The effect of starch and starch-bioactive glass composite microparticles on the adhesion and expression of the osteoblastic phenotype of a bone cell line

Bioactive glass-polymer nanocomposites: a comprehensive review on unveiling their biomedical applications

Most natural and synthetic polymers are promising materials for biomedical applications because of their biocompatibility, abundant availability, and biodegradability. Their properties can be tailored according to the intended application by fabricating composites with other polymers or ceramics. The incorporation of ceramic nanoparticles such as bioactive glass (BG) and hydroxyapatite aids in the improvement of mechanical and biological characteristics and alters the degradation kinetics of polymers. BG can be used in the form of nanoparticles, nanofibers, scaffolds, pastes, hydrogels, or coatings and is significantly employed in different applications. This biomaterial is highly preferred because of its excellent biocompatibility, bone-stimulating activity, and favourable mechanical and degradation characteristics. Different compositions of nano BG are incorporated into the polymer system and studied for positive results such as enhanced bioactivity, better cell adherence, and proliferation rate. This review summarizes the fabrication and the progress of natural/synthetic polymer-nano BG systems for biomedical applications such as drug delivery, wound healing, and tissue engineering. The challenges and the future perspectives of the composite system are also addressed.

Sterile and Dual-Porous Aerogels Scaffolds Obtained through a Multistep Supercritical CO₂-Based Approach

Aerogels from natural polymers are endowed with attractive textural and biological properties for biomedical applications due to their high open mesoporosity, low density, and reduced toxicity. Nevertheless, the lack of macroporosity in the aerogel structure and of a sterilization method suitable for these materials restrict their use for regenerative medicine purposes and prompt the research on getting ready-to-implant dual (macro + meso)porous aerogels. In this work, zein, a family of proteins present in materials for tissue engineering, was evaluated as a sacrificial porogen to obtain macroporous starch aerogels. This approach was particularly advantageous since it could be integrated in the conventional aerogel processing method without extra leaching steps. Physicochemical, morphological, and mechanical characterization were performed to study the effect of porogen zein at various proportions (0:1, 1:2, and 1:1 zein:starch weight ratio) on the properties of the obtained starch-based aerogels. From a forward-looking perspective for its clinical application, a supercritical CO₂ sterilization treatment was implemented for these aerogels. The sterilization efficacy and the influence of the treatment on the aerogel final properties were evaluated mainly in terms of absence of microbial growth, cytocompatibility, as well as physicochemical, structural, and mechanical modifications.

Fabrication and characterization of carboxymethyl cellulose novel microparticles for bone tissue engineering

In this study we developed carboxymethyl cellulose (CMC) microparticles through ionic crosslinking with the aqueous ion complex of zirconium (Zr) and further complexing with chitosan (CS) and determined the physio-chemical and biological properties of these novel microparticles. In order to assess the role of Zr, microparticles were prepared in 5% and 10% (w/v) zirconium tetrachloride solution. Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS) results showed that Zr was uniformly distributed on the surface of the microparticles as a result of which uniform groovy surface was obtained. We found that Zr enhances the surface roughness of the microparticles and stability studies showed that it also increases the stability of microparticles in phosphate buffered saline. The crosslinking of anionic CMC with cationic Zr and CS was confirmed by Fourier transform infrared spectroscopy (FTIR) results. The response of murine pre-osteoblasts (OB-6) when cultured with microparticles was investigated. Live/dead cell assay showed that microparticles did not induce any cytotoxic effects as cells were attaching and proliferating on the well plate as well as along the surface of microparticles. In addition, SEM images showed that microparticles support the attachment of cells and they appeared to be directly interacting with the surface of microparticle. Within 10days of culture most of the top surface of microparticles was covered with a layer of cells indicating that they were proliferating well throughout the surface of microparticles. We observed that Zr enhances the cell attachment and proliferation as more cells were present on microparticles with 10% Zr. These promising results show the potential applications of CMC-Zr microparticles in bone tissue engineering.

Low viscosity-PLGA scaffolds by compressed CO2foaming for growth factor delivery

Foaming technology using supercritical and compressed fluids has emerged as a promising solution in regenerative medicine for manufacturing porous polymeric scaffolds.

