高分子膜材料及人工脏器

概要地介绍高聚物与生物体的关系、对医用高分子材料的要求、医用高分子材料的生物相容性、材料在生物体内的降解和吸收，以及高分子膜在人工脏器的应用概况．     

胶原基生物材料制备与应用研究进展

胶原因具有良好的亲水性、柔韧性和趋化性、生物相容性、生物降解性，被认为是改善组织再生最重要的生物材料之一，并广泛应用于食品、化妆品以及再生医学领域。但是，在提取过程中，胶原的结构和自然交联键会遭到破坏，导致其机械强度、热稳定性和抗酶解能力都低于自然状态。受到天然胶原在组织重塑和修复过程中自然交联的启发，研究人员通过引入外源性交联（化学、物理和生物）来优化胶原基材料的机械强度和稳定性。目前，外源性化学、物理或生物交联已被用于修饰胶原的分子结构，通过这些方法制备的胶原基支架材料的刚度、抗张强度和压缩模量都明显提高，但是材料的延展性降低。这些方法主要是通过限制胶原三螺旋结构分子间α链的自由度，防止胶原微纤维排列的破坏，从而提高胶原的热稳定性和机械强度。另外，通过分子间交联掩盖胶原的酶切割位点，能够提高胶原对酶促降解的抵抗力。但是这些方法仍然有一些缺陷，如存在细胞毒性和降低胶原的活性等。研究者们制备了不同物理结构的胶原基材料（脱细胞基质、海绵、水凝胶、自组装纤维、膜、管和多孔球等），以更好地促进不同组织或器官的再生。因此，了解胶原基材料的交联方法和制备技术进展，对开发新型的胶原基生物支架材料至...     

壳聚糖即型水凝胶的体内代谢研究

壳聚糖及其衍生物作为生物医用高分子材料已被广泛应用,研究其在动物体内的吸收降解是此类生物医用材料应用于人体的必要前提。壳聚糖即型水凝胶是以壳聚糖为主要材料制备的新型生物医用材料,可在体内降解吸收。以异硫氰酸酯(FITC)标记法研究了该水凝胶经大鼠腹腔注射后的吸收、降解和分布,为该水凝胶应用于体内提供实验数据。实验结果显示,壳聚糖即型水凝胶经大鼠腹腔注射后能够较快被腹腔吸收,并经血液转运至各代谢器官,在肝脏内有一过性的积累,在其它脏器内分布较少,其主要代谢途径是血液→肝脏→肾脏→尿液,在17d时,通过此途径排出的量占注射量的88%,排出体外的分子量均小于10kD。     

胶原基复合止血材料的研究进展及展望

胶原蛋白可用于多种止血场景，并凭借优越的性能和易于获取的特点逐渐取代传统止血材料。然而，不同剂型的胶原止血剂都存在各自的缺陷，如力学性能差、粘附性差等。虽然提纯或交联改性胶原能在一定程度上获得改善，但作用有限，临床应用仍深受限制。天然生物及其衍生物材料是来源丰富的止血剂，具有生物相容性和良好的吸收和降解性能。广泛使用的材料包括壳聚糖、纤维蛋白胶、藻酸盐和氧化纤维素，以及近年来逐渐受到重视的传统中药材。因此，胶原蛋白与天然生物及其衍生物材料交联而成的胶原蛋白基复合止血材料，有望成为极具前景的生物医用止血材料。本文综述了不同类型胶原基复合止血材料的研究进展，总结了各自的优缺点，最后对胶原基复合止血材料的未来发展方向进行了探讨。     

魔芋葡甘聚糖/Ⅱ型胶原/壳聚糖复合材料的制备及性能

以魔芋葡甘聚糖、Ⅱ型胶原和壳聚糖为主要原料,采用36%的乙酸溶解壳聚糖、Ⅱ型胶原的甘油溶液通过共混的方法制备魔芋葡甘聚糖/Ⅱ型胶原/壳聚糖共混膜液,经静置减压脱泡、倒模、干燥制膜,并采取与乙酸等量的氢氧化钠对膜进行处理。用FT-IR、XRD、生物学显微镜和SEM对共混膜进行性能表征,测定了共混膜的透光率、力学性能、吸水率及水蒸气透过系数,还做了复合材料的细胞相容性实验,主要进行了骨髓间充质干细胞、牙周膜成纤维细胞的体外培养,另外对膜进行了体外模拟降解实验。结果表明其有望作为一种潜在的皮肤组织工程支架材料和牙周膜材料。     

