Preparation and characterization of three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold for tissue engineering

We fabricated a three-dimensional nanostructured macroporous bacterial cellulose scaffold (3D BC scaffold) and a three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold (3D BC/A). Results of scanning electron microscopy (SEM) and mercury intrusion porosimeter showed that both the 3D BC and the 3D BC/A have interconnected macropores characterized by nanofibrous pore walls (The diameter of the dominant pores was about 100 μm and ranges from <1 μm to >1,000 μm). 3D BC/A also has high surface area (80 ± 5 m²/g) and sufficient porosity (88.5 ± 0.4%) compare with 3D BC (surface area: 92.81 ± 2.02 m²/g; porosity 90.42 ± 0.24%). 3D BC/A do support C5.18 cell and hBMSC attachment, proliferation evaluated with SEM, confocal microscopy and cell proliferation assay. Furthermore, 3D/ABC has enhanced mechanical property (ultimate compressive strength: 26.26 ± 4.6 kPa, Young’s modulus: 39.26 ± 5.72 kPa)) than that 3D/BC has (ultimate compressive strength: 7.04 ± 2.34 kPa, Young’s modulus: 10.76 ± 3.52 kPa). Overall, the 3D BC/A scaffold had more potential than 3D BC scaffold for using as a scaffold for tissue engineering and tissue repair applications.     

纤维素氨基甲酸酯法制备纤维素海绵

海绵因具有蓬松度好、质地柔软、吸水性好等优点而得以广泛应用。但目前市面上的聚氨酯海绵,不仅原料紧缺,制备过程有污染物产生,而且废弃后难降解,会产生二次污染。为开发可自然降解的纤维素海绵无污染制备工艺,研究了采用纤维素氨基甲酸酯法制备纤维素海绵的工艺。结果表明：由纤维素氨基甲酸酯的氢氧化钠溶液捏合而成的海绵混合体经蒸煮,纤维素再生,成孔剂溶于水中而留下空隙,所得纤维素海绵孔径均一,表面光滑平整,具有较好的柔韧性和黏弹性,完全具有普通聚氨酯海绵的基本特征。     

Preparation and characterization of degradable oxidized bacterial cellulose reacted with nitrogen dioxide

Bacterial cellulose (BC) is regarded as one of the most attractive and promising biomaterials in medical applications owing to its high purity and mechanical properties and excellent biocompatibility. In this study, a new kind of degradable oxidized bacterial cellulose (OBC) was prepared by oxidizing BC in the presence of nitrogen dioxide (NO₂), which could be used as a scaffold for tissue engineering and tissue regeneration. The chemical structures, micromorphology, and in vitro degradability of OBC were characterized. The results demonstrated that the oxidation reaction was controllable for tailoring the degree of degradation of BC. After oxidation, the degradation of BC was accelerated, depending on the oxidation time. In the case of oxidation for 12 days, the mass loss rate of OBC increased sharply, up to 45% after being immersed in phosphate buffered saline (PBS) for 60 days, compared with only 10% for original BC in the same condition. The oxidation did not affect the crystal structure of BC, however, changed the morphology of its network. The original dense microfibril network of BC could be gradually degraded and disappeared within a desirable period of time in vitro through controlling the degree of the selective oxidation.     

Preparation and characterization of porous scaffold composite films by blending chitosan and gelatin solutions for skin tissue engineering

Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. In the present investigation blends of chitosan and gelatin with various compositions were produced as candidate materials for biomedical applications. Fourier transform infrared spectral analysis showed good compatibility between these two biodegradable polymers. The composite films showed improved tensile properties, highly porous structure, antimicrobial activities, low water dissolution, low water uptake and high buffer uptake compared to pure chitosan or gelatin films. These enhanced properties could be explained by the introduction of free ? OH, ? NH₂ and ? NHOCOCH₃ groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (? NH³⁺) of the chitosan and the carboxylate ions (? COO^?) of the gelatin. Scanning electron microscopy images of the blend composite films showed homogeneous and smooth surfaces which indicate good miscibility between gelatin and chitosan. The leafy morphologies of the scaffolds indicate a large and homogeneous porous structure, which would cause increased ion diffusion into the gel that could lead to an increase in stability in aqueous solution, buffer and temperature compared to the gelatin/chitosan system. In vivo testing was done in a Wistar rat (Rattus norvegicus) model and the healing efficiencies of the scaffolds containing various compositions of chitosan were measured. The healing efficiencies in Wistar rat of composites with gelatin to chitosan ratios of 10:3 and 10:4 were compared with that of a commercially available scaffold (Eco‐plast). It was observed that, after 5 days of application, the scaffold with a gelatin to chitosan ratio of 10:3 showed 100% healing in the Wistar rat; however, the commercial Eco‐plast showed only a little above 40% healing of the dissected rat wound. Copyright © 2012 Society of Chemical Industry     

Preparation and characterization of porous,biomorphic SiC ceramic with hybrid pore structure

Bio-carbon template (charcoal) was prepared by carbonizing pine wood at 1200 °C under vacuum, and was impregnated with phenolic resin/SiO₂ sol mixture by vacuum/pressure processing. Porous SiC ceramics with hybrid pore structure, a combination of tubular pores and network SiC struts in the tubular pores, were fabricated via sol–gel conversion, carbonization and carbothermal reduction reaction at elevated temperatures in Ar atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) were employed to characterize the phase identification and microstructural changes during the C/SiO₂ composites-to-porous SiC ceramic conversion. Experimental results show that the density of C/SiO₂ composite increases with the number of impregnation procedure, and increases from 0.32 g cm⁻³ of pine-derived charcoal to 1.5 g cm⁻³ of C/SiO₂ composite after the sixth impregnation. The conversion degree of charcoal to porous SiC ceramic increases as reaction time is lengthened. The resulting SiC ceramic consists of β-SiC with a small amount of α-SiC. The conversion from pine charcoal to porous SiC ceramic with hybrid pore structure improves bending strength from 16.4 to 42.2 MPa, and decreases porosity from 76.1% to 48.3%.     

改性二氧化硅-乙基纤维素复合膜的制备及性能

乙基纤维素(EC)与改性二氧化硅(m-SiO_2)醇溶胶通过共混方式制备了复合膜EC-Six(x=1、2、3、4)。通过SEM、FTIR对复合膜的微观结构进行了表征,对复合膜的水接触角、机械性能和水蒸气透过系数(WVP)进行了测试。结果表明:当m-SiO_2醇溶胶与EC醇溶液体积比为3︰2时,纳米粒子均匀地分布于复合膜EC-Si_3中,并与EC形成均一的多孔状结构。该复合膜具有很好的表面疏水性,膜表面水静态接触角(WCA)可达145°。复合膜的抗张强度(TS)为10.452 MPa,断裂伸长率(EB)为5.405%,其WVP值为0.549 g·mm/(m~2·h·kPa)。抗菌剂的释放性结果表明,EC-Si_3膜中姜黄素在正己烷中的释放率高于在蒸馏水中的释放率。     

Preparation and characterization of nanohydroxyapatite strengthening nanofibrous poly(L‐lactide) scaffold for bone tissue engineering

A biomimetic nanofibrous poly(L ‐lactide) scaffold strengthened by nanohydroxyapatite particles was fabricated via a thermally induced phase separation technique. Scanning electron microscopy results showed that nanohydroxyapatite particles uniformly dispersed in the nanofibrous poly(L ‐lactide) scaffold (50–500 nm in fiber diameter) with slight aggregation at a high nHA content, but showed no influence on the interconnected macroporous and nanofibrous structure of the scaffold. The nanofibrous poly(L ‐lactide) scaffold presented a specific surface area of 34.06 m² g^?1, which was much higher than that of 2.79 m² g^?1 for the poly(L ‐lactide) scaffold with platelet structure. Moreover, the specific surface area of the nanofibrous scaffold was further enhanced by incorporating nanohydroxyapatite particles. With increasing the nanohydroxyapatite content, the compressive modulus and amount of bovine serum albumin adsorbed on the surface of the nanofibrous composite scaffold were markedly improved, as opposed to the decreased crystallinity. In comparison to poly(L ‐lactide) scaffold, both the nanofibrous poly(L ‐lactide) and poly(L ‐lactide)/nanohydroxyapatite scaffolds exhibited a faster degradation rate for their much larger specific surface area. The culture of bone mesenchymal stem cell indicated that the composite nanofibrous poly(L ‐lactide) scaffold with 50 wt % nanohydroxyapatite showed the highest cells viability among various poly(L ‐lactide)‐based scaffolds. The strengthened biomimetic nanofibrous poly(L ‐lactide)/nanohydroxyapatite composite scaffold will be a potential candidate for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Natural origin hydroxyapatite scaffold as potential bone tissue engineering substitute

