Antibacterial activation of hydroxyapatite (HA) with controlled porosity by different antibiotics

In order to prevent the increasing frequency of per-operative infections, bioceramics can be loaded with anti-bacterial agents, which will release with respect to their chemical characteristics. A novel hydroxyapatite (HA) was elaborated with specific internal porosities for using as a bone-bioactive antibiotic (ATB) carrier material. UV spectrophotometry and bacteria inhibition tests were performed for testing the ATB adsorption and the microbiological effectiveness after loading with different antibiotics. The impregnation time, ATB impregnating concentration, impregnation condition and other factors, which might influence the ATB loading effect, were studied by exposure to different releasing solvents and different pathogenic bacteria: Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli. It clearly showed that the facility of ATB loading on this porous HA is even possible just under simple non-vacuum impregnation conditions in a not-so-long impregnating interval. The results also showed that, for all three types of ATB (vancomycin, ciprofloxacin and gentamicin), adsorbed amount on the micro-porous HA were hugely higher than that on dense HA. The micro-porosity of test HA had also significantly prolonged the release time of antibiotics even under mimic physiological conditions. Furthermore, it also has primarily proved by a pilot test that the antibacterial efficiency of crude micro-porous HA could be further significantly improved by other methods of functionalization such as cold plasma technique.     

经基磷灰石(H A )的制备方法及其研究进展

HA生物材料作为最有发展前途的生物硬组织替代材料之一。已经成为生物医用材料研究的重点内容。本文在综合了大量的国内外文献的基础上,对羟基磷灰石的不同制备方法及国内外研究现状进行了总结及评论。并提出了相应的设想与展望。     

Development of waxy cassava with different Biological and physico-chemical characteristics of starches for industrial applications

The quality of cassava starch, an important trait in cassava breeding programs, determines its applications in various industries. For example, development of waxy (having a low level of amylose) cassava is in demand. Amylose is synthesized by granule-bound starch synthase I (GBSSI) in plants, and therefore, down-regulation of GBSSI expression in cassava might lead to reduced amylose content. We produced 63 transgenic cassava plant lines that express hair-pin dsRNAs homologous to the cassava GBSSI conserved region under the control of the vascular-specific promoter p54/1.0 from cassava (p54/1.0::GBSSI-RNAi) or cauliflower mosaic virus (CaMV) 35S (35S::GBSSI-RNAi). After the screening storage roots and starch granules from field-grown plants with iodine staining, the waxy phenotype was discovered: p54/1.0::GBSSI-RNAi line A8 and 35S::GBSSI-RNAi lines B9, B10, and B23. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that there was no detectable GBSSI protein in the starch granules of plants with the waxy phenotype. Further, the amylose content of transgenic starches was significantly reduced (<5%) compared with the level in starch granules from the wild-type (about 25%). The inner structure of the waxy starch granules differed from that of the untransformed ones, as revealed by transmission electron microscopy analysis as well as morphological changes in the iodine-starch complex. Endothermic enthalpy was reduced in waxy cassava starches, according to differential scanning calorimeter analysis. Except B9, all waxy starches displayed the A-type X-ray diffraction pattern. Amylogram patterns of the waxy cassava starches were analyzed using a rapid viscosity analyzer and found to have increased values for clarity, peak viscosity, gel breakdown, and swelling index. Setback, consistency, and solubility were notably reduced. Therefore, waxy cassava with novel starch in its storage roots was produced using the biotechnological approach, promoting its industrial utilization.     

A complete structural performance analysis and modelling of hydroxyapatite scaffolds with variable porosity

The use of hydroxyapatite (HA) scaffolds for bone regeneration is an alternative procedure to treat bone defects due to cancer, other diseases or traumas. Although the use of HA has been widely studied in the literature, there are still some disparities regarding its mechanical performance. This paper presents a complete analysis of the structural performance of porous HA scaffolds based on experimental tests, numerical simulations and theoretical studies. HA scaffolds with variable porosity were considered and fabricated by the water-soluble polymer method, using poly vinyl alcohol as pore former. These scaffolds were then characterised by scanning electron microscopy, stereo microscopy, X-ray diffraction, porosity analysis and mechanical tests. Different scaffold models were proposed and analysed by the finite element method to obtain numerical predictions of the mechanical properties. Also theoretical predictions based on the (Gibson LJ, Ashby MF. 1988. Cellular solids: structure and properties. Oxford: Pergamon Press) model were obtained. Finally the experimental, numerical and theoretical results were compared. From this comparison, it was observed that the proposed numerical and theoretical models can be used to predict, with adequate accuracy, the mechanical performance of HA scaffolds for different porosity values.     

