Electrospinning of polyvinylalcohol–polycaprolactone composite scaffolds for tissue engineering applications

Random nanofibrous composite scaffolds of PVA/PCL bilayer were fabricated by electrospinning method. The bilayer nanofibrous scaffolds were subjected to detailed structural, morphological, chemical, and thermal analysis using XRD, SEM, FTIR, and DSC. Morphological investigations revealed that the prepared nanofibers have uniform morphology and the average fiber diameters for bilayer samples A, B, and C are 203, 252, and 244 nm, respectively. The obtained scaffolds have a porous structure with porosity of 77, 89.2, and 78.3 % for bilayer samples A, B, and C, respectively. FTIR analysis ensured complete evaporation of solvent and formation of non-interactive bilayers. Biocompatibility of the membranes was investigated by studying the adhesion of mouse NIH 3T3 fibroblasts for 72 h, and its enhanced adhesion and proliferation proved its mettle as a potential scaffold for tissue engineering applications.     

Preparation and characterization of vancomycin releasing PHBV coated 45S5 Bioglass®-based glass–ceramic scaffolds for bone tissue engineering

Porous 45S5 Bioglass^®-based glass–ceramic scaffolds with high porosity (96%) and interconnected pore structure (average pore size 300 μm) were prepared by foam replication method. In order to improve the mechanical properties and to incorporate a drug release function, the scaffolds were coated with a drug loaded solution, consisting of PHBV and vancomycin. The mechanical properties of the scaffolds were significantly improved by the PHBV coating. The bioactivity of scaffolds upon immersion in SBF was maintained in PHBV coated scaffolds although the formation of hydroxyapatite was slightly retarded by the presence of the coating. The encapsulated drug in coated scaffolds was released in a sustained manner (99.9% in 6 days) as compared to the rapid release (99.5% in 3 days) of drug directly adsorbed on the uncoated scaffolds. The obtained drug loaded and bioactive composite scaffolds represent promising candidates for bone tissue engineering applications.     

Synthesis and characterisation of gelatin–nano hydroxyapatite composite scaffolds for bone tissue engineering

Abstract

Gelatin–hydroxyapatite (HAp) nanocomposites have been prepared by particulate leaching technique using glutaraldehyde (GTA) as cross-linking agent for polymer. The porosity in the scaffolds was controlled using sodium chloride as porogen agent. Microstructural investigation by scanning electron microscopy (SEM), revealed the formation of a well interconnected porous scaffold with pore size in the range of 100–200 μm. X-ray diffraction and Fourier transform infrared spectroscopy were used to confirm the formation of crystalline HAp as well the presence of both constituents in the composite samples. The bioactivity of the samples was evaluated by conducting MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay and cell adhesion tests. The results suggest that the use of GTA in excess of 0˙25% can be detrimental to cell survival. Cell attachment on the nanocomposite scaffold was verified by microscopic analysis.     

Fabrication and characterization of poly(ε-caprolactone)/gelatin nanofibrous scaffolds for retinal tissue engineering

Different ratios of poly(ε-caprolactone) (PCL) and gelatinwere used to fabricate scaffolds for regeneration of retinal pigment epithelium (RPE) layer. Physical and chemical characterizations were performed and the behavior of human RPE cells on the scaffolds was evaluated subsequently. An increase in gelatin content in the scaffold enhanced hydrophilicity, RPE cell attachment, proliferation, and spreading over PCL scaffolds. Granular and cytoplasmic expressions of RPE65 and Cytokeratin 8/18 markers confirmed the presence of RPE cells. It was believed that PCL/gelatin scaffolds could be used as substrates to replace RPE extracellular matrix to facilitate regeneration of RPE layer in retinal diseases.     

