Characterization of surface properties and cytocompatibility of ion-etched chitosan films

Surface modification of biomaterials has been highlighted by biomedical engineers as a facile method for improving cell-biomaterial interactions without the expense and time required to develop new materials. In the present study, we investigated the influence of ion-etching on the surface characteristics of chitosan films using XPS and ATR FT-IR. The physiological behavior of human dermal fibroblasts (hDFs) grown on such surfaces was studied by evaluating adhesive and proliferative properties, and by examining surface morphologies of hDFs using AFM. hDFs displayed different shapes depending on the ion-etching time. hDFs grown on chitosan films ion-etched for 5 min displayed better development of lamellipodia and filopodia around the hDF periphery than did cells grown on nonmodified chitosan film, whereas hDFs did not spread well on films ion-etched for 20 min. Films ion-etched for 5 min or less had higher NH(2) and COOH contents, leading to enhanced hDF adhesion and proliferation.     

New small-molecular benzimidazole derivatives for photovoltaics: Synthesis,optical and electrochemical properties and application in perovskite solar cells

New small molecule photovoltaic materials containing benzimidazole fragment were prepared by cross-coupling of the corresponding 1-bromo-4-(imidazol-2-yl)benzenes with multiborylated/stannylated polycyclic (het)arenes. Energies of HOMO/LUMO levels were calculated from cyclic voltammetry and UV/VIS spectroscopy data and are within the ranges –5.27... –5.73 and –2.33...–2.89 eV, respectively. Solar cells based on three different perovskites as light absorbing layers and compound SM7 as electron transporting material demonstrated power conversion efficiency values up to 10.78% without doping additives or perovskite engineering.     

Polystyrene-coated micropallets for culture and separation of primary muscle cells

Despite identification of a large number of adult stem cell types, current primary cell isolation and identification techniques yield heterogeneous samples, making detailed biological studies challenging. To identify subsets of isolated cells, technologies capable of simultaneous cell culture and cloning are necessary. Micropallet arrays, a new cloning platform for adherent cell types, hold great potential. However, the microstructures composing these arrays are fabricated from an epoxy photoresist 1002F, a growth surface unsuitable for many cell types. Optimization of the microstructures’ surface properties was conducted for the culture of satellite cells, primary muscle cells for which improved cell isolation techniques are desired. A variety of surface materials were screened for satellite cell adhesion and proliferation and compared to their optimal substrate, gelatin-coated Petri dishes. A 1-μm thick, polystyrene copolymer was applied to the microstructures by contact printing. A negatively charged copolymer of 5% acrylic acid in 95% styrene was found to be equivalent to the control Petri dishes for cell adhesion and proliferation. Cells cultured on control dishes and optimal copolymer-coated surfaces maintained an undifferentiated state and showed similar mRNA expression for two genes indicative of cell differentiation during a standard differentiation protocol. Experiments using additional contact-printed layers of extracellular matrix proteins collagen and gelatin showed no further improvements. This micropallet coating strategy is readily adaptable to optimize the array surface for other types of primary cells.     

Effect of microcrystal cellulose and cellulose whisker on biocompatibility of cellulose-based electrospun scaffolds

To investigate the potential application of microcrystal cellulose (MCC) and cellulose whisker (CW) in the electrospun vascular tissue scaffolds, cellulose acetate (CA) and cellulose composite scaffolds containing MCC and CW were electrospun from CA solutions and deacetylation. Structure and morphology of MCC, CW and the fibrous composite scaffolds were investigated using FT-IR, SEM, TEM and AFM. The wettability of the scaffolds was evaluated by water contact angle analysis. The effect of MCC and CW on the biocompatibility of the scaffolds for vascular smooth muscle cells (VSMC) was assayed by MTT test, fluorescent imaging and SEM. The biocomposite scaffolds displayed multi-scaled structure and morphology. The scaffolds containing MCC and CW simultaneously exhibited significantly higher cell viability compared to those with only MCC or CW and no filler. Cell viability and morphology within the scaffolds become better with increasing content of MCC and CW. The composite scaffolds with both micro- and nano-scale organization could mimic the native extracellular matrix more closely, and further produce synergistic enhancement on VSMC viability, adhesion and proliferation. This study provides the potential applications of renewable cellulose-based particulates in biomedical field.     

