Polyvinyl Alcohol Scaffolds Research Articles

Cellulose nano-dispersions enhanced by ultrasound assisted chemical modification drive osteoblast proliferation and differentiation in PVA/HA bone tissue engineering scaffolds

To develop a biological bone tissue scaffold with uniform pore size and good cell adhesion was both challenging and imperative. We prepared modified cellulose nanocrystals (CNCs) dispersants (K-PCNCs) by ultrasound-assisted alkylation modification. Subsequently, nano-hydroxyapatite (HC-K) was synthesized using K-PCNCs as a dispersant and composited with polyvinyl alcohol (PVA) to prepare the scaffold using the ice template method. The results showed that the water contact angle and degree of substitution (135°, 1.53) of the K-PCNCs were highest when the ultrasound power was 450 W and the time was 2 h. The dispersion of K-PCNCs prepared under this condition was optimal. SEM showed that the pore distribution of the composite scaffolds was more homogeneous than the PVA scaffold. The porosity, equilibrium swelling rate, and mechanical properties of the composite scaffolds increased and then decreased with the increase of HC-K content, and reached the maximum values (56.1 %, 807.7 %, and 0.085 ± 0.004 MPa) at 9 % (w/w) of HC-K content. Cell experiments confirmed scaffold has good cytocompatibility and mineralization capacity. The ALP activity reached 1.71 ± 0.25 (ALP activity/mg protein). In conclusion, the scaffolds we developed have good biocompatibility and mechanical properties and have great potential in promoting bone defect repair.

Development of porous hydroxyapatite/PVA/gelatin/alginate hybrid flexible scaffolds with improved mechanical properties for bone tissue engineering

Porous scaffolds based on gelatin and hydroxyapatite particles (HAp) are promising for applications in bone tissue engineering and regenerative medicine. However, they are not ideal for stress and shock protection due to low compressive strength, brittleness, and poor toughness. Herein, we developed porous hybrid scaffolds by combining multiple components into a single bone scaffold, including hydroxyapatite nanoparticles (HAp NPs), alginate, polyvinyl alcohol (PVA), and gelatin with different gelatin/PVA composition ratios. HAp NPs were synthesized in situ in PVA solution and scaffolds were fabricated using a freeze-drying method. The results showed good physicochemical properties of the scaffolds: formation of pure HAp NPs phase, high porosity, large pore sizes, large swelling capacity depending on varying gelatin/PVA ratios, as well as a long-term degradation rate up to 28 days. The porous scaffolds exhibited compressive strength close to the cancellous bone with stress-strain behavior exhibiting three-stage flexible behavior indicating improved fracture resistance with an energy absorbing capability up to 1.9 MJ/m3. The scaffolds have a yield strength of 70–403 kPa, a compressive strength at 65 % strain of 0.96–1.80 MPa, a nonporous elastic modulus of 10.44–12.40 GPa, and a densification strain of approximately 0.92 %. This work develops three-dimensional (3D) porous hybrid bone scaffolds with mechanical strength within the minimum compressive strength of cancellous bone and mechanical energy absorption capacity favor for cancellous bone repair, bone tissue engineering, and regenerative medicine applications.

Facile crosslinking of PVA scaffolds using quercetin for biomaterial applications

Polyvinyl alcohol (PVA) is water soluble and biodegradable polymer known for its biocompatibility, low protein adhesion and minimal toxicity. However, inadequate mechanical stability limits its usage in various biomedical applications. This study explored the usage of quercetin as a promising crosslinking agent for PVA to significantly improve mechanical strength and water resistance. PVA was crosslinked with four concentrations of quercetin in ratios (1:0.005, 1:0.01, 1:0.015, 1:0.02 w/w). Scaffolds of uniform thickness (0.5 mm) were prepared using freeze-drying technique. The crosslinking efficiency and durability of PVA and PVA-quercetin scaffolds were studied based on residual weight ratio upon swelling, thermogravimetric, and Fourier Transform Infrared (FTIR) spectroscopic analysis. Results indicate that PVA-quercetin (1:0.02) showed better crosslinking efficiency with enhanced stability when compared with uncross-linked PVA which was further confirmed by the reduction of solubility in water which is substatiated by lower hydroxyl peak at 3200 cm−1. Further, the present work describes a facile methodology to crosslink PVA for developing a biomaterial with the potential antioxidant ability of quercetin.