胶原-壳聚糖二元膜材料的制备与性能表征

通过热脱氢交联（DHT）、戊二醛改性以及碳化二亚胺改性（EDC）等方法对胶原基膜材料进行改性，探讨其作为生物医用材料较为理想的改性方法。以胶原及壳聚糖为主要原料制备大孔径高孔率二元膜材料，通过单一或复合改性以后比较二元膜材料的各项性能。适当的DHT改性后获得的二元膜孔径为20～100μm，孔率90％左右，但膜材料机械性能较差，抗酶解能力提高不明显；0．02％的戊二醛．EDC复合改性交联程度较为合适，DHT改性可以一定程度减少戊二醛用量；DHT-EDC复合改性得到的二元膜孔径20～200μm，孔率95％左右，机械强度和耐酶稳定性较高，吸水率高且在水中不溶胀。DHT-EDC复合改性是较为理想的胶原基膜材料作为生物医用材料的改性方法。     

纳米羟基磷灰石/聚酰胺复合材料屏障膜的体外生物相容性

用相转移法制备了用于引导骨再生的纳米磷灰石/聚酰胺66(n-HA/PA66)和载银纳米羟基磷灰石/二氧化钛/聚酰胺66(Ag-HA-TiO₂/PA66)复合生物材料屏障膜, 并通过与骨髓基质干细胞(BMSC)共培养评价了其体外生物相容性。扫描电子显微镜(SEM)观察显示,制备的复合材料膜为不对称多孔膜,一面是孔径小于10μm的微孔层,另一面是孔径在30～200μm的大孔结构。四唑盐比色(MTT)和流式细胞术(FCM)试验结果表明：n-HA/PA66膜具有良好的细胞亲和力,有利于BMSC的黏附、生长和减少凋亡;Ag-HA-TiO₂/PA66 膜也具有良好的生物相容性,但加速了BMSC的凋亡。2种膜的结构和生物相容性能够满足引导骨组织再生膜材料的要求。     

多巴胺表面修饰胶原膜促进细胞粘附和增殖的研究

多巴胺已经被广泛地用于材料的表面修饰改性,能够提高材料的生物相容性,赋予材料新的反应活性.为了考察多巴胺表面修饰胶原膜对其机械强度、湿热稳定性、亲水性和生物相容性的影响,对多巴胺自组装表面修饰胶原膜不同时间形成的膜材料进行研究,结果发现,经过多巴胺自组装表面修饰后,胶原保持完整的三股螺旋结构,膜材料的机械强度、湿热稳定性和亲水性均得到提高,而且成纤维细胞更易于在膜上粘附和增殖.     

多巴胺表面修饰胶原膜促进细胞粘附和增殖的研究

多巴胺已经被广泛地用于材料的表面修饰改性,能够提高材料的生物相容性,赋予材料新的反应活性。为了考察多巴胺表面修饰胶原膜对其机械强度、湿热稳定性、亲水性和生物相容性的影响,对多巴胺自组装表面修饰胶原膜不同时间形成的膜材料进行研究,结果发现,经过多巴胺自组装表面修饰后,胶原保持完整的三股螺旋结构,膜材料的机械强度、湿热稳定性和亲水性均得到提高,而且成纤维细胞更易于在膜上粘附和增殖。     