Fish scales derived natural hydroxyapatite (FS-HAp) scaffolds were prepared through solvent casting technique, which could mimic the structure of cortical and cancellous bone tissues of body system. The hydroxyapatite (HAp) biomaterial was synthesized by thermal decomposition of chemically treated fish scales. Fabricated scaffolds were characterized through morphological analysis, volumetric shrinkage, mechanical tests, and in vitro, in vivo biological studies. The projected scaffolds successfully mimic the cancellous/cortical bone system in terms of structure, porosity, mechanical strength, and exhibit excellent bioactive behavior. The FS-HAp scaffolds manifest good mechanical behaviors with Vickers Hardness (HV) of ~0.78 GPa, 0.52 GPa compressive stress, 190 MPa tensile stress and ~35% porosity on sintering at 1200 °C. In vitro and in vivo studies suggest these nontoxic HAp scaffolds graft with osteoconductive support, facilitating new cell growth on the developed scaffold surface. The graded grafts have a great potential for application as traumatized tissue augmentation substitute, and ideal for load-bearing bone applications.     

Preparation and characterization of quaternary bacterial cellulose composites for antimicrobial oil-absorbing materials

The treatment of various types of oily wastewater is paramount for environmental protection. Bacterial cellulose (BC) stands out as a highly promising material for oil/water separation, owing to its exceptional mechanical properties and three-dimensional porous structures. However, excessive hydroxyl groups on BC make it highly hydrophilic, reducing oil absorption and promoting bacterial growth, affecting its stability. To address these challenges, we developed a straightforward in situ polymerization method for the preparation of BC-DMC composites. The innovation lies in the concurrent enhancement of BC's hydrophobicity and antimicrobial properties only through the addition of 2-(Methacryloyloxy)ethyltrimethylammonium chloride (DMC), considerably simplifying the synthesis of materials possessing oil-absorbing and antimicrobial properties. Morphological and structural characterization results confirmed the successful combination of DMC onto BC while maintaining its porous structure. After process parameter optimization, the BC-DMC composites exhibited a remarkable increase in contact angle (117.7° compared with pure BC's 19.5°). It also demonstrated excellent oil absorption performance, with maximum capacities exceeding 30 g/g for different oils, maintaining values above 20 g/g even after eight cycles. In addition, the BC-DMC composites exhibited strong antibacterial activity, with rates of 82.4% against Escherichia coli and 97.5% against Staphylococcus aureus. The antibacterial mechanism of the BC-DMC composites was also discussed. Our novel BC-DMC composites provides excellent oil absorption and antibacterial properties, making it highly applicable in the field of oily wastewater treatment and serving as a valuable reference for other researchers.     

高活性木炭的制备与孔结构表征

介绍了二步炭化法制备高活性木炭工艺。研究了保温时间和温度对活性木炭吸附性能的影响,并通过ESEM和HRTEM等对其孔结构进行表征。结果表明:二步炭化法可很好地提高木炭的性能,可制得孔径主要集中在0.6～2.0nm的活性木炭;随着保温时间延长,活性木炭的比表面积、孔容积均增大。在较佳实验条件下,所制高活性木炭的比表面积、总孔容积和微孔容积分别为1288.4m2/g、0.784mL/g、0.407mL/g。     