2D and 3D PVA electrospun scaffold evaluation for ligament implant replacement: A mechanical testing, modelling and experimental biomechanics approach

The gold standard to characterise anterior cruciate ligament (ACL) implants is through the evaluation of mechanical properties such as Young's modulus or ultimate tensile stress. Currently, no studies have been performed to relate the in-vivo hyper-elastic behaviour of the ACL with the design of tissue engineered ligaments. The aim of this work is to determine the most comparable 2D/3D polyvinyl alcohol (PVA) electrospun structure to the in-vivo mechanical behaviour of the natural ligament. Biomechanics of 12 young participants were captured while daily and high impact activities were performed. A musculoskeletal knee model and kinematic data were used to estimate the in-vivo ACL length and strain. The in-vivo ACL tensile forces were determined with a non-linear force/strain relationship. 2D scaffolds, 1 twisted filament scaffolds, 3 twisted filaments scaffolds and 3 twisted/braided filaments scaffolds were fabricated using electrospinning and characterised morphologically and mechanically using scanning electron microscopy and tensile testing respectively. Cyclic tensile and shear tests were performed in dry and wet conditions to crosslinked and non-crosslinked samples. The hyper-elastic behaviour of our PVA scaffolds was characterised with the Mooney Rivlin model and a non-linear string-based model, and both models compared with the in-vivo mechanical behaviour of the native ACL. Crosslinked 3 twisted/braided filaments scaffolds faithfully mimicked the morphology and the hyper-elastic behaviour of the natural ACL, showed a good resistance to shear loading and remained undegraded in phosphate-buffer saline solution. This study demonstrated, for the first time, that 3 twisted/braided filaments PVA electrospun scaffolds have an excellent potential for ACL replacements.

Controlled Delivery of Amoxicillin and Rifampicin by Three‐Dimensional Polyvinyl alcohol/Bismuth Ferrite Scaffolds

AbstractSkin is a protective barrier that can protect against environmental influences and renew itself. However, in some cases, this regenerative property is lost, and this causes delays in wound healing. Wound healing is a complex and long‐lasting phase. Any bacterial infection during the wound healing process delays wound healing. The therapeutic efficacy can be increased by using nanocarrier drug delivery systems to the target tissue with modern wound dressings. Controlled nano drug delivery systems increase the therapeutic efficacy in the treatment of diseases and provide a faster recovery process. In this study, amoxicillin (AMX) and rifampicin (RIF) were loaded into the bismuth ferrite (BFO) particles which were synthesized with the co‐precipitation method. Then, these drug‐loaded BFO particles (0.075 %) were added separately to 13 % polyvinyl alcohol (PVA) solution and the solutions were printed three‐dimensionally to obtain three dimensional scaffolds. With these designed scaffolds, it is aimed to reduce the risk of inflammation in wound tissues and increase therapeutic efficacy with controlled release. The SEM images proved that homogeneous pore distributions could be achieved with these combinations. The tensile test results showed that drug‐loaded BFO addition increased the mechanical strength of the 13 % PVA scaffold. The biocompatibility test results demonstrated that the highest viability values of the human adipose tissue‐derived mesenchymal stem cells were obtained for AMX‐added 13 % PVA scaffolds.

Towards the ideal vascular implant: Use of machine learning and statistical approaches to optimise manufacturing parameters

