Novel two-step synthesis of gold nanoparticles capped with bile acid conjugates

Bile acids and their conjugates are physiologically important molecules. Syntheses and structure elucidation combined with investigation of properties and applications of bile acids and their derivatives are of academic interest. The concept of using bile acids and their conjugates in nanoscience is a novel idea, which opens up fascinating prospects. In this article, an easy and simple route for obtaining N-lithocholyl-l-(cysteine ethyl ester) (3), capable of effectively capping and stabilizing metal nanoparticles, is described. The whole synthetic route needs only two steps giving a moderate to good yield. The gold NPs are characterized by elemental analysis, UV spectroscopy, and TEM. Additionally, ¹³C CP/MAS NMR studies for different ligand/Au ratios have been performed.     

Novel dental nanocomposites: fabrication and investigation of their physicochemical,mechanical and biological properties

The aim of this study was to investigate biological, physicochemical and mechanical characteristics of a series of novel dental restorative nanocomposites that comprise dendritic methacrylate end-caped monomers, triethylene glycol dimethacrylate (TEGDMA; as diluting monomer) and modified silica nanoparticles (\(\hbox {M-SiO}_{2}\); as inorganic filler). The cytotoxicity effects of the monomers and fabricated nanocomposites were examined against NIH3T3 cells (the standard fibroblast cell line) through MTT and trypan blue cell viability tests, respectively. The antibacterial activities of the monomers were evaluated against Lactobacillus plantarum by standard agar disk diffusion approach. The mechanical properties (flexural strength (FS) and compressive strength (CS)) as well as some physicochemical characteristics such as water sorption (WS), sol fraction (SF) and double bond conversion (DC) were also investigated, and compared with corresponding characteristics of 3M Filtek Z250 as a reference. Thus, the fabricated nanocomposites have potential as dental restorative materials mainly due to their suitable biological, physicochemical and mechanical properties.     

抗菌剂用于牙科复合树脂的研究进展

龋病是常见的口腔疾病,填充修复是治疗的重要手段。复合树脂凭借色泽美观和理化性能优异等特点,广泛应用于牙科修复材料中。继发龋是临床应用中导致修复失败的主要原因之一。为了抑制继发龋、延长树脂使用寿命,研发具有长期抗菌功能的牙科复合树脂具有重要意义。目前,主要通过向复合树脂体系中添加抗菌型无机粒子或抗菌型有机单体赋予材料抗菌性能。基于抗菌剂的抗菌机理,本文概述了上述抗菌剂对复合树脂抗菌性能及理化性能影响的研究进展,指出了多数抗菌剂在满足复合树脂抗菌性能的同时,无法避免对树脂材料力学性能和美观性产生负面影响。最后,对抗菌型牙科复合树脂的发展趋势进行了展望,有助于推动该类材料的临床应用。     

Synthesis of Polymerizable Cyclodextrin Derivatives for Use in Adhesion-Promoting Monomer Formulations

The synthesis of the cyclodextrin derivatives reported herein was assisted by extensive literature research together with structure-property relationships derived from three-dimensional molecular modeling. These studies led to the hypothesis that many of the 21 hydroxyl groups on beta-cyclodextrin molecules could be derivatized to form a closely related family of analogous chemical compounds containing both polymerizable groups and hydrophilic ionizable ligand (substrate-binding) groups, each attached via hydrolytically-stable ether-linkages. The vinylbenzylether polymerizable groups should readily homopolymerize and also copolymerize with methacrylates. This could be highly useful for dental applications because substantially all contemporary dental resins and composites are based on methacrylate monomers. Due to hydrophilic ligands and residual hydroxyl groups, these cyclodextrin derivatives should penetrate hydrated layers of dentin and enamel to interact with collagen and tooth mineral. Analyses indicated that the diverse reaction products resulting from the method of synthesis reported herein should comprise a family of copolymerizable molecules that collectively contain about 30 different combinations of vinylbenzyl and hexanoate groups on the various molecules, with up to approximately seven of such groups combined on some of the molecules. Although the hypothesis was supported, and adhesive bonding to dentin is expected to be significantly improved by the use of these polymerizable cyclodextrin derivatives, other efforts are planned for improved synthetic methods to ensure that each of the reaction-product molecules will contain at least one copolymerizable moiety. The long-term objective is to enable stronger and more durable attachments of densely cross-linked polymers to hydrated hydrophilic substrates. Capabilities for bonding of hydrolytically stable polymers to dental and perhaps other hydrous biological tissues could provide widespread benefits.     

