In vitro degradation performance and biological response of a Mg-Zn-Zr alloy

The feasibility of a Mg-Zn-Zr alloy for biomedical applications was studied through microstructure characterization, corrosion tests in different biological media, and cell proliferation, differentiation and adhesion tests. Corrosion tests showed that the ZK60 alloy in the as-extruded state with finer grain sizes exhibited slower corrosion rates than the same alloy in the as-cast state. The tests in different biological fluids showed that the corrosion rates of the as-cast and as-extruded ZK60 alloy in DMEM + FBS were the highest, while those in Hank's solution were the lowest. The corrosion rate of the as-extruded ZK60 alloy was similar to the corrosion rates of other commercial magnesium alloys, namely the die-cast AZ91D, die-cast AM50, extruded AZ31 and extruded WE43 alloys. The results obtained from the indirect cytotoxicity evaluation showed that the 100% concentrated cast and extruded ZK60 alloy extracts resulted in significantly reduced cell numbers and total protein amounts, as compared to the negative control. The cell number and total protein amount increased with the gradual dilution of the extracts, but the protein normalized ALP activity showed an opposite trend. For the direct assay, L-929 and MG63 cells exhibited good adhesion with spread pseudopod on the surface of extruded ZK60 alloy samples after 24 h culture. In short, the as-extruded ZK60 alloy could be a good candidate material for biodegradable implants.     

钛酸钾生物薄膜/钛合金生物复合材料的制备及其体外生物相容性

用仿生化学方法制备钛酸钾生物薄膜/Ti-15Mo-3Nb生物复合材料,然后通过模拟体液培养试验、动态凝血试验及体外细胞培养试验对Ti-15Mo-3Nb和钛酸钾生物薄膜/Ti-15Mo-3Nb生物复合材料的体外生物相容性进行研究,以验证钛酸钾作为一种新型的生物活性涂层材料的可行性.对比试验的结果表明:(1)在模拟体液培养实验中,Ti-15Mo-3Nb表面未见钙磷沉积,表现为生物惰性,而呈多孔网状结构的钛酸钾生物薄膜具有很强的钙磷吸附能力,表现出很好的生物活性;(2)以动态凝血时间为指标,钛酸钾生物薄膜＞Ti-15Mo-3Nb,表现出良好的血液相容性;(3)细胞培养实验表明,二者均具有良好的细胞相容性,但在细胞培养初期钛酸钾生物薄膜具有更好的细胞附壁生长趋势,这将有利于损伤部位的早期愈合.钛酸钾生物薄膜/Ti-15Mo-3Nb生物复合材料表现出更好的生物相容性和生物活性.     

In vitro and in vivo studies on biocompatibility of carbon fibres

In the present study we focused on the in vitro and in vivo evaluation of two types of carbon fibres (CFs): hydroxyapatite modified carbon fibres and porous carbon fibres. Porous CFs used as scaffold for tissues regeneration could simultaneously serve as a support for drug delivery or biologically active agents which would stimulate the tissue growth; while addition of nanohydroxyapatite to CFs precursor can modify their biological properties (such as bioactivity) without subsequent surface modifications, making the process cost and time effective. Presented results indicated that fibre modification with HAp promoted formation of apatite on the fibre surface during incubation in simulated body fluid. The materials biocompatibility was determined by culturing human osteoblast-like cells of the line MG 63 in contact with both types of CFs. Both tested materials gave good support to adhesion and growth of bone-derived cells. Materials were implanted into the skeletal rat muscle and a comparative analysis of tissue reaction to the presence of the two types of CFs was done. Activities of marker metabolic enzymes: cytochrome c oxidase (CCO) and acid phosphatase were examined to estimate the effect of implants on the metabolic state of surrounding tissues. Presented results evidence the biocompatibility of porous CFs and activity that stimulates the growth of connective tissues. In case of CFs modified with hydroxyapatite the time of inflammatory reaction was shorter than in case of traditional CFs.     

Evaluation of monolithic osmotic tablet system for nifedipine delivery in vitro and in vivo

The aim of this study was to evaluate the monolithic osmotic tablet system (MOTS) containing a solid dispersion with the practically water-insoluble drug nifedipine in vitro and in vivo. In the drug release study in vitro, the release profiles of this system had almost zero-order kinetics. The influences of tablet formulation variables, sizes of the delivery orifice, membrane variables, and values of pH in the dissolution medium on nifedipine release from MOTS have been investigated. The results provided evidence that the tablet core played an important role in MOTS. While orifice sizes and membrane variables affected the nifedipine release rate, MOTS was independent of the dissolution medium. The appropriate orifice size was found to be in the range of 0.5-1.0 mm. The coating membrane incorporating hydrophilic polyethylene glycol (PEG) formed a porous structure. The human pharmacokinetics and relative bioavailability of MOTS containing nifedipine were compared with a commercial Adalat® osmotic tablet system containing an equivalent dose of nifedipine following an oral single dose of 30 mg given to each of 11 healthy volunteers in an open, randomized crossover study in vivo. The relative bioavailability for MOTS was 112%. There was no statistically significant difference in the pharmacokinetic parameters between two dosage forms. It is concluded that the monolithic osmotic tablet controlled release system is feasible for a long-acting preparation as a once-daily treatment.     

