Characterization of smooth muscle cells on poly(ε-caprolactone) films

Fabrication and Plasma Modification of Nanofibrous Tissue Engineering Scaffolds

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

Investigation and Characterization of Plasma-Treated Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers for an In Vitro Cellular Study of Mouse Adipose-Derived Stem Cells

Polyhydroxyalkanoates (PHAs) are a type of thermoprocessable and biodegradable polyester, which represent a potential sustainable replacement for fossil-fuel synthetic polymers, such as polypropylene and polyethylene. In recent years, copolymers of PHAs, i.e., poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), have received attention for medical and packaging industrial applications, due to their biodegradable, toxic-free, and biocompatible nature. This study investigated and characterized plasma-treated PHB and PHBV films fermented with Ralstonia eutropha H16. The X-ray photoelectron spectroscopy (XPS) and water contact angle analyses on the plasma-treated PHB and PHBV film surfaces revealed an increase in the number of functional groups and contact angle degree, respectively, compared to that of the untreated films. In addition, an in vitro experiment of mouse adipose-derived stem cells showed better growth and adhesion of the cells on the surface of plasma-treated PHBV film. Overall, these results reveal that plasma surface modifications are useful in biomaterial development.

Plasma-induced surface modification of polydimethylsiloxane aimed at reducing salt and protein deposition

Polydimethylsiloxane (PDMS) is an elastomer that is widely used in construction and for biological and biomedical applications. The biocompatibility of PDMS was improved by different surface treatment methods, i.e., plasma treatment or a combination of plasma treatment with UV-irradiation or redox initiator, to minimize the effects of deposition of salts and proteins. In this work we used the vinyl monomers sulfobetaine and AMPS which have good biocompatible properties.

Double protein functionalized poly-ε-caprolactone surfaces: in depth ToF-SIMS and XPS characterization

In biomaterial research, great attention has focussed on the immobilization of biomolecules with the aim to increase cell-adhesive properties of materials. Many different strategies can be applied. In previously published work, our group focussed on the treatment of poly-ε-caprolactone (PCL) films by an Ar-plasma, followed by the grafting of 2-aminoethyl methacrylate (AEMA) under UV-irradiation. The functional groups introduced, enabled the subsequent covalent immobilisation of gelatin. The obtained coating was finally applied for the physisorption of fibronectin. The successful PCL surface functionalization was preliminary confirmed using XPS, wettability studies, AFM and SEM. In the present article, we report on an in-depth characterization of the materials developed using ToF-SIMS and XPS analysis. The homogeneous AEMA grafting and the subsequent protein coating steps could be confirmed by both XPS and ToF-SIMS. Using ToF-SIMS, it was possible to demonstrate the presence of polymethacrylates on the surface. From peak deconvoluted XPS results (C- and N-peak), the presence of proteins could be confirmed. Using ToF-SIMS, different positive ions, correlating to specific amino-acids could be identified. Importantly, the gelatin and the fibronectin coatings could be qualitatively distinguished. Interestingly for biomedical applications, ethylene oxide sterilization did not affect the surface chemical composition. This research clearly demonstrates the complementarities of XPS and ToF-SIMS in biomedical surface modification research.

The Effect of Polymer Molecular Weight and UV Radiation on Physical Properties and Bioactivities of PCL Films

Biodegradable polymers, such as polycaprolactone (PCL), have been well studied in the application of tissue engineering and drug delivery systems due to their favourable biocompatibility profiles. However, little research has discussed the influence of the molecular weight of these polymers on cell behaviours. Here, PCL films were synthesized using polymers with various molecular weight and the physical characteristics of these films and their effect on cell growth were evaluated. Results showed that the tensile strength and elongation rate of PCL films increased from 1.82 MPa and 95.3% to 2.01 MPa and 741.6% when the molecular weight (Mn) of polymers increased from 40,000 to 80,000. A significant difference in polymer crystallinity was also observed between these formulations. Moreover, we found that prolonged exposure to UV radiation of these films could lead to the breakdown of polymer chains and consequently increased the crystallinity of PCL films with a corresponding reduction in the tensile strength. Using Hs68 human foreskin fibroblasts, PCL films prepared using high molecular weight polymers (CAPA 6800) displayed a higher cell proliferation rate compared to ones prepared using low molecular weight polymers (CAPA 6400 and 6500). In contrast, a higher cell proliferation rate was observed for PCL films made of low molecular weight polymers, especially CAPA 6500, when H9c2 rat heart myoblasts were used. In conclusion, polymer molecular weight can alter the

Both sides nanopatterned tubular collagen scaffolds as tissue-engineered vascular grafts

Two major requirements for a tissue-engineered vessel are the establishment of a continuous endothelium and adequate mechanical properties. In this study, a novel tubular collagen scaffold possessing nanopatterns in the form of channels (with a 650 nm periodicity) on both sides was designed and examined after seeding and co-culturing with vascular cells. Initially, the exterior of the tube was seeded with human vascular smooth muscle cells (VSMCs), cultured for 14 days, and then human internal thoracic artery endothelial cells (HITAECs) were seeded on the inside of the tube and cultured for a further week. Microscopy revealed that nano-scale patterns could be reproduced on collagen with high fidelity and preserved during incubation in vitro. The VSMCs were circumferentially orientated with the help of these nanopatterns and formed multilayers on the exterior, while HITAECs formed a continuous layer on the interior, as is the case in natural vessels. Both cell types were observed to proliferate and retain their phenotypes in the co-culture.