Introduction: Electrospinning is a manufacturing technique that creates a net of nano and microfibres able to mimic the natural extracellular matrix (ECM) of biological tissue. Electrospun scaffolds' morphology and mechanical behaviour can be tailored by modifying the environmental, solution and process parameters. This study aims to produce biomimetic vascular implants optimising the manufacturing set up through two machine learning techniques and statistical approaches.Methods: Polyvinyl alcohol (PVA) based scaffolds were produced by modifying the concentration of the polymer, flow rate, voltage, type of collector, diameter of the needle, distance between needle and collector and revolutions of the mandrel. The scaffolds were morphologically and mechanically characterised using scanning electron microscopy and mechanical testing respectively to inform the morphological model (simultaneously predicting diameter of the fibres and inter-fibre separation) and mechanical model (predicting strain at rupture and ultimate tensile strength).Results: Prediction and traditional techniques led to an optimum set up of: 12% PVA, 1 ml/h flow rate, 20 kV, 8 cm between the needle, 18 G gauge needle, rotational mandrel of 15 cm and 2000 rpm. Optimised PVA scaffolds replicated the mechanical properties and morphology of the vascular tissue with an ultimate tensile strength of 6.17 ± 0.18 MPa, a strain at break of 97.39 ± 5.06, fibre diameters of 126 ± 6.11 nm and inter-fibre separation of 1488 ± 91.99 nm.Discussion: This work revealed for the first time that machine learning Chi-squared Automatic Interaction Detection (CHAID) models are a novel and visual route to elect the optimum manufacturing set up to develop biomimetic vascular implants. Novel two-output Artificial Neural Networks (ANN) and multivariate analysis of variance and covariance (MANOVA, MANCOVA) models presented comparable prediction results (R2=0.91); however, two-output ANN predicted models demonstrated to be the most powerful tool for non-parametric conditions, showing cross-validation mean squared errors (MSE) of 0.0001943. Multi Linear Regression models (MLR) exhibited the lowest accuracy in their predictions (R2=0.6). Machine learning, statistical approaches and traditional characterisation methods were studied to successfully achieve vascular substitutes with analogous biomechanical behaviour and physical structure to the native vascular tissue.

Engineered 3D-Printed Polyvinyl Alcohol Scaffolds Incorporating β-Tricalcium Phosphate and Icariin Induce Bone Regeneration in Rat Skull Defect Model.

The skull defects are challenging to self-heal, and autologous bone graft repair has numerous drawbacks. The scaffolds for the rapid and effective repair of skull defects have become an important research topic. In this study, polyvinyl alcohol (PVA)/β-tricalcium phosphate(β-TCP) composite scaffolds containing icariin (ICA) were prepared through direct-ink three-dimensional (3D) printing technology. β-TCP in the composite scaffold had osteoconductive capability, and the ICA molecule had osteoinductive capacity. The β-TCP and ICA components in the composite scaffold can enhance the capability to repair skull defects. We show that ICA exhibited a slow-release behaviour within 80 days. This behaviour helped the scaffold to continuously stimulate the formation of new bone. The results of in vitro cell compatibility experiments showed that the addition of ICA molecules contributed to the adhesion and proliferation of MC-3T3-E1 cells. The level of alkaline phosphatase secretion demonstrated that the slow release of ICA can promote the osteogenic differentiation of MC-3T3-E1 cells. The introduction of ICA molecules accelerated the in situ bone regeneration in in vivo. It is concluded that the 3D-printed PVA scaffold with β-TCP and ICA has a wide range of potential applications in the field of skull defect treatment.

Electrospinning production of polymer nanofibers containing Ag nanoparticles or carbon nanotubes

Recent years’ electrospinning technology for fabrication of nanofibers of polymers with incorporation of nanoparticles made noticeable progress in different fields, including biomedicine due to their biocompatibility, adhesiveness, antibacterial properties, and sterile nature. In this study, the electrospinning production of antibacterial polyvinyl alcohol (PVA) nanofibers containing silver nanoparticles (AgNPs) was considered. The synthesis of the AgNPs was performed from the polymer-encapsulated AgNO3 precursor material in water with Ag atom reduction by an ultrasonication treatment. The effect of the AgNO3 concentration and the sonication time on the size and quantity of the obtained AgNPs on the PVA scaffold was studied. Absorption spectra were exploited for the control of the appearance of AgNPs in the suspension. From the peak position of the plasmon band observed in the absorption spectrum of the composite the average diameter of the as-prepared AgNPs was estimated as 55–60 nm. As it follows from scanning electron microscopy images the diameter of PVA:AgNPs nanofibers is about 250 nm. Nanofibers formed by polyvinylpyrrolidone (PVP) with incorporation of single-walled carbon nanotubes (SWNTs) were fabricated from the PVP alcohol solution containing SWNTs. The diameter of the nanofibers was in the range of 1–3 μm. Using a dielectric substrate and the collector of a special shape, a mat of fibers with preferred fiber orientation was prepared. Our estimation shows that about 90% of the fibers are oriented.

Fabrication and Characterization of Gelatin/Polyvinyl Alcohol Composite Scaffold.

