Levan nanostructured thin films by MAPLE assembling

Synthesis of nanostructured thin films of pure and oxidized levan exopolysaccharide by matrix-assisted pulsed laser evaporation is reported. Solutions of pure exopolysaccharides in dimethyl sulfoxide were frozen in liquid nitrogen to obtain solid cryogenic pellets that have been used as targets in pulsed laser evaporation experiments with a KrF* excimer source. The expulsed material was collected and assembled onto glass slides and Si wafers. The contact angle studies evidenced a higher hydrophilic behavior in the case of oxidized levan structures because of the presence of acidic aldehyde-hydrogen bonds of the coating formed after oxidation. The obtained films preserved the base material composition as confirmed by Fourier transform infrared spectroscopy. They were compact with high specific surface areas, as demonstrated by scanning electron and atomic force microscopy investigations. In vitro colorimetric assays revealed a high potential for cell proliferation for all coatings with certain predominance for oxidized levan.     

Mineralization of pristine chitosan film through biomimetic process

The biomineralization of pristine chitosan film without any prior surface treatment was evaluated by immersing the film in simulated body fluid (SBF) at 37 °C for 3 weeks. The film was prepared by solvent casting method using chitosan of known degree of deacetylation (DD). The formation of the hydroxyapatite (HA) phase on the film surface after immersion was studied periodically by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) methods. The electron micrographs showed the morphology of the deposited apatite as small globules appearing uniformly throughout the films surfaces. The Ca/P ratio of the apatite was found to increase with increase in immersion time and approaching towards the stoichiometric value of the HA phase. The mineralized chitosan film could be of promising support to hard tissue regeneration.     

Cryogel biocomposite containing chitosan-gelatin/cerium–zinc doped hydroxyapatite for bone tissue engineering

The present examination includes manufacture and portrayal of cryogel bio-composite implants containing chitosan-gelatin (CS-GT), cerium–zinc doped hydroxyapatite (CS-GT/Ce-Zn-HA) by cryogelation technique. The prepared cryogel biocomposites (CS-GT/HA and CS-GT/Ce-Zn-HA) were described by scanning electron microscope (SEM) and X-Ray diffraction (XRD) contemplates. The expansion of Ce-Zn in the CS-GT implants essentially expanded growing, diminished swelling, expanded protein sorption, and expanded bactericidal movement. The CS-GT/Ce-Zn-HA biocomposite had non-toxic towards rodent osteoblast cells. So the created CS-GT/Ce-Zn-HA biocomposite has favorable and potential applications over the CS-GT/HA platforms for bone tissue engineering.     

Synthesis and in vitro behavior of β-TCP zirconia/polymeric biocomposites for bio-applications

Novel biocomposites were fabricated by impregnating β-tricalcium phosphate (β-TCP)/zirconia particles into the polymers matrix. The composite materials were characterized using thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) analyzes and Scanning Electron Microscopy (SEM). The results confirmed the conversion of hydroxyapatite (HA) to β-TCP at a sintering temperature of 1150 °C with or without zirconia powder. The in vitro behavior was assessed via measurement of calcium and phosphorus ions in SBF (simulated body fluid). FT-IR and SEM of the composites were performed pre and post immersion in SBF. The results prove that the bone like apatite layer formation was enhanced on the β-TCP-Z20/polymeric composite surface more than that on the β-TCP-Z10/polymeric composite. Therefore, the data confirmed that zirconia plays an important role in the enhancement of the apatite formation. The conclusions proved that the β-TCP-Z20/polymeric biocomposites, containing 20% of zirconia, are promising for bone remodeling applications.     

准分子激光的医学应用

由于准分子激光对生物组织作用的独特机理─光化学分解作用,解决了许多临床治疗难题。近年来,难分子激光在激光医学中得到较广泛的应用。医用准分子激光种类主要有XeCl,308nm;ArF,193nm;KrF,248nm。本文介绍了准分子激光在医学中的几种典型应用。     

