Biomedical Materials

This investigation describes the production and characterization of calcium phosphate scaffolds with defined and reproducible porous macro‐architectures and their preliminary in vitro and in vivo bone‐tissue‐engineered response. Fugitive wax molds were designed and produced using a rapid prototyping technique. An aqueous hydroxyapatite slurry was cast in these molds. After sintering at 1250°C and then cleaning, dimensional and material characterizations of the scaffolds were performed. The resulting scaffolds represented the design, and their dimensions were remarkably consistent. A texture inherent to the layer‐by‐layer production of the mold was impressed onto the vertical surfaces of the scaffolds. The surface roughness (Ra) of the textured surfaces was significantly greater than that of the nontextured surfaces. Material analyses revealed a β‐TCP phase in addition to hydroxyapatite for the molded ceramics. Non‐molded control ceramics exhibited only hydroxyapatite. Thirty scaffol...

Purpose. Polymeric porous foams have been evaluated as possible new pharmaceutical dosage forms. Methods. These materials were obtained by polymerization in the continuous phase of highly concentrated emulsions prepared by the phase inversion temperature method. Their porosity, specific surface and surface topography were characterized, and the incorporation and release of active principles was studied using ketoprofen as model lipophilic molecule. Results. Solid foams with very high pore volume, mainly inside macropores, were obtained by this method. The pore morphology of the materials was characterized, and very rough topography was observed, which contributed to their nearly superhydrophobic properties. These solid foams could be used as delivery systems for active principles with pharmaceutical interest, and in the present work ketoprofen was used as a model lipophilic molecule. Conclusions. Drug incorporation and release was studied from solid foam disks, using different conce...

In this research, effect of temperature and calcium to phosphorus (Ca/P) ratio of raw materials on the type and the amounts of formed phases were investigated by solid state method. Calcium carbonate and dicalcium phosphate were provided as raw materials and mixed with different percentages in a way that final (Ca/P) ratio was between 1.50 to 1.67 in different batches. Then each of these mixtures was heated at temperatures of 800 to 1200 ° C for 3 hours. Phases were identified with XRD technique and quantitative assessment of phases was evaluated by RIR method and Chung relation. Results showed that in all relations and desired temperatures sintered below 1100 ° C beta tri-calcium phosphate is the dominant phase and hydroxyapatite present as second phase in the composition. In samples which sintered at 1200° C, beta TCP is transferred significantly to alpha TCP. In samples with Ca/p ratio: 1.62, 1.67, hydroxyapatite is dominant phase at 1200° C.

Natural-derived biomaterials can be used as substrates for the growth, proliferation, and differentiation of cells. In this study, bovine vitreous humor as a biological material was cross-linked to silk fibroin with different concentration ratios to design a suitable substrate for corneal tissue regeneration. The cross-linked samples were evaluated with different analyses such as structural, physical (optical, swelling, and degradation), mechanical, and biological (viability, cell adhesion) assays. The results showed that all samples had excellent transparency, especially those with higher silk fibroin content. Increasing the ratio of vitreous humor to silk fibroin decreased mechanical strength and increased swelling and degradation, respectively. There was no significant difference in the toxicity of the samples, and with the increase in vitreous humor ratio, adhesion and cell proliferation increased. Generally, silk fibroin with vitreous humor can provide desirable characteristics as a transparent film for corneal wound healing.

Cell microencapsulation is an attractive strategy for cell-based therapies that allows the implantation of genetically engineered cells and the continuous delivery of de novo produced therapeutic products. However, the establishment of a way to retrieve the implanted encapsulated cells in case the treatment needs to be halted or when cells need to be renewed is still a big challenge. The combination of micro and macroencapsulation approaches could provide the requirements to achieve a proper immunoisolation, while maintaining the cells localized into the body. We present the development and characterization of a porous implantable macrocapsule device for the loading of microencapsulated cells. The device was fabricated in polyamide by selective laser sintering (SLS), with controlled porosity defined by the design and the sintering conditions. Two types of microencapsulated cells were tested in order to evaluate the suitability of this device; erythropoietin (EPO) producing CC myobla...