丝素蛋白对胶原膜性能改善的研究

天然高分子由于其良好的生物相容性而受到广泛的关注。本研究用酶法自制了具有一定水溶性的猪皮胶原。尝试利用丝素和胶原蛋白各自的优点。用简单的溶液浇铸法制备了胶原-丝素共混膜。并通过FTIR、TGA、SEM等手段对其结构进行了表征。结果表明。由于共混膜中俩组份间存在的分子间作用力，加入小于50％的丝素的胶原膜经乙醇处理后与纯胶原膜相比。其力学性能及热稳定性有所的改善。通过改变丝素比例可以调整共混膜的吸水性。由于两组分良好的生物相容性，预料该共混膜可用作生物材料。     

Evaluation of Injectable Composite Material Comprising Biphasic Bone Substitutes and Crosslinked Collagen

Bone tissue engineering has emerged as a promising approach to regenerate bone tissue, and injectable biomaterials have shown potential for bone regeneration applications due to their ease of administration and ability to fill irregularly shaped defects. This study aims to develop and characterize an injectable composite material comprising biphasic bone substitutes (BBS) and crosslinked porcine collagen type I for bone regeneration applications. The collagen is crosslinked via a UVA-riboflavin crosslinking strategy and evaluated by testing the physicochemical properties, including the rheological behavior, dynamic storage modulus (G′) and loss modulus (G″), and in vitro degradation process. The results show that the crosslinked collagen (xCol) exhibits suitable physicochemical properties for injectability and improved viscoelasticity and degradation resistance. Furthermore, xCol is then combined with BBS in a predetermined ratio, obtaining the injectable composite material. The biocompatibility of the materials is evaluated in vitro by XTT and BrdU assays on fibroblasts and preosteoblasts. The results demonstrate that the composite material is biocompatible and supporting pre-osteoblasts proliferation. In conclusion, the injectable composite material BBS-xCol has promising physiochemical and biological properties for bone regeneration applications. Further studies are warranted to evaluate its efficacy in vivo and optimize its composition for clinical translation.     

Characterisation of a collagen membrane for its potential use in cardiovascular tissue engineering applications

In this study, Biomend, a collagen membrane conventionally used in the regeneration of periodontal tissue, is investigated for its possible use in the field of cardiovascular tissue engineering. A key requirement of most potential tissue engineering scaffolds is that degradation occurs in tandem with tissue regeneration and extra cellular matrix remodelling. To this end, it is crucial to understand the degradation mechanics and mechanisms of the material and to investigate the practicability of using Biomend as a possible scaffold material. With this in mind, methodologies for the initial characterisation of the scaffold material were determined. The mechanical properties of Biomend samples, subjected to various degrees of hydration and enzymatic degradation, were examined primarily through tensile testing experiments. The effects of enzymatic degradation were monitored quantitatively, by observing weight loss, and visually, by studying micrographs. Cell adhesion and viability were of primary concern. Confocal laser scanning microscopy was employed to illustrate endothelialisation on the surface of this collagen membrane. Fluorescence microscopy was used to visualise cell viability on the membrane surface. These images, coupled with assays to measure cell activity, suggest that Biomend is not a suitable substrate to allow endothelialisation. In summary, this collagen membrane has suitable mechanical properties with the potential to control its degradation rate. However, since poor endothelial cell viability was observed on the membrane, it may not be suitable for use in cardiovascular tissue engineering applications.     

Extruded collagen fibres for tissue engineering applications: effect of crosslinking method on mechanical and biological properties

Reconstituted collagen fibres are promising candidates for tendon and ligament tissue regeneration. The crosslinking procedure determines the fibres’ mechanical properties, degradation rate, and cell–fibre interactions. We aimed to compare mechanical and biological properties of collagen fibres resulting from two different types of crosslinking chemistry based on 1-ethyl-3-(3-dimethyllaminopropyl)carbodiimide (EDC). Fibres were crosslinked with either EDC or with EDC and ethylene-glycol-diglycidyl-ether (EDC/EGDE). Single fibres were mechanically tested to failure and bundles of fibres were seeded with tendon fibroblasts (TFs) and cell attachment and proliferation were determined over 14 days in culture. Collagen type I and tenascin-C production were assessed by immunohistochemistry and dot-blotting. EDC chemistry resulted in fibres with average mechanical properties but the highest cell proliferation rate and matrix protein production. EDC/EGDE chemistry resulted in fibres with improved mechanical properties but with a lower biocompatibility profile. Both chemistries may provide useful structures for scaffolding regeneration of tendon and ligament tissue and will be evaluated for in vivo tendon regeneration in future experiments.     