Transplantation of human placenta-derived mesenchymal stem cells in a silk fibroin/hydroxyapatite scaffold improves bone repair in rabbits

The main requirements for successful tissue engineering of the bone are non-immunogenic cells with osteogenic potential and a porous biodegradable scaffold. The purpose of this study is to evaluate the potential of a silk fibroin/hydroxyapatite (SF/HA) porous material as a delivery vehicle for human placenta-derived mesenchymal stem cells (PMSCs) in a rabbit radius defect model. In this study, we randomly assigned 16 healthy adult New Zealand rabbits into two groups, subjected to transplantation with either SF/HA and PMSCs (experimental group) or SF/HA alone (control group). To evaluate fracture healing, we assessed the extent of graft absorption, the quantity of newly formed bone, and re-canalization of the cavitas medullaris using radiographic and histological tools. We performed flow cytometric analysis to characterize PMSCs, and found that while they express CD90, CD105 and CD73, they stain negative for HLA-DR and the hematopoietic cell surface markers CD34 and CD45. When PMSCs were exposed to osteogenic induction medium, they secreted calcium crystals that were identified by von Kossa staining. Furthermore, when seeded on the surface of SF/HA scaffold, they actively secreted extracellular matrix components. Here, we show, through radiographic and histological analyses, that fracture healing in the experimental group is significantly improved over the control group. This strongly suggests that transplantation of human PMSCs grown in an SF/HA scaffold into injured radius segmental bone in rabbits, can markedly enhance tissue repair. Our finding provides evidence supporting the utility of human placenta as a potential source of stem cells for bone tissue engineering.

Integrin-mediated osteoblastic adhesion on a porous manganese-incorporated TiO2 coating prepared by plasma electrolytic oxidation

This study was conducted to evaluate the bioactivity of manganese-incorporated TiO₂ (Mn-TiO₂) coating prepared on titanium (Ti) plate by plasma electrolytic oxidation (PEO) technique in Ca-, P- and Mn-containing electrolytes. The surface topography, phase and element compositions of the coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS), respectively. The adhesion of osteoblast-like MG63 cells onto Ti, TiO₂ and Mn-TiO₂ surfaces was evaluated, and the signal transduction pathway involved was confirmed by the sequential expression of the genes for integrins β₁, β₃, α₁ and α₃, focal adhesion kinase (FAK), and the extracellular regulated kinases (ERKs), including ERK1 and ERK2. The results obtained indicated that Mn was successfully incorporated into the porous nanostructured TiO₂ coating, and did not alter the surface topography or the phase composition of the coating. The adhesion of the MG63 cells onto the Mn-incorporated TiO₂ coating was significantly enhanced compared with that on the Mn-free TiO₂ coating and the pure Ti plates. In addition, the enhanced cell adhesion on the Mn-TiO₂ coatings may have been mediated by the binding of the integrin subunits, β₁ and α₁, and the subsequent signal transduction pathway, involving FAK and ERK2. The study indicated that the novel Mn-TiO₂ coating has potential for orthopedic implant applications, and that further investigations are required.

Attachment and Proliferation of Human-Adipose-Tissue-Derived Stem Cells on Bioactive Glass/PVA Hybrid Scaffolds

Bioactive glass/polymer hybrids are promising materials for biomedical applications because they combine the bioactivity of bioceramics with the flexibility of polymers. These advantages may be used in porous scaffolds for tissue-engineering applications. In previous works, hybrid foams bioactive glass/polyvinyl alcohol (PVA) were prepared by the sol-gel process. The hybrid foam 50% PVA/50% bioactive glass was chosen in the composition range studied as the scaffold with better compromise in terms of pore structure and mechanical behavior. The aim of the present study was to evaluate the adhesion, viability, and growth behavior of human-adipose-tissue-derived stem cells on bioactive glass/PVA foams in vitro and their potential as scaffold for application in bone-tissue engineering. The pore structure of the hybrid samples used in the study was analyzed by microcomputed tomography, showing a modal pore diameter of 284 μm and modal interconnect diameter of 138 μm. We found that cells are capable of adhesion, proliferation, growth, and ECM production on the scaffolds tested. The results show that the hybrid bioactive glass/PVA is a promising material for bone repair, providing a good environment for the adhesion and proliferation of human-adipose-tissue-derived stem cells in vitro.