Exceptional biocompatibility of 3D fibrous scaffold for cardiac tissue engineering fabricated from biodegradable polyurethane blended with cellulose

The auhtors report 3D biomimetic scaffolds using polymer blend of polyurethane and cellulose for cardiac tissue engineering. The biocompatible and biodegradable polyurethane is designed, synthesized and characterized. By incorporating 10 wt% of naturally ordered cellulose into the polyurethane and electrospinning them into 3D scaffold, the scaffold exhibits good biocompatibility and mechanical property to support and accommodate constant cycles of contraction/expansion of cardiac tissue. The biocompatibility is further improved using scaffold fabricated from aligned fibers due to synergistic effects between cells and ordered macromolecules. The anisotropic structured scaffold is mimicked the extracellular matrix and has therapeutic potential in reconstruction of damaged myocardium.     

Gold microspheres with hierarchical structure/conducting polymer composite film: Preparation, characterization and application as catalyst

Monodisperse gold microspheres with novel hierarchical structure and their composite integrated with a conducting film obtained from a new conducting copolymer, poly(acrylonitrile-co-vinyl acetate) -graft- poly(3,4-ethylenedioxythiophene), have been successfully prepared in one step via the in-situ reduction of AuCl₄^- on the conducting film surface. The morphology and structure of the as-prepared composite film are characterized, and its catalytic effect on reduction of p-nitrophenol is investigated. By controlling the concentration of HAuCl₄ and the conductivity (or PEDOT content) of P(AN-co-VA)-g-PEDOT copolymer film, the amount and the size of gold microspheres can be effectively adjusted. It is suggested that the side poly(3,4-ethylenedioxythiophene) chains of the conducting copolymer play both reducing and structure-directing roles during the formation of Au microspheres with hierarchical structure.     

Inorganic calcium filled bacterial cellulose based hydrogel scaffold: novel biomaterial for bone tissue regeneration

Abstract

This work emphasizes the structural, physio-chemical characterization and cell biological efficiency analysis of novel inorganic calcium (only calcium phosphate and in combination of calcium phosphate & CaCO₃) filled bacterial cellulose (BC) based hydrogel scaffolds. FTIR and TG analysis indicates the presence of BC and inorganic calcium within the hydrogel scaffolds. SEM establishes the porous structures (50–200 µm). Swelling study indicates significant swelling ability in both calcium phosphate filled and calcium phosphate & CaCO₃ filled hydrogel scaffolds. Compressive strength (0.24–0.60?MPa) of the calcium filled hydrogel scaffolds are similar like trabecular bone. Significant cell viability (Lep-3) was further noticed until 72,120 and 168?h.     

Preparation of biomimetic three-dimensional gelatin/montmorillonite–chitosan scaffold for tissue engineering

A novel gelatin/montmorillonite–chitosan (Gel/MMT–CS) nanocomposite scaffold was prepared via the intercalation process and the freeze-drying technique, using the ice particulates as the porogen materials. Properties including pore structure, water adsorption content, in vitro degradation and tensile strength were investigated. It was demonstrated that the introduced intercalation structure endowed the Gel/MMT–CS scaffold with good mechanical properties and a controllable degradation rate. Scanning of the electron microscope images revealed that the scaffold obtained was highly porous and suitable for the implanted cells to adhere and grow. The mitochondrial activity assay provided good evidences of cells viability on the Gel/MMT–CS membranes, giving an indication of possible application as a matrix for tissue engineering.     

细菌纤维素膜的合成及表征

以海南椰子水为主要培养体系,实验室自行筛选的木醋杆菌(Acetobacter xylinum)为菌种,采用静态培养方法制备了细菌纤维素（BC）。对该BC和商业BC的结构和性能进行了测试对比,观察BC的微结构特点。结果表明: 制备的BC和商业BC在结构和一些性能方面是相似的,都是无色透明膜,呈三维网状结构和孔洞结构,具有良好的纳米纤维网络特征, 具有良好的吸湿性和极佳的持水能力,本实验制备的BC生产成本低,可根据需要大量制备,在生物医学领域具有良好的、广泛的应用前景。     