In this study, porous scaffold materials based on polyvinyl alcohol (PVA) and gelatin (Gel) were successfully fabricated and characterized. The mechanism of the reaction, morphology, and crystallinity were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, thermogravimetric analysis (TGA) was performed together with differential scanning calorimetry (DSC) for examining the thermostability and phase transformation of the scaffolds. Degradation and swelling studies of PVA/Gel composite scaffold materials were performed in phosphate-buffered saline. Finally, the mechanical performances had been determined. According to the results, the polymer matrix that was formed by the combination of PVA and gelatin had better thermal stability. The synthesized composite scaffold was amorphous in nature. The addition of gelatin did not affect the fishbone-like microstructure of PVA, which ensures the excellent mechanical properties of the PVA scaffold. The denaturation temperature and elastic modulus of the PVA scaffold were improved by the gelatin addition, but the physical and chemical properties of the PVA scaffold were weakened when the gelatin content exceeded 10%. In addition, the PVA-10G sample has suitable degradability. Therefore, the PVA/Gel composite scaffold might potentially be applied in the field of tissue engineering that demands high strength.

Study on the cytocompatibility, mechanical and antimicrobial properties of 3D printed composite scaffolds based on PVA/ Gold nanoparticles (AuNP)/ Ampicillin (AMP) for bone tissue engineering

Over the years, gold nanoparticles (AuNP) have been widely used in several biomedical applications related to the diagnosis, drug delivery, bio-imaging, photo-thermal therapy and regenerative medicine, owing to their unique features such as surface plasmon resonance, fluorescence and easy surface functionality. Recent studies showed that gold nanoparticles display positive effect on osteogenic differentiation. In line with this effect, 3-Dimesional (3D) scaffolds that can be used in bone tissue were produced by exploiting the properties of gold nanoparticles that increase biocompatibility and support bone tissue development. In addition, ampicillin was added to the scaffolds containing gold nanoparticles as a model drug to improve its antimicrobial properties. The scaffolds were produced as composites of polyvinyl alcohol (PVA) main matrix as PVA, PVA/AuNP, PVA/Ampicillin (AMP) and PVA/AuNP/AMP. Scanning Electron Microscopy (SEM) Fourier Transform Infrared Spectroscopy (FTIR), tensile measurement tests, and in vitro applications of 3D scaffolds were performed. As depicted by SEM, scaffolds were produced at pore sizes appropriate for bone tissue regeneration. According to FTIR results, there was no modification observed in the AMP, PVA and gold nanoparticles due to mixing in the resultant scaffolds. In vitro results show that 3D printed composite scaffold based on PVA/AuNP/AMP are biocompatible, osteo-inductive and exhibit antimicrobial properties, compared to PVA scaffolds. This study has implications for addressing infections during orthopedic surgeries. The PVA-based gold nanoparticle 3D tissue scaffold study containing ampicillin covers a new study compared to other articles based on gold nanoparticles.

Polyvinyl alcohol scaffolds and supplementation support 3D and sphere culturing of human cancer cell lines by reducing apoptosis and promoting cellular proliferation.

Three-dimensional (3D) culturing mimics the heterogeneous cellular conditions of the in vivo tumor microenvironment compared to 2D monolayer-cultured cells and 3D cultures of established cancer cell lines (sphere culture) or patient-derived cancer cells (organoid culture) are frequently used for cancer research or drug screening and evaluation. To establish more cost and time-efficient 3D culture methods for cancer cell lines, we supplemented sphere culture medium with polyvinyl alcohol (PVA) and found that 3D sphere cultures of breast and pancreatic cancer cell lines were significantly increased. Mechanistically, we found that PVA prevented cell death and promoted cellular proliferation while maintaining levels of stemness-related gene expression. Furthermore, we showed that polyvinyl formal resin (PVF) 3D scaffolds made by cross-linked PVA can function in serum-free, long-term 3D cultures to support maintenance of sphere- or tumor-like cell masses for diverse cancer cell types. Taken together, we demonstrate the effectiveness of PVA and PVF in human cancer cell line culture protocols.

Bioartificial injectable cartilage implants from demineralized bone matrix/PVA and related studies in rabbit animal model.

