Title: Periodic Mesoporous（Organo)Silicas (PM(O)Ss): From Synthesis to Applications
Abstract:Mesoporous materials featuring well-defined symmetry, highsurface area, and ordered “periodic” pore arrays have emerged as excellent research platforms for efficient intrapore chemistry, and have been extensively applied in catalysis, biology, drug delivery, adsorption and separation. Subtle changes of the synthesis parameters can markedly affect
the physical and chemical properties of the final nanostructured materials, such as the surface structure/morphology (hydrophobicity and hydrophilicity, the distribution of surface species), the catalytic reactivity and selectivity, and the spatial environment. The present presentation will focus on synthesis of PM(O)Ss, surface modification and their applications in catalysis, drug release etc.
Title:Cellular Effect and Biomimetic Properties in vitro of Novel 4,5-Dialkylated Imidazolium NHC Salts
Abstract: 4,5-Dialkylimidazolium N-heterocyclic (NHC) salts are a novel class of alkylated imidazolium derivatives showing extraordinary biological activities, especially their cellular toxicity.1 In comparison to simple 1-alkylimidazolium cations, 4,5-dialkylation in the backbone of the imidazole core greatly contribute to the improvement of an approximately three orders of magnitude high cellular effect due to their structurally resemblance to natural membrane lipids.2 In order to clarify the structure-activity relationship (SAR) of such imidazolium lipids, they were tailor-made by varying the alkyl chain length (C7, C11 and C15) as well as by fine-turning the N-substituents (wingtip groups) of the imidazolium ring, which is furnished by either N-methylation or N-benzylation. 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), was used as a representative monolayer and bilayer model membrane system in vitro. The membrane behavior of the imidazolium lipids within DPPC monolayers was characterized by surface pressure-area (π-A) isotherms using a Wilhelmy film balance in combination with epi-fluorescence microscopy (EFM). For a mixed lipid bilayer system, membrane binding and insertion of the imidazolium lipids were analyzed by a quartz crystal microbalance (QCM) and confocal laser scanning microscopy (CLSM). Further, all-atom molecular dynamics (MD) simulations were performed to provide mechanistic insights on a molecular level. The long alkyl chains (C15) exhibit a rigidification effect on both DPPC monolayer and bilayer structures, allowing to highly mimic the biophysical behavior of phospholipids. Howerver, the incorporation of the medium chains (C11) results in a thermodynamically unfavored mixed monolayer with DPPC and disordered DPPC liposomes. The short chains (C7) display negligible membrane effect due to their poor contribution to the surface activity. On the other hand, N-benzylation of the imidazole core not only remarkably improves the surface activity but also endows the imidazolium lipids to strongly disintegrate membranes. We conclude that for 4,5-dialkylated imidazolium NHC salts, both, the steric effect of the N-substituents as well as the hydrophobic mismatch from the backbone alkyl chains modulate their potential biological activities.
Title:Functional Analysis of WildType and N471D Strumpellin In Hereditary Spastic Paraplegia
Abstract: Hereditary Spastic Paraplegias (HSPs) are clinically characterized by lower limb weakness and spasticity. Several point mutations of human strumpellin (Str), with N471D being the most frequent one, have been shown to cause HSP (SPG8). To investigate the molecular function of wild-type and StrN471D, we generated Dictyostelium discoideum Str¯ cells as well as cells that ectopically expressed StrWT-GFP or StrN471D-GFP in AX2 wild-type and Str¯ cells and analyzed the resulting strains. Here, we describe their phenotypes in comparison to AX2 in cell division, cell growth, macropinocytosis, exocytosis, lysosome properties and secretion of lysosomal enzymes. We found that knock-out of strumpellin resulted in significant defects in all of these cellular processes. Expression of StrWT-GFP in Str¯ cells rescued all of the observed defects while expression of StrN471D-GFP could only rescue some of the defects, indicating the importance of the StrN471D residue for full functionality of the protein. The results indicate that strumpellin plays a key role in the endo-lysosomal system. The N471D mutation apparently interferes with some of the essential functions of strumpellin in this system. In summary, our data provide a basis for a better understanding of the molecular mechanism of SPG8.
Title: Synthesis of Nanoscale bioactive glass and Their Application on Bone Tissue Engineering
Abstract:生物玻璃（bioactive glasses）具有优异的生物活性和骨结合性，其降解产物能够促进生长因子的生成和细胞的增殖、增强成骨细胞的基因表达以及骨组织的生长。生物玻璃既能够与骨组织成键结合，同时又能与软组织相连接，因此可以用于人工骨、齿科以及软骨修复领域。通过调节组分和形貌，生物玻璃也可以用于创面愈合以及抗癌等应用。相比于微米级生物玻璃，纳米生物玻璃（nanocale bioactive glasses）其尺寸、形貌可控性较好，比表面积也较大，因此其生物活性也较高。纳米生物玻璃主要用做复合材料的填料来提高基体材料的性能，比如提高高分子基体的生物矿化性和生物活性。通过调控掺杂比例，纳米生物玻璃也能够提高基体材料的力学性能。本次报告主要介绍常用的生物玻璃纳米微球的合成策略以及其组分和形貌的调控。同时，也对本课题组在生物活性玻璃/高分子复合材料在骨修复以及创面愈合中的工作进行介绍。