Nanoscale modifications of PET polymer surfaces via oxygen-plasma discharge yield minimal changes in attachment and growth of mammalian epithelial and mesenchymal cells in vitro

Sustained release of N-acetylcysteine by sandwich structured polycaprolactone/collagen scaffolds for wound healing

PCL (poly-caprolactone) nanofibers have good biocompatibility and high porosity, which are usually utilized for application in wound dressings. However, wound healing could be hindered by the overproduction of reactive oxygen species (ROS) and different factors. Pure nanofibers cannot satisfy these requirements of wound healing. N-acetylcysteine (NAC), as an antioxidant, meets the requirements for wound healing by resisting the overproduction of ROS and by promoting angiogenesis and maturation of the epidermis. In this study, we prepared a sandwich structured PCL-Col/NAC scaffold using the molding method, which consisted of PCL nanofibers at the core and NAC-loaded collagen on both sides. The hydroscopicity and tensile modulus of PCL-Col/NAC scaffolds showed best performance of these properties among groups. Meanwhile, the drug release profiles of PCL-Col/NAC scaffolds were investigated using the HPLC method and the results suggested a sustained drug release of NAC for PCL-Col/NAC scaffolds. In addition, PCL-Col/NAC scaffolds presented better properties than the control groups in cell migration and proliferation. The in vivo wound healing therapy effect was studied using an oval (2 × 1 cm) full-thickness skin defect wound model for SD rats. After 21 days, gross view and histological analysis showed a favorable beneficial therapeutic effect as well as better epidermal maturation compared with the control groups. CD31 immunohistology results revealed relatively more new vessels in the PCL-Col/NAC group than the control groups. This study developed novel PCL-Col/NAC scaffolds with an excellent hydroscopicity, tensile modulus and the ability to promote epidermal maturation and angiogenesis, demonstrating its promising potential in wound healing treatment. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Media-based effects on the hydrolytic degradation and crystallization of electrospun synthetic-biologic blends

Tissue engineering scaffold degradation in aqueous environments is a widely recognized factor determining the fate of the associated anchorage-dependent cells. Electrospun blends of synthetic polycaprolactone (PCL) and a biological polymer, gelatin, of 25, 50, and 75 wt% were investigated for alterations in crystallinity, microstructure and morphology following widely used in vitro biological exposures. To our knowledge, the effects of these different aqueous-based biological media compositions on the degradation of these blends have never been directly compared. X-ray diffraction (XRD) analysis exposed that differences in PCL crystallinity were observed following exposures to phosphate buffered solution (PBS), Dulbecco's modified eagle medium (DMEM) cell culture media, and DI water following 7 days of exposure at 37 °C. XRD data suggested that in vitro medium exposures aid in providing chain mobility and rearrangement due to hydrolytic degradation of the gelatin phase, allowing previously constrained, poorly crystalline PCL regions to achieve more intense reflections resulting in the presence of crystalline peaks. The dry, as-spun modulus of relatively soft 100 % PCL fibers was approximately 10 % of any gelatin-containing composition. Tensile testing results indicate that hydrated gelatin containing scaffolds on average had a fivefold increase in elongation compared to as-spun scaffolds. After 24-h of aqueous exposure, the elastic modulus decreased in proportion to increasing gelatin content. After 1 day of exposure, the 75 and 100 % gelatin compositions largely ceased to display measurable values of modulus, elongation or tensile strength due to considerable hydrolytic degradation. On a relative basis, common aqueous in vitro medium exposures (deionized water, PBS, and DMEM) resulted in significantly divergent amounts of crystalline PCL, overall microstructure and fiber morphology in the blended compositions, subsequently 'shielding' scaffolds from significant changes in mechanical properties after 24-h of exposure. Understanding electrospun PCL-gelatin scaffold dynamics in different aqueous-based cell culture medias enables the ability to tailor scaffold composition to 'tune' degradation rate, microstructure, and long-term mechanical stability for optimal cellular growth, proliferation, and maturation.