Functional cartilage tissue engineering needs a substantial, easy to handle scaffold with proper mechanical strength to repair defected area in articular cartilage. In this study, we report the development and characterization of demineralized bone matrix (DBM) in with a poly vinyl alcohol (PVA) to have a proper homogenous injectable scaffold. Injectabiliy of the biodegradable scaffolds, degradation rate, swelling ratio compression and tensile mechanical properties, and viability and proliferation of bone marrow mesenchymal stem cells (BM-MSCs) followed by differentiation of them In-vitro and In-vivo seeded within the scaffold were studied. It demonstrated that the PVA 20% could increase significantly (p < 0.05) the biodegradability of DBM after 720 hours.DBM with 20% of PVA scaffold has significantly higher (p < 0.05) compression and tensile mechanical strength and viscosity. SEM images showed a multilayer of cells on DBM scaffold incorporated with PVA 20%.BM-MSCs on scaffolds, DBM+PVA 20% had a significant growth rate (p < 0.0001) compare to 2D and low concentration of PVA after 21 days of culture. Viability of cells was significantly higher (p < 0.05) on DBM+PVA scaffold compare to DBM. DBM+PVA 20% enhanced cell viability (P < 0.05) compare to DBM scaffold. The PVA presence enhanced chondrogenesis differentiation at the cellular and molecular levels, as evidenced by increased COL II (P < 0.05) and SOX2 upregulation of Chondrogensis-specific genes (p < 0.001). Hyline-like cartilage covered the defect which was confirmed by microscopy and histology assessments. Having considered percentages of PVA with a constant amount of DBM, injectability, compressive mechanical properties, homogeneity of the scaffold, and providing sufficient surface area (12.25 cm2/ml) for cell attachment; 0.35 g/ml of DBM in 20% PVA (w/v) has applicable properties within the ranges of studies which can be proposed for the injectable engineered articular cartilage.

Synergistic effects of conductive PVA/PEDOT electrospun scaffolds and electrical stimulation for more effective neural tissue engineering

Fabrication and optimization of conductive scaffolds capable of inducing proper intercellular connections through electrical signals is critical for neural tissue engineering. In this research, electrospun conductive PVA (Polyvinyl alcohol)/PEDOT(poly(3,4-ethylenedioxythiophene)) scaffolds were fabricated in different compositions. Conductivity of electrospinning solutions and electrospun scaffolds were measured. Morphology and topography, mechanical properties and water contact angle of scaffolds were analyzed. Chemistry of scaffolds were studied using FTIR analysis, while biocompatibility and cellular interactions with scaffolds were tested using MTT assay and cellular attachment and spreading testing. Our results show improvements in PEDOT-containing scaffolds, in terms of physiochemical properties, and cell viability compared to pure PVA scaffolds. After optimization of scaffolds, real-time PCR analysis was used to study neural differentiation of rat mesenchymal stem cells (MSCs). Scaffold samples with and without induction of electrical stimulation are shown to upregulate β-tubulin, nestin and enolase as compared to TCP samples. Additionally, expression of nestin gene in scaffold samples with electrical stimulation was 1.5 times more significant than scaffold sample. Overall, this study shows that using PVA/PEDOT conductive scaffolds with electrical stimulation can improve cellular response and neural differentiation through mimicking the properties of native neural tissue.

Three dimensional polyvinyl alcohol scaffolds modified with collagen for HepG2 cell culture.

The creation of in vitro functional hepatic tissue simulating micro environmental niche of the native liver is a keen area of research due to its demand in bioartificial liver. However, it is still unclear how to maintain benign cell function while achieving the sufficient cell quantity. In this work, we aim to prepare a novel scaffold for the culture of HepG2 cells, a liver cell line, by modifying polyvinyl alcohol (PVA) scaffold with collagen (COL). PVA is a kind of synthetic biostable polymer with high hydrophilicity in the human body, has been widely used in the biomedical field. However, the use of PVA is limited in cell cultures due to lack of biologically active functional groups. In this study, amino silane (KH-550), glutaraldehyde and native type I collagen were used to modify three-dimensional PVA scaffold to establish a suitable composite scaffold for hepatocyte culture. Three types of composite scaffolds were prepared for different collagen content, named as PVA/COL (0.2%), PVA/COL (0.5%) and PVA/COL (0.8%), respectively. The composite scaffolds were characterized by SEM, XPS, FTIR, MS, porosity estimation and water contact angle measurement. The PVA/COL (0.8%) scaffolds had the highest collagen content of 12.13%. The composite scaffold showed high porosity with interconnected pores. Furthermore, the biocompatibility between HepG2 cells and scaffolds was evaluated by the ability of cell proliferation, albumin secretion, as well as urea synthesis. The coating of collagen on PVA scaffolds promoted hydrophilicity and HepG2 cell adhesion. Additionally, enhanced cell proliferation, increased albumin secretion and urea synthesis were observed in HepG2 cells growing on collagen-coated three-dimensional PVA scaffolds.