Differentiation of isomeric conjugated bile acids using positive-ion B/E linked scans.

The main objective of this work was to use positive-ion fast atom bombardment mass spectrometry (FAB-MS) B/E linked scan spectra to investigate the possibility of differentiating positional isomers of various authentic glycine- and taurine-conjugated bile acids. Sodium salts of 14 conjugated bile acids were individually ionized by FAB-MS and characterized by scanning simultaneously the magnetic field B and the electric sector field E such that B/E remained constant throughout the scan. The dominant fragment ions could be related to cleavage of the aliphatic side chain with charge retention on the conjugated end of the bile acids. However, fragment ions arising from ring cleavages were also observed and could be used to distinguish the positions of substituent hydroxyl groups. For example, ring cleavage of conjugated dihydroxy bile acids at C-7/C-8 and C-9/C-10 permitted the differentiation of chenodeoxycholyltaurine (3 alpha,7 alpha-substitution pattern) from deoxycholyltaurine (3 alpha,12 alpha-substitution pattern) based on the presence of fragment ions at m/z 388 or m/z 404, which were indicative of hydroxyl group substitutions at either the 7- or 12-positions, respectively. It was concluded that B/E linked scans can be used to discriminate positional isomers of conjugated bile acids.     

Synthetic Light‐Curable Polymeric Materials Provide a Supportive Niche for Dental Pulp Stem Cells

Dental disease annually affects billions of patients, and while regenerative dentistry aims to heal dental tissue after injury, existing polymeric restorative materials, or fillings, do not directly participate in the healing process in a bioinstructive manner. There is a need for restorative materials that can support native functions of dental pulp stem cells (DPSCs), which are capable of regenerating dentin. A polymer microarray formed from commercially available monomers to rapidly identify materials that support DPSC adhesion is used. Based on these findings, thiol‐ene chemistry is employed to achieve rapid light‐curing and minimize residual monomer of the lead materials. Several triacrylate bulk polymers support DPSC adhesion, proliferation, and differentiation in vitro, and exhibit stiffness and tensile strength similar to existing dental materials. Conversely, materials composed of a trimethacrylate monomer or bisphenol A glycidyl methacrylate, which is a monomer standard in dental materials, do not support stem cell adhesion and negatively impact matrix and signaling pathways. Furthermore, thiol‐ene polymerized triacrylates are used as permanent filling materials at the dentin‐pulp interface in direct contact with irreversibly injured pulp tissue. These novel triacrylate‐based biomaterials have potential to enable novel regenerative dental therapies in the clinic by both restoring teeth and providing a supportive niche for DPSCs.     

聚苯并咪唑树脂的合成与性能

聚苯并咪唑因其具有耐高温、耐腐蚀、阻燃、以及良好的力学性能、介电性能等多种优异性能而备受关注。我们合成了数种未见报道的新型聚苯并咪唑树脂,并用FT-IR、TGA、DSC进行了表征。在研究中我们对四胺合成路线进行了优化,改进了水解以及还原反应。实验以4,4’-二氨基联苯和邻硝基苯胺为原料合成了3,3’-二氨基联苯胺、3,3’,4,4’-四氨基二苯甲烷两种单体,通过两种单体与多种二元羧酸进行聚合制备了两个系列的聚苯并咪唑,在这些聚合物中我们选取了12种聚合物对它们的溶解性、耐热性进行了深入研究,多种数据显示这两类聚合物具有非常优异的热稳定性。     

Amorphous Calcium Phosphate-Based Bioactive Polymeric Composites for Mineralized Tissue Regeneration

Amorphous calcium phosphate (ACP), a postulated precursor in the formation of biological hydroxyapatite, has been evaluated as a filler phase in bioactive polymeric composites that utilize dental monomers to form the matrix phase on polymerization. In addition to excellent biocompatibility, these composites provided sustained release of calcium and phosphate ions into simulated saliva milieus. In an effort to enhance the physicochemical and mechanical properties and extend the utility of remineralizing ACP composites to a greater variety of dental applications, we have focused on: a) hybridizing ACP by introducing silica and/or zirconia, b) assessing the efficacy of potential coupling agents, c) investigating the effects of chemical structure and compositional variation of the resin matrices on the mechanical strength and ion-releasing properties of the composites, and d) improving the intrinsic adhesiveness of composites by using bifunctional monomers with an affinity for tooth structure in resin formulations. Si- and Zr-modified ACPs along with several monomer systems are found useful in formulating composites with improved mechanical and remineralizing properties. Structure-property studies have proven helpful in advancing our understanding of the remineralizing behavior of these bioactive composites. It is expected that this knowledge base will direct future research and lead to clinically valuable products, especially therapeutic materials appropriate for the healing or even regeneration of defective teeth and bone structures.     