Selective adsorption of L1210 leukemia cells/human leukocytes on micropatterned surfaces prepared from polystyrene/polypropylene-polyethylene blends

The objective of this study is to prepare polymeric surfaces which will adsorb L1210 leukemia cells selectively more than that of healthy human leukocytes in order to develop new treatment options for people with leukemia. Chemically heterogeneous and micropatterned surfaces were formed on round glass slides by dip coating with accompanying phase-separation process where only commercial polymers were used. Surface properties were determined by using optical microscopy, 3D profilometry, SEM and measuring contact angles. Polymer, solvent/nonsolvent types, blend composition and temperature were found to be effective in controlling the dimensions of surface microislands. MTT tests were applied for cell viability performance of these surfaces. Polystyrene/polyethylene-polypropylene blend surfaces were found to show considerable positive selectivity to L1210 leukemia cells where L1210/healthy leukocytes adsorption ratio approached to 9-fold in vitro. Effects of wettability, surface free energy, microisland size geometry on the adsorption performances of L1210/leukocytes pairs are discussed.

Nanoscale surfacing for regenerative medicine

Cells in most tissues reside in microenvironment surrounded with specific three-dimensional features. The extracellular matrix or substratum with which cells interact often includes topography at the nanoscale. For example, the basement membrane of many tissues displays features of pores, fibers and ridges in the nanometer range. The nanoscale topography has significant effects on cellular behavior. Knowledge of the cell-substratum interactions is crucial to the understanding of many fundamental biological questions and to regenerative medicine. Rapid advances in nanotechnology enable cellular study on engineered nanoscale surfaces. Recent findings underscore the phenomenon that mammalian cells do respond to nanosized features on a synthetic surface. This review covers the commonly used techniques of engineering nanoscale surface and the techniques which have not been adapted but are of great potential in regenerative medicine, surveys the applications of nanoscale surface in regenerative medicine including vascular, bone, neural and stem cell tissue engineering, and discusses the possible mechanisms of cellular responses to nanoscale surface. A better understanding of the interactions between cells and nanoscale surfacing will help advance the field of regenerative medicine.

Oxygen plasma-treated thermoresponsive polymer surfaces for cell sheet engineering

Although cell sheet tissue engineering is a potent and promising method for tissue engineering, an increase of mechanical strength of a cell sheet is needed for easy manipulation of it during transplantation or 3D tissue fabrication. Previously, we developed a cell sheet-polymer film complex that had enough mechanical strength that can be manipulated even by tweezers (Fujita et al., 2009. Biotechnol Bioeng 103(2): 370-377). We confirmed the polymer film involving a temperature sensitive polymer and extracellular matrix (ECM) proteins could be removed by lowering temperature after transplantation, and its potential use in regenerative medicine was demonstrated. However, the use of ECM proteins conflicted with high stability in long-term storage and low cost. In the present study, to overcome these drawbacks, we employed the oxygen plasma treatment instead of using the ECM proteins. A cast and dried film of thermoresponsive poly-N-isopropylacrylamide (PNIPAAm) was fabricated and treated with high-intensity oxygen plasma. The cells became possible to adhere to the oxygen plasma-treated PNIPAAm surface, whereas could not to the inherent surface of bulk PNIPAAm without treatment. Characterizations of the treated surface revealed the surface had high stability. The surface roughness, wettability, and composition were changed, depending on the plasma intensity. Interestingly, although bulk PNIPAAm layer had thermoresponsiveness and dissolved below lower critical solution temperature (LCST), it was found that the oxygen plasma-treated PNIPAAm surface lost its thermoresponsiveness and remained insoluble in water below LCST as a thin layer. Skeletal muscle C2C12 cells could be cultured on the oxygen plasma-treated PNIPAAm surface, a skeletal muscle cell sheet with the insoluble thin layer could be released in the medium, and thus the possibility of use of the cell sheet for transplantation was demonstrated.

Effects of tensile strain and fluid flow on osteoarthritic human chondrocyte metabolism in vitro

This study examined the hypothesis that tensile strain and fluid flow differentially influence osteoarthritic human chondrocyte metabolism. Primary high-density monolayer chondrocytes cultures were exposed to varying magnitudes of tensile strain and fluid-flow using a four-point bending system. Metabolic changes were quantified by real-time PCR measurement of aggrecan, IL-6, SOX-9, and type II collagen gene expression, and by determination of nitric oxide levels in the culture medium. A linear regression model was used to investigate the roles of strain, fluid flow, and their interaction on metabolic activity. Aggrecan, type II collagen, and SOX9 mRNA expression were negatively correlated to increases in applied strain and fluid flow. An effect of the strain on the induction of nitric oxide release and IL-6 gene expression varied by level of fluid flow (and visa versa). This interaction between strain and fluid flow was negative for nitric oxide and positive for IL-6. These results confirm that articular chondrocyte metabolism is responsive to tensile strain and fluid flow under in vitro loading conditions. Although the articular chondrocytes reacted to the mechanically applied stress, it was notable that there was a differential effect of tensile strain and fluid flow on anabolic and catabolic markers.