羟基磷灰石/柞蚕丝素（HA/TSF骨仿生纳米纤维的生物学性能研究

目的：柞蚕丝素（tussah silk fibroin,TSF）和羟基磷灰石（hydroxyapatite,HA）均具有良好的生物活性和生物相容性,是组织工程研究的热点i,但结构单一及微米级的材料所表现出的性能简单,不能满足人们对生物材料支架性能的要求,本课题将两者按不同比例进行复合,探讨不同皮芯比例羟基磷灰石／柞蚕丝素（HA／TSF）的骨仿生纳米纤维的生物学性能。方法：首先利用同轴静电纺丝技术,以TSF水溶液为皮,HA水溶液为芯,制备不同皮芯比例的HA／TSF骨仿生纳米纤维,然后将人成骨肉瘤细胞（MG-63）种植在不同皮芯比例的HA／TSF纳米纤维上。在不同的时间点分别通过倒置显微镜、扫描电镜观察细胞形态学变化;通过四甲基偶氮噻唑蓝比色（Four methyl azo thiazole blue colorimetric, MTT）法、碱性磷酸酶（alkaline phosphatase,ALP）活性检测法观察细胞在材料表面的增殖和分化,从多角度来评价材料的生物学性能。结果：通过形态学观察,SEM观察以及MTT检测,发现除空白对照组外,各组样品均显示良好的生物相容性,均能促进细胞的黏附、增殖,尤以HA／TSF为2：1时最明显;通过MG-63细胞的ALP活性检测,发现当HA／TSF比例为2：1时,最能促进细胞ALP活性的表达,有利于诱导成骨细胞的分化。结论：皮芯结构的HA／TSF骨仿生纳米纤维具有良好的生物学性能,且二者在自然界来源丰富,价格便宜,为临床骨组织缺损修复的应用奠定了一定的实验基础     

Thin Film Encapsulation of Organic Solar Cells by Direct Deposition of Polysilazanes from Solution

Organic electronic devices (OEDs), e.g., organic solar cells, degrade quickly in the presence of ambient gases, such as water vapor and oxygen. Thus, in order to extend the lifetime of flexible OEDs, they have to be protected by encapsulation. A solution‐based encapsulation method is developed, which allows the direct deposition of the diffusion barrier on top of OEDs, thus avoiding lamination of barrier films. The method is based on the deposition of a perhydropolysilazane (PHPS) ink and its subsequent conversion into a silica layer by deep UV irradiation. The resulting barrier films show water vapor transmission rates (WVTRs) of <10^?2 g m^?2 d^?1 (40 °C/85% relative humidity (RH)) and oxygen transmission rates (OTRs) of <10^?2 cm³ m^?2 d^?1 bar^?1 at ambient conditions. Flexibility of the resulting barrier films is improved by coating a barrier stack of several thin PHPS layers alternating with organic polymer interlayers. These stacks show an increase of WVTR values by less than 10% after 3000 bending cycles. Direct coating of the PHPS films on top of organic solar cells enhances the device lifetime in damp heat conditions from a few hours to beyond 300 h.     

Magnesium and strontium doped octacalcium phosphate thin films by matrix assisted pulsed laser evaporation

Octacalcium phosphate (OCP) is a promising alternative to hydroxyapatite as biomaterial for hard tissue repair. In this study we successfully applied Matrix Assisted Pulsed Laser Evaporation (MAPLE) to deposit Mg and Sr doped OCP (MgOCP and SrOCP), as well as OCP, thin films on titanium substrates. OCP, Mg-substituted and Sr-substituted OCP were synthesized in aqueous medium, then were suspended in deionised water, frozen at liquid nitrogen temperature and used as targets for MAPLE experiments. The depositions were carried out using a KrF* excimer laser source (λ = 248 nm, τ_FWHM = 25 ns) in mild conditions of temperature and pressure. The results of X-ray diffraction, infrared spectroscopy, scanning electron microscopy and energy dispersive spectroscopy investigations revealed that the OCP thin films are deposited in the form of cauliflower-like aggregates and droplets, as well as crystal fragments, with a homogeneous distribution of magnesium and strontium on the surface of the coatings. Human osteoblast-like MG-63 cells were cultured on the different biomaterials up to 14 days. MgOCP and SrOCP coatings promote osteoblast proliferation and differentiation with respect to OCP. Under these experimental conditions, the production of procollagen-type I, transforming growth factor-β1, alkaline phosphatase and osteocalcin indicated that the level of differentiation of the cells grown on the different coatings increased in the order OCP < MgOCP < SrOCP.     

Rapid microwave-assisted synthesis and characterization of cellulose-hydroxyapatite nanocomposites in N,N-dimethylacetamide solvent

Preparation of nanocomposites was carried out using microcrystalline cellulose, CaCl₂, and NaH₂PO₄ in N,N-dimethylacetamide (DMAc) solvent by a microwave-assisted method at 150 °C. XRD results showed that the nanocomposites consisted of cellulose and hydroxyapatite (HA). The cellulose existed as a matrix in the nanocomposites. SEM and TEM analysis showed that HA nanorods were homogeneously dispersed in the cellulose matrix. The effects of the microwave heating time on the products were investigated. This method has advantages of being simple, rapid, low-cost, and environmentally friendly.     