Evaluation of the ability of collagen-glycosaminoglycan scaffolds with or without mesenchymal stem cells to heal bone defects in Wistar rats

PURPOSE

The aim of this experiment was to examine the capacity of collagen-glycosaminoglycan scaffolds, with or without mesenchymal stem cells, to satisfactorily repair a 5-mm rat calvarial defect.

METHODS

Fifty-five Wistar rats were used in the study. The defects were either left empty to serve as controls (n = 7) or filled with cell-free scaffolds (n = 11), cell-seeded scaffolds that were pre-cultured in standard culture medium (n = 13), cell-seeded scaffolds that were pre-cultured in osteoinductive factor-supplemented medium (n = 12) or particulate autogenous bone (n = 12). The animals were sacrificed at 12 weeks after surgery, and specimens were prepared for histomorphometric analysis. The linear bone healing and the bone area within the defect were measured.

RESULTS

Comparable results were obtained using cell-free collagen-glycosaminoglycan scaffolds and autogenous bone both in terms of linear bone healing (P < 0.986) and area of new bone (P < 0.846). While the test groups showed significantly more bone formation compared to the empty defect control group, the linear bone healing and area of new bone within the defect were significantly lower in the cell-seeded scaffolds than in the cell-free scaffolds. The results have demonstrated that a cell-free collagen-glycosaminoglycan scaffold is capable of repairing a 5-mm rat calvarial defect as effectively as autogenous bone and that seeding the scaffold with pre-cultured mesenchymal stem cells prior to implantation offered no beneficial effect and resulted in incomplete healing of the defect.

CONCLUSIONS

The results thus suggest that the scaffold has immense potential for tissue repair showing favorable osteoconductive properties, biocompatibility and degradability.

Evaluation of cross-linked chitosan microparticles for bone regeneration

The objective of this preliminary study was to evaluate the applying of chitosan (CS)-based microparticles (MPs) in bone regeneration in vivo. The CS MPs were fabricated using our scale-up method, as previously described. Mesenchymal stem cells (MSC) were harvested from the femora and tibiae of Dark Agouti (DA) rats and seeded on CS MPs. An in vitro MSCs attachment experiment was conducted by trypsinizing the cells attached to the MPs at 5, 10, 20 and 30 h. Fluorescence images of MSCs attached to the MPs were taken at 24 and 48 h, using a LIVE/DEAD cell assay. The MSC/osteoblasts (OB) seeded on MPs were then cultured in vitro using osteogenic media and implanted into partial thickness bone defects in rat femurs. There were two groups of rats, including experimental animals and controls, for the in vivo studies. The experimental group were implanted with MSC-seeded MPs and observed at 4 and 8 weeks. The control group of rats did not receive any implant material except the stainless steel plate to support the defect. Four rats per group were used for the study. The femurs were extracted at 4 and 8 weeks post-implantation and bone formation at the defect site was analysed using radiography, microcomputed tomography (µCT) and histology. Among all groups, a significant increase in bone formation was observed in the experimental group at 8 weeks implantation. The results of this study suggested that CS MPs prove to be a successful biomaterial for bone regeneration.

Impact of biological agents and tissue engineering approaches on the treatment of rheumatic diseases

The treatment of rheumatic diseases has been the focus of many clinical studies aiming to achieve the best combination of drugs for symptom reduction. Although improved understanding of the pathophysiology of rheumatic diseases has led to the identification of effective therapeutic strategies, its cure remains unknown. Biological agents are a breakthrough in the treatment of these diseases. They proved to be more effective than the other conventional therapies in refractory inflammatory rheumatic diseases. Among them, tumor necrosis factor inhibitors are widely used, namely Etanercept, Infliximab, or Adalimumab, alone or in combination with disease-modifying antirheumatic drugs. Nevertheless, severe adverse effects have been detected in patients with history of recurrent infections, including cardiac failure or malignancy. Currently, most of the available therapies for rheumatic diseases do not have sufficient tissue specificity. Consequently, high drug doses must be administrated systemically, leading to adverse side effects associated with its possible toxicity. Drug delivery systems, by its targeted nature, are excellent solutions to overcome this problem. In this review, we will describe the state-of-the-art in clinical studies on the treatment of rheumatic diseases, emphasizing the use of biological agents and target drug delivery systems. Some alternative novel strategies of regenerative medicine and its implications for rheumatic diseases will also be discussed.

