明胶/胶原改性的研究进展

明胶/胶原因其优良的理化性质和生物学性能而在生物材料、食品包装等方面得到了广泛的应用,但其热稳定性差、机械强度低、水汽阻隔性能差等缺点限制了它的应用,因此在很多应用场合需要对明胶/胶原进行交联改性处理。本文主要综述了近年来国内外对明胶/胶原进行共混和化学交联改性以及物理改性的研究进展,并对其作用效果进行了分析。     

负载蛋白质的胶原/聚两性电解质IPN角膜替代物

以碳二亚胺/N-羟基琥珀酰亚胺(EDC/NHS)和聚乙二醇二丙烯酸酯(PEGDA)为交联剂分别对猪皮去端肽Ⅰ型胶原和3-(甲基丙烯酰胺)丙基-二甲基(3-磺丙)胺(MPDSAH)进行交联, 制备了具有互穿聚合物网络(IPN)结构的角膜替代物. 胶原基IPN角膜替代物的折光指数和白光透过率与天然人角膜相似. IPN水凝胶具有优于纯胶原凝胶的力学性能, 同时PMPDSAH网络的引入明显提高了IPN凝胶在胶原酶中的稳定性. 体外细胞培养实验结果表明, IPN角膜替代物支持人角膜上皮细胞生长. 通过冷冻干燥-溶胀后包覆技术可将牛血清白蛋白(BSA)和神经生长因子(NGF)装载到角膜替代物中, 负载药物的冻干凝胶可干态保存, 避免了湿态下蛋白质等活性因子的失活和漏泄; 再吸水恢复原状的特性可使角膜替代物完好地移植病灶部位, NGF具有良好的缓释效果. 此负载NGF的复合角膜替代物有望促进角膜组织和神经的再生.     

Collagen mimetic dendrimers

The synthesis of single-chain, scaffold (TRIS)- and dendrimer-assembled collagen mimetics (both Gly-Pro-Nleu and Gly-Nleu-Pro sequences) is reported. From the CD spectra and the thermal denaturation studies it can be readily seen that mimetics prepared from the Gly-Nleu-Pro sequence form more thermally stable triple helices than the Gly-Pro-Nleu sequence. Furthermore, the 162-residue collagen mimetic dendrimers exhibit enhanced triple helical stability compared to equivalent scaffold-terminated structures by a substantial increase in the melting temperature in H2O and 2:1 EG/H2O. The concentration dependence for the melting transition was measured which determined that the stabilization effect arises from the intramolecular clustering of the triple helical arrays about the core structure. This ensemble excludes solvent from the interior portion of the array which stabilizes the triple helical bundle.     

Molecular Understanding of Collagen Stabilization: Interaction of Valeraldehyde with Collagen

The present study explains the molecular level interaction of valeraldehyde with collagen. Valeraldehyde is a monoaldehyde, which involves crosslinking with protein through covalent linkages. The role of valeraldehyde as a crosslinking agent for collagen stabilization was studied. Molecular modeling approaches was used to understand the interaction of collagen like peptide with valeraldehyde, which mimic the aldehyde tanning processes involved in protein stabilization. Crosslinking efficiency of valeraldehyde was found to increase with an increase in concentration due to the higher availability of aldehydic groups involved in crosslinking with collagen. Valeraldehyde interacted collagen membrane showed an increase in thermal stability by 25°C at pH 8. In the presence of valeraldehyde, collagen fibrils nucleation center was shifted from a lower to a higher range. Shift in the nucleation center was observed in the reduction of gelling time. Water accessibility in valeraldehyde interacted collagen membrane was reduced due to a higher crosslinking rate in the collagen. Modified collagen membrane by valeraldehyde at incubation of about 96 h showed higher resistance to collagenolytic activity of 81%. The amino groups reacting appear to be involved in crosslinking with valeraldehyde. Several interaction sites were identified and the docking energy obtained was ?5.539 kcal/mol. The participation of the aldehyde group with amino groups in collagen was observed, which plays a dominant role in the stabilization of peptide by valeraldehyde. It was found that complexes exhibit covalent bonding, hydrogen bonding and electrostatic interaction in the process of stabilization.     

