, including noninvasive techniques based on ultrasonic focused beams for biological objectives. In this study we explored the tensile behavior of poly(L-lactide) nonwoven polymer scaffolds using high-frequency ultrasound microscopy combined with a horizontal testing machine, which provided a visualization of the reorganization and transformation of the dynamic volume microstructure. The mechanisms of unwinding, elongation, orientation, and deformation of polymer fibers under uniaxial tension were revealed. We observed an association between the lined plastic deformation from 100 to 400% and the formation of multiple necks in the fibers, which caused stress relaxation and significant rarefaction of the fibrous microstructure. It was shown that both peaks on the stress–strain curve corresponded to the microstructure of aligned fibers in terms of initial diameter and thinning fibers. We discuss the possible influence of these microstructure transformations on cell behavior.

Influence of Processing Methods on the Mechanical Behavior of Poly‐3‐hydroxybutyrate Nonwoven Scaffolds

AbstractThe theoretical prediction of the mechanical behavior of fibrous materials for medicine in different environments is of great scientific interest. The deformation mechanisms under loading of biopolymer electrospun fibrous materials differ significantly in dependence on the phase state of the medium, namely, liquid state, gaseous state, or at their interface. In this paper, the influence of various mediums on the mechanical behavior of fibrous materials based on poly‐3‐hydroxybutyrate under tension is examined. The oxidative stress (ozone treatment) and the incorporation of low concentrations of modifying additives (complexes of tetraphenyl‐porphyrin with Zn) are proposed as the most effective methods of directed control of stress‐related characteristics without a negative effect on the functional properties of medical materials.

Novel In Situ-Cross-Linked Electrospun Gelatin/Hydroxyapatite Nonwoven Scaffolds Prove Suitable for Periodontal Tissue Engineering.

Periodontal diseases affect millions of people worldwide and can result in tooth loss. Regenerative treatment options for clinical use are thus needed. We aimed at developing new nonwoven-based scaffolds for periodontal tissue engineering. Nonwovens of 16% gelatin/5% hydroxyapatite were produced by electrospinning and in situ glyoxal cross-linking. In a subset of scaffolds, additional porosity was incorporated via extractable polyethylene glycol fibers. Cell colonization and penetration by human mesenchymal stem cells (hMSCs), periodontal ligament fibroblasts (PDLFs), or cocultures of both were visualized by scanning electron microscopy and 4′,6-diamidin-2-phenylindole (DAPI) staining. Metabolic activity was assessed via Alamar Blue® staining. Cell type and differentiation were analyzed by immunocytochemical staining of Oct4, osteopontin, and periostin. The electrospun nonwovens were efficiently populated by both hMSCs and PDLFs, while scaffolds with additional porosity harbored significantly more cells. The metabolic activity was higher for cocultures of hMSCs and PDLFs, or for PDLF-seeded scaffolds. Periostin and osteopontin expression was more pronounced in cocultures of hMSCs and PDLFs, whereas Oct4 staining was limited to hMSCs. These novel in situ-cross-linked electrospun nonwoven scaffolds allow for efficient adhesion and survival of hMSCs and PDLFs. Coordinated expression of differentiation markers was observed, which rendered this platform an interesting candidate for periodontal tissue engineering.

Marine Biopolymers as Bioactive Functional Ingredients of Electrospun Nanofibrous Scaffolds for Biomedical Applications.

Marine biopolymers, abundantly present in seaweeds and marine animals, feature diverse structures and functionalities, and possess a wide range of beneficial biological activities. Characterized by high biocompatibility and biodegradability, as well as unique physicochemical properties, marine biopolymers are attracting a constantly increasing interest for the development of advanced systems for applications in the biomedical field. The development of electrospinning offers an innovative technological platform for the production of nonwoven nanofibrous scaffolds with increased surface area, high encapsulation efficacy, intrinsic interconnectivity, and structural analogy to the natural extracellular matrix. Marine biopolymer-based electrospun nanofibrous scaffolds with multifunctional characteristics and tunable mechanical properties now attract significant attention for biomedical applications, such as tissue engineering, drug delivery, and wound healing. The present review, covering the literature up to the end of 2021, highlights the advancements in the development of marine biopolymer-based electrospun nanofibers for their utilization as cell proliferation scaffolds, bioadhesives, release modifiers, and wound dressings.

Recent Advances in Development of Natural Cellulosic Non-Woven Scaffolds for Tissue Engineering.

In recent years, tissue engineering researchers have exploited a variety of biomaterials that can potentially mimic the extracellular matrix (ECM) for tissue regeneration. Natural cellulose, mainly obtained from bacterial (BC) and plant-based (PC) sources, can serve as a high-potential scaffold material for different regenerative purposes. Natural cellulose has drawn the attention of researchers due to its advantages over synthetic cellulose including its availability, cost effectiveness, perfusability, biocompatibility, negligible toxicity, mild immune response, and imitation of native tissues. In this article, we review recent in vivo and in vitro studies which aimed to assess the potential of natural cellulose for the purpose of soft (skin, heart, vein, nerve, etc.) and hard (bone and tooth) tissue engineering. Based on the current research progress report, it is sensible to conclude that this emerging field of study is yet to satisfy the clinical translation criteria, though reaching that level of application does not seem far-fetched.

Adult Human Vascular Smooth Muscle Cells on 3D Silk Fibroin Nonwovens Release Exosomes Enriched in Angiogenic and Growth-Promoting Factors.