Nitrogen-rich coatings for promoting healing around stent-grafts after endovascular aneurysm repair

Complications following endovascular aneurysm repair (EVAR) are related to deficient healing around the stent-graft (SG). New generations of SG with surface properties that foster vascular repair could overcome this limitation. Our goal was to evaluate the potential of a new nitrogen-rich plasma-polymerised biomaterial, designated PPE:N, as an external coating for polyethylene terephtalate (PET)- or polytetrafluoro-ethylene (PTFE)-based SGs, to promote healing around the implant. Thin PPE:N coatings were deposited on PET and PTFE films. Then, adhesion, growth, migration and resistance to apoptosis of vascular smooth muscle cells (VSMCs) and fibroblasts, as well as myofibroblast differentiation, were assessed in vitro. In another experimental group, chondroitin sulphate (CS), a newly described mediator of vascular repair, was added to normal culture medium, to search for possible additional benefit. PPE:N-coatings, especially on PET, increased and accelerated cell adhesion and growth, compared with control PET and with standard polystyrene culture plates (PCP). PPE:N was also found to increase the resistance to apoptosis in VSMC, an important finding as aneurysms are characterised by VMSC depletion caused by a pro-apoptotic phenotype. Addition of CS in solution further increased migration and resistance to apoptosis. In conclusion, PPE:N-coating and/or CS could promote vascular repair around SGs following EVAR.

Adipogenesis of murine embryonic stem cells in a three-dimensional culture system using electrospun polymer scaffolds

A mechanistic understanding of adipose tissue differentiation is critical for the treatment and prevention of obesity and type 2 diabetes. Conventional in vitro models of adipogenesis are preadipocytes or freshly isolated adipocytes grown in two-dimensional (2D) cultures. Optimal results using in vitro tissue culture models can be expected only when adipocyte models closely resemble adipose tissue in vivo. Thus the design of an in vitro three-dimensional (3D) model which faithfully mimics the in vivo environment is needed to effectively study adipogenesis. Pluripotent embryonic stem (ES) cells are a self-renewing cell type that can readily be differentiated into adipocytes. In this study, a 3D culture system was developed to mimic the geometry of adipose tissue in vivo. Murine ES cells were seeded into electrospun polycaprolactone scaffolds and differentiated into adipocytes in situ by hormone induction as demonstrated using a battery of gene and protein expression markers along with the accumulation of neutral lipid droplets. Insulin-responsive Akt phosphorylation, and beta-adrenergic stimulation of cyclic AMP synthesis were demonstrated in ES cell-derived adipocytes. Morphologically, ES cell-derived adipocytes resembled native fat cells by scanning electron and phase contrast microscopy. This tissue engineered ES cell-matrix model has potential uses in drug screening and other therapeutic developments.

3D scaffolds for bone marrow stem cell support in bone repair

Bone tissue repair is one of the major concerns of regenerative medicine. The current need for tissue replacements has necessitated the development of a new science termed ‘bone tissue engineering’. The basic organization of bone tissue requires the design and fabrication of a porous 3D structure or ‘scaffold’ to contain the bone-forming cells. This scaffold should be formulated from biocompatible, osteoconductive materials that are not immunoreactive. 3D scaffolds provide the necessary support for cells to proliferate and maintain their capacity to differentiate and scaffolds containing bone marrow-derived osteoprogenitors can be employed within implants to enhance bone repair. The complex construct is intended to mimic the native in vivo microenvironment and this demands construction of bioactive scaffolds that are also capable of supporting vascularization as well as cell proliferation and osteogenic differentiation. 3D bioactive scaffolds containing committed osteoprogenitors can provide a promising surgical tool for bone tissue engineering directed at orthopedic and cranio-maxillofacial clinical applications.

Preparation of polylactic acid-O-carboxymethylated chitosan nanoparticles and their influences on the cultured porcine hepatocytes

AIM: To prepare polylactic acid-O-carboxyme-thylated chitosan (PLA-O-CMC) nanoparticles and evaluate their influences on the morphology and functions of cultured porcine hepatocytes.