Collagen in silicotischem Gewebe

Ohne Zusammenfassung     

胶原矿化与仿生修复

脊椎动物硬组织（牙和骨）是通过生命系统的矿化过程形成的,其中矿化胶原是这些生物材料的基本结构单元。矿化胶原是由胶原分子与纳米磷酸钙矿物形成的有机-无机复合材料,其所特有的纳米有序多级结构赋予了生物硬组织材料优异的机械性能（如硬度和韧性）。该结构特性和矿化过程可为新型硬组织修复材料制备提供有益的启示。其中,胶原纤维内有序矿化是仿生重构的难点,也是开展硬组织修复的关键。本文综述了骨的分层结构特征、胶原分子的组装和矿化胶原的多级结构特点,胶原分子和非胶原蛋白与磷酸钙材料的相互作用,功能调控分子对胶原和矿物的界面修饰,以及胶原矿化技术在硬组织修复中的应用;指出了目前胶原矿化亟须解决的一些关键问题,如调控无定形矿物进入胶原纤维、胶原矿化速度和程度,大规模有序胶原纤维制备等。     

胶原蛋白静电纺丝纳米纤维研究进展

由于胶原蛋白静电纺丝纳米纤维具有胶原蛋白的生物活性以及纳米结构材料的优异性能,其在生物医学领域的研究和应用开发取得了非常大的进展。本文首先综述了胶原蛋白静电纺丝纳米纤维的研究现状,讨论了胶原蛋白静电纺丝纳米纤维在组织工程、止血及伤口愈合、载药和防粘连等生物医学领域的应用,最后针对胶原蛋白静电纺丝纳米纤维存在的问题及其未来的发展方向进行了展望。     

Ultrasonic Study of Collagen Solutions

Ultrasonic propagation characteristics of collagen solutions are reported. The concentration dependences of the various ultrasonic parameters of the solvent (acetic acid) and the solute (collagen) are compared. The ultrasonic velocities for acetic acid and collagen are comparable, while the attenuation is very high in collagen solutions. The adiabatic compressibility and the free length in collagen solutions decrease with increasing concentration. The relaxation time increases rapidly with concentration of collagen, unlike that for acetic acid.     

Formation of Highly Aligned Collagen Nanofibers by Continuous Cyclic Stretch of a Collagen Hydrogel Sheet

A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The rearrangement of the collagen fibers depends on the different process parameters of the cyclic stretch, including magnitude, frequency, and period of stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells cultivated on the highly aligned collagen sheet show alignment along the collagen fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine.

     

胶原静电纺丝研究进展

胶原是细胞外基质的主要结构蛋白,广泛存在于各类动物机体中。天然胶原存在纤维形态不一、机械性能差等不足,限制了其工业规模化应用。因此,如何有效地制备出性能优良的胶原材料成为热点问题。静电纺丝技术是一种新兴的纳米材料制造技术,利用该技术可获得具有不同结构和性能的胶原基纳米纤维材料,制成的纳米纤维材料展现出密度低、弹性高等优异特性,有望广泛应用于组织工程、医学、载体等领域。本文将从胶原的单独静电纺丝及其影响因素、胶原共混静电纺丝和影响因素以及应用等方面介绍胶原静电纺丝技术的研究进展,并针对存在的问题和发展方向进行了讨论和展望,为胶原的应用提供一定的理论指导和技术支撑。     

Collagen microsphere production on a chip

We have developed an integrated microfluidic material processing chip and demonstrated the rapid production of collagen microspheres encapsulating cells with high uniformity and cell viability. The chip integrated three material processing steps. Monodisperse microdroplets were generated at a microfluidic T junction between aqueous and mineral oil flows. The flow was heated immediately to 37 °C to initiate collagen fiber assembly within a gelation channel. Gelled microspheres were extracted from the mineral oil phase into cell culture media within an extraction chamber. Collagen gelation immediately after microdroplet generation significantly reduced coalescence among microdroplets that led to non-uniform microsphere production. The microfluidic extraction approach led to higher microsphere recovery and cell viability than when a conventional centrifugation extraction approach was employed. These results indicate that chip-based material processing is a promising approach for cell-ECM microenvironment generation for applications such as tissue engineering and stem cell delivery.     