Preparation and characterization of PLLA–ESO/surface-grafted silica nanocomposites

Various amounts of surface-grafted silica (g-SiO₂) and un-grafted (SiO₂) nanoparticles were solution blended with a copolymer of l-lactide and epoxidized soybean oil (PLLA–ESO) or PLLA. Chemical reaction between the low molecular weight (LMW) PLLA and surface of silica nanoparticles is confirmed by FTIR and TGA analyses. The amount of grafted LMW PLLA investigated by thermal gravimetric analysis (TGA) was about 14.9%–28.2% in weight. g-SiO₂ nanoparticles can be easily dispersed into PLLA–ESO matrix to form a uniform PLLA–ESO/g-SiO₂ composite. Thermal properties of PLLA–ESO/g-SiO₂ and PLLA/g-SiO₂ nanocomposites were subsequently investigated by the differential scanning calorimeter measurements (DSC). DSC analyses indicated that g-SiO₂ nanoparticles can serve as a nucleating agent for the crystallization of PLLA–ESO in the composites, while the melting temperature (T _m) and the glass transition temperature (T _g) of PLLA–ESO/g-SiO₂ nanocomposites seemed to be independent of loading of g-SiO₂ particles. The DSC curves of PLLA/g-SiO₂ nanocomposite obviously showed double melting peaks, while that of PLLA–ESO/g-SiO₂ nanocomposites only a single melting peak. PLLA–ESO/g-SiO₂ composites exhibited a higher tensile strength and elongation than that of PLLA–ESO/SiO₂ composites.     

Development of a novel glucosamine/silk fibroin–chitosan blend porous scaffold for cartilage tissue engineering applications

Silk fibroin–chitosan blend is reported to be an attractive scaffold material for tissue engineering applications. In our earlier study, we developed a scaffold having an optimal silk fibroin–chitosan blend ratio of 80:20 and proved its potentiality for cartilage tissue engineering applications. Glucosamine is one of the major structural components of cartilage tissue. The present work investigates the effect of glucosamine components on the physicochemical and biocompatibility properties of this scaffold. To this end, varied amounts of glucosamine were added to silk fibroin–chitosan blend with the aim of improving various scaffold properties. The addition of glucosamine components did not show any significant change in physicochemical properties of silk fibroin–chitosan blend scaffolds. The composite scaffold showed an open pore structure with desired pore size and porosity. However, cell culture study using human mesenchymal stem cells derived from umbilical cord blood revealed an overall increase in cell supportive properties of glucosamine-added scaffolds. Cell viability, cell proliferation and glycosaminoglycan assays confirmed enhanced cell viability and proliferation of mesenchymal stem cells. Thus, this study demonstrated the beneficial effect of glucosamine on improving the cell supportive property of silk fibroin–chitosan blend scaffolds making it more potential for cartilage tissue regeneration. To the best of our knowledge, this is the first report on the study of glucosamine-added silk fibroin–chitosan blend porous scaffolds seeded with mesenchymal stem cells derived from umbilical cord blood.     

Preparation and characterization of alkali-free glass substrates with enhanced properties for TFT–LCDs applications

To obtain an alkali-free glass substrate with enhanced properties for thin-film transistor–liquid crystal displays (TFT–LCDs) applications, we chose a base glass composed of 3B₂O₃-15Al₂O₃-58SiO₂-22MgO-0.5SrO-1.5MgF₂ (mol%) for nucleation–crystallization. The results show that when the nucleation–crystallization processes of the base glass are 810 °C/6 h + 880 °C/6–9 h, the prepared GC/6–GC/9 glass-ceramics exhibit enhanced properties because of the precipitation of nano-sized cordierite. The transmittances in the visible range of the GC/6–GC/9 glass-ceramics exceed 85%, the densities are 2.564–2.567 g/cm³, thermal expansion coefficients are 2.934–3.059 × 10^-6/°C (25–300 °C), compressive strengths are 417–589 MPa, bending strengths are 141–259 MPa, Vickers hardnesses are 6.8–7.8 GPa, and strain points are approximately 735 °C. Considering these properties, the prepared GC/6–GC/9 glass-ceramics have good potential as candidate materials for alkali-free glass substrates. Additionally, these results demonstrate that it is feasible to improve the properties of alkali-free glass substrates by nucleation–crystallization.     

Porous β-Ca2SiO4 ceramic scaffolds for bone tissue engineering: In vitro and in vivo characterization

The biodegradable ceramic scaffolds with desirable pore size, porosity and mechanical properties play a crucial role in bone tissue engineering and bone transplantation. A novel porous β-dicalcium silicate (β-Ca₂SiO₄) ceramic scaffold was prepared by sintering the green body consisting of CaCO₃ and SiO₂ at 1300 °C, which generated interconnected pore network with proper pore size of about 300 μm and high compressive strength (28.13±5.37–10.36±0.83 MPa) following the porosity from 53.54±5.37% to 71.44±0.83%. Porous β-Ca₂SiO₄ ceramic scaffolds displayed a good biocompatibility, since human osteoblast-like MG-63 cells and goat bone mesenchymal stem cells (BMSCs) proliferated continuously on the scaffolds after 7 d culture. The porous β-Ca₂SiO₄ ceramic scaffolds revealed well apatite-forming ability when incubated in the simulated body fluid (SBF). According to the histological test, the degradation of porous β-Ca₂SiO₄ ceramic scaffolds and the new bone tissue generation in vivo were observed following 9 weeks implantation in nude mice. These results suggested that the porous β-Ca₂SiO₄ ceramic scaffolds could be potentially applied in bone tissue engineering.     

Preparation and characterization of natural rubber/ultrafine full-vulcanized powdered styrene–butadiene rubber blends

In this paper, natural rubber (NR)/ultrafine full-vulcanized styrene–butadiene powdered rubber (UFPSBR) blends were prepared and studied for the first time. Scanning electron microscopy and thermogravimetric analysis were employed to characterize UFPSBR. Equilibrium swelling method was used to determine the crosslink density of NR/UFPSBR vulcanizates. The results on mechanical properties showed that when NR/UFPSBR ratio was 100/5, the formulation exhibited favorable performances compared to pure NR vulcanizates. The heat build-up temperature also decreased after adding UFPSBR into the NR formulation. In dynamic mechanical analysis, in the temperature range of ?10 to ?5 °C, loss factor (tanδ) values of NR/UFPSBR vulcanizates showed an increasing trend over the given temperature range and exhibited a peak value at approximate ?5 °C. This indicates that wet traction and rolling resistance of samples were improved after UFPSBR was added in NR. This research demonstrates that UFPSBR can be incorporated into a conventional NR formula to successfully improve the comprehensive performances and dynamic mechanical properties of NR formula.     

Preparation and characterization of gentamycin sulfate-impregnated gelatin microspheres/collagen–cellulose/nanocrystal scaffolds

Polymer Bulletin - In this study, a kind of antibacterial collagen (Coll)/cellulose nanocrystals (CNCs) scaffolds was prepared and characterized, which can be applied in skin trauma as a promising...     

Synthesis,characterization, and cytotoxicity of PCL–PEG–PCL diacrylate and agarose interpenetrating network hydrogels for cartilage tissue engineering

Hydrogels are suitable biomaterials for cartilage tissue engineering due to the excellent ability to retain water to provide suitable environment for the tissue, however, the insufficient mechanical properties often prevent their wider applications. The objective of this study was to fabricate biocompatible hydrogels with good mechanical performance, high-water content, and porous microstructure for cartilage regeneration. Photocrosslinked hydrogels are one of the most widely used systems in tissue engineering due to the superior mechanical properties. In this study, block copolymer, poly(ε -caprolactone)-poly(ethylene)-poly(ε -caprolactone) diacrylate (PCL–PEG–PCL; PEC), was prepared by ring-opening polymerization, and PEC hydrogels were made through free radical crosslinking mechanism. Agarose network is chosen as another component of the hydrogels, because of the high-swelling behavior and cartilage-like microstructure, which is helpful for chondrocytes growth. Interpenetrating networks (IPN) were fabricated by diffusing PEC into agarose network followed by photo-crosslinking process. It was noted that incorporating PEC into the agarose network increased the elastic modulus and the compressive failure properties of individual component networks. In addition, high-swelling ratio and uniform porosity microstructures were found in the IPN hydrogels. IPN and PEC showed low cytotoxicity and good biocompatibility in elution test method. The results suggest promising characteristics of IPN hydrogels as a potential biomaterial for cartilage tissue engineering.     