体外模拟胶原纤维矿化的研究进展

矿化胶原纤维是天然骨的主要成分,掌握胶原纤维的生物矿化过程、原理和调控机制对于骨修复材料的设计及骨组织的再生修复发展有重要意义。综述了体外模拟胶原纤维矿化的研究进展,主要包括胶原纤维内矿化机理和非胶原蛋白对胶原生物矿化的调控作用,以期为胶原生物矿化机理的探讨及骨组织再生修复的研究提供借鉴。     

Accumulative Rolling Mg/PLLA Composite Membrane with Lamellar Heterostructure for Enhanced Bacteria Inhibition and Rapid Bone Regeneration

Developing composite materials with optimized mechanics, degradation, and bioactivity for bone regeneration has long been a crucial mission. Herein, a multifunctional Mg/Poly-l -lactic acid (Mg/PLLA) composite membrane based on the “materials plain” concept through the accumulative rolling (AR) method is proposed. Results show that at a rolling ratio of 75%, the comprehensive mechanical properties of the membrane in the rolling direction are self-reinforced significantly (elongation at break ≈53.2%, tensile strength ≈104.0 MPa, Young's modulus ≈2.13 GPa). This enhancement is attributed to the directional arrangement and increased crystallization of PLLA molecular chains, as demonstrated by SAXS and DSC results. Furthermore, the AR composite membrane presents a lamellar heterostructure, which not only avoids the accumulation of Mg microparticles (MgMPs) but also regulates the degradation rate. Through the contribution of bioactive MgMPs and their photothermal effect synergistically, the membrane effectively eliminates bacterial infection and accelerates vascularized bone regeneration both in vitro and in vivo. Notably, the membrane exhibits outstanding rat skull bone regeneration performance in only 4 weeks, surpassing most literature reports. In short, this work develops a composite membrane with a “one stone, four birds” effect, opening an efficient avenue toward high-performance orthopedic materials.     

胶原羟基磷灰石/阿拉伯树胶复合材料的制备与表征

以硝酸钙、 磷酸氢二铵、 酸溶胶原和阿拉伯树胶为原料, 采用原位合成法制备了胶原羟基磷灰石/阿拉伯树胶(ColHA/Gum A)复合材料。利用X射线衍射仪(XRD)、 扫描电镜(SEM)、 傅里叶变换红外光谱仪(FTIR) 研究与表征了复合材料的结构特征, 并研究了其力学性能、 吸水性、 酶降解性及急性细胞毒性。结果表明, 所得到的复合材料中无机相主要是低结晶度的羟基磷灰石, 这种羟基磷灰石均匀地分散于胶原---阿拉伯树胶所构成的复合体中, 形成了新的界面。力学性能、 吸水性能、 酶降解性及急性细胞毒性的研究结果表明, 该复合材料是一种颇有前途的骨组织替代材料。      

Synthetic collagen fibers coated with a synthetic peptide containing the YIGSR sequence of laminin to promote peripheral nerve regeneration in vivo

The usefulness of collagen fibers and the YIGSR sequence (Tyr-lle-Gly-Ser-Arg) of laminin for nerve regeneration were examined in vivo. Type I collagen gel (G-group), Type I collagen fibers (F-group), Type I collagen fibers coated with laminin (L-group) or the YIGSR sequence (Y-group) were packed into silicone tubes, 15 mm long, and transplanted to the sciatic nerves of Wistar rats. Empty silicone tubes were used as the control. The animals were sacrificed 8 weeks after transplantation. Bridging of the nerve was confirmed in the F-(7/12), Y-(7/10) and L-group (6/10), but no bridging was observed in any of the animals of the G- and control group. Nerve regeneration among the space of collagen fibers was observed, and it was suggested that fibroblasts infiltrated the gap in the substance of the degenerated collagen fibers were followed by Schwann cells on the basis of immunocytochemistry. The number of myelinated axons per regenerated tissue in the tube (density), and total area of myelinated axons per measured regenerated tissue in the tube (% axon area) in each the L- and Y-group were significantly higher than that in the F-group (P < 0.05). These results suggest the possibility of obtaining adequate nerve regeneration with new artificial materials only. © 1999 Kluwer Academic Publishers     