Simple functionalization of cellulose beads with pre-propargylated chitosan for clickable scaffold substrates

Concerning the increased market for bio-based materials and environmentally safe practices, cellulose-based beads are one of the more attractive alternatives. Thus, this work focuses on the generation of functional cellulose-based beads with a relatively simple and direct method of blending a pre-modified chitosan bearing the targeted functional groups and cellulose, prior to the formation of the beads, as a mean to have functional groups in the formed structure. To this end, chitosan was chemically modified with propargyl bromide in homogenous reaction conditions and then combined with cellulose in sodium hydroxide/urea solution and coagulated in nitric acid to produce spherical shaped beads. The successful chemical modification of chitosan was assessed by elemental analysis, as well as by Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The alkynyl moieties from the chitosan derivative, served as reactive functional groups for click-chemistry as demonstrated by the tagging of the commercial fluorophore Azide-Fluor 488 via CuI-catalysed alkyne-azide cycloaddition reaction, in aqueous media. This work demonstrates the one-step processing of multiple polysaccharides for functional spherical beads as a template for bio-based scaffolds such as enzyme immobilization for stimuli-response applications and bioconjugations.

     

Bioactive Properties of Chitin/Chitosan—Calcium Phosphate Composite Materials

Calcium phosphate coating over phosphorylated derivatives of chitin/chitosan material was produced by a process based on phosphorylation, Ca(OH)₂ treatment and SBF (simulated body fluid solution) immersion. Chitin/chitosan phosphorylated using urea and H₃PO₄ and then soaked in saturated Ca(OH)₂ solution at ambient temperature, which lead to the formation of thin coatings formed by partial hydrolysis of the PO₄ functionalities, were found to stimulate the growth of a calcium phosphate coating on their surfaces after soaking in 1.5 × SBF solution for as little as one day. The Ca(OH)₂ treatment facilitates the formation of a calcium phosphate precursor over the phosphorylated chitin/chitosan, which in turn encourages the growth of a calcium deficient apatite coating over the surface upon immersion in SBF solution. The bio-compatibility of calcium phosphate compound—chitin/chitosan composite materials was evaluated by cell culture test using L-929 cells. The initial anchoring ratio and the adhesive strength of L-929 cells for composites was higher than that for the polystyrene disk (LUX, control). The results of in-vitro evaluation suggested that the calcium phosphate—chitin/chitosan composite materials were suitable for cell carrier materials.     

The effect of surface electrolytic treatment on carbon fibers and the microstructure of pyrocarbon around it during chemical vapor deposition

Before chemical vapor deposition, carbon fibers were electrolyzed for different time, using 33 wt% nitric acid and 5 wt% ammonium bicarbonate solution as electrolyte solution respectively. Effects of the electrolytic treatments on the morphology and chemical functional groups of carbon fibers were deeply analyzed. The influence of these surface treatments on the deposition of pyrocarbon during chemical vapor deposition was also investigated. Results show that the electrolytic treatments for proper time improve the surface morphology and adjust the surface functional groups of carbon fibers. The main functional groups on fiber surface are HBS and –COOH groups, which then induce the efficient deposition of pyrocarbon and improve the microstructure of pyrocarbon during chemical vapor deposition.     

Re-Emerging Field of Lignocellulosic Fiber – Polymer Composites and Ionizing Radiation Technology in their Formulation

Natural cellulose-based fibers offer low cost, low density composite reinforcement with good strength and stiffness. Because of their annual renewability and biodegradability, natural fibers have materialized as environmentally-friendly alternatives to synthetic fibers in the last two decades. They are replacing synthetic materials in some traditional composites in industrial manufacturing sectors such as automotive, construction, furniture, and other consumer goods. In this work, the use of lignocellulosic fibers in green materials engineering, particularly their application as polymeric composite reinforcement and surface treatment via ionizing radiation are reviewed. Because these cellulose-based materials are intrinsically hydrophilic, they require surface modification to improve their affinity for hydrophobic polymeric matrices, which enhances the strength, durability, and service lifetime of the resulting lignocellulosic fiber-polymer composites. In spite of a long history of using chemical methods in the modification of material surfaces, including the surface of lignocellulosic fibers, recent research leans instead towards application of ionizing radiation. Ionizing radiation methods are considered superior to chemical methods, as they are viewed as clean, energy saving, and environmentally friendly. Recent applications of controlled ionizing radiation doses in the formulation of natural fiber –reinforced polymeric composites resulted in products with enhanced fiber-polymer interfacial bonding without affecting the inner structure of lignocellulosic fibers. These applications are critically reviewed in this contribution.     