Development of dual-responsive chitosan–collagen scaffolds for pulsatile release of bioactive molecules

Advancement in polymer science and engineering has led to the development of new polymeric systems for well-controlled delivery of therapeutic agents. In this work, thermo and pH responsive chitosan–collagen (CHT–CLG) scaffolds were prepared using a non-residue strategy. CHT–CLG scaffolds (pH sensitive) were produced by freeze drying method, cross-linked with glutaraldehyde, and coated with poly(N,N′-diethylacrylamide) (PDEAAm) in supercritical media to confer the thermoresponsive behavior. This green and integrated process generated a wide range of porous structures with different mechanical properties, reversible swelling ability and controlled biodegradability, depending on the scaffold composition and cross-linking degree. Microarchitectural analysis by scanning electron microscopy and mercury intrusion porosimetry demonstrated that the coating of the pores inner surface was efficiently achieved without compromising the porosity. The ability of these dual sensitive structures to control the release of a low molecular weight drug (ibuprofen, Ibu) and a model protein (BSA) was investigated. Additionally, a mathematical model was adjusted to the experimental release profiles in order to quantitatively describe the drug release and elucidate the underlying drug release mechanisms. The tunable morphological and mechanical properties together with the well-controlled pulsatile release of bioactive molecules make these structures attractive ON–OFF systems in biomedical and pharmaceutical fields.     

Compressive strength of β-TCP scaffolds fabricated via lithography-based manufacturing for bone tissue engineering

Bone is a vital organ that is responsible for the support and movement of body as well as the storage and transportation of cells and nutrients. Disease, along with traumatic events, can leave regions of bone with large voids and/or defects. Related surgical procedures, such as allografts, autografts, and arthroplasty, are reported to amount to roughly €9.6bn annually, emphasising the need for bone repair/replacement globally. Tricalcium phosphate (TCP) is a bioactive ceramic that has been identified as a suitable material for bone tissue engineering applications due to its excellent bioresorbability and overall biocompatibility. Through lithography-based ceramic manufacturing (LCM), β -TCP scaffolds were fabricated across nine different designs in this work. Pore size, unit cell size, and unit cell geometry were altered to vary the porosity of these scaffolds. Following fabrication, the material composition, topography, macrostructure, and microstructure of the β-TCP scaffolds were characterised. The effects of porosity and unit cell geometry on the compressive strengths of β -TCP scaffolds were analysed in detail. Compressive strengths of the scaffolds were measured between 1.4 ± 0.5 MPa and 67.6 ± 13.3 MPa across a porosity range of 5.58 ± 0.09% to 59.36 ± 0.18%. The strength of these scaffolds was considerably lower than that of the compressive strength of cortical bone (100–200 MPa), but mimic the compressive strength of cancellous bone well (0.1–16 MPa). While scaffolds of β-TCP alone may not be suitable for load-bearing applications, they demonstrate enough mechanical stability for bone regeneration/tissue engineering applications. They hold more potential in the regeneration of small bone defects/voids or in composite materials.     

Development and characterization of printable PLA/β-TCP bioactive composites for bone tissue applications

In this study, poly(lactic acid) (PLA) and PLA/β-tricalcium phosphate (TCP) biocomposites were developed by melt compounding using an internal melt mixer with three different TCP contents (5, 10, and 25 wt%). A comprehensive analysis of the thermal, rheological, and mechanical properties of these biocomposites was performed. TCP presented proper distribution in the PLA/TCP biocomposites: PLA5TCP and PLA10TCP exhibited rheological behavior similar to that of neat PLA. However, PLA25TCP presented significant agglomeration and reduction in thermal stability. Addition of TCP to the biocomposites enhanced their bioactivity and biocompatibility. The bioactivity assay was conducted by immersing the samples in SBF solution for 7 and 21 days, and the SEM and XRD surface analyses of the PLA/TCP biocomposites presented evidence of carbonated hydroxyapatite formation. The biocompatibility assay was performed using the extract method until 7 days, and PLA10TCP presented improved relative cell viability compared with the control. Finally, since the materials presented suitable thermal and rheological properties, filaments for additive manufacturing (AM) were developed, and they were used to produce screw models for bone-ligament fixation. The 3D printed screws exhibited excellent printability and accuracy. Therefore, the PLA/TCP biocomposites developed can be used in further biomedical applications using AM, namely, guided bone tissue engineering.     