Synthesis of unsaturated polyphosphoester as a potential injectable tissue engineering scaffold materials

Polyphosphoester is a kind of biodegradable polymer with excellent biocompatibility and have been used in drug delivery, tissue engineering, and other bioapplications. A novel unsaturated polyphosphoester (UPPE) based on bis(1,2‐propylene glycol) fumarate (BPGF) and ethyl dichlorophosphate was synthesized by polycondensation reaction, and crosslinkable double bonds was introduced into the resulting polymer through the fumarate groups. NMR results indicate that there are three possible bonding models in polyphosphoester because of three isomers of BPGF. The GPC results express that increase in polymerization time leads to high molecular weight of polyphosphester and narrow distribution of molecular weight. After 18 h of polymerization reaction, the molecular weight reached to 5956 g mol^?1 and the polydispersity index was 1.12. The UPPE was soluble in N‐vinyl pyrrolidone and easily crosslinked by free‐radical polymerization. At the constant temperature (37°C), the maximum temperature due to heat release during crosslinking reaction varied from 41.1°C to 82.30°C and the setting time was between 1.95 and 10.28 min, according to different formulas. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3095–3101, 2006     

Preparation and characterization of TiO2 anode film with hierarchical structure by photo-induced polymerization method

The TiO₂ photoanode film with hierarchical structure which consists of porous structure and spinodal phase separation structure with macroporous continuous skeleton was fabricated by photopolymerization induced phase separation method. The influence of the different photomonomers, different coating layers and different heat treatment temperatures on the structure and photoelectric property of TiO₂ film has been investigated and the possible mechanism was proposed. The performances of the TiO₂ anode film were characterized by scanning electron microscopy, X-ray diffraction and I–V test. The results indicated that, in contrast with the TiO₂ anode film with single structure, the as-prepared TiO₂ anode film with hierarchical structure showed higher photoelectric conversion efficiency which is 0.272 %. Even though the photoelectric conversion efficiency is not very high, the strategy presented in the paper should be valuable and it still provides the ideas for the new structure and new preparation method on photoanode film of dye-sensitized solar cells, meanwhile, it lays the foundation for designing the solar cells with high photoelectric conversion efficiency.     

Synthesis,characterization and in-vitro behavior of natural chitosan-hydroxyapatite-diopside nanocomposite scaffold for bone tissue engineering

Composite materials based on a combination of biodegradable polymers and bioactive ceramics, including chitosan and hydroxyapatite are discussed as suitable materials for scaffold fabrication. Diopside is a member of bioactive silicates; it is a good choice for hard tissue engineering because of its biocompatibility with host tissue and high mechanical strength. Chitosan and hydroxyapatite were extracted from shrimp shell and bovine bone, respectively and diopside nanoparticles were prepared by the sol-gel method. The present study reports on a chitosan composite which was reinforced by hydroxyapatite and diopside; the scaffolds were fabricated by the freeze-drying method. The so-produced chitosan-hydroxyapatite-diopside (CS-HA-DP) scaffolds were further cross-linked using tripolyphosphate (TPP) to achieve enhanced mechanical strength. The ratios of the ceramic components in composites were 5-58-37, 10-55-35, and 15-52-33 (diopside-hydroxyapatite-chitosan, w/w %). The physicochemical properties of scaffolds were investigated using Fourier-transform infrared spectrometry (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The effect of scaffolds composition on bioactivity and biodegradability were studied well. To investigate mechanical properties of samples, compression test was done. Results showed that the composite scaffold with 5% DP has the highest mechanical strength. The porosity of composites dropped from 92% to 76% by increasing the amount of DP. Cytocompatibility of the scaffolds was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase (ALP) activity, and cell attachment studies using human osteoblast cells. Results demonstrated no sign of toxicity and cells were found to be attached to the pore walls within the scaffolds; moreover, results illustrated that the developed composite scaffolds could be a potential candidate for tissue engineering.     

Preparation and characterization of Beta/MCM-41composite zeolite with a stepwise-distributed pore structure

A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation.