Characterization of Chitosan-Gelatin Blend Scaffolds

Vacuum freeze-drying was used to prepare chitosan-gelatin (CG) scaffolds from hydrogels, with glutaraldehyde (GA) used as a crosslinker. The effects of the changes in volume ratios of the 2?wt% CG and GA solutions on scaffold performance were studied. The ratio of chitosan to gelatin solution volumes, vr(C/G), was adjusted to 1/2 or 1/1, with the 0.25?wt% GA volume at 3, 6, or 8% of the CG/GA volume. Six groups of CG scaffolds were fabricated and the scaffolds performance compared. After the cells were incubated for 4?days, hematoxylin eosin (HE) staining was used to observe the spreading of human skin keratinocyte (HaCaT) cells on these scaffolds, with the MTT method also used to detect the cells proliferation. The inhibition zone method was used on cells cultures to determine the antibacterial properties of the scaffolds against S. aureus and E. coli. Scaffolds were also examined for degradation in lysozyme and their compression properties were tested after degradation. The results showed that the HaCaT cells grew well on these scaffolds and proliferated significantly, indicating that these scaffolds possessed good cytocompatibility. With increased chitosan volume, the antibacterial properties of the scaffolds against S. aureus increased, however, there was no significant change in the antibacterial properties toward E. coli. Increased volumes of chitosan and GA decreased the scaffolds degradation rates and improved the elastic compressive moduli of the scaffolds after degradation. The scaffolds in the vr(C/G) = 1/1, 8% GA group have potential application prospects in the field of skin regeneration.     

Effect of surface roughness of chitosan-based microspheres on cell adhesion

Microspheres are novel candidate materials for microcarriers and tissue-engineering scaffolds. Chitosan microspheres were selected as the base materials because of their excellent properties for biomedical applications. But their smooth surfaces were not adapted for cell attachment. Hence, in order to improve the roughness of chitosan microspheres, β-TCP/chitosan composite microspheres were developed. From SEM photographs, the coarse surfaces of composite microspheres were observed, there were some ceramic particles standing out of the chitosan matrix. And their roughness measured by profilometers was about 2.0 μm. Mouse MC3T3-E1 osteoblasts were seeded on the microspheres for evaluating the attachment interaction between cells and materials. According to the ESEM photographs and MTT assay, the adherence and proliferation of osteoblasts on the surfaces of modified microspheres were better than those on the chitosan microspheres, which were mainly attributed to the improved roughness of surface.     

Effect of the internal microstructure in rapid-prototyped polycaprolactone scaffolds on physical and cellular properties for bone tissue regeneration

Biomedical scaffolds should be designed to optimize their inter-microstructure to enable cell infiltration and nutrient/waste transport. To acquire these properties, several structural parameters, such as pore size, pore shape, porosity, pore interconnectivity, permeability, and tortuosity are required. In this study, we explored the effect of tortuosity on the viable cell proliferation and mineralization of osteoblast-like-cells (MG63) in polycaprolactone scaffolds. For analysis, we designed four different scaffolds of various tortuosities ranging from 1.0 to 1.3 under the same porosity (56?%) and 100?% pore interconnectivity. The pore size of the scaffolds was set as 150 and 300?μm, and a mixture of these sizes. We found that despite the porosity being same, the elastic modulus was dependent on the pore size of the scaffolds due to the distributed stress concentration. In addition, the relative water movement within scaffolds was also related to the internal microstructure. Cell viability and Ca²⁺ deposition of the cell-seeded scaffolds showed that the proliferation of viable cells and mineralization in the scaffolds with appropriate tortuosity (1.2) was relatively high compared to those of the scaffolds displaying low (1.05 and 1.1) or high (1.3) tortuosity. Our findings indicated that the internal microstructure of the scaffolds may influence not only the physical properties, but in addition the cellular behavior.     