Rapid biomineralization of chitosan microparticles to apply in bone regeneration

The aim of this study was to prepare bone like mineral (BLM) layers rapidly on the exterior surfaces of chitosan (CS) microparticles (MPs). The CS MPs were fabricated using a scale-up double emulsification method. The CS MPs were in the spherical shape and the size of 30-60 microm. The MPs were then placed in 5x concentrated simulated body fluid (5 x SBF) and allowed to undergo biomineralization to form a BLM layers on the surface of CS MPs at 37 degrees C over a 24 h period. The BML layers on the exterior surface of CS MPs were characterized using wide angle X-ray diffraction (XRD), Fourier transform infrared microscopy (FTIR), and scanning electron microscopy (SEM). Insulin like growth factor-1 (IGF-1) was dissolved at a concentration of 1 microg/ml in 5 x SBF to incorporate into the BLM layer. The CS MPs (100 mg) were incubated in a sample of 4 ml of 5 x SBF containing IGF-1 at a concentration of 1 microg/ml for 24 h. The IGF-1 release from BML layers on CS MPs were studied by placing MPs in 4 ml of phosphate buffered saline (PBS) and incubating MPs at 37 degrees C for 30 days. Samples (100 microl) were taken over the course of the 30 days and analyzed using Enzyme-linked Immunosorbent assay (ELISA). The release IGF-1 from BML layers was in a burst manner followed by a sustained release during the 30-day period. This study suggests that the CS MPs have the potential to be used to help deliver therapeutic drugs to localized areas and hence increase and accelerate bone growth.

Effect of CaTiO(3)-CaCO(3) prepared by alkoxide method on cell response

In recent years, calcium titanate (CaTiO(3)) and carbon-containing materials have gained much attention in a number of biomedical material researches. To maximize the advantages of both materials, we developed a novel alkoxide method to get "calcium titanate with calcium carbonate" (CaTiO(3)-CaCO(3)). The objective was to evaluate the crystallinity and elemental composition of CaTiO(3)-CaCO(3) prepared by alkoxide method, CaTiO(3)-aC elaborated by modified thermal decomposition method, commercially-prepared CaTiO(3), and the effect of these materials on the bone marrow stromal cell. Hydroxyapatite was used as positive control material. We examined the cellular proliferation, osteoblastic differentiation, and mineralization of KUSA/A1 cells cultured with the materials. The results showed that CaTiO(3)-CaCO(3) and CaTiO(3)-aC contained evidence of calcium carbonate enhancing cell proliferation, osteoblastic differentiation, and mineralization. On the contrary, the commercially-prepared CaTiO(3) revealed absence of calcium carbonate with lower cell response than the other groups. The results indicated that calcium carbonate could play a key role in the cell response of CaTiO(3) material. In conclusion, our findings suggest that CaTiO(3)-CaCO(3) could be considered an important candidate as a biomaterial for medical and dental applications.

Fabrication, chemical composition change and phase evolution of biomorphic hydroxyapatite

Biomorphous, highly porous hydroxyapatite (HA) ceramics have been prepared by a combination of a novel biotemplating process and a sol-gel method, using natural plants like cane and pine as biotemplates. A HA sol was first synthesized from triethylphosphate and calcium nitrate used as the phosphorus and calcium precursors, respectively, and infiltrated into the biotemplates, and subsequently they were sintered at elevated temperatures to obtain porous HA ceramics. The microstructural changes, phase and chemical composition evolutions during the biotemplate-to-HA conversion were investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD and FT-IR analysis revealed that the dominant phase of the product was HA, which contained a small amount of mixed A/B-type carbonated HA, closely resembling that of human bone apatite. Moreover, the appearance of a small amount of secondary phase CaCO(3) seemed unavoidable. The HA was not transformed to the other calcium phosphate phases up to 1400 degrees C, but it contained a trace amount of CaO when sintered at above 1100 degrees C. The possible transformation mechanism was proposed. The SEM observation and mechanical property test showed that as-produced HA ceramics retained the macro-/micro-porous structures of the biotemplates with high precision, and possessed acceptable mechanical strength, which is suggested to be potential scaffolds for bone tissue engineering.

Preparation and in vitro characterization of scaffolds of poly(L-lactic acid) containing bioactive glass ceramic nanoparticles

Porous nanocomposite scaffolds of poly(l-lactic acid) (PLLA) containing different quantities of bioactive glass ceramic (BGC) nanoparticles (SiO(2):CaO:P(2)O(5) approximately 55:40:5 (mol)) were prepared by a thermally induced phase-separation method. Dioxane was used as the solvent for PLLA. Introduction of less than 20wt.% of BGC nanoparticles did not remarkably affect the porosity of PLLA foam. However, as the BGC content increased to 30wt.%, the porosity of the composite was observed to decrease rapidly. The compressive modulus of the scaffolds increased from 5.5 to 8.0MPa, while the compressive strength increased from 0.28 to 0.35MPa as the BGC content increased from 0 to 30wt.%. The in vitro bioactivity and biodegradability of nanocomposites were investigated by incubation in simulated body fluid (SBF) and phosphate-buffered saline, respectively. Scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction were employed to monitor the surface variation of neat PLLA and PLLA/BGC porous scaffolds during incubation. PLLA/(20wt.%)BGC composite exhibited the best mineralization property in SBF, while the PLLA/(10wt.%)BGC composite showed the highest water absorption ability.

Bioluminescence imaging of calvarial bone repair using bone marrow and adipose tissue-derived mesenchymal stem cells

A combined strategy using bioluminescence imaging, bone densitometry and histology was used to analyze the bone regeneration capacity of human bone marrow (hBMSC) and adipose tissue (hAMSC) mesenchymal stem cells, seeded in an osteoconductive arginine-glycine-aspartate (RGD) crosslinked hydrogel scaffold, implanted in a mouse calvarial bone defect. We show that firefly luciferase labeled stem cells can be monitored in vivo through a prolonged 90 days period, during which hBMSCs survive better than hAMSCs and that the density of scaffold bearing defects increased significantly more than that of defects without scaffolds.

Starch-Based Microparticles as Vehicles for the Delivery of Active Platelet-Derived Growth Factor

In a previous work, we described the use of starch-based microparticles as vehicles for the controlled release of corticosteroids. The goal of the present work is to evaluate the potential of these microparticles to incorporate and release platelet-derived growth factor (PDGF). The loading efficiency and release profile were evaluated, and PDGF was incorporated into and released from the matrix of starch-based microparticles. The release profile shows rapid release of PDGF in the first 24 h, after which there was a slow but constant release for up to 8 weeks. The maintenance of the PDGF biological activity after incorporation and release was evaluated by its mitogenic effect over osteoblastic cells, and it was shown to be comparable to that of PDGF supplemented to the culture medium. This proves that the incorporation and release did not affect the biological activity of the growth factor (GF). The results clearly demonstrate that starch-based microparticles are suitable vehicles for the incorporation and release of GFs. When combined with previous results, these materials also suggest their ability to enhance the regenerating potential of tissue engineering hybrid constructs.

Natural-origin polymers as carriers and scaffolds for biomolecules and cell delivery in tissue engineering applications

The present paper intends to overview a wide range of natural-origin polymers with special focus on proteins and polysaccharides (the systems more inspired on the extracellular matrix) that are being used in research, or might be potentially useful as carriers systems for active biomolecules or as cell carriers with application in the tissue engineering field targeting several biological tissues. The combination of both applications into a single material has proven to be very challenging though. The paper presents also some examples of commercially available natural-origin polymers with applications in research or in clinical use in several applications. As it is recognized, this class of polymers is being widely used due to their similarities with the extracellular matrix, high chemical versatility, typically good biological performance and inherent cellular interaction and, also very significant, the cell or enzyme-controlled degradability. These biocharacteristics classify the natural-origin polymers as one of the most attractive options to be used in the tissue engineering field and drug delivery applications.