METHODS: PLA-O-CMC nanoparticles were prepared from PLA and O-CMC by ultrasonic method. The nanoparticles were characterized by atomic force microscopy and X-ray photoelectron spectrometry. Isolated porcine hepatocytes were divided into two groups: commonly culturing group and nanomaterial group (co-culturing hepatocytes with PLA-O-CMC nanoparticles). The morphology and functions of the cultured hepatocytes were observed within 1 wk.

RESULTS: PLA-O-CMC nanoparticles were successfully prepared, and the diameter was 300-500 nm under atomic force microscope. X-ray photoelectron spectrometry showed that the proportions of C, O, and N element were 72.51%, 23.69%, and 3.80%, respectively. The hepatocytes lost their features of polygons after common culture for 48 h. However, after co-culture with PLA-O-CMC nanoparticles, the hepatocytes clustered into conglobulations, and most of them restored their cell polarities, shaping as typical polygons. After culture for 1, 3, and 5 d, the content of albumin (ALB) was significantly higher in nanomaterial group than that in commonly culturing group (3.53 ± 0.052, 3.48 ± 0.075, 3.57 ± 0.137 g/L vs 3.10 ± 0.179, 3.17 ± 0.186, 3.10 ± 0.219 g/L, all P < 0.05), while on day 3, 5 and 7, the level of alanine aminotransferase (ALT) was markedly lower (15.33 ± 13.05, 8.84 ± 8.87, 7.00 ± 5.22 nkat/L vs 24.17 ± 20.35, 16.17 ± 27.49, 15.50 ± 11.95 nkat/L, all P < 0.05). From day 3 to 7, the content of supernant blood urea nitrogen (BUN) was higher in nanomaterial group than that in commonly culturing group, but there was no significant difference (P > 0.05).

CONCLUSION: PLA-O-CMC nanoparticles are successfully prepared, and can be used in the culture of hepatocytes.

Physico-chemical and biological evaluation of excimer laser irradiated polyethylene terephthalate (pet) surfaces

The aim of this work was to investigate the consequences of excimer laser irradiation on the physico-chemical and biological properties of polyethylene terephthalate (PET) films, currently used for medical devices. Three PET films from different origins were studied in the present work, chosen with respect to their chemical and physical properties, which are of high importance for ulterior medical application as vascular prostheses. Multiple assays were carried out to characterize the physical and chemical effects of the laser irradiation: surface morphology tests (light microscopy, Dektak profilometer and confocal laser scanning microscopy) showed the strong transformation of the surface with the laser treatment. Contact angle measurements revealed a significant increase of the surface energy for each PET depending on the applied fluency. Finally XPS characterization of the surface demonstrated the appearance of new chemical species favorable for cell attachment. This aspect had to be strongly considered regarding to the multiple biological effects of laser irradiated surfaces on living cells. Different cell culture experiments were carried out with L132 human epithelial cells after 6-days culture: proliferation and vitality rate, cell adhesion and cell morphology. Results clearly revealed that laser treatment improved cell proliferation (up to 140% with respect to controls), vitality (10% higher than controls), morphology and adhesion kinetics (more than 16% of control). A significant correlation (R2=0.906) was also established on one PET between the fluencies of laser treatment and the cellular response. These results emphasized high importance of the choice of the PET material for a medical application: only one of the three considered PET films showed really improved cellular response.

Strategies for directing the differentiation of stem cells into the osteogenic lineage in vitro

A major area in regenerative medicine is the application of stem cells in bone reconstruction and bone tissue engineering. This will require well-defined and efficient protocols for directing the differentiation of stem cells into the osteogenic lineage, followed by their selective purification and proliferation in vitro. The development of such protocols would reduce the likelihood of spontaneous differentiation of stem cells into divergent lineages on transplantation, as well as reduce the risk of teratoma formation in the case of embryonic stem cells. Additionally, such protocols could provide useful in vitro models for studying osteogenesis and bone development, and facilitate the genetic manipulation of stem cells for therapeutic applications. The development of pharmokinetic and cytotoxicity/genotoxicity screening tests for bone-related biomaterials and drugs could also use protocols developed for the osteogenic differentiation of stem cells. This review critically examines the various strategies that could be used to direct the differentiation of stem cells into the osteogenic lineage in vitro.