Processing and characterization of elastomeric polycaprolactone triol–citrate coatings for biomedical applications

In this paper we describe the synthesis, processing and characterization of a novel elastic polyester coating created by carrying out catalyst-free polyesterification between biocompatible and non-toxic multifunctional reactants, namely polycaprolactone triol and citric acid. The physico-chemical and surface properties of the resulting polyester coatings and films have been investigated. This new material has been characterized by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infra-red spectroscopy (FTIR), water-in-air contact angle measurements, scanning electron microscopy (SEM), thermal analysis (DSC), mechanical tests and swelling experiments. The polymer structure, surface properties (morphology and chemistry), mechanical integrity and hydration of the elastomer can be controlled by simple variation of the initial citric acid concentration in the polymer formation. This feature of the novel polyester material presents a significant development in the production of advanced coatings for biomedical applications.     

Manufacturing of silicon – Bioactive glass scaffolds by selective laser melting for bone tissue engineering

The irruption of additive manufacturing techniques opens the possibility to develop three-dimensional structures with complex geometries and high precision. In the current investigation a newly designed composite combining silicon (30, 40 and 50 wt%) with a bioactive glass and printed into scaffolds was obtained, using a direct selective laser melting (SLM) approach for the first time. Samples were computer-aided designed (CAD) to have cylindrical pores of 400 μm in diameter in order to be used as biomaterials for bone replacement. X – Ray diffraction was used to characterize the appearance of a new phase of pseudowollastonite precipitated by the partial devitrification of the glassy phase after the incidence of laser radiation. The mechanical behaviour of each composition was studied trough stress-strain curves, obtaining higher values of compressive strength as the silicon content increases. Scanning electron microscopy coupled to energy dispersive X – Ray spectroscopy (SEM-EDS) and Raman spectroscopy were used to study the bioactivity of each composite after soaking in the simulated body fluid (SBF) for 7 days, confirming this behaviour.     

Poly-3-hydroxybutyrate-based constructs with novel characteristics for drug delivery and tissue engineering applications—A review

Herein, we reviewed polymeric constructs of polyhydroxyalkanoates (PHAs) at large and poly-3-hydroxybutyrate (P3HB), in particular, for drug delivery and tissue engineering applications. Polymeric constructs that can efficiently respond to numerous variations in their surroundings have gained notable attention from different industrial sectors such as biomedical, clinical, pharmaceutical, and cosmeceutical. Among them, considerable importance is given to their drug delivery and tissue engineering applications. PHAs with peculiar reference to P3HB are gaining prominence attention as candidate materials with such requisite potentialities. The unique structural and functional characteristics of PHAs and P3HB are of supreme interest and being used to engineer novel constructs for efficient drug delivery and tissue regeneration purposes. So far, an array of methodological approaches, such as in vitro, in vivo, and ex vivo techniques have been exploited though using different materials with different geometries for a said purpose. However, a low-level production majorly limits their proper exploitation. Various physiochemical characteristics and production strategies have been introduced in this review. The data have been summarized on PHAs production by several microorganisms aiming to cover the scope of the last 10 years. The present review highlights the recent applications of PHAs and P3HB-based constructs, such as micro/nanoparticles, biocomposite, nanofibers, and hydrogels as novel drug carries for regenerative medicine and tissue engineering. In summary, drug delivery and tissue engineering potentialities of PHAs and P3HB-based constructs are discussed with suitable examples and envisioned directions of future developments.