Influence of the Degree of Deacetylation of Chitosan and BMP-2 Concentration on Biocompatibility and Osteogenic Properties of BMP-2/PLA Granule-Loaded Chitosan/β-Glycerophosphate Hydrogels

Compositions based on chitosan/β-glycerophosphate hydrogels with highly porous polylactide granules can be used to obtain moldable bone graft materials that have osteoinductive and osteoconductive properties. To eliminate the influence of such characteristics as chain length, degree of purification, and molecular weight on a designed material, the one-stock chitosan sample was reacetylated to degrees of deacetylation (DD%) of 19.5, 39, 49, 55, and 56. A study of the chitosan/β-glycerophosphate hydrogel with chitosan of a reduced DD% showed that a low degree of deacetylation increased the MSCs (multipotent stromal cells) viability rate in vitro and reduced the leukocyte infiltration in subcutaneous implantation to Wistar rats in vivo. The addition of 12 wt% polylactide granules resulted in optimal composite mechanical and moldable properties, and increased the modulus of elasticity of the hydrogel-based material by approximately 100 times. Excessive filling of the material with PLA (polylactide) granules (more than 20%) led to material destruction at a ~10% strain. Osteoinductive and osteoconductive properties of the chitosan hydrogel-based material with reacetylated chitosan (39 DD%) and highly porous polylactide granules impregnated with BMP-2 (bone morphogenetic protein-2) have been demonstrated in models of orthotopic and ectopic bone formation. When implanted into a critical-size calvarial defect in rats, the optimal concentration of BMP-2 was 10 μg/mL: bone tissue areas filled the entire material’s thickness. Implantation of the material with 50 μg/mL BMP-2 was accompanied with excessive growth of bone tissue and material displacement beyond the defect. Significant osteoinductive and osteoconductive properties of the material with 10 μg/mL of BMP-2 were also shown in subcutaneous implantation.     

Viability study of HL60 cells in contact with commonly used microchip materials

This paper presents a study in which different commonly used microchip materials (silicon oxide, borosilicate glass, and PDMS) were analyzed for their effect on human promyelocytic leukemic (HL60) cells. Copper-coated silicon was analyzed for its toxicity and therefore served as a positive control. With quantitative PCR, the expression of the proliferation marker Cyclin D1 and the apoptosis marker tissue transglutaminase were measured. Flow cytometry was used to analyze the distribution through the different phases of the cell cycle (propidium iodide, PI) and the apoptotic cascade (Annexin V in combination with PI). All microchip materials, with the exception of Cu, appeared to be suitable for HL60 cells, showing a ratio apoptosis/proliferation (R(ap)) comparable to materials used in conventional cell culture (polystyrene). These results were confirmed with cell cycle analysis and apoptosis studies. Precoating the microchip material surfaces with serum favor the proliferation, as demonstrated by a lower R(ap) as compared to uncoated surfaces. The Cu-coated surface appeared to be toxic for HL60 cells, showing over 90% decreased viability within 24 h. From these results, it can be concluded that the chosen protocol is suitable for selection of the cell culture material, and that the most commonly used microchip materials are compatible with HL60 culturing.     

Consecutive preparation of hydrochar catalyst functionalized in situ with sulfonic groups for efficient cellulose hydrolysis

Hydrochars in situ functionalized with –SO₃H groups were generated from kenaf core via a low-temperature hydrothermal carbonization process of 105 °C with a consecutive catalysis of H₂SO₄. The micro-morphology of the hydrochars was strongly affected by the sulfuric acid concentration. Sphere-like particles with size varying between 200 nm and 1 μm were obtained when the acid concentration was 52 wt%. Acid density of the hydrochar increased with the H₂SO₄ concentration increasing. The presence of considerable acidic groups of –SO₃H, –COOH, and –OH on the surface of hydrochars was evidenced by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hydrochar obtained can be used directly for effective catalytic hydrolysis of cellulose without any post-modification. This study proposed a promising sustainable and cost-effective route for facile production of acidic hydrochar from crude plant with tunable properties.     

