Preparation and characterization of a novel COL/BC composite for potential tissue engineering scaffolds

This paper describes the biosynthesis of a novel collagen-bacterial cellulose (COL/BC) composite by adding collagen to the culture medium of Acetobacter xylinum. The morphology of COL/BC composite was observed by SEM and TEM and compared with pristine BC. The composite was further characterized by FTIR and XRD. It is found that the structure of BC network changes when collagen is present in the nutrient medium. Further work is underway to gain insights into the mechanisms governing the experimental phenomena.     

Effects of osteoblast-like cell seeding on the mechanical properties of porous composite scaffolds

In tissue engineering technology, polymer–ceramics or polymer–polymer composites have been considered as advanced scaffolds having mechanical stability, biocompatibility, cell proliferation, and easy processability. However, the relationship between the mechanical properties and the cell proliferation behavior of such composite scaffolds has not been clarified yet. In this study, two types of composite scaffolds, poly(ethylene terephthalate) (PET) fiber/collagen and β-tricalcium phosphate (β-TCP)/gelatin scaffolds, were investigated. MC3T3-E1 cells were cultured in these scaffolds under appropriate conditions. Compression tests were then periodically conducted to evaluate the compressive elastic modulus. It was found that the modulus of the scaffolds containing cells increased with the cell culture period. It is noted that the modulus of the β-TCP/gelatin with cells was approximately seven times larger than that of the PET fiber/collagen with cells.     

制备条件对聚乳酸多孔支架微观结构的影响

采用粒子沥滤结合气体发泡的方法制备聚乳酸(PLA)多孔支架,探讨浓度、发泡剂、温度等条件对支架宏观形貌和微观性质的影响,研究各个因素之间的相互关系,研究其表面形貌与微观结构之间的关系。研究发现对于不同尺寸制孔剂制备的支架,通过调节浓度、温度等条件,可以得到相似的薄层多孔的表面形貌,其对应的微观结构和性能(力学、孔隙率、贯通性)较好。     

Effect of graphene oxide nanosheets on the physico-mechanical properties of chitosan/bacterial cellulose nanofibrous composites

In this work, novel chitosan/bacterial cellulose (CS/BC) nanofibrous composites reinforced with graphene oxide (GO) nanosheets are introduced. As cell attachment and permeability of nanofibrous membranes highly depend on their fiber diameter, the working window for successful electrospinning to attain sound nanofibrous composites with a minimum fiber diameter was determined by using the response surface methodology. It is shown that the addition of GO nanosheets to CS/BC significantly reduces the average size of the polymeric fibers. Their mechanical properties are also influenced and can be tailored by the concentration of GO. Fourier transform infrared spectroscopy reveals hydrogen bonding between the GO nanosheets and the polymer matrix. A decrease in the hydrophilicity of the electrospun nanofibers and their water vapor permeability with the addition of GO are also reported. The prepared nanofibrous composites are potentially suitable candidates for biomedical applications such as skin tissue engineering and wound dressing.     

Immobilization of gelatin on bacterial cellulose nanofibers surface via crosslinking technique

Bacterial cellulose is considered to be a potential material for tissue engineering. However, the absence of enough activity restricts its practical application as tissue engineering scaffold. This paper describes the synthesis of a novel bacterial cellulose/gelatin composite via crosslinking by procyanidin (PA). The morphology of the bacterial cellulose/gelatin composite was observed by field emission scanning electron microscopy (FE-SEM) and transmission electronic microscope (TEM). The composites were further characterized by fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It was found that the 0.25 wt.% Gel solution was the appropriate concentration for the BC/Gel composite. Furthermore, the proliferation, infiltration and adhesion of NIH3T3 cells on the BC/Gel-025 composite were evaluated. The results showed that the composite had better bioactivity than pure bacterial cellulose, and the composite supported cell growth.     

Dehydration of bacterial cellulose and the water content effects on its viscoelastic and electrochemical properties

Bacterial cellulose (BC) has interesting properties including high crystallinity, tensile strength, degree of polymerisation, water holding capacity (98%) and an overall attractive 3D nanofibrillar structure. The mechanical and electrochemical properties can be tailored upon incomplete BC dehydration. Under different water contents (100, 80 and 50%), the rheology and electrochemistry of BC were evaluated, showing a progressive stiffening and increasing resistance with lower capacitance after partial dehydration. BC water loss was mathematically modelled for predicting its water content and for understanding the structural changes of post-dried BC. The dehydration of the samples was determined via water evaporation at 37 °C for different diameters and thicknesses. The gradual water evaporation observed was well-described by the model proposed (R² up to 0.99). The mathematical model for BC water loss may allow the optimisation of these properties for an intended application and may be extendable for other conditions and purposes.     