A facile method to fabricate propolis enriched biomimetic PVA architectures by co-electrospinning

This study depicts easy process of propolis by co-electrospinning without using any toxic agent for biomedical applications. To achieve this, polyvinyl alcohol was utilized as co-spinning agent to fabricate biomimetic Propolis/PVA scaffold. Here, whilst PVA was used as a supportive material to accumulate propolis in scaffold, propolis was employed to enrich biologic aspect of scaffold. This strategy overcomes challenges of propolis processing originated from solubility problems and offers easy processability of propolis in order to use in biomedical applications. Electrospun Propolis/PVA scaffolds were crosslinked with glutaraldehyde and drop-cast model was utilized as a control. Formation of porous, bead-free nanofiber architectures was confirmed through surface morphology analysis, while drop-cast model shows non-porous morphology. Wettability results confirmed both crosslinking and integration of propolis into polyvinyl alcohol scaffold moved contact angle to hydrophobic region. Presence and amount of propolis in hybrid scaffolds were validated via absorbance spectrum results. Bioactivity and biocompatibility of propolis-enriched scaffolds were analyzed through protein adsorption capacity. Obtained findings are evidence that electrospinning methodology offers easy and biosafe process of propolis. Electrospun Propolis/PVA exhibits desired properties and could be potentially utilized as scaffold for tissue engineering or as a wound dressing graft in biomedical field.

Electrospun PVA nanoscaffolds associated with propolis nanoparticles with wound healing activity

Tissue engineering and nanotechnology have developed polymeric nanofibrous scaffolds for tissue regeneration. Propolis is a featured natural product due to its biological properties, including enhancement of the wound healing process. This study developed a polymeric nanofibrous wound dressing of polyvinyl alcohol (PVA) and propolis, and evaluated both in vitro and in vivo its potential in the wound healing process. The optimization of the experimental conditions was performed based on the evaluation of electrospinning process stability and morphology of the resulting nanofibers. The resulting scaffolds were evaluated through cell culture studies, using murine NIH/3T3 fibroblasts as study model, and then in vivo in a diabetic non-contractile wound healing model. PVA scaffolds associated with nanoparticles showed an adequate fiber morphology and did not present any cytotoxicity to fibroblasts in vitro. Furthermore, PVA scaffold with propolis nanoparticles showed the best wound closure rate (68%) after 7 days in comparison with treated (54%) and untreated controls (20%). Withal, preliminary results showed that PVA scaffold associated with propolis nanoparticles has potential to be applied in tissue regeneration. Furthermore, this work features as innovation the development of a nanoscaffold/nanoparticles system, which can be used not only for propolis, but for any natural extract, especially for those insoluble in water.

Growth of Human Dermal Fibroblasts on Polyvinyl Alcohol-Silk Fibroin Nanofiber Scaffold

Skin tissue engineering is a developing technology to heal severe wounds. Combining polyvinyl alcohol (PVA) and silk fibroin (SF) nanofibers is a promising method of developing a skin scaffold because the resulting structure mimics collagen fibers. The aim of this research was to study the growth of human dermal fibroblasts (HDF) on a polyvinyl alcohol-silk fibroin (PVA-SF) nanofiber scaffold that was produced by electrospinning. Morphological characterization and chemical analysis of the scaffold were performed by scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), and contact angle measurement. The biocompatibility of the scaffold was tested by MTT cytotoxicity assay, SEM analysis, adherence ratio calculation, and analysis of the HDF growth curve for 9 days. The FTIR results confirmed the presence of SF and PVA. The average fiber diameter and pore size of the PVA scaffold were greater than those of the PVA-SF scaffold. Both scaffolds had hydrophilic properties and were not cytotoxic. Thus, HDF can attach and grow on both types of scaffold better than HDF seeded on a polystyrene plate. In conclusion, the addition of SF to the PVA nanofibers caused bead formation, which affected the substrate topography, decreased hydrophilicity and also decreased the fiber diameter and pore size in the nanofiber scaffold compared to the PVA nanofiber scaffold without SF addition. SF addition increases cell attachment to the nanofiber scaffold and has potential to facilitate HDF cell growth.