Cellulose-based hydrogels with excellent microstructural replication ability and cytocompatibility for microfluidic devices

In the face of challenges in the development of excellent biocompatible materials for microfluidic device fabrication, we demonstrated that cross-linked cellulose (RCC) hydrogel can be used as the bulk material for microchips. The cellulose hydrogel was prepared from cellulose solution dissolved in an 8 wt% LiOH/15 wt% urea aqueous system with cooling by crosslinking with epichlorohydrin. Collagen as a key extracellular matrix component for promoting cell cultivation was cross-linked in the cellulose hydrogel to obtain cellulose–collagen (RCC/C) hybrid hydrogels. The experimental results revealed that cellulose-based hydrogel microchips with well-defined 2D or 3D microstructures possessed excellent structural replication ability, good mechanical properties, and cytocompatibility for cell culture as well as excellent dimensional stability at elevated temperature. The hydrogel, as a transparent microchip material, had no effect on the fluorescence behaviors of FITC-dextran and rhodamine-dextran, leading to the good conjunction with fluorescent detection and imaging. Moreover, collagen could be immobilized in the RCC/C hydrogel scaffold for promoting cell growth and generating stable chemical concentration gradients, leading to superior cytocompatibility. This work provides new hydrogel materials for the microfluidic technology field and mimicks a 3D cell culture microenvironment for cell-based tissue engineering and drug screening.     

人工细胞外基质对血管内皮细胞生存的影响

通过物理吸附方法, 利用胶原、 聚赖氨酸和融合蛋白VEGF-Fc对聚苯乙烯培养板表面进行改性, 以研究细胞外基质材料对血管内皮细胞的影响. 结果表明, 3种蛋白显著提高了聚苯乙烯表面的亲水性. 内皮细胞的黏附、 增殖、 细胞骨架蛋白染色和血管性血友病因子(vWF)免疫染色实验结果表明, 胶原、 聚赖氨酸和VEGF-Fc基质均能有效提高血管内皮细胞的黏附, 其中胶原可与VEGF协同作用促进内皮细胞分化表型的表达; VEGF-Fc基质兼具了VEGF的生物学活性, 可促进内皮细胞的黏附和增殖以及vWF功能性蛋白的表达. 本研究为诱导材料表面内皮化和血管新生的生物活性材料的设计开发提供了新思路.     

Mechanically robust,flame-retardant and anti-bacterial nanocomposite films comprised of cellulose nanofibrils and magnesium hydroxide nanoplatelets in a regenerated cellulose matrix

Nanocomposite films consisting of cellulose nanofibrils (CNFs), magnesium hydroxide nanoplatelets (MHNPs) and regenerated cellulose were prepared via simple blending and casting processes. The CNFs were obtained from bamboo pulp by ultrasonic treatment coupled with high shear homogenization. The morphology, structure and properties of the nanocomposite films were comprehensively analyzed using various characterization techniques, including the scanning electron microscope, digital microscope, limiting oxygen index (LOI), micro-scale combustion calorimetry, antibacterial assays, tensile testing, etc. When the MHNP content was optimized to 30 wt%, the nanocomposite film exhibited the best overall properties. The LOI of the composite film increased from 20.0 (0 wt% MHNPs) to 32.7 (30 wt% MHNPs), making it a flame-retardant material in air. In addition, the film containing 30 wt% MHNPs showed excellent antibacterial activity. However, the increase in MHNP content would result in gradual deterioration of the films’ mechanical properties. However, the incorporation of CNFs could significantly suppress this trend. The present work provided a promising pathway for manufacturing multifunctional and high-performance cellulose-based composite films, which were potentially useful for a variety of packaging materials, especially in the biomedical and food packaging fields.     

基于纤维素的先进功能材料（专题报道）

 收集整理了近几年间发表在国内外重要期刊上的约360篇文献,以纤维素功能材料的制备方法为线索,简要综述了该领域的最新进展,对纤维素基纤维材料、膜材料、光电材料、杂化材料、智能材料、生物医用材料等功能材料的制备过程、功能和应用前景做了概括性描述.     

An investigation on dispersion of carbon nanotubes in chitosan aqueous solutions

The dispersion of carbon nanotubes (CNT) in water of different pH and in chitosan aqueous solution of three acids, acetic acid, formic acid, and hydrochloric acid, was investigated. Chitosan was soluble in water of pH ≤3 and could well disperse untreated CNT and acid-treated CNT, both of which had poor dispersion in water of pH ≤3. With the presence of 0.1 wt% chitosan in solution, particle sizes of the CNT dispersion were found to decrease with increasing COOH contents on the CNT. Particle sizes of CNT, untreated and acid-treated, in the three acidic aqueous solutions were found to increase with increasing chitosan contents in solutions. Among the three acids, hydrochloric acid gave the smallest particle size of the CNT dispersion. Without chitosan, the dispersibility of the acid-treated CNT in aqueous solutions of three acids was in the order of acetic acid > formic acid > hydrochloric acid.     

Polypyrrole thin films formed by admicellar polymerization support the osteogenic differentiation of mesenchymal stem cells

The objective of this study was to evaluate the attachment, proliferation, and differentiation of rat mesenchymal stem cells (MSC) toward the osteoblastic phenotype seeded on polypyrrole (PPy) thin films made by admicellar polymerization. Three different concentrations of pyrrole (Py) monomer (20, 35, and 50 x 10(-3) M) were used with the PPy films deposited on tissue culture polystyrene dishes (TCP). Regular TCP dishes and PPy polymerized on TCP by chemical polymerization without surfactant using 5 x 10(-3) M Py, were used as controls. Rat MSC were seeded on these surfaces and cultured for up to 20 d in osteogenic media. Surface topography was characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and static contact angle. Cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium content were measured to evaluate the ability of MSC to adhere and differentiate on PPy-coated TCP. Increased monomer concentrations resulted in PPy films of increased thickness and surface roughness. PPy films generated by different monomer concentrations induced drastically different cellular events. A wide spectrum of cell attachment characteristics (from excellent cell attachment to the complete inability to adhere) were obtained by varying the monomer concentration from 20 m to 50 x 10(-3) M. In particular the 20 x 10(-3) M PPy thin films demonstrated superior induction of MSC osteogenicity, which was comparable to standard TCP dishes, unlike PPy films of similar thickness prepared by chemical polymerization without surfactant. Adhesion of mesenchymal stem cells on tissue culture plates (TCP) coated with polypyrrole thin films made by admicellar polymerization.     

Carboxylic‐group distribution of carboxylated acrylate copolymer latexes with their properties in the presence of acrylic acid and monobutyl itaconate

A series of carboxylated acrylate copolymer latexes were prepared via two different emulsion polymerization technologies with different carboxylic‐group distribution and morphologies. The effects of the emulsifier, the initiator, and the carboxylic monomers [acrylic acid (AA) or monobutyl itaconate (MBI)] on the total conversion of the monomers and the properties of acrylate latexes and films have been investigated. The distribution of carboxylic groups (?COOH) measured by conductometric titration shows that the concentration of surface –COOH (C_s) and embedded –COOH (C_b) both increase with the increase of the amount of carboxylic monomers. For the latexes containing AA, –COOH tends to distribute on the surface of latex particles and in the aqueous phase, whereas –COOH tends to concentrate inside the core of latex particles for the latexes containing MBI. Transmission electron microscopy demonstrates that the latex particles are regular with narrow size distribution and have significant differences in morphologies when different carboxylic monomers and polymerization technologies were used. The stability of latex is satisfactory through the results of common stability and zeta potential tests. Moreover, the water absorption and contact angle experiment tests also revealed that the water resistance of the latex films is good. Copyright © 2011 John Wiley & Sons, Ltd.     

Carbon Nanofiber–Polystyrene Composite Electrodes for Electroanalytical Processes

Carbon nanofibers provide an active and well‐defined high surface area material for electroanalytical processes. In this study a novel procedure is suggested for compacting carbon nanofiber (CNF) materials (diameter typically 100–200 nm) with a polystyrene (PS) binder and additives into highly conducting and re‐polishable CNF‐PS composite electrodes. Three types of carbon nanofibers (Pyrograf III, 70–200 nm diameter) and a range of compositions are surveyed. A 33 wt% carbon nanofibers in polystyrene electrode provides optimum electrical conductivity and reactivity.