In vitro and in vivo assessment of the biocompatibility of an Mg–6Zn alloy in the bile

There is a great clinical need for biodegradable bile duct stents. Biodegradable stents made of an Mg–6Zn alloy were investigated in both vivo animal experiment and in vitro cell experiments. During the in vivo experiments, blood biochemical tests were performed to determine serum magnesium, serum creatinine (CREA), blood urea nitro-gen (BUN), serum lipase (LPS), total bilirubin (TB) and glutamic-pyruvic transaminase (GPT) levels. Moreover, tissue samples of common bile duct (CBD), liver and kidney were taken for histological evaluation. In the in vitro experiments, primary mouse extrahepatic bile duct epithelial cells (MEBDECs) were isolated and cultured. Cytotoxicity testing was carried out using the MTT method. Flow cytometry analyses with propidium iodide staining were performed to evaluate the effect of Mg–6Zn alloy extracts on cell cycle. The in vivo experiments revealed no significant differences (P > 0.05) in serum magnesium, CREA, BUN, LPS, TB or GPT before and after the operation. Based on the HE results, hepatocytes, bile duct epithelial cells, renal glomerulus and renal tubule tissues did not present significant necrosis. In the in vitro experiments, the cell relative growth rate curve did not change significantly from 20 to 40 % extracts. In vitro experiments showed that 20–40 % Mg–6Zn extracts are bio-safe for MEBDECs. In vivo experiments showed that Mg–6Zn stents did not affect several important bio-chemical parameters or, harm the function or morphology of the CBD, kidney, pancreas and liver. Our data suggested that this Mg–6Zn alloy is a safe biocompatible material for CBD.     

In vitro and in vivo biocompatibility of apatite-coated magnetite nanoparticles for cancer therapy

The aim of this study was to determine the biocompatibility and potential toxicity of apatite-coated magnetite nanoparticles. The in vitro biocompatibility with human red blood cells was evaluated, not hemolytic effects were found at concentrations lower than 3 mg/ml. For the in vivo study, Balb/c mice were used. The animals were injected intravenously or intraperitoneally, the doses ranged from 100 to 2,500 mg/Kg. All the injected animals showed normal kidney and liver function. No significant changes were found in the body weight, the organs weight and the iron levels in liver due to the administration. In conclusion, apatite-coated magnetite nanoparticles did not induce any abnormal clinical signs in the laboratory animals. The results demonstrated that apatite-coated magnetite nanoparticles of 8 ± 2 nm in size did not have hemolytic effect in human erythrocytes and did not cause apparent toxicity in Balb/c mice under the experimental conditions of this study.     

Celecoxib-cyclodextrin systems: characterization and evaluation of in vitro and in vivo advantage

Solid dispersions of Celecoxib were prepared with hydroxypropyl β cyclodextrin by various methods such as physical mixture, cogrinding, kneading, and coevaporation. The dispersions were characterized by differential scanning calorimetry (DSC), X-ray diffraction patterns, infrared spectroscopy, and nuclear magnetic resonance studies. The DSC thermograms of the dispersions indicated potential of heat-induced interaction between Celecoxib and cyclodextrin that could influence in vitro drug dissolution. The dispersions exhibited faster rates of dissolution compared to that of Celecoxib. The kneaded dispersion with the fastest in vitro dissolution rate when compressed into tablets showed a better release profile compared to the tablets of pure Celecoxib. In vivo studies revealed that the kneaded dispersion provided for quicker response and was more effective in inhibiting rat paw edema as compared to Celecoxib alone, thus confirming the advantage of improved pharmacological activity of Celecoxib when administered as a solid dispersion with cyclodextrin.     