In vitro and in vivo testing of novel ultrathin PCL and PCL/PLA blend films as peripheral nerve conduit

In an attempt to obviate the drawbacks of nerve autograft, ultrathin microporous biodegradable PCL and PCL/PLA films were tested for their compatibility with motor neuron-like NG108-15 cells and primary Schwann cells. Data obtained from MTS colorimetric and DNA fluorimetric assays showed that both cell lines readily attached and proliferated on these materials. Images taken using scanning electron microscope and fluorescence microscope confirmed these observations. Enhanced cell-surface interaction was achieved by pretreating the films in NaOH solution. Importantly, NG108-15 cells could be induced into differentiated phenotype with long, un-branched neurites growing across the surface of the materials. The bipolar spindle-shaped phenotype of Schwann cells was also retained on these scaffolds. Positive immunochemical staining using antibodies against neurofilament for NG108-15 cells and S100 for Schwann cells indicated the expression of these marker proteins. In a small-scaled pilot testing, the performance of PCL conduits in bridging up a 10 mm gap in rat sciatic nerve model was assessed. Immunohistochemical staining showed that regenerated nerve tissue and penetrated Schwann cells have the potential to span the whole length of the conduit in 2 weeks.

Nanopatterning of collagen scaffolds improve the mechanical properties of tissue engineered vascular grafts

Tissue engineered constructs with cells growing in an organized manner have been shown to have improved mechanical properties. This can be especially important when constructing tissues that need to perform under load, such as cardiac and vascular tissue. Enhancement of mechanical properties of tissue engineered vascular grafts via orientation of smooth muscle cells by the help of topographical cues have not been reported yet. In the present study, collagen scaffolds with 650, 500, and 332.5 nm wide nanochannels and ridges were designed and seeded with smooth muscle cells isolated from the human saphenous vein. Cell alignment on the construct was shown by SEM and fluorescence microscopy. The ultimate tensile strength (UTS) and Young's modulus of the scaffolds were determined after 45 and 75 days. Alamar Blue assay was used to determine the number of viable cells on surfaces with different dimensioned patterns. Presence of nanopatterns increased the UTS from 0.55 +/- 0.11 to as much as 1.63 +/- 0.46 MPa, a value within the range of natural arteries and veins. Similarly, Young's modulus values were found to be around 4 MPa, again in the range of natural vessels. The study thus showed that nanopatterns as small as 332.5 nm could align the smooth muscle cells and that alignment significantly improved mechanical properties, indicating that nanopatterned collagen scaffolds have the potential for use in the tissue engineering of small diameter blood vessels.

Surface modifications of photocrosslinked biodegradable elastomers and their influence on smooth muscle cell adhesion and proliferation

Photocrosslinked, biodegradable elastomers based on aliphatic polyesters have many desirable features as scaffolds for smooth muscle tissue engineering. However, they lack cell adhesion motifs. To address this shortcoming, two different modification procedures were studied utilizing a high and a low crosslink density elastomer: base etching and the incorporation of acryloyl-poly(ethylene glycol) (PEG)-Gly-Arg-Gly-Asp-Ser (GRGDS) into the elastomer network during photocrosslinking. Base etching improved surface hydrophilicity without altering surface topography, but did not improve bovine aortic smooth muscle cell adhesion. Incorporation of PEG-GRGDS into the elastomer network significantly improved cell adhesion for both high and low crosslink density elastomers, with a greater effect with the higher crosslink density elastomer. Incorporation of GRGDS into the high crosslink density elastomer also enhanced smooth muscle cell proliferation, while proliferation on the low crosslink density unmodified, base etched, and PEG-GRGDS incorporated elastomers was significantly greater than on the high crosslink density unmodified and base etched elastomer.

Physicochemical characterisation of novel ultra-thin biodegradable scaffolds for peripheral nerve repair

In this study, the physicochemical properties of microporous poly (epsilon-caprolactone) (PCL) films and a composite material made of PCL and polylactic acid (PLA) blend were tested. Fabricated by solvent casting using dichloromethane, these ultra-thin films (60 +/- 5 microm in thickness) have a novel double-sided surface topography, i.e. a porous surface with pores 1-10 microm in diameter and a relatively smooth surface with nano-scaled texture. Porous surfaces were found to be associated with increased protein adsorption and the treatment of these polyester scaffolds with NaOH rendered them more hydrophilic. Differential Scanning Calorimetry (DSC) showed that the incorporation of PLA reduced the crystallinity of the original homopolymer. Chemical changes were investigated by means of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Average surface roughness (Ra), hydrophilicity/hydrophobicity and mechanical properties of these materials were also assessed for the suitability of these materials as nerve conduits.

Macromolecular biomaterials for scaffold-based vascular tissue engineering

Cardiovascular diseases are increasingly becoming the main cause of death all over the world, which has led to an increase in the economic and social burden of such diseases. Vascular tissue engineering (VTE) is providing a route towards interesting applications, mainly focussing on the in vitro, in vivo, or combined in vitro/in vivo regeneration of small-diameter blood vessels (<6 mm) for coronary or peripheral vascular substitutions. Although different approaches have been investigated in the past two decades to achieve this aim, the most common method uses a macromolecular-based structure to scaffold cells during the regeneration process. Therefore, the aim of this work is to comprehensively review macromolecular biomaterials that were designed, developed, fabricated, and tested for scaffolding VTE. In an effort to provide a comprehensive overview, this review will mainly focus on the mechanical properties of the construct and its biological performance that results from the scaffold colonization during cell growth.