Phagocytosis of hydroxyapatite or calcium pyrophosphate dihydrate crystals by rabbit articular chondrocytes stimulates release of collagenase, neutral protease, and prostaglandins E2 and F2 alpha

Synthetic hydroxyapatite (HA) and calcium pyrophosphate dihydrate (CPPD) microcrystals are phagocytosed by rabbit articular-cartilage chondrocytes in primary culture. The ingestion of crystals greatly stimulated the release of collagenase, neutral protease, and prostaglandins E2 and F2 alpha into the ambient medium. Lactate dehydrogenase was not released by either crystal despite electron microscopic evidence of cell damage by HA crystals (partial loss of phagolysosomal membrane and increased myelin figures). HA, but not CPPD crystals, stimulated release of beta-glucuronidase. HA crystal concentrations from 50 to 200 micrograms ml-1 induced a dose-dependent release of collagenase and of extracellular protein. Both phagocytosis and collagenase release were greatly attenuated when HA crystals were added to the chondrocyte monolayers in the absence of serum. As HA and CPPD crystals have been identified in human articular cartilage in association with degenerative changes, it is possible that the cell-crystal interaction described here may be pathogenetically important.     

Capillary electrophoresis with laser-induced native fluorescence detection for profiling body fluids

Laser-induced native fluorescence detection with a KrF excimer laser (λ=248 nm) was used to investigate the capillary electrophoretic (CE) profiles of human urine, saliva and serum without the need for sample derivatization. All separations were carried out in sodium phosphate and/or sodium tetraborate buffers at alkaline pH in a 50-μm I.D. capillary. Sodium dodecyl sulfate was added to the buffer for micellar electrokinetic chromatography (MEKC) analysis of human urine. Although inherently a pulsed source, the KrF excimer laser was operated at a high pulse repetition rate of 553, 1001 or 2009 Hz to simulate a continuous wave excitation source. Detection limits were found to vary with pulse rate, as expected, in proportion to average excitation power. The following detection limits (3σ) were determined in free solution CE: tryptophan, 4 nM; conalbumin, 10 nM; α-lactalbumin, 30 nM. Detection limits for indole-based compounds and catecholamine urinary metabolites under MEKC separation conditions were in the range 7–170 nM.     

Properties and Characteristics of Multi-Layered Films from Tilapia Skin Gelatin and Poly(Lactic Acid)

Multi-layered films based on tilapia skin gelatin and poly(lactic acid) (PLA) were characterized, in comparison with the control gelatin and PLA films. Three different layers of multi-layered films (PLA/Gelatin/PLA) were visualized by scanning electron microscopic (SEM) analysis. The synergetic effect of lamination was evidenced by the increased mechanical properties (P < 0.05). Multi-layered films had higher water vapor barrier property and water resistance, compared to control gelatin film (P < 0.05). Gelatin films showed increased lightness (L*) with coincidental decrease in total color difference (?E*) in the presence of PLA layers (P < 0.05). Transparency and solubility of films decreased with increasing ratio of PLA (P < 0.05). In addition, multi-layered films showed the enhanced hydrophobicity and thermal stability as evidenced by increased water contact angle and degradation temperature, respectively. Thus, PLA/Gelatin/PLA multi-layered film with improved water vapour barrier property could serve as bio-degradable packaging material for wider applications.     

Osteogenic Properties of PBLG-g-HA/PLLA Nanocomposites

New development of biomaterial scaffolds remains a prominent issue for the regeneration of lost or fractured bone. Of these scaffolds, a number of bioactive polymers have been synthesized and fabricated for diverse biological roles. Although recent evidence has demonstrated that composite scaffolds such as HA/PLLA have improved properties when compared to either HA or PLLA alone, recent investigations have demonstrated that the phase compatibility between HA and PLLA layers is weak preventing optimal enhancement of the mechanical properties and making the composites prone to breakdown. In the present study, poly (γ-benzyl-L-glutamate) modified hydroxyapatite/(poly (L-lactic acid)) (PBLG-g-HA/PLLA) composite scaffolds were fabricated with improved phase compatibility and tested for their osteogenic properties in 18 Wistar female rats by analyzing new bone formation in 3 mm bilateral femur defects in vivo. At time points, 2, 4 and 8 weeks post surgery, bone formation was evaluated by µ-CT and histological analysis by comparing 4 treatment groups; 1) blank defect, 2) PLLA, 3) HA/PLLA and 4) PBLG-g-HA/PLLA scaffolds. The in vivo analysis demonstrated that new bone formation was much more prominent in HA/PLLA and PBLG-g-HA/PLLA groups as depicted by µ-CT, H&E staining and immunohistochemistry for collagen I. TRAP staining was also utilized to determine the influence of osteoclast cell number and staining intensity to the various scaffolds. No significant differences in either staining intensity or osteoclast numbers between all treatment modalities was observed, however blank defects did contain a higher number of osteoclast-like cells. The results from the present study illustrate the potential of PBLG-g-HA/PLLA scaffolds for bone tissue engineering applications by demonstrating favorable osteogenic properties.     