Characterization of polyvinyl alcohol hydrogels as tissue-engineered cartilage scaffolds using a coupled finite element-optimization algorithm

Mechanical strength along with high biocompatibility and water absorbing are among main characteristics of a desirable scaffold for cartilage tissue engineering. Having these properties, polyvinyl alcohol (PVA) can be a good option for constructing cartilage tissue engineering scaffolds. In this study, PVA hydrogel was produced by freeze-thaw crosslinking method, and its mechanical properties such as viscoelastic and hyperplastic behavior, which cannot be obtained analytically, was investigated with a coupled finite element (FE)-optimization algorithm and stress relaxation experimental data. To obtain isotropic hyper-viscoelastic constitutive parameters of PVA scaffolds, the Mooney-Rivlin and Neo-Hooke strain energy functions, in which shear and bulk moduli varies with time, were applied. Results showed that predicted mechanical responses of scaffolds by the Mooney-Rivlin model better fitted stress-relaxation experiments than those obtained by Neo-Hooke one. Also, the properties obtained from the finite element model, such as the bulk and the shear moduli, showed that, after successful in vitro and in vivo experiments, PVA hydrogel may be introduced as a cartilage substitute for future tissue engineering therapies.

Chemically and physically cross-linked polyvinyl alcohol-borosilicate gel hybrid scaffolds for bone regeneration

The composite scaffolds of bioactive glasses and polymers are often used in bone regeneration which could improve the stiffness, compressive strength and bioactivity of polymers while maintaining the osteoconductivity and osteoinductivity of bioactive glasses. But due to complicated situations and limitations of compositing process, the prepared composite materials have low uniformity and obvious phase separation, leading to problems such as poor mechanical properties and inferior new bone formation capacity. In this paper, a modified sol-gel processing technique was used to realize the homogeneous inorganic-organic composites. After hydrolysis of the metal alkoxide, the sol was mixed with the aqueous solution of polyvinyl alcohol (PVA), and through gelation and chemical reaction, the mixture was solidified into the inorganic-organic composite hydrogel. The composites showed as a uniform single phase with interpenetrating networks of PVA gel and borosilicate gel (BG) that chemically and physically interacted at the scale of molecular or nanometer, therefore PVA-BG hybrids were obtained. When immersed in phosphate-buffered saline, the PVA-BG hybrid-derived scaffolds released beneficial ions into the medium and converted to hydroxyapatite. The scaffolds were not toxic to the rat bone marrow-derived mesenchymal stem cells (rBMSCs), and supported rBMSCs proliferation. Furthermore, the alkaline phosphatase activity of the rBMSCs and the expression levels of osteogenic-related genes (alkaline phosphatase, osteocalcin and runt-related transcription factor 2) increased significantly with increasing amount of BG in the hybrid scaffolds. Finally, the bone defect repair results of critical-sized femoral condyle defect rat model demonstrated that PVA-BG hybrid scaffolds could enhance bone regeneration compared with PVA scaffolds. The results suggested that PVA-BG hybrid scaffolds may be a promising biomaterial for bone regeneration.

Poly-ε-caprolactone and polyvinyl alcohol electrospun wound dressings: adhesion properties and wound management of skin defects in rabbits.

Aim: This study evaluates the effect of electrospun dressings in critical sized full-thickness skin defects in rabbits. Materials & methods: Electrospun poly-ε-caprolactone (PCL) and polyvinyl alcohol (PVA) nanofibers were tested in vitro and in vivo. Results: The PCL scaffold supported the proliferation of mesenchymal stem cells, fibroblasts and keratinocytes. The PVA scaffold showed significant swelling, high elongation capacity, limited protein adsorption and stimulation of cells. Nanofibrous dressings improved wound healing compared with the control group in vivo. A change of the PCL dressing every 7days resulted in a decreased epithelial thickness and type I collagen level in the adhesive group, indicating peeling off of the newly formed tissue. In the PVA dressings, the exchange did not affect healing. Conclusion: The results demonstrate the importance of proper dressing exchange.