Poly (Vinyl Alcohol)/Chitosan/Akermanite Nanofibrous Scaffolds Prepared by Electrospinning

Abstract

Electrospinning, as an effective method for preparation of scaffolds for cell growth templates, has attracted great attention. In this study electrospinning was used to prepare poly (vinyl alcohol) (PVA)/chitosan scaffolds for bone tissue engineering. In order to improve the bioactivity and mechanical properties of the fibrous scaffolds, 0.5, 1 and 2?wt% akermanite, a calcium silicate based bioceramic, was added to the electrospinning solution. The morphology of the electrospun scaffolds was observed by using field emission-scanning electron microscopy and their mechanical strengths were analyzed by tension tests. The results showed that the formed scaffolds consisted of fibers with less than 100?nm diameter. In the case of the composite containing 1?wt% akermanite, the fibers were more homogeneous and no beads were formed during electrospinning, while in the composite containing 2?wt% akermanite a considerable number of beads were formed which we attribute to an improper viscosity of the electrospinning solution. Among the different compositions, the composite containing 1?wt% akermanite showed higher ultimate tensile strength (10.6?MPa) and fracture strain (9%). These values were increased by crosslinking the scaffold by reaction with glutaraldehyde, up to 13?MPa and 9.4%, respectively.     

Preparation and Characterization of a Novel Composite of Chitosan/Shell Particles

Nanometer sized (mean size: 433.9 nm) pearl shell particles (SP) were prepared with a ball mill. Thermal analysis and Fourier transform infrared (FTIR) results proved that the SP contained mainly CaCO₃ (about 95%) and a small organic phase (about 5%). Novel biodegradable composites based upon chitosan (CS) and SPs were prepared using an in situ precipitation method. The organic components of SP are highly compatible with both CS and glutaraldehyde (GA). The strength and modulus of CS gel rods, prepared by coagulation of a CS/SP/GA solution in NaOH, in both the dry and wet state, were improved remarkably with addition of appropriate amounts of SP together with GA. For example, with a composition of 3% SP and 0.3% GA added, the strength and modulus were 42.9 MPa and 1.41 GPa, increasing 75 and 464% compared with CS alone, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that GA acts as not only a crosslinking agent for CS, but also a compatibilizer for CS and SP. It was found that the modified rods have smaller free volume size but nearly the same free volume fraction as pure CS rods. The good interfacial adhesion and more compact microstructure can sensitively reflect the changes in the free volume of the composites.     

A Novel Chitosan/Polyvinyl Pyrrolidone (CS/PVP) Three-Dimensional Composite and Its Mechanism of Strength Improvement

Novel biodegradable three-dimensional (3D) composites with good mechanical properties have been prepared by coagulation of a chitosan/polyvinyl pyrrolidone (CS/PVP) solution in NaOH. For example, the strength and modulus of CS/PVP (1/1) were 82.5 MPa and 1.86 GPa, increasing 237% and 644% compared with CS, respectively. Scanning electron microscopy and Fourier transform infrared analysis suggest that the PVP component did not dissolve during the preparation process. The nonsolution of the composites is attributed to the extremely strong hydrogen bonding formed between the CS and PVP macromolecules. It was also found that there are synergistic effects between the formation of hydrogen bonding with PVP and cross-linking with glutaraldehyde (GA) for the improvement in the mechanical properties of CS. The mechanism of strength improvement has been discussed thoroughly from the aspects of free volume.     

Functionalized alginate/chitosan biocomposites consisted of cylindrical struts and biologically designed for chitosan release

A novel alginate/chitosan composite scaffold was developed. The composite scaffolds were fabricated at low temperature using a three-axis robot system connected to a micro-dispenser and a core/shell nozzle. The structure of the composite scaffolds included hollow struts; deposited chitosan on the inner walls (core region) of the struts reacted electrostatically with the alginate layer (shell region). The fabricated, highly porous composite scaffolds exhibited excellent mechanical properties and controllable chitosan release, which was closely dependent on the weight fraction of the alginate in the shell region. The tensile strength in the dry state was ∼1.8-fold greater than that of pure alginate scaffold due to the ionic interaction between alginate and chitosan. To determine the feasibility of using the developed scaffold in tissue regeneration applications, in vitro cellular responses were evaluated using osteoblast-like-cells (MG63). The cell proliferation on the composite scaffold was ∼3.4-fold greater than that on the pure alginate scaffold. Alkaline phosphate activity and calcium deposition of the composite scaffold after 14 and 21 days of cell culture were significantly enhanced (1.6- and 1.8-fold greater, respectively) compared with those of the pure alginate scaffold. These results suggested that the alginate/chitosan composite scaffolds with a controlled chitosan release have great potential for use in regenerating various tissues.     

Silver nanoparticle containing silk fibroin bionanotextiles

Development of new generation bionanotextiles is an important growing field, and they have found applications as wound dressings, bandages, tissue scaffolds, etc. In this study, silver nanoparticle (AgNP) containing silk-based bionanotextiles were fabricated by electrospinning, and processing parameters were optimized and discussed in detail. AgNPs were in situ synthesized within fibroin nanofibers by UV reduction of silver ions to metallic silver. The influence of post-treatments via methanol treatment and glutaraldehyde (GA) vapor exhibited changes in the secondary structure of silk. Methanol treatment increased the tensile properties of fibers due to supported crystalline silk structure, while GA vapor promoted amorphous secondary structure. AgNP containing silk fibroin bionanotextiles had strong antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa.     

Influences of Process Variables on Size of Chitosan Microspheres

Chitosan microspheres, with a size range of 20–550 μm, were obtained by using an emulsification–coacervation method. The surface morphology and the structure of microspheres were characterized by scanning electron microscopy and X-ray diffraction. The effects of process variables, including stirring rate, chitosan concentration, emulsifier concentration, and cross-linker (glutaraldehyde) concentration, on the diameter of chitosan microspheres were investigated. The results showed that spherical microspheres, without aggregation phenomena and with a very smooth and uniform surface, were obtained when emulsifier concentration, chitosan concentration, stirring rate, and glutaraldehyde concentration were kept at 0.010–0.025 mL/mL, 0.05–0.20 g/mL, 800–2400 rpm, and 0.5–1.5% (v/v) respectively. The chitosan microsphere crystallinity degree decreased after cross-linking. The microsphere size increased with decreasing of stirring rate, emulsifier, and cross-linker concentration; however, the microsphere size increased with increase of chitosan concentration. This indicated that different diameters of chitosan microspheres can be achieved by controlling process variables.     

Preparation of nanocomposite superabsorbents based on hydrotalcite and poly(acrylic-co-acrylamide) by inverse suspension polymerization

Firstly, hydrotalcite (HT) was synthesized by the urea method. Then, sodium methyl allyl sulfonate (SMAS) was used as intercalation agent to prepare intercalated HT (SMAS–HT). Finally, a novel poly(acrylic-co-acrylamide)/HT nanocomposite superabsorbent was prepared by inverse suspension polymerization, using N,N′-methylenebisacrylamide (NMBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The morphology of the superabsorbents was characterized by FT-IR, XRD, SEM and TEM. The influences of the amount of SMAS–HT on the water (salt) absorbency were investigated. Results showed that the intercalation was successful and the intercalated SMAS–HT incorporated into the superabsorbent was completely exfoliated. The superabsorbent particles approach a spherical shape and the average size is 200–300 nm. The particle sizes of the superabsorbents decrease with increasing the content of SMAS–HT. In addition, the superabsorbent acquired its highest water (salt) absorbency when the content of SMAS–HT is 3 wt%. The highest absorbencies of the superabsorbent for deionized water and 0.9% NaCl_(aq) were 900 g/g and 140 g/g, respectively.     

Swelling Properties and Environmental Responsiveness of Superabsorbent Composite Based on Starch-G-Poly Acrylic Acid/Organo-Zeolite

Star-g-poly (acrylic acid)/organo-zeolite 4A (S-g-PAA/OZ) superabsorbent composite was prepared by grafting partially neutralized acrylic acid onto starch in the presence of organo-zeolite 4A (OZ) as an inorganic component. The morphology was characterized with scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) analysis revealed the fine distribution of OZ in superabsorbent composite. The swelling kinetics of the composites were characterized by means of a Schott's second-order model. The effect of OZ concentration in the composite on the water absorbency and swelling behavior were tested. The swelling properties of the composites were evaluated in various environments; pH, salinity, temperature, urea solution, and solvent-water mixtures. The activation energy (ΔE) for water during the swelling process was also determined through Arrhenius plots. The results showed that the proper amount of OZ was beneficial for improvement of the water absorbent capacity and the initial swelling rate in distilled water. The optimum prepared composite with 10 wt % OZ, possessed the maximum water absorption (511g/g) in distilled water and (521 g/g) in 0.1 wt % urea solution. The results inferred that S-g-PAA/OZ superabsorbent composite can be exploited for agriculture and medical applications.     

Preparation and Characterization of Biopolymers Chitosan/Alginate/Gelatin Gel Spheres Crosslinked by Glutaraldehyde

Twelve different samples of gel spheres were prepared from the biopolymers chitosan, alginate, and gelatin via polyion complex formation in aqueous solution with crosslinking by glutaraldehyde. Dropwise addition of a chitosan/gelatin solution into a solution containing alginate and glutaraldehyde gave the gel spheres. The effects of different ratios of glutaraldehyde (0.25%, 0.50%, 1.0%, and 2.0%), and gelatin (2.5%, 5.0%, and 10.0%) on the characteristics of the gel spheres were evaluated. An increase in the concentration of the glutaraldehyde led to forming true spheres in rigid form. By scanning electron microscopy (SEM), the gel spheres showed fibrous network propagation along the gel membrane surface. Fourier transform infrared (FT-IR) spectroscopy confirmed the crosslinking of the amino groups by the glutaraldehyde and the presence of crosslinking bonds between the amino groups of chitosan and the carboxyl groups in the alginate molecule. Swelling studies showed that increasing the degree of crosslinking increased the density of the polymer network, which led to a decrease in the degree of swelling. The characteristics of the gel spheres will be useful for immobilization and prolonged release of biologically active substances.     

Exploring the utility of coarse-grained water models for computational studies of interfacial systems

Molecular dynamics simulations have become a standard tool for the investigation of biological and soft matter systems. Water models serve as the basis of force fields used in molecular dynamics simulations of these systems. This article reports on an examination of the utility of a set of coarse-grained (CG) water models, with different resolutions, interaction potentials (Lennard–Jones, Morse), and cut-off distances. The relationships between the parameters under specific choices of the above options and the thermodynamic properties, such as density, surface tension, and compressibility, were found to fit simple mathematical equations. The limits of applicability of these CG water models were explored by checking the melting temperature. If a CG site is mapped to one or two real water molecules, a simple model with appropriate combinations of cut-off distances, functional forms, and parameters can be found to simultaneously match the experimental values of density, surface tension, and compressibility under ambient conditions. If more water molecules are included in a CG site, either the melting temperature approaches or surpasses room temperature, or the surface tension and compressibility cannot both be matched simultaneously. In striving for computational efficiency, it is still possible to find a simple CG water model with three water molecules contained in a CG bead that generates a liquid state of water with realistic values of density, surface tension and compressibility at ambient condition, but coarser models are not recommended.     

High-intensity ultrasound-assisted formation of cellulose nanofiber scaffold with low and high lignin content and their cytocompatibility with gingival fibroblast cells

Cellulose nanofiber (CNF) hydrogels with low lignin (8%) (LL-CNF) and high lignin (18%) (HL-CNF) content were produced at nominal powers of 240, 720 and 1200 W using high-intensity ultrasound technology (HIUS). Freeze-dried CNF hydrogels were evaluated as scaffolds for gingival fibroblast cells proliferation aiming biomedical applications. HIUS processing improved the dispersibility of the CNF and increased the water retention value by more than 5 times. The LL-CNF had a maximum fibrillation yield of 46 wt.%, whereas the HL-CNF had a maximum fibrillation yield of 40 wt.% at nominal power of ≥720 W. Regardless of the lignin content, the CNF hydrogels exhibited a typical elastic gel-like behavior with the highest elasticity of 263 Pa. After freeze-drying, the CNF aerogels had porosity ≥ 96.8%, and swelling capacity up to 42.1 g PBS/g aerogel. Moreover, the cell proliferation assay showed no differences in proliferation among the LL-CNF and HL-CNF scaffolds up to 11 days. Therefore, CNF scaffolds prepared with lignin content up to 18% present promising application in the biomedical field.     

Preparation and Characterization of Poly(L-lactide-co-glycolide-co-ε-caprolactone) Scaffolds by Thermally Induced Phase Separation

Abstract

The technique of thermally induced phase separation (TIPS) is favorable for the fabrication of a porous scaffold due to a number of advantages. In this work the poly(L-lactide-co-glycolide-co-ε-caprolactone) (PLLGC) terpolymer was synthesized by melt copolymerization and porous scaffolds thereof from its solution in 1,4-dioxane were fabricated by using the TIPS method. The effects of fabrication parameters, including polymer concentration and freezing temperature, on the morphology, pore size and mechanical properties were studied. The results showed that the average pore size of the PLLGC porous scaffold increased with a decrease in PLLGC concentration and the pore size resulting from freezing at 4?°C (about 20–100?μm) was significantly larger than for other samples (20–50?μm) frozen at lower temperatures. The porosity of the scaffolds decreased with increasing PLLGC concentration or decreasing freezing temperature. On the other hand, the compressive strength of the scaffolds increased with the increase of PLLGC concentration or the decrease of freezing temperature, as would be expected. The present results can be applied in design to control the processing parameters of TIPS for a scaffold with desired pore morphology.     

Ultrasonic compatibilization of polyelectrolyte complex based on polysaccharides for biomedical applications

In recent years, there has been an increasing interest in the design of biomaterials for cartilage tissue engineering. This type of materials must meet several requirements. In this study, we apply ultrasound to prepare a compatibilized blend of polyelectrolyte complexes (PEC) based on carboxymethyl cellulose (CMC) and chitosan (CHI), in order to improve stability and mechanical properties through the inter-polymer macroradicals coupling produced by sonochemical reaction. We study the kinetic of the sonochemical degradation of each component in order to optimize the experimental conditions for PEC compatibilization. Scaffolds obtained applying this methodology and scaffolds without ultrasound processing were prepared and their morphology (by scanning electron microscopy), polyelectrolyte interactions (by FTIR), stability and mechanical properties were analyzed. The swelling kinetics was studied and interpreted based on the structural differences between the two kinds of scaffolds. In addition we evaluate the possible in vitro cytotoxicity of the scaffolds using macrophage cells in culture. Our results demonstrate that the ultrasound is a very efficient methodology to compatibilize PEC, exhibiting improved properties compared with the simple mixture of the two polysaccharides. The test with murine macrophage RAW 264.7 cells showed no evince of cytotoxicity, suggesting that PEC biomaterials obtained under ultrasound conditions could be useful in the cartilage tissue engineering field.     

Preparation and Characterization of Nanocomposite Scaffolds Based on Polycaprolactone-Polyethylene Glycol/Methylene Diphenyl Diisocyanate/Diethylene Glycol and Nano-Bioactive Glass

Designing and fabricating nanocomposite scaffolds based on biodegradable polymers and bioactive materials are an important topic in the area of bone regeneration. A novel nanocomposite scaffold composed of polyurethane (BPU) and nano-bioactive glass (NBAG) was prepared. The effects of the NBAG content on the properties of the BPU/NBAG composite scaffolds, including the morphologies, porosity and compressive strength, were investigated. The BPU/NBAG composite scaffolds showed an interconnected pore structure with the pore size ranging from 50 to 500?μm for all samples. The porosity percent and swelling ability decreased with increasing NBAG content; however, the compressive strength was enhanced.     

低强度脉冲超声激发的声微流增强藻酸钙凝胶支架材料的孔隙率和通透性研究

低强度脉冲超声(LIPUS)激发的声微流场所产生的剪切应力可作用于细胞膜表面,从而显著增强细胞膜的通透性。构建了三维藻酸钙凝胶支架培养系统,来模拟有利于细胞生长的营养供给和新陈代谢体内微环境;基于扫描电子显微镜、体内荧光图像和激光共聚焦图像观测技术,对LIPUS增强三维藻酸钙凝胶支架材料的孔隙率和通透性的作用机制和参数相关性进行了系统的研究。结果表明,三维藻酸钙凝胶支架材料的孔隙率和通透性可随着LIPUS的驱动声压的升高而显著增强。此外,通过对三维支架材料内的细胞增殖情况分析,发现在适当的LIPUS驱动声压(如P-=0.055 MPa)下,HeLa细胞在LIPUS作用下的三维藻酸钙凝胶支架材料中可获得更高的增殖率。     

基于金属有机框架材料复合基底表面增强拉曼光谱测定水中的戊二醛

戊二醛在精细化工中的使用,导致大量戊二醛产品如鞣革剂、消毒剂、蛋白质交联剂、组织固化剂等被排放到水体中,对水体生物及生态环境造成严重污染,对整个生态系统带来危害,因此开发对戊二醛快速简易的检测技术至关重要。表面增强拉曼光谱法(SERS)是一种基于待测物分子对光的散射效应而建立起来的定量检测技术,具有灵敏度高,所需样品量少,水干扰小等优势,功能强大,被广泛应用于分析检测领域中。目前尚未见文献报道基于SERS技术用于定量检测环境水体中戊二醛的案例。基于金纳米粒子（AuNPs）的局域表面等离子体共振效应、金属有机框架材料MIL-101(Cr)的富集能力以及对氨基苯硫酚（PATP）与戊二醛之间的席夫碱反应,基于Au@MIL-101/PATP复合材料建立了一种检测水中戊二醛的表面增强拉曼光谱分析方法。通过溶液浸渍法制备Au@MIL-101材料,再利用Au-S共价键作用将PATP修饰到AuNPs表面得到Au@MIL-101/PATP复合基底。利用透射电镜(TEM)、能量色散X射线光谱(EDS)、X射线衍射(XRD)、X射线光电子能谱(XPS)和拉曼光谱等方法对基底材料进行表征。论文研究了MIL-101(Cr)中AuNPs的密度对拉曼增强效果的影响,氯金酸浓度为0.6 g·L-1时增强效果最好。戊二醛与PATP的席夫碱反应产物在1 621 cm-1处产生C═N特征峰,戊二醛浓度与I_{1 078}/I_{1 621}信号比值在1×10-7~1×10-5 mol·L-1范围内具有良好的线性,检出限(LOD)为3.5×10-8 mol·L-1。实际样品分析结果表明,自来水和河水水样中戊二醛的加标回收率分别为91.4%~111.8%,89.8%~114.2%,相对标准偏差分别为5.2%~14.5%,8.6%~13.4%。本方法具有操作简单、分析时间短、绿色等优点,为检测水中的痕量戊二醛提供了新思路。     

Sound absorption properties of a sunflower composite made from crushed stem particles and from chitosan bio-binder

A recent study investigated the mechanical, thermal and acoustical properties of a bio-based composite made from crushed particles of sunflower stalks binded together by chitosan, a bio-based binder. The acoustical performance in absorption was found to be poor as the material was highly compacted and with low porosity. The present study focuses on the acoustical properties of a higher porosity composite, with lower density while the mechanical rigidity remains fairly high. A higher absorption coefficient is obtained. The experimental results on the absorption coefficient are compared to the prediction of a model involving 5 physical parameters (porosity, tortuosity, airflow resistivity, thermal and viscous characteristic lengths). The characterization methods to determine these parameters are described. The comparison between experimental and theoretical results shows that this material exhibits peculiar microstructural features. It is found that the sound absorption properties can involve dead-end pores or clusters and multiple porosity scales in the material.