人工种植牙材料及表面处理的研究进展

牙齿缺失是较为常见的口腔问题,牙齿缺失不仅影响患者的面部美观,还将对患者的生理及心理造成较大影响,进而给患者的正常生活、社交、工作等带来不利影响.此外,牙齿的缺失还将影响牙槽骨的功能,降低牙槽骨代谢能力,加快牙槽脊骨质的吸收及改建.人工种植牙因其美观性、稳定性、种植无需打磨邻牙等优势,逐渐成为缺牙修复的首选方式.口腔的...     

Specific distribution of sialic acids in animal tissues as examined by LC-ESI-MS after derivatization with 1,2-diamino-4,5-methylenedioxybenzene

Simultaneous analysis of sialic acids has been a challenging target, because sialic acids having N- or O-acetyl, glycolyl, and sulfonic acid ester groups are labile during their release from carbohydrate chains and analytical procedures. In the present paper, we propose a method using high-performance liquid chromatography coupled with eletrospray ionization mass spectrometry (HPLC-ESI-MS). The method was evaluated by applying to the analysis of sialic acids in various tissues, especially digestive organs in mice and rats. The method was based on the in situ precolumn derivatization of sialic acids after releasing them by hydrolysis. The sialic acids were derivatized with 1,2-diamino-4,5-methylenedioxybenzene to form highly fluorescent quinoxaline derivatives. By using two different hydrolysis conditions (i.e., with 2 M acetic acid and with 0.1 M hydrochloric acid), both total sialic acids and sialic acid distributions were easily determined. We found that sialic acids showed characteristic distributions in the tissues of mice and rats. Further, HPLC-ESI-MS revealed that all the tissues examined in mice and rats commonly contained highly acetylated sialic acids and 8-O-sulfated N-acetylneuraminic acid.     

Structural and electrical studies of alternating layers of porphyrins and fatty acids

Langmuir-Blodgett multilayers were formed by the alternate deposition of amphiphilic derivatives of mesoporphyrin IX and protoporphyrin IX and of various fatty acids. These films were studied by low angle X-ray diffraction, scanning electron microscopy and by conductivity measurement in the plane of the film. It is shown that, in the case of diol porphyrin derivatives, a well-ordered superlattice is produced. In contrast, the use of diesters leads to the segregation of the two materials in the plane of the film. Such segregation implies the diffusion of molecules after deposition over distances of the order of 1 μm.     

Enhancement of the LC/MS analysis of fatty acids through derivatization and stable isotope coding

This paper focuses on the development of an enhanced LC/ESI-MS method for the identification and quantification of fatty acids through derivatization. Fatty acids were derivatized with 2-bromo-1-methylpyridinium iodide and 3-carbinol-1-methylpyridinium iodide, forming 3-acyloxymethyl-1-methylpyridinium iodide (AMMP). This process attaches a quaternary amine to analytes and enabled ESI-MS in the positive mode of ionization with common LC mobile phases. Moreover, detection sensitivity was generally 2500-fold higher than in the negative mode of ionization used with underivatized fatty acids. The limits of detection were roughly 1.0-4.0 nM (or 10 pg/injection) for standard fatty acids from C10 to C24 and spanned approximately 2 orders of magnitude in linearity. AMMP derivatives had unique tandem mass spectra characterized by common ions at m/z 107.0, 124.0, and 178.0. Individual fatty acids also had unique fingerprint regions that allowed identification of their carbon skeleton number, number of double bonds, and double bond position. The derivatization method also allowed coding of analytes as a means of recognizing derivatives and enhancing quantification. 2H-Coding was achieved through derivatization with deuterated 3-carbinol-1-methyl-d3-pyridinium iodide. The 2H-coded derivatization reagent, 3-acyloxymethyl-1-methyl-d3-pyridinium iodide, was used in two ways. One was to differentially label equal fractions of a sample such that after being recombined and analyzed by ESI-MS all fatty acids appeared as doublet clusters of ions separated by roughly 3 amu. This greatly facilitated identification of fatty acids in complex mixtures. Another use of stable isotope coding was in comparative quantification. Control and experimental samples were differentially labeled with nondeuterated and deuterated isotopomers of CPM, respectively. After mixing the two samples, they were analyzed by ESI-MS. The abundance of a fatty acid in an experimental sample relative to the control was established by the isotope ratio of the isotopomeric fatty acids. Absolute quantification was achieved by adding differentially labeled fatty acid standards to experimental samples containing unknown quantities of fatty acids. Utility of the method was examined in the analysis of human serum samples.     