Immunologic and physico-chemical properties of hyperimmune antibodies with different affinities

By immune chromatography fractions with various reaction rates of antigen precipitation and neutralization of toxin "in vivo" have been isolated from a common pool of antibodies. Antibodies of higher pI possessed an elevated relation of basis amino acid residues to unsubstituted dicarboxylic residues as well as greater affinity. The data suggest an important role of ion interaction and a general scheme of antigen and antibody molecules structure for immune reactions.     

Analysis of toxicity and biocompatibility of chitosan derivatives with different physico-chemical properties

A comparative study of the toxicity and hemocompatibility of chitosan and its derivatives with different acetylation degrees, molecular masses, charges, and hydrophobicity has been performed. It has been shown that only positively charged chitosan derivatives activate platelets and suppress cell proliferation, regardless of the acetylation degree, molecular mass, and hydrophobicity. Chitosan quaternization decreases toxicity at a low degree of substitution and abruptly increases it at a high one. Negatively charged chitosan derivatives were nontoxic and compatible with blood components. It was concluded that the toxicity of chitosan and its derivatives is defined by their charge and solubility at a neutral pH.     

Regulation of Hyaluronan (HA) Metabolism Mediated by HYBID (Hyaluronan-binding Protein Involved in HA Depolymerization,KIAA1199) and HA Synthases in Growth Factor-stimulated Fibroblasts

Regulation of hyaluronan (HA) synthesis and degradation is essential to maintenance of extracellular matrix homeostasis. We recently reported that HYBID (HYaluronan-Binding protein Involved in hyaluronan Depolymerization), also called KIAA1199, plays a key role in HA depolymerization in skin and arthritic synovial fibroblasts. However, regulation of HA metabolism mediated by HYBID and HA synthases (HASs) under stimulation with growth factors remains obscure. Here we report that TGF-β1, basic FGF, EGF, and PDGF-BB commonly enhance total amount of HA in skin fibroblasts through up-regulation of HAS expression, but molecular size of newly produced HA is dependent on HYBID expression levels. Stimulation of HAS1/2 expression and suppression of HYBID expression by TGF-β1 were abrogated by blockade of the MAPK and/or Smad signaling and the PI3K-Akt signaling, respectively. In normal human skin, expression of the TGF-β1 receptors correlated positively with HAS2 expression and inversely with HYBID expression. On the other hand, TGF-β1 up-regulated HAS1/2 expression but exerted only a slight suppressive effect on HYBID expression in synovial fibroblasts from the patients with osteoarthritis or rheumatoid arthritis, resulting in the production of lower molecular weight HA compared with normal skin and synovial fibroblasts. These data demonstrate that although TGF-β1, basic FGF, EGF, and PDGF-BB enhance HA production in skin fibroblasts, TGF-β1 most efficiently contributes to production of high molecular weight HA by HAS up-regulation and HYBID down-regulation and suggests that inefficient down-regulation of HYBID by TGF-β1 in arthritic synovial fibroblasts may be linked to accumulation of depolymerized HA in synovial fluids in arthritis patients.     

Synthesis and physico-chemical studies of bimetallic alkoxy derivatives of chromium(III) with niobium(V) and tantalum(V)

Reactions of CrCl₃·3thf with KM(OPrⁱ)₆ in 1:3 molar ratios in benzene yield soluble complexes of the type Cr[M(OPrⁱ)₆]₃ (M=Nb or Ta). On heating under vacuum, these complexes tend to disproportionate into Cr(OPrⁱ)₃ and M(OPrⁱ)₅ (M=Nb or Ta). A number of bimetallic alkoxides have also been synthesized by the alcoholysis of Cr[M(OPrⁱ)₆]₃ with alcohols (methanol, ethanol and t-amyl alcohol). The IR, visible, electron spin resonance and magnetic properties of these newly synthesized complexes throw light on the structural features.     

Fabrication of porous polycaprolactone/hydroxyapatite (PCL/HA) blend scaffolds using a 3D plotting system for bone tissue engineering

For tissue engineering and regeneration, a porous scaffold with interconnected networks is needed to guide cell attachment and growth/ingrowth in three-dimensional (3D) structure. Using a rapid prototyping (RP) technique, we designed and fabricated 3D plotting system and three types of scaffolds: those from polycaprolactone (PCL), those from PCL and hydroxyapatite (HA), and those from PCL/HA and with a shifted pattern structure (PCL/HA/SP scaffold). Shifted pattern structure was fabricated to increase the cell attachment/adhesion. The PCL/HA/SP scaffold had a lower compressive modulus than PCL and PCL/HA scaffold. However, it has a better cell attachment than the scaffolds without a shifted pattern. MTT assay and alkaline phosphatase activity results for the PCL/HA/SP scaffolds were significantly enhanced compared to the results for the PCL and PCL/HA scaffolds. According to their degree of cell proliferation/differentiation, the scaffolds were in the following order: PCL/HA/SP > PCL/HA > PCL. These 3D scaffolds will be applicable for tissue engineering based on unique plotting system.     