Microstructural characterization of yam starch films

Yam starch films were produced by thermal gelatinization of starch suspensions using different starch and glycerol concentrations and were compared to control samples without glycerol. Films were characterized by polarized light microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermomechanical analysis (TMA), X-ray diffraction, water vapor permeability (WVP) and water sorption isotherms. The polarized light microscopy and DSC data showed that starch gelatinization for film formation was complete. Plasticized films have a homogeneous structure as observed by SEM. At water activities >0.43, glycerol increased the equilibrium moisture content of the films due to its hydrophilic character. X-ray pattern of the yam films could be assigned to a B-type starch; during storage this pattern remained almost the same, however a slight recrystallization process could be observed. Amylopectin retrogradation was not observed by DSC with storage time of the films. Glass transition temperatures of films with glycerol were lower than those of control films as measured by DSC and TMA. WVP of yam starch films increased with the presence of glycerol.     

3D Bio-Plotted Composite Scaffold Made of Collagen Treated Hydroxyapatite-Tricalciumphosphate for Rabbit Tibia Bone Regeneration

Biphasic calcium phosphate scaffolds with 20/80 HA/TCP ratio were fabricated using the 3D-Bioplotting system to heal critical size defects in rabbit tibia bone. Four different architectures were printed in a layer by layer fashion with lay down patterns viz. (a) 0°– 90°, (b) 0°– 45°– 90°– 135°, (c) 0°–108°– 216° and (d) 0°– 60°– 120°. After high-temperature sintering scaffolds were coated with collagen and were further characterized by (FTIR) Fourier Transform Infrared Spectroscopy, (SEM) Scanning Electron Microscopy, (XRD) X-Ray diffraction, Porosity analysis and Mechanical testing. Scaffold samples were tested for its ability to induce cytotoxicity in Balb/c 3T3 cells at in vitro condition using elution method. Skin sensitization potential of scaffolds was evaluated in male guinea pigs using guinea pig maximization test (GPMT). Further, scaffolds were implanted in eight rabbit tibia bones and biocompatibility and histological evaluations were carried out after 4 and 8 weeks implantation periods. In-vitro results include bonding, surface morphology, phases, porosity, mechanical strength and Cytotoxicity. In-vivo results include sensitization, capsule formation, inflammation, presence of polymorphonuclear cells, giant cells, plasma cells, X-Rays and degradation of the material. It was concluded that HA/TCP/Collagen scaffold with 0°– 45°– 90°– 135° architecture exhibits the most excellent properties in healing critical size bone defects in rabbits.     

Preparation,characterization, bioactive and metal uptake studies of alginate/phosphorylated chitin blend films

Alginate/phosphorylated chitin (P-chitin) blend films were prepared by mixing of 2% of alginate and P-chitin in water and then cross-linked with 4% CaCl₂ solution. The blended films were characterized by FT-IR. Then, the bioactivity of blend films was studied by biomimetic method in simulated body fluid solution (SBF) for 7, 14 and 21 days. After 7, 14 and 21 days and films were characterized by FT-IR and SEM studies. The SEM and FT-IR studies showed that the hydroxyapatite was formed on the surface of the blend films after 7, 14 and 21 days in the SBF solution. These studies confirmed that the alginate/P-chitin blend films are bioactive. Furthermore, the adsorption of Ni²⁺, Zn²⁺and Cu²⁺onto alginate/P-chitin blend films has been investigated. The parameters studied include the pH, contact time, and initial metal ion concentrations. The maximum adsorption capacity of alginate/P-chitin blend films for Ni²⁺, Zn²⁺and Cu²⁺ at pH 5.0 was found to be 5.67, 2.85 and 11.7 mg/g, respectively. These results suggest that alginate/P-chitin blend films-based technologies may be developed for water purification and metal ions separation and enrichment.     