Manufacture of Co-Cr dental crowns and bridges by selective laser Melting technology

Currently, one of the most important applications of the Selective Laser Melting (SLM) process is dental frameworks manufacturing. The objective of the present study is to analyse mechanical and microstructural properties of dental crowns and bridges manufactured by SLM technology from Co-Cr alloy using a Phenix PM 100T Dental Machine over a production period of 14 months. The obtained results show clearly a successful application of the SLM technology to the design and manufacture of dental crowns and bridges. Dental parts with adequate density, geometrical accuracy, mechanical properties, and microstructure have been produced. Based on regular analyses results, of initial Co-Cr powder materials and final crowns properties characteristics, one can conclude that the Selective Laser Melting Process can be used for the manufacturing of dental parts in correlation with the required traditional standards. The good repeatability of the SLM process has been demonstrated.     

Derivatization of chiral amino acids in supercritical carbon dioxide

A new method is proposed to perform the derivatization of chiral amino acids occurring in complex samples using supercritical carbon dioxide as both the reaction medium and the agent used to extract the obtained derivatives prior to accomplishing the subsequent enantiomeric chromatographic analysis. The derivatization step under supercritical conditions involves the esterification of the carboxyl group and the acylation of the amino group of the amino acids without using a catalyst. A Chirasil-L-Val capillary column enabled the separation of the D- and L-forms of the amino acids as their N(O)-pentafluoropropionyl 1-propyl esters. Relative standard deviation values obtained from the gas chromatographic analysis for the derivatized amino acids ranged from 5 to 15%.     

Potential Pharmaceutical Applications of a New Beta Cyclodextrin Derivative

Abstract

The three major natural cyclodextrins viz alpha, beta and gamma, consist of six, seven or eight glucose units, respectively (1). In addition to the natural cyclodextrins, numerous new products have been shown to have potential for the pharmaceutical industry (2,3). A clear distinction has to be made between cyclodextrin polymers, which are mainly used as separation materials in analytical chemistry (4) and cyclodextrin derivatives, which are monomers of substituted cyclodextrins (5). In the synthesis process of the latter, both the C(2) and C(3) secondary and the C(6) primary hydroxyl groups have been the target of many chemical substitutions (6), leading to the development and the characterization of cyclodextrin derivatives of pharmaceutical interest (7). Such derivatives have been successfully used in the design of new drug carrier systems (3,5), Hence, in addition to their increased solubility, these chemically modified cyclodextrins exhibit excellent complexing abilities (8). The different possibilities of modifying cyclodextrins have been reviewed by Sebille (2), Szejtli (1) and Uekama (3). Szjetli also published an extensive list of the major cyclodextrin derivatives under investigation until 1982 (1).     

牙科陶瓷材料的摩擦学性能研究进展

陶瓷材料因其优异的耐磨性、化学稳定性、生物相容性和美观性被广泛用于牙齿缺损和缺失修复。本文首先介绍了牙科陶瓷材料的化学成分、微观结构和力学性能,基于陶瓷材料的磨损与磨蚀机制,归纳总结了牙科陶瓷材料摩擦学性能优化方面所取得的进展,指出陶瓷材料和天然人牙摩擦学性能失配严重制约了陶瓷修复体的临床应用,进而从室验介质、对摩副以及载荷、位移和循环次数等方面分析汇总牙科陶瓷材料摩擦学性能的体外测试方法。最后,从仿生摩擦学角度探讨了牙科陶瓷材料的未来发展趋势,并指出研制仿生陶瓷基复合材料是解决陶瓷修复体与天然人牙摩擦学性能失配难题最具潜力的策略。     

Electrochemical characteristics of amino acids and peptides derivatized with naphthalene-2,3-dicarboxaldehyde: pH effects and differences in oxidation potentials.