Biological and physico-chemical properties of an atypical mutant of tobacco mosaic virus

Summary A mutant of tobacco mosaic virus (TMV) was isolated from a population of TMV-RNA molecules inactivated to 0.1% level of survival by treatment with nitrous acid This mutant is poorly transported in Samsun tobacco and induces chlorotic spots, oak-leaf patterns, ringspots and necrosis. Rate zonal sucrose density-gradient and equilibrium sedimentations in sucrose and CsCl indicate that the purified mutant preparations contain a heterogenous population of particles including some free coat protein. These vary in length, but approximately 5–10% are infectious rods of standard (15×300 nm) dimensions. Purified mutant RNA contain an overabundance of fragmented and a few infectious molecules. Compared to the parent strain, the mutant capsid protein contains two additional residues of arginine and one of glycine, but lacks one residue each of glutamic acid (or glutamine), serine and threonine. These observations and other data based on temperature sensitivity, exposure to urea and serology indicate that the mutant particles are inherently unstable and break during the purification procedure.     

Sequential backbone assignment of isotopically enriched proteins in D2O by deuterium-decoupled HA(CA)N and HA(CACO)N

Summary It is demonstrated that sequential resonance assignment of the backbone ¹H and ¹⁵N resonances of proteins can be obtained without recourse to the backbone amide protons, an approach which should be useful for assignment of regions with rapidly exchanging backbone amide protons and for proteins rich in proline residues. The method relies on the combined use of two 2D experiments, HA(CA)N and HA(CACO)N or their 3D analogs, which correlate ¹H with the intraresidue ¹⁵N and with the ¹⁵N resonance of the next residue. The experiments are preferably conducted in D₂O, where very high resolution in the ¹⁵N dimension can be achieved by using ²H decoupling. The approach is demonstrated for a sample of human ubiquitin, uniformly enriched in ¹³C and ¹⁵N. Complete backbone and ¹³C/¹H resonance assignments are presented.     

Resistance of liposomes with different physico-chemical characteristics to the effect of plasma

The chemical composition, liquid content sign and value of charge as well as structure and size of lipid vesicles are studied for the effect they exert on the liposome permeability for 22Na+ in the presence of human blood plasma. The rate of the isotope outlet from the electroneutral lecithin liposomes is determined by the size of vesicles and the quantity of phospholipid bilayers in their membrane. The presence either of a negative or a positive charge on the surface of the liposome membrane has no essential effect on the outlet rate of the radioactive marker. Introduction of different amounts of cholesterol or sphingomyelin into the liposome composition decreases considerably the lipid vesicle permeability and an increase in the liquid content of their membranes due to the temperature elevation is accompanied by a sharp rise in the isotope outlet rate. A conclusion is drawn on the possibility to control the outlet rate of the liposome content in the presence of blood plasma.     

流感病毒血凝素基因、神经氨酸酶基因在小鼠中的免疫效果观察

流感病毒血凝素基因,神经氨酸酶基因免疫BALB／c小鼠,获得特异阳性抗体反应,抗体滴度与基因免疫量呈正相关性,各实验组免疫小鼠抗同型流感病毒攻击存活率为100％,血凝素基因免疫小鼠抗异型流感病毒攻击存活率为100％,神经氨酸酶基因免疫小鼠抗异型流感病毒攻击存活率为75％,血凝素基因与神经氨酸酶基因联合免疫小鼠抗异型流感病毒攻击存活率为100％。     

Synthesis of [cyclo(Glu gamma-----epsilon Lys(Gly)]ACTH-(5-14) undecapeptide. Biological and physico-chemical properties of analogs of ACTH-(5-10)- and ACTH-(5-14)-peptides

Modified corticotropin fragment - [Lys11 (Gly)]ACTH-(5-14)- and its cyclic analogue - [cyclo (Glu gamma----epsilon Lys (Gly)] ACTH-(5-14)-undecapeptides have been synthesized by classical approach. The cyclic structure has been fixed by amide bond between gamma-COOH group of glutamic acid and alpha-NH2 group of glycine coupled to the epsilon-NH2 group of lysine. Fragment condensation has been achieved by azide or dicyclohexylcarbodiimide methods. Cyclization has been performed using diphenylphosphorylazide. The melanotropic activity of the cyclicanalogue on isolated frog skin exceeds by two orders of magnitude that of the linear undecapeptide, however the steroidogenic activity in isolated cells of rat adrenal cortex is diminished by an order of magnitude as compared with that of the linear precursor. A similarity of the CD spectra for the cyclic ACTH peptides and their linear counterparts in water and trifluoroethanol points to the similarity and relative rigidity of their structures.