Nano-crystalline hydroxyapatite bio-mineral for the treatment of strontium from aqueous solutions

Hydroxyapatites were analysed using electron microscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis. Examination of a bacterially produced hydroxyapatite (Bio-HA) by scanning electron microscopy showed agglomerated nano-sized particles; XRD analysis confirmed that the Bio-HA was hydroxyapatite, with an organic matter content of 7.6%; XRF analysis gave a Ca/P ratio of 1.55, also indicative of HA. The size of the Bio-HA crystals was calculated as ~25 nm from XRD data using the Scherrer equation, whereas Comm-HA powder size was measured as ≤50 μm. The nano-crystalline Bio-HA was ~7 times more efficient in removing Sr²⁺ from synthetic groundwater than Comm-HA. Dissolution of HA as indicated by the release of phosphate into the solution phase was higher in the Comm-HA than the Bio-HA, indicating a more stable biomaterial which has a potential for the remediation of contaminated sites.     

Chitosan/polyethylene glycol diacrylate films as potential wound dressing material

Michael addition reaction of Chitosan (CS) and polyethylene glycol diacrylate (PEGDA) was carried out successfully in acidic solution. Films with CS/PEGDA weight ratios from 100/0 to 0/100 in 10% increments were analyzed by Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). Additionally, the films were characterized by measuring mechanical property, swelling property. The potential application of the CS/PEGDA film as wound dressing material was evaluated in vitro by using mouse fibroblasts (L929) as reference cell lines, indirect cytotoxicity assessment indicated that CS/PEGDA films were nontoxic to L929 cell.     

Synthesis and character investigation of new collagen Hydrolysate/polyvinyl alcohol/hydroxyapatite Polymer-Nano-Porous Membranes: I. Experimental design optimization in thermal and structural properties

Abstract

Development of bioorganic–inorganic composites has drawn eyes to extensive attention in biomedical fields and tissue engineering. So many attempts to prepare hydroxyapatite (HA), in conjunction with various binders including polyvinyl alcohol (PVA), and collagen has performed for late 20 years. We applied a method based on the phase separation for making of polymer porous membranes. This procedure is induced through the addition of a small quantity of water (polymer-rich phase) to a solution with HA precursors (polymer-poor phase). Thermal and structural composite properties of collagen Hydrolysate (CH)–PVA/HA Polymer-Nano-Porous Membranes were analyzed by Design of experiment that was undertaken using D-optimal approach, to select the optimal combination of nano composites precursor. The resulted composite characters were investigated by Fourier transform infrared, scanning electron microscopy (SEM) and thermal gravimetric analysis. Based on the SEM images, this new method could be clearly concluded to porous CH–PVA/HA hybrid materials. Finally the hemocompatibility of nanocomposite membranes were evaluated by the hemolysis study.

Graphical Abstract

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碳/碳材料含硅羟基磷灰石涂层体外成骨细胞相容性研究

目的:成骨细胞在碳/碳复合材料表面羟基磷灰石涂层上有良好的长入,该实验在羟基磷灰石(hydroxyapatite HA)涂层中掺入硅后,研究成骨细胞对该涂层的生物活性,为临床骨科应用提供实验基础。方法:本研究采用化学液相气化沉积/水热法在碳/碳材料表面制备了含硅羟基磷灰石(silicon-hydroxyapatite Si-HA)涂层。在体外成骨细胞相容性的研究中,以HA涂层为对照,通过甲基噻唑基四唑(methylthiazolyl tetrazolium MTT)法测定细胞增殖反应和对细胞毒性反应,碱性磷酸酶(alkaline phosphatase ALP)测定细胞的分化,扫描电镜观察细胞生长形态,免疫荧光显影技术测定细胞的长入。结果:在HA涂层中引入硅后,Si-HA涂层和HA涂层在第2天、第4天的成骨细胞增殖实验表明前者的细胞长入数较后者多,两者的差异有统计学意义,而Si-HA涂层浸泡液中的ALP活性下降较HA涂层而言更明显,两者的差异有统计学意义,电镜扫描及荧光染色均提示在Si-HA涂层中成骨细胞的增值数更多。结论:在HA涂层中引入硅后,改变了涂层自身的晶体结构及表面电荷,同时诱导成骨细胞分泌胶原,使得成骨细胞更好的贴壁生长和增殖,成骨能力增加。在临床骨科植入物表面涂层改性上有很好的应用前景。