In vitro release studies of flurbiprofen from different topical formulations

The release profiles of flurbiprofen (F) from different gel and ointment formulations were studied in order to evaluate factors governing the release process. Carbopol 934P (CAB), poloxamer 407 (POL), and eudragit S100 (EUD) gel bases were used, while emulsion (EML) and polyethylene glycol (PEG) ointments were employed. The release studies were conducted using membraneless diffusion cells and lipophilic receptor medium, isopropyl myristate (IPM). The effects of gelling agent concentrations and the initial drug load on drug release were determined. Hydrogels were observed to give higher amounts of drug release than hydrophobic EUD gel and ointments, despite the lower bulk viscosity of these bases. Flurbiprofen release from CAB gels was 3.06-1.56-fold higher than from other formulations. Over a 4-hr period, the amount of F released was 492.8 and 316.0 µg/cm² from 2% CAB and 25% POL gels, while it was 213.05, 168.61, and 160.9 µg/cm² from EML, 40% EUD, and PEG bases, respectively. The diffusivity of F in the gel bases was an inverse function of the polymer concentrations over the range of 1-3% CAB, 20-30% POL, and 35-45% EUD gels. Drug release was increased from the bases as the initial F concentration increased over the range 0.25-1.0%, while the diffusion coefficient observed an inverse relationship. The CAB and POL gels could be the vehicles of choice for the rapid release and onset of F after topical application.     

Development of sustained-release tablets containing sodium valproate: in vitro and in vivo correlation

We have developed a 200 mg and 400 mg sustained-release sodium valproate tablet that allows effective blood concentration of the active drug with once-a-day dosing. The controlled dissolution or sustained release of the drug was attained by a membrane-controlled system. A single-coating system did not adequately control the dissolution rate, and therefore double-coated tablets were prepared and a human pharmacokinetic study was conducted. With the 200 mg VPA-Na tablets, the nonfasting C_max was only 20% higher than the fasting C_max. An in vitro dissolution test was conducted to predict the effects of food on drug dissolution after administration of this tablet. A relatively good correlation was observed between the absorption profiles and the dissolution profiles of the drug.     

In vitro evaluation of hydroxyapatite reinforced polyhydroxybutyrate composite

Particulate hydroxyapatite (HA) was incorporated into polyhydroxybutyrate (PHB) to form a bioactive and biodegradable composite for applications in hard tissue replacement and regeneration. HA/PHB composite containing 10, 20, and 30 vol.% of HA was made for in vitro evaluation. In vitro studies were conducted using an acellular simulated body fluid (SBF). Composite specimens were immersed in SBF at 37 °C for various periods of time prior to surface analysis and mechanical testing. Results obtained from scanning electron microscopic (SEM) examination, thin film X-ray diffraction (TF-XRD) analysis, and Fourier transform infrared (FTIR) spectroscopy showed that a layer of bone-like apatite formed within a short period on HA/PHB composite after its immersion in SBF, demonstrating high in vitro bioactivity of the composite. The bioactivity and mechanical properties of the composite could be changed by varying the amount of HA in the composite. Dynamic mechanical analysis (DMA) revealed that the storage modulus (E′) of HA/PHB composite increased initially with immersion time in SBF, due to apatite formation on composite surface and decreased after prolonged immersion in SBF, indicating degradation of the composite in a simulated body environment. HA/PHB composite thus has the potential for its intended applications.     

磷酸钙涂覆炭织物体外细胞毒性的评价

医用植人体的成功与否常常取决于器件植入后细胞与材料表面间的相互作用.采用生物体外测试法考察了声电化学法制备的磷酸钙涂层对炭织物的骨细胞附着、增殖能力的影响.借助MTS检测技术、扫描电子显微镜,选择人类成骨细胞(MG63)作为细胞模型,通过测定细胞与炭织物、磷酸钙涂覆炭织物、以及其各自的提取液作用后的存活能力,研究了细胞/材料的相互作用,并对基底材料的细胞毒性进行了评价.结果表明,炭织物、磷酸钙涂覆炭织物均不具有细胞毒性,且磷酸钙涂层可提高成骨细胞的附着和增殖.SEM图像显示,细胞形貌正常,与对照组相比较生长增殖情况相似.     

In vitro Biological Effects of Ti2448 Alloy Modified by Micro-arc Oxidation and Alkali Heatment

The purpose of this study was to test the hypothesis that the combination of micro-arc oxidation and alkali heatment (MAH) would improve the cytocompatibility of a newly designed Ti-24Nb-4Zr-8Sn alloy.In this study,commercially pure titanium (cp Ti) and Ti-24Nb-4Zr-8Sn were used.Surface modification of Ti-24Nb4Zr-8Sn by a two-step treatment of micro-arc oxidation (MAO) and alkali heatment was reported.Surface characterizations were performed by scanning electron microscopy (SEM),thin film X-ray diffraction (TF-XRD) and X-ray photoelectron spectroscopy (XPS).The MAH layer consisted of finer crystals and possessed a higher degree of crystallity and stability than the MAO layer.A biocompatibility study on treated and untreated Ti24Nb-4Zr-8Sn in comparison with cp Ti was carried out to investigate the effect of the different surfaces on the bone integration property in vitro.The cellular assays revealed that the MAO and MAH layer favored the initial adhesion of MC3T3-E1 cells and that the growth rate of MC3T3-E1 cells on MAH layer was significantly higher than that on the conventional MAO-treated layer after 3-day and 5-day incubation,demonstrating the greater potential of the hybrid treatment of micro-arc oxidation followed with alkali heatment as a novel surface modification method for implanting materials.     

In situ observation of ageing process and new morphologies of continuous precipitates in AZ91 magnesium alloy

An in situ observation of the precipitating process of γ-Mg₁₇Al₁₂ phase in die-cast AZ91 magnesium alloy, was carried out with a transmission electron microscope equipped with a heating stage maintained at 473 K for 8 h. In addition to the thin plate-shaped continuous precipitates, continuous precipitates with rod-shaped and the Potter orientation relationship were observed and analyzed with transmission electron microscopy including high-resolution transmission electron microscopy techniques. It was also observed firstly that there exist plate-shaped continuous precipitates with the Pitsch-Schrader orientation relationship in the die-cast AZ91 magnesium alloy.     

A new in vitro/in vivo kinetic correlation method for nitrofurantoin matrix tablet formulations

The kinetic distributions of in vitro percentage release and in vivo percentage urinary excretion rates of nitrofurantoin from matrix tablets were plotted using a kinetic program. In vitro release rates were determined using the USP paddle and half-change methods. Urinary excretion curves of the drug were characterized by means of the statistical moments. The individual linear correlations between each in vitro and in vivo kinetic distribution were established, and regression equations were calculated. The application results of the best correlations obtained were evaluated according to in vivo results. A reversed kinetic procedure was applied for transformation of the correlated kinetic values to the drug percentage release rates. The modified Langenbucher kinetic showed excellent linear correlation (r = .9985). The method that is proposed in this study, the kinetic correlation program, is simple, independent of time, and suggests that it is possible to use kinetic distributions in the in vitro/in vivo correlation. This study also suggests using kinetic correlation to investigate the suitability of the in vitro dissolution methods with the in vivo drug dissolution.     

In vitro calcification of UHMWPE/PU composite membrane

Polyurethane composite made from biaxially drawn ultrahigh molecular weight polyethylene (BDUHMWPE) is likely an alternative for polyurethane currently being plagued for medical applications. In this study, an in vitro calcification protocol was used to determine the relative resistance to calcification of the composite membranes. The results demonstrated that the composite membranes were susceptible to extrinsic calcification that was closely related to the matrix polyurethane material used. The calcification of the composite was different from that of the solution cast polyurethane membranes. The incorporation of hydrophobic reinforcement BDUHMWPE effectively postponed the calcification. The differences of calcification between composite and polyurethane were greatly due to the differences in surface structures and properties of the as-cast polyurethane.     

Chitosan formulations for steroid delivery: effect of formulation variables on in vitro characteristics

Chitosan film formulations for steroid delivery after craniomaxillofacial surgery were formulated by using three different types of chitosan with respect to their molecular weight as low, medium and high. Film formulations were prepared by casting/solvent evaporation technique. In vitro characterization, film thickness, equilibrium swelling degree, in vitro release profiles and surface morphologies were investigated. For two different types of crosslinkings, the release of dexamethasone sodium phosphate (DSP) can be extended as the molecular weight increases. As a result, chitosan film formulations should be beneficial for steroid delivery for a certain time after craniomaxillofacial surgery.     

Evaluation of Monolithic Osmotic Tablet System for Nifedipine Delivery In Vitro and In Vivo

Abstract

The aim of this study was to evaluate the monolithic osmotic tablet system (MOTS) containing a solid dispersion with the practically water-insoluble drug nifedipine in vitro and in vivo. In the drug release study in vitro, the release profiles of this system had almost zero-order kinetics. The influences of tablet formulation variables, sizes of the delivery orifice, membrane variables, and values of pH in the dissolution medium on nifedipine release from MOTS have been investigated. The results provided evidence that the tablet core played an important role in MOTS. While orifice sizes and membrane variables affected the nifedipine release rate, MOTS was independent of the dissolution medium. The appropriate orifice size was found to be in the range of 0.5–1.0 mm. The coating membrane incorporating hydrophilic polyethylene glycol (PEG) formed a porous structure. The human pharmacokinetics and relative bioavailability of MOTS containing nifedipine were compared with a commercial Adalat® osmotic tablet system containing an equivalent dose of nifedipine following an oral single dose of 30 mg given to each of 11 healthy volunteers in an open, randomized crossover study in vivo. The relative bioavailability for MOTS was 112%. There was no statistically significant difference in the pharmacokinetic parameters between two dosage forms. It is concluded that the monolithic osmotic tablet controlled release system is feasible for a long-acting preparation as a once-daily treatment.     

In vitro evaluation of idebenone-loaded solid lipid nanoparticles for drug delivery to the brain

Context: Solid lipid nanoparticles (SLN) are regarded as interesting drug delivery systems and their preparation techniques have gained a great deal of attention.

Objective: To evaluate the feasibility of preparing idebenone (IDE) loaded SLN from O/W microemulsions by the phase-inversion temperature (PIT) method. Since SLN have been proposed to improve drug delivery to the brain, IDE was chosen as model drug due to its activity in the treatment of neurodegenerative diseases.

Materials and Methods: Cetyl palmitate was used as solid lipid to prepare SLN containing two surfactant/cosurfactant mixtures, isoceteth-20/glyceryl oleate (SLN A) and ceteth-20/glyceryl oleate (SLN B) by the PIT method.

Results and discussion: All the formulations tested showed a mean particle diameter ranging from 30 to 95?nm and a single peak in size distribution. Stability tests showed that SLN B were more stable than SLN A. IDE release was dependent both on the type of primary surfactant used and the amount of loaded drug. IDE-loaded SLN were effective in inhibiting 2,2′-azobis-(2-amidinopropane)dihydrochloride (APPH)-induced lactic dehydrogenase (LDH) release and reactive oxygen species (ROS) production in primary cultures of astrocytes obtained from rat cerebral cortex. It is noteworthy that SLN B2 (containing ceteth-20 as primary surfactant and 0.7% w/w IDE) were able to prevent entirely both the LDH release and ROS production induced by APPH.

Conclusion: The PIT method provided SLN with good technological properties. The tested SLN could be regarded as interesting carriers to overcome the blood brain barrier and increase the efficacy of the loaded drug.     

Fabrication and biocompatibility of polyethyleneimine/heparin self-assembly coating on NiTi alloy

NiTi alloy has been used widely as biomaterials. But because of toxic effects possibly caused by excess Ni ions released during the corrosion process in the physiological environment, it is still a controversial material. Fabricating medicine-loaded coating, which is expected to decrease the release of Ni ions and improve the biocompatibility of the materials, is a potential way to solve the problem. In this paper, NiTi alloy is coated by polyethyleneimine/heparin films via layer-by-layer (LBL) self-assembly method. UV-Vis, FT-IR, atomic force microscopy (AFM) and contact angle measurements are used to characterize the microstructure of coatings and select the best fabrication conditions. Potentiodynamic polarization researches in sodium chloride and dynamic clotting time experiment are utilized to study its corrosion resistance capability and biocompatibility of coatings, respectively. The results indicate that PEI/heparin multilayer coating can improve the biocompatibility of NiTi alloy surface.     

In vitro release studies of piroxicam from oil-in-water creams and hydroalcoholic gel topical formulations

The importance of piroxicam, a therapeutic anti-inflammatory drug, is well known. Because of gastrointestinal disorders, dermatological dosage forms are recommended most. In our first studies, oil-in-water (O/W) creams of piroxicam (1% concentration) were prepared using glyceryl monostearate (GMS), stearic acid, and triethanolamine as additive ingredients. In our second studies, hydroalcoholic transparent gel formulations of this drug in a 0.5% concentration were prepared using hydroxypropylcellulose (HPC) as the gelling agent. The release of piroxicam from all formulations via dialysis through a cellulose membrane into phosphate buffer pH 6.8 at 37°C was studied. The effects of additives such as propylene glycol and 2-propanol on the drug release were also investigated. The release profiles from the standpoint of diffusion-controlled processes, as well as zero-order and first-order kinetics, were evaluated, and relevant parameters, such as diffusion coefficient, permeability coefficient, and partition coefficient, were calculated. The release obeys both the diffusion mechanism and first-order kinetics. The drug release from gel formulations containing 10%, 20%, and 30% propylene glycol was decreased due to the enhancement of viscosity. However, the limpidity of these formulations was improved. Moreover, the release of drug from gel formulations containing 15% and 20% of 2-propanol was increased. These results show that a hydroalcoholic gel formulation with HPC is a more suitable preparation of piroxicam when compared with an O/W cream formulation.