氧化纤维素增强胶原水凝胶

对纤维素进行氧化,得到醛基化的氧化纤维素,将其作为大分子交联剂制备了氧化纤维素改性胶原水凝胶.通过扫描电镜、力学性能及流变学测试,对改性胶原水凝胶的结构和性能进行了表征.研究结果表明,与纯胶原水凝胶相比,氧化纤维素改性胶原水凝胶的力学性能和热稳定性都得到了明显改善,其压缩破坏强度比纯胶原水凝胶提高了1个数量级以上.此外,氧化纤维素的引入,并未出现一般化学交联剂改性所带来的细胞毒性,并保持了胶原水凝胶良好的生物相容性.为改性胶原水凝胶在组织工程材料领域的应用提供依据.     

胶原大分子自组装研究进展

胶原是人类最主要的结构蛋白,在体内通过自组装形成具有D带的纤维结构,构成人体的各种组织。胶原蛋白具有优异的生物相容性、生物可降解性、无毒性、低免疫性等特点,在材料科学、生物医学、组织工程、生物传感器等领域得到了越来越多的研究和应用。近年来,人们发现,通过合理调控外界环境,胶原蛋白在体外能自组装形成有序的超分子聚集结构,胶原蛋白在体外的自组装行为引起了研究者的广泛关注,逐渐成为研究的热点。本文概括了胶原的自组装机理、外界环境条件对胶原自组装的影响以及胶原自组装基复合材料等方面的工作。     

Unusual Fragmentation Pathways in Collagen Glycopeptides

Collagens are the most abundant glycoproteins in the body. One characteristic of this protein family is that the amino acid sequence consists of repeats of three amino acids –(X—Y—Gly)_n. Within this motif, the Y residue is often 4-hydroxyproline (HyP) or 5-hydroxylysine (HyK). Glycosylation in collagen occurs at the 5-OH group in HyK in the form of two glycosides, galactosylhydroxylysine (Gal-HyK) and glucosyl galactosylhydroxylysine (GlcGal-HyK). In collision induced dissociation (CID), collagen tryptic glycopeptides exhibit unexpected gas-phase dissociation behavior compared to typical N- and O-linked glycopeptides (i.e., in addition to glycosidic bond cleavages, extensive cleavages of the amide bonds are observed). The Gal- or GlcGal- glycan modifications are largely retained on the fragment ions. These features enable unambiguous determination of the amino acid sequence of collagen glycopeptides and the location of the glycosylation site. This dissociation pattern was consistent for all analyzed collagen glycopeptides, regardless of their length or amino acid composition, collagen type or tissue. The two fragmentation pathways—amide bond and glycosidic bond cleavage—are highly competitive in collagen tryptic glycopeptides. The number of ionizing protons relative to the number of basic sites (i.e., Arg, Lys, HyK, and N-terminus) is a major driving force of the fragmentation. We present here our experimental results and employ quantum mechanics calculations to understand the factors enhancing the labile character of the amide bonds and the stability of hydroxylysine glycosides in gas phase dissociation of collagen glycopeptides.

Videofluorometric Analysis of Aging Human Collagen

Abstract

The development of fluorescent pigments in aging human collagen has been observed, but neither the source of these compounds nor their nature has been described. Recently two distinct fluorophores were isolated from aging insoluble human collagen rich tissue following a sequence of proteolytic digestions and chromatographic separations. Using the videofluormeter, which monitors the fluorescence intensity of a sample as a function of several excitation and emission wavelengths, the fluorescence of the collagen rich tissue at various stages of the separation process was analyzed to determine the number of fluorescent components in each of the samples and estimate their fluorescence spectra. The analysis indicated that the isolated fluorophores were indeed single-component samples and that the insoluble collagen-rich fraction contains two major fluorophores whose spectra are consistent with the spectra of the isolated compounds.