Quantifying the 3D macrostructure of tissue scaffolds

The need to shift from tissue replacement to tissue regeneration has led to the development of tissue engineering and in situ tissue regeneration. Both of these strategies often employ the use of scaffolds--templates that allow cells to attach and then guide the new tissue growth. There are many design criteria for an ideal scaffold. These criteria vary depending on the tissue type and location in the body. In any application of a scaffold it is vital to be able to characterise the scaffold before it goes into in vitro testing. In vitro testing allows the cell response to be investigated before its in vivo performance is assessed. A full characterisation of events in vitro and in vivo, in three dimensions (3D), is necessary if a scaffold's performance and effectiveness is to be fully quantified. This paper focuses on porous scaffolds for bone regeneration, suggests appropriate design criteria for a bone regenerating scaffold and then reviews techniques for obtaining the vitally important quantification of its pore structure. The techniques discussed will include newly developed methods of quantifying X-ray microtomography (microCT) images in 3D and for predicting the scaffolds mechanical properties and the likely paths of fluid flow (and hence potential cell migration). The complications in investigating scaffold performance in vitro are then discussed. Finally, the use of microCT for imaging scaffolds for in vivo tests is reviewed.     

Tenocyte proliferation on collagen scaffolds protects against degradation and improves scaffold properties

Tissue engineering scaffolds encourage cell proliferation whilst degrading to facilitate tissue regeneration. Their mechanical properties therefore change, decreasing due to scaffold degradation and increasing due to extracellular matrix deposition. This work compares the changing properties of collagen scaffolds incubated in culture medium, with and without human tenocytes, in order to investigate the relationship between degradation and tenocyte proliferation. The material properties of scaffolds are compared over 26 days using mechanical testing, differential scanning calorimetry, infra-red spectroscopy, and histology and biochemical assays. For medium-only scaffolds, the mechanical properties decrease rapidly, while culture medium sulfhydryl content increases significantly, with no significant changes in the denaturation temperature of scaffold collagen content. Conversely, the mechanical properties and collagen content of tenocyte-seeded scaffolds increase significantly while culture medium sulfhydryl content decreases and denaturation temperature remains the same. These results indicate that tenocytes proliferation both reduces the degradation of collagen scaffolds incubated in culture medium and produces scaffolds with improved properties.     

Tailoring material properties of a nanofibrous extracellular matrix derived hydrogel

In the native tissue, the interaction between cells and the extracellular matrix (ECM) is essential for cell migration, proliferation, differentiation, mechanical stability, and signaling. It has been shown that decellularized ECMs can be processed into injectable formulations, thereby allowing for minimally invasive delivery. Upon injection and increase in temperature, these materials self-assemble into porous gels forming a complex network of fibers with nanoscale structure. In this study we aimed to examine and tailor the material properties of a self-assembling ECM hydrogel derived from porcine myocardial tissue, which was developed as a tissue specific injectable scaffold for cardiac tissue engineering. The impact of gelation parameters on ECM hydrogels has not previously been explored. We examined how modulating pH, temperature, ionic strength, and concentration affected the nanoscale architecture, mechanical properties, and gelation kinetics. These material characteristics were assessed using scanning electron microscopy, rheometry, and spectrophotometry, respectively. Since the main component of the myocardial matrix is collagen, many similarities between the ECM hydrogel and collagen gels were observed in terms of the nanofibrous structure and modulation of properties by altering ionic strength. However, variation from collagen gels was noted for the gelation temperature along with varied times and rates of gelation. These discrepancies when compared to collagen are likely due to the presence of other ECM components in the decellularized ECM based hydrogel. These results demonstrate how the material properties of ECM hydrogels could be tailored for future in vitro and in vivo applications.