Background. Our earlier works showed the quick vascularization of mouse skin grafted Bombyx mori 3D silk fibroin nonwoven scaffolds (3D-SFnws) and the release of exosomes enriched in angiogenic/growth factors (AGFs) from in vitro 3D-SFnws-stuck human dermal fibroblasts (HDFs). Here, we explored whether coronary artery adult human smooth muscle cells (AHSMCs) also release AGFs-enriched exosomes when cultured on 3D-SFnws in vitro. Methods. Media with exosome-depleted FBS served for AHSMCs and human endothelial cells (HECs) cultures on 3D-SFnws or polystyrene. Biochemical methods and double-antibody arrays assessed cell growth, metabolism, and intracellular TGF-β and NF-κB signalling pathways activation. AGFs conveyed by CD9+/CD81+ exosomes released from AHSMCs were double-antibody array analysed and their angiogenic power evaluated on HECs in vitro. Results. AHSMCs grew and consumed D-glucose more intensely and showed a stronger phosphorylation/activation of TAK-1, SMAD-1/-2/-4/-5, ATF-2, c-JUN, ATM, CREB, and an IκBα phosphorylation/inactivation on SFnws vs. polystyrene, consistent overall with a proliferative/secretory phenotype. SFnws-stuck AHSMCs also released exosomes richer in IL-1α/-2/-4/-6/-8; bFGF; GM-CSF; and GRO-α/-β/-γ, which strongly stimulated HECs’ growth, migration, and tubes/nodes assembly in vitro. Conclusions. Altogether, the intensified AGFs exosomal release from 3D-SFnws-attached AHSMCs and HDFs could advance grafts’ colonization, vascularization, and take in vivo—noteworthy assets for prospective clinical applications.

Sustained Biochemical Signaling and Contact Guidance by Electrospun Bicomponents as Promising Scaffolds for Nerve Tissue Regeneration.

Electrospun fibers are excellent delivery vehicles enabling a sustained release of growth factors to elicit favorable cell responses and are increasingly used in tissue engineering. Scaffolds with specific physical/topographical features can also guide cell migration and maturation. Therefore, growth factor-loaded electrospun scaffolds with a designed topography are promising for tissue regeneration. In this investigation, aligned-fiber scaffolds composed of poly(lactic-co-glycolic acid) nanofibers incorporating a glial cell line-derived growth factor and poly (d,l-lactic acid) nanofibers incorporating a nerve growth factor were produced by electrospinning. The scaffolds provided an aligned fibrous topography and a dual release of growth factors. The rat pheochromocytoma cell (PC12 cell) response to produced non-woven and aligned-fiber scaffolds with/without growth factors was studied. The dual release of growth factors and topographical cues provided by aligned-fiber bicomponent scaffolds induced significant neurite extension, neuronal differentiation, and neurite alignment in a synergistic manner. The scaffolds with predesigned biochemical/topographical cues demonstrated in this study might be promising for nerve tissue repair.

142 Epidermal equivalents on nonwoven collagen scaffolds

The use of natural polymers such as collagen for tissue engineering has many advantages providing cells with an environment of natural topography and rich of bioactive cues. Nevertheless, as compared to synthetic polymers, electrospinning of such materials is still a methodological challenge. Two nonwoven scaffolds were fabricated by collagen dispersion in hexafluoroisopropanol (HFIP) (microfibrous) and in acetic acid (nanofibrous) and stabilized by genipin. The helical structure of collagen was retained in acetic acid, but not in HFIP. Epidermal equivalents were prepared using human primary keratinocytes on both types of materials. There were up to seven layers of live cells with well-defined granular layer in the stratified epithelium obtained on nanofibrous scaffolds. The stratum corneum (SC) was well pronounced and desquamation was evident. The patterns of involucrin expression were similar, but not identical to the normal epidermis: it demarcated all suprabasal layers, not the uppermost ones as it was shown for filaggrin. The basement membrane (BM) component laminin 5 was deposited on the surface of the fibers, but a compact BM structure was not formed. CK5 expression was not limited to the basal layer, but observed in all living layers of the equivalent. The stratified epithelium formed on the microfiber materials also had a well-distinguishable granular layer and SC. But SC was thinner as compared to nanofiber samples. The expression pattern of involucrin was much closer to normal than on nanofiber scaffold while filaggrin and CK5 showed localization similar to nanofiber scaffolds. The laminin 5 positivity was insignificant. Thus, we have managed to obtain nonwoven collagen matrices of two different types (nanofibrous and microfibrous) which both support the formation of stratified epithelium. Of note, the use of nanofibrous material yields epidermal equivalents with more prominent basal layer and synthesis of BM components, while equivalents on microfibrous material gave more “normal” patterns of involucrin and filaggrin expression.

Effects of Process Parameters on Structure and Properties of Melt-Blown Poly(Lactic Acid) Nonwovens for Skin Regeneration.

Skin regeneration requires a three-dimensional (3D) scaffold for cell adhesion, growth and proliferation. A type of the scaffold offering a 3D structure is a nonwoven material produced via a melt-blown technique. Process parameters of this technique can be adapted to improve the cellular response. Polylactic acid (PLA) was used to produce a nonwoven scaffold by a melt-blown technique. The key process parameters, i.e., the head and air temperature, were changed in the range from 180–270 °C to obtain eight different materials (MB1–MB8). The relationships between the process parameters, morphology, porosity, thermal properties and the cellular response were explored in this study. The mean fiber diameters ranged from 3 to 120 µm. The average material roughness values were between 47 and 160 µm, whereas the pore diameters ranged from 5 to 400 µm. The calorimetry thermograms revealed a correlation between the temperature parameters and crystallization. The response of keratinocytes and macrophages exhibited a higher cell viability on thicker fibers. The cell-scaffold interaction was observed via SEM after 7 days. This result proved that the features of melt-blown nonwoven scaffolds depended on the processing parameters, such as head temperature and air temperature. Thanks to examinations, the most suitable scaffolds for skin tissue regeneration were selected.