Sintered dicalcium pyrophosphate (SDCP), a synthetic compound, has proved to be both bioabsorbable and biocompatible in vivo. Recent work in our institute also has demonstrated that the ingestion of SDCP can increase bone mass in the ovariectomized rat. In this study, we used an in vitro cell culture model to investigate the ultrastructural changes and fate of osteoclasts induced by SDCP. Quantitative evaluation of osteoblasts and osteoclasts after administration of SDCP was performed. We studied immunohistochemical and ultrastructural features of osteoclasts undergoing apoptosis. The results showed that at 10−4 M SDCP, the osteoblast cell count increased significantly, whereas the osteoclast population decreased significantly. Apoptosis of the osteoclast population was well demonstrated by immunohistochemical study. Ultrastructural study showed that the Golgi apparatus was degraded or dispersed in the cytoplasm. Later, osteoclasts revealed pyknotic nuclei showing condensation and m...

The mechanisms underlying the development of osteolysis and aseptic loosening have an impact on the longevity of total hip replacements (THRs). This study examines the specific roles of lymphocytes in the TH1 and TH2 subsets in osteolysis and aseptic loosening of THR. Tissue from periprosthetic regions from patients with loose, cemented acetabular components were used to determine the TH1 and TH2 cytokine profile. Twelve tissue specimens from patients with radiographic signs of osteolysis, and nine tissue specimens from patients with no signs of osteolysis were harvested during revision surgery. Immunohistochemistry using primary antibodies against CD3, interferon (IFN)‐γ, interleukin (IL)‐2, IL‐4, and IL‐10 was performed on frozen sections to determine the percentage of positive cells for each of the sections. No statistically significant differences in the percentage of positive cells expressing cytokines characteristic of the TH1 pathway (IFN‐γ, IL‐2) or TH2 pathway (IL‐4, IL‐10)...

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon‐plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface‐modified silicone after 1 h. C. albicans exhibited very low adherence to all silane‐treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion tha...

Type I diabetes is an autoimmune disorder characterized by the loss of insulin producing islet cell mass. While daily insulin injection provides an easy means of glycemic control, it does not prevent long-term complications associated with diabetes. Islet transplantation has been suggested as a permanent cure for type 1 diabetes. However, the recurrence of host immunity and shortage of donor islets hinder the prevalence of islet transplantation. Biomaterial strategies provide an alternative route to solving the problems associated with host immune response and shortage of donor islets. One highly recognized platform for achieving these goals are hydrogels, which are hydrophilic crosslinked polymers with tissue-like elasticity and high permeability. Hydrogels prepared from poly(ethylene glycol) (PEG) derivatives are increasingly used for a variety of tissue engineering applications, including encapsulation of pancreatic islets and serving as a material platform for pseudo-islet diffe...

Titanium is a successful biomaterial that possesses good biocompatibility. It is covered by a surface layer of titanium dioxide, and this oxide may play a critical role in inhibiting reactive oxygen species, such as peroxynitrite, produced during the inflammatory response. In the present study, titanium dioxide was coated onto silicone substrates by radio‐frequency sputtering. Silicone coating with titanium dioxide enhanced the breakdown of peroxynitrite by 79%. At physiologic pH, the peroxynitrite donor 3‐morpholinosydnonimine‐N‐ethylcarbamide (SIN‐1) was used to nitrate 4‐hydroxyphenylacetic acid (4‐HPA) to form 4‐hydroxy‐3‐nitrophenyl acetic acid (NHPA). Titanium dioxide‐coated silicone inhibited the nitration of 4‐HPA by 61% compared to aluminum oxide‐coated silicone and 55% compared to uncoated silicone. J774A.1 mouse macrophages were plated on oxide‐coated silicone and polystyrene and stimulated to produce superoxide and interleukin‐6. Superoxide production was measured by the...

Exturded filaments of unmodified polypropylene (PP) with and without antioxidant were implanted subcutaneously in hamsters in order to determine their rate of degradation. Specimens were removed periodically during a 5 month test period and analyzed by infrared spectroscopy and dynamic mechanical testing. The analyses show that degradation begins to occur after only a few days. Although the reaction sequence is not known, several factors suggest that the in vivo degradation process is similar to autoxidation which occurs in air or oxygen.The infrared data indicate that the hydroxyl content of the implants increases at a rate of 0.061 mg/g polypropylene per day during the initiation phase of the reaction. An induction time of 108 days was established. Carbonyl bonds appear after an implantation time of 50–90 days and increase thereafter. Mechanical tests indicate a decrease in the dynamic loss tangent, tan δ, during the first month of implantation for unmodified polypropylene. No cha...

J. Funct. Biomater. 2015, 6 193 Abstract: Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosphate (Na-β-GP) have been studied as biomaterials for drug delivery and tissue regeneration. Magnesium (Mg) has been reported to stimulate adhesion and proliferation of bone forming cells. With the aim of improving the suitability of the aforementioned