Green and up-scalable fabrication of superior anodes for lithium storage based on biomass bacterial cellulose

An extremely facile and up-scalable approach has been proposed to disperse ferric grains onto bacterial cellulose (BC) nanofibers. The BC-induced hydrolytic deposition can be performed at room temperature without using any organic solvents, toxic reagents, or complicated apparatuses, enabling a green pathway in realizing industrialization. After carbonization, the randomly oriented carbonized BC (CBC) nanofibers transmit the electrons throughout the electrode, while the inherited reticular morphology boosts the thorough penetration of electrolyte. Moreover, the sufficient space created by interconnected CBC nanofibers is able to accommodate the volume change of the nanosized Fe₃O₄ active materials during repeated Li⁺ intercalation and deintercalation. As a result, the as-prepared Fe₃O₄/CBC composites deliver the superior electrochemical performance as the free-standing anodes in Li-ion batteries (LIBs), including the impressive reversible capacity of 702 mAh g^?1 after 400 cycles at 400 mA g^?1, decent rate capability with capacity of 437 mAh g^?1 at 2000 mA g^?1, and a long cycling lifespan up to 1000 cycles at 800 mA g^?1. This work provides a scalable and green approach to fabricate high-performance LIBs anode with the natural sustainable biomass.     

甲醇、戊二醛交联剂对丝素蛋白/明胶多孔支架的性能影响

为了对比甲醇、戊二醛两种交联剂对丝素蛋白/明胶复合多孔支架的性能影响,采用冷冻干燥法等比例制备该支架,分两组分别用甲醇和戊二醛进行交联。通过观察支架的微观形貌,测量支架的孔隙率、吸水率、溶胀率,测试热稳定性及力学性能,比较经两种交联剂处理后支架结构和性能的变化。结果表明,经戊二醛交联后的支架孔隙分布更加规则、均匀,孔隙率、吸水率、溶胀率更高,力学性能更强。采用戊二醛交联丝素蛋白/明胶复合多孔支架,能够使支架性能更加优良。     

A comparison study of different physical treatments on cartilage matrix derived porous scaffolds for tissue engineering applications

Native cartilage matrix derived (CMD) scaffolds from various animal and human sources have drawn attention in cartilage tissue engineering due to the demonstrable presence of bioactive components. Different chemical and physical treatments have been employed to enhance the micro-architecture of CMD scaffolds. In this study we have assessed the typical effects of physical cross-linking methods, namely ultraviolet (UV) light, dehydrothermal (DHT) treatment, and combinations of them on bovine articular CMD porous scaffolds with three different matrix concentrations (5%, 15% and 30%) to assess the relative strengths of each treatment. Our findings suggest that UV and UV–DHT treatments on 15% CMD scaffolds can yield architecturally optimal scaffolds for cartilage tissue engineering.     

浆料粘度对纳米羟基磷灰石/聚酰胺66复合支架孔结构与力学性能的影响

浆料粘度是热诱导相分离法制备支架材料的关键因素,采用不同粘度的纳米羟基磷灰石/聚酰胺66(n-HA/PA66)复合浆料制备了相应的n-HA/PA66多孔支架,并对不同粘度浆料制备支架材料的泡孔结构和力学性能等进行了对比研究。结果表明,浆料粘度对n-HA/PA66复合多孔支架的孔径、孔径分布、孔隙率、开孔率、力学强度等性能有显著的影响。随着浆料粘度的增大,制备支架的孔径、孔隙率、开孔率逐渐减小,而力学强度却逐渐增大。当浆料粘度为330Pa.s时,制备出的n-HA/PA66复合多孔支架综合性能最好,其孔径主要分布在200～500μm,平均孔径(324±67.1)μm,孔隙率为(75±1.6)%,开孔率为(59±2.5)%,抗压强度为(2.12±0.90)MPa,能够较好地满足骨组织工程支架材料对孔径、孔隙率和力学性能的要求。     

Coating of collagen on a poly(l-lactic acid) sponge surface for tissue engineering

Porous scaffolds play important roles in tissue engineering. Biodegradable synthetic polymers, such as poly(l-lactic acid) (PLLA), frequently are used in the preparation of porous scaffolds. Pretreating the surface of a PLLA porous scaffold is required to increase its wettability for smooth cell seeding due to the hydrophobic property of the scaffold's surface. In this study, a simple coating method was used to modify the surface of the PLLA sponges. The coating method included three steps: filling the PLLA sponge pores with collagen aqueous solution, centrifuging to remove excess collagen, and, finally, freeze-drying. Compared with the uncoated PLLA sponge, the collagen-coated PLLA sponge demonstrated both improved wettability and high water absorption. Cells were smoothly seeded in the collagen-coated PLLA sponges by dropping a cell suspension solution onto the sponges. Cells adhered to the collagen-coated sponge and were distributed homogeneously throughout the collagen-coated PLLA sponge.     

Effect of coupling treatment on mechanical properties of bacterial cellulose nanofibre-reinforced UPR ecocomposites

Bacterial cellulose nanofiber-reinforced unsaturated polyester resin composites (BC/UPR) were prepared using vinyl-triethoxy silane coupling modified BC fibres by the method of resin transfer molding (RTM) and subjected to mechanical tests in order to study the effect of surface treatment on the properties of composites. The results show that coupling treatment did not change the morphology of BC nanofibers, while it changed the chemical states of the BC fiber's surface. The XPS result indicates that chemical bonding was formed at the interface between UPR matrix and BC fibers after surface treatment, which enhanced the mechanical properties of composites. After treatment, tensile strength, flexure strength, shear strength and tensile modulus of the composites with a fiber volume fraction (V_f) of 10% were increased by 117.7%, 38.4%, 38.7% and 27.6%, respectively.     

3D打印纯钛骨支架表面掺银介孔生物活性玻璃涂层的性能研究EI北大核心CSCD

术后感染是临床上常见且最具挑战性的问题之一,开发新型抗菌涂层是解决该问题的有效策略,具有重要的科学及社会意义。在3D打印多孔钛骨支架表面制备了具有抗菌功能的生物活性涂层,研究发现,银(Ag)以单质的形式存在于介孔生物玻璃(MBG)涂层之中,随着Ag含量的增加(0%,0.5%,1%,1.5%,摩尔分数),介孔涂层的比表面积从377.6 m^(2)/g下降到363.35 m^(2)/g。体外矿化结果表明,随着Ag含量的增加,磷灰石诱导能力略微下降。抗菌实验表明,银的添加显著提高了支架的抗菌性能。添加少量的银(0.5%)即可达到100%的抗菌率。支架与MC3T3-E1细胞共培养的实验结果表明,Ag掺杂的MBG涂层具有良好细胞相容性,且添加少量银能促进MC3T3-E1细胞增殖。使用一种简单的浸渍提拉法将掺Ag的MBG涂层应用于具有复杂的多孔结构3D打印钛支架上,使得支架的矿化性能、杀菌性能以及细胞相容性显著提高。本研究为进一步开发多功能骨植入支架提供了新思路。     

The influence of fiber thickness, wall thickness and gap distance on the spiral nanofibrous scaffolds for bone tissue engineering

We have developed a 3D nanofibrous spiral scaffold for bone tissue engineering which has shown enhanced cell attachment, proliferation and differentiation compared to traditional cylindrical scaffolds due to the spiral structures and the nanofiber incorporation. Some important parameters of these spiral scaffolds including gap distance, wall thickness and especially fiber thickness are crucial to the performance of the spiral structured scaffolds. In this study, we investigated the fiber thickness, gap distance and wall thickness of the spiral structure on the behavior of osteoblast cells. The human osteoblast cells are seeded on spiral structured scaffolds with various fiber thickness, gap distance and wall thickness and cell attachment, proliferation, differentiation and mineralized matrix deposition on the scaffolds are evaluated. It was found that increasing the thickness of nanofiber layer not only limited the cell infiltration into the scaffolds, but also restrained the osteoblastic cell phenotype development. Moreover, the geometric effect studies indicated that scaffolds with the thinner wall and gap distance 0.2 mm show the best bioactivity for osteoblasts.     

Effects of chondrogenic and osteogenic regulatory factors on composite constructs grown using human mesenchymal stem cells, silk scaffolds and bioreactors.

Human mesenchymal stem cells (hMSCs) isolated from bone marrow aspirates were cultured on silk scaffolds in rotating bioreactors for three weeks with either chondrogenic or osteogenic medium supplements to engineer cartilage- or bone-like tissue constructs. Osteochondral composites formed from these cartilage and bone constructs were cultured for an additional three weeks in culture medium that was supplemented with chondrogenic factors, supplemented with osteogenic factors or unsupplemented. Progression of cartilage and bone formation and the integration between the two regions were assessed by medical imaging (magnetic resonance imaging and micro-computerized tomography imaging), and by biochemical, histological and mechanical assays. During composite culture (three to six weeks), bone-like tissue formation progressed in all three media to a markedly larger extent than cartilage-like tissue formation. The integration of the constructs was most enhanced in composites cultured in chondrogenic medium. The results suggest that tissue composites with well-mineralized regions and substantially less developed cartilage regions can be generated in vitro by culturing hMSCs on silk scaffolds in bioreactors, that hMSCs have markedly higher capacity for producing engineered bone than engineered cartilage, and that chondrogenic factors play major roles at early stages of bone formation by hMSCs and in the integration of the two tissue constructs into a tissue composite.     

A study on the in vitro degradation of poly(L-lactide)/chitosan microspheres scaffolds

Recent research shows that the addition of chitosan microspheres (CMs) to poly(L-lactide) (PLLA) can result in a composite scaffold material with improved biocompatibility and mechanical properties for tissue engineering applications. However, research regarding the influence of CMs on scaffold degradation is absent in the literature. This paper presents a study on the in vitro degradation of scaffolds made from PLLA with CMs. In this study, the PLLA/CMs scaffolds with a 25% ratio of CMs to PLLA were immersed in phosphate-buffered saline (PBS) solution at 37°C for 8 weeks. The in vitro degradation of the scaffolds was investigated using micro-computed tomography (μCT), weight loss analysis, Raman spectroscopy, and differential scanning calorimetry (DSC). Microstructure changes during degradation were monitored using μCT. The μCT results were consistent with the results obtained from Raman spectra and DSC analysis, which reflected that adding CMs into PLLA can decrease the degradation rate compared with pure PLLA scaffolds. The results suggest that PLLA/CMs scaffold degradation can be regulated and controlled to meet requirements imposed a given tissue engineering application.     

Effect of fiber diameter on the deformation behavior of self-assembled carbon nanotube reinforced electrospun Polyamide 6,6 fibers

High precision electrospinning technique was used to obtain self-assembled carbon nano-tube (CNT) reinforced polyamide (PA) 6,6 fibers. The reinforcement factors were critically evaluated with respect to the effects of fiber diameter and inclusion of CNTs. The average fiber diameter ranged from 240 to 1400 nm and the CNT contents were 0, 1 and 2.5 wt%. A sharp increase in modulus and strength of the fibers was demonstrated when the size of the fiber was decreased below ∼500 nm, which could be attributed to ordered arrangement of crystals and the spatial confinement effect of the fibers. Also, investigation of the deformation behavior of fibers as a function of CNT content revealed that tensile fiber modulus and strength improved significantly with increase of CNTs. Addition of CNTs restricted the segmental motion of polymer chains and provided the confinement effect to the neighboring molecules.     

羧甲基纤维素对铜版纸涂料流变行为的影响

通过在铜版纸面涂涂料中增加羧甲基纤维素用量来改善涂料流变性和保水性,对涂料的稳态剪切流变行为进行了研究。结果表明,随着剪切速率的增加,涂料表现出剪切稀化,呈现假塑性流体特性;另外,在同一剪切速率下,增加羧甲基纤维素加入量,涂料的表观粘度变大。采用两参数的Bingham,三参数的Herschel-Bulkley及四参数的Carreau方程对涂料的流变曲线进行了数学拟合。结果表明,Carreau方程能够准确地描述涂料的流变曲线,Herschel-Bulkley方程次之,而Bingham方程拟合效果较差。根据Carreau方程拟合结果,羧甲基纤维素加入量为0.5%,0.8%和1.0%时,涂料的零剪切粘度分别为100.8,155.7,161.8 Pa·s,极限粘度相应为0.03170,0.03934和0.05764 Pa·s,这说明羧甲基纤维素对铜版纸涂料具有明显的增稠作用。另外,涂料流动特性指数均小于1.0,呈现明显的假塑性流体特性,这与剪切稀化的实验流变结果吻合。