The electrochemical oxidations of the cyanobenz[f]isoindole (CBI) derivatives of 18 amino acids and 15 peptides, including enkephalins and several enkephalin fragments, were studied. Cyclic voltammetry indicated that the oxidation potentials of derivatized amino acids were virtually independent of pH. The utility of this pH-independence was demonstrated by controlling, through varying the pH, the selectivity with which CBI derivatives could be detected in the presence of phenolic compounds. In addition, hydrodynamic voltammograms of derivatized amino acids and peptides were constructed from chromatographic data and compared. The E1/2 values among the derivatized amino acids covered a range of 215 mV, with the derivatives of the basic amino acids being the easiest to oxidize and those of the acidic amino acids being the most difficult to oxidize. The E1/2 values of the derivatized peptides examined varied by 270 mV, with minor variations in structure capable of producing marked changes in oxidation potential. These results indicate that voltammetry can aid in identification or selective detection of CBI derivatives of amino acids or peptides.     

K+ and Ca2+ modified Na-X zeolites as possible bile acids sequestrant

Modified zeolite X, previously exchanged with K⁺ and Ca²⁺ cations were characterized by XRD, FT-IR, chemical analysis and BET techniques. Different masses of these solids were mixed with an ox bile solution at different reaction times. The supernatants obtained by centrifugations were submitted to bile acid and phospholipids quantitative determinations. The amount of bile acids adsorbed was 65, 28 and 77% and for phospholipids was 45, 67 and 98% for KX, NaX and CaX respectively. As expected, as the amount of mass used increases more bile acids and phospholipids are adsorbed due to a larger surface of the solid being available for adsorption. On the other hand, 120 min of reaction time were sufficient for the adsorption of both components. The solids, after incubations with bile solutions were treated with abundant distilled water and dried at room temperature. The FT-IR analysis of these solids did not detect any bile and on the zeolite surface with suggested that the bile acid adsorption on the exchanged zeolites is moderated by weak and non covalent interactions.     

Surface modification and functionalization of electroactive polymer films via grafting of polyelectrolyte,polyampholyte and polymeric acids

Films of electroactive polymers, such as polyaniline (PAN) in its emeraldine base form, and poly(3-alkylthiophene), poly(3-hexylthiophene) (P6TH), poly(3-octylthiophene) (P8TH), and poly(3-dodecylthiophene) (P12TH) can be readily functionalized via thermal or near ultraviolet-light-induced surface graft copolymerization with monomers of polyelectrolyte, polyampholyte and polymeric acids. The monomers used in the present work include dimethyl sulphate quaternized dimethylamino-ethylmethacrylate (DMAEM·C₂H₆SO₄), 3-dimethyl(methacryloyloxyethyl)ammonium propane sulphonate (DMAPS), acrylic acid (AAc) and a sodium salt of styrene sulphonic acid (NaSS). The surface structures and compositions of the electroactive polymer films after functionalization via graft copolymerization were characterized by angle-resolved X-ray photoelectron spectroscopy. Graft copolymerization of poly(3-alkylthiophene) films, but not PAN films, with the hydrophilic monomers readily results in a stratified surface microstructure arising from the migration of the hydrophilic graft chains beneath a thin surface layer which is much richer in the substrate chains. On the other hand, graft copolymerization of PAN films with AAc and NaSS readily gives rise to a self-protonated (and thus conductive) surface structure.     

牙科椅不同俯仰角度的人体舒适度研究

目的通过研究牙科椅俯仰角度的变化与人体舒适度之间的关系,为改善牙科椅的设计提供有力的参考依据。方法测试不同俯仰角度下人体主观舒适度,基于CATIA(交互式CAD/CAE/CAM系统)人机工程设计与分析模块,在导入的牙科椅模型中引入三维人体模型,建立虚拟人机关系,结合人机工程学理论,对不同俯仰角度下人体姿态的舒适度进行仿真分析,利用SPSS统计分析软件对所得的数据处理。结论牙科椅俯仰角度从0°转到60°的过程中,人体舒适度分值呈先上升后下降的趋势。人体最舒适的牙科椅俯仰角度为30°,最不舒适的角度为0°,同时验证了CATIA人机工程设计与分析的可行性。