An injectable calcium phosphate-alginate hydrogel-umbilical cord mesenchymal stem cell paste for bone tissue engineering

The ability to probe morphology and phase distribution in complex systems at multiple length scales unravels the interplay of nano- and micrometer-scale factors at the origin of macroscopic behavior. While different electron- and X-ray-based imaging techniques can be combined with spectroscopy at high resolutions, owing to experimental time limitations the resulting fields of view are too small to be representative of a composite sample. Here a new X-ray imaging set-up is proposed, combining full-field transmission X-ray microscopy (TXM) with X-ray absorption near-edge structure (XANES) spectroscopy to follow two-dimensional and three-dimensional morphological and chemical changes in large volumes at high resolution (tens of nanometers). TXM XANES imaging offers chemical speciation at the nanoscale in thick samples (>20 µm) with minimal preparation requirements. Further, its high throughput allows the analysis of large areas (up to millimeters) in minutes to a few hours. Proof of concept is provided using battery electrodes, although its versatility will lead to impact in a number of diverse research fields.

/pdf/three-dimensional-imaging-of-chemical-phase-transformations-4fxiarlfzt.pdf

Three-dimensional imaging of chemical phase transformations at the nanoscale with full-field transmission X-ray microscopy

Aligned PLLA nanofibrous scaffolds coated with graphene oxide for promoting neural cell growth

Contemporary methods for dispersion of carbon nanotubes in water and non-aqueous media are discussed. Most attention is paid to ultrasonic and plasma techniques and other physical techniques, as well as to the use of surfactants, functionalizing and debundling agents of distinct nature (elemental substances, metal and organic salts, mineral and organic acids, oxides, inorganic and organic peroxides, organic sulfonates, polymers, dyes, natural products, biomolecules, and coordination compounds). Special studies on CNTs solubilization are examined.

Dispersion of carbon nanotubes in water and non-aqueous solvents

Alkaloids and Isoprenoids Modification by Copper(I)-Catalyzed Huisgen 1,3-Dipolar Cycloaddition (Click Chemistry): Toward New Functions and Molecular Architectures.

The aim of the present work is to assemble extracellular matrix components onto poly (L-lactic acid) (PLLA) films using layer-by-layer (LBL) depositing method to enhance the cell-material interaction. To introduce charges onto the hydrophobic and neutral PLLA surface so that the electronic assembly can be processed, poly (ethylene imine) (PEI) was covalently bonded to modify the PLLA films. Positively charged collagen I (Col I) was then deposited onto the aminolyzed PLLA film surface in a LBL assembly manner using hyaluronic acid (HA) as a negatively charged polyelectrolyte. The PEI modification efficiency was monitored via X-ray photoelectron spectroscopy (XPS) measurements. The results of Surface Plasmon Resonance (SPR) and Water contact angle (WCA) monitoring the LBL assemble process presented that the HA/Col I deposited alternately onto the PLLA surface. The surface topography of the films was observed by Atomic force microscope (AFM). In vitro osteoblast culture found that the presence of Col I layer greatly improved the cytocompatibility of the PLLA films in terms of cell viability, cell proliferation and Alkaline Phosphatase (ALP) expression. Furthermore, osteoblast extensions were found to be directed by contact guidance of the aligned Col I fibrils. Thus, these very flexible systems may allow broad applications for improve the bioactivity of polymeric materials, which might be a potential application for bone tissue engineering.

http://www.expresspolymlett.com/letolt.php?file=EPL-0004933&mi=c

LBL coating of type I collagen and hyaluronic acid on aminolyzed PLLA to enhance the cell-material interaction

Calcium phosphate cement (CPC) sets in situ to form solid hydroxyapatite, can conform to complex cavity shapes without machining, has excellent osteoinductivity, and is able to be resorbed and replaced by new bone. Therefore, CPC is promising for craniofacial and orthopaedic repairs. However, its low strength and lack of macroporosity limit its use. This study investigated CPC reinforcement with absorbable fibers, the effects of fiber volume fraction on mechanical properties and macroporosity, and the biocompatibility of CPC-fiber composite. The liquid phase of CPC in this study was the weak acidic solution of chitosan. Chitosan has favourable biocompatibility, which has high viscosity in solution. The incorporation of chitosan could improve the handling properties of CPC. The liquid phase contained citric acid could strongly improve the hydration rate of CPC, which shortened the setting time and increased the compressive strength of CPC. In addition, the weak acidic environment around the biomaterials could accelerate the degradation of CPC, which was important to bone tissue engineering. The rationale was that large-diameter absorbable fibers would initially strengthen the CPC graft, then dissolve to form long cylindrical macropores for colonization by osteoblasts. Compressive strength was measured vs. fiber volume fraction from 0% (CPC Control without fibers) to 70%. Animal experiment showed that the material had osteoinductivity and biodegradability when the material was implanted into the muscle pouches in the thigh of rabbits. Compressive strength (mean ± SD; n=3) of CPC with 70% fibers was 0.8± 0.1 MPa. Long cylindrical macropores 100~300 μm in diameter were created in CPC after fiber dissolution, and the CPC-fiber scaffold reached a total porosity of 75.1±1.2% with 70% fibers. The new CPC-fiber formulation had good potentiality of ectopic bone induction. The method of using large-diameter absorbable fibers in bone graft for mechanical properties and formation of long cylindrical macropores for bone ingrowth may be applicable to other tissue engineering materials.

Self-Hardening Calcium Phosphate Composite Scaffold for Bone Tissue Engineering

Biomimetic mineralization was performed on a large scale by a rapid and efficient approach. Chitosan scaffolds were placed in a mixed solution of urea, ethanol and distilled water, followed by the introduction of dibasic sodium phos- phate (0.1M) and calcium chloride (0.1M) with the molar ratio of 1.67. These mixed solvents was then adjusted to weakly alkaline by adding sodium hydroxide solution. Finally the reaction mixture was sealed and kept at 80oC for predetermined time. The composition and morphology of the apatite and the hybrid scaffolds were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR) and environmental scanning electron microscopy (ESEM). The mechanism of nucleation and growth of crystals was discussed as well. The results revealed that chitosan scaffolds improved the crystallinity of hydroxyapatite (HAP) crystals. With the extension of mineralization time, the mineral layers on the outer surface and inner section of chitosan scaffolds increased as well. Fur- thermore, the compressive strength and modulus of the HAP-chitosan scaffolds biocomposites increased to 0.55±0.003 and 29.29±1.25 MPa respectively. Such one-pot approach may be extended to the mineralization of other materials and will have a broad application in the future.

/pdf/rapid-biomimetic-mineralization-of-chitosan-scaffolds-with-a-1c52ndbhha.pdf

Rapid biomimetic mineralization of chitosan scaffolds with a precursor sacrificed method in ethanol/water mixed solution

0Objective :This study is to retain the biological calcium in the crab shell, stripped of protein, calcium biological chitin chitin that is retained characteristics have unique biological calcium carbonate mosaic structure. the traditional preparation of chitin commoly adopts acid to remove calcium carbonae,applys alkali to extract protein, while inorgaic calcium salts is mixed with it as a source of calcium or an enhancement.Methods :Superfine pulverizing technology is used to smash crab shell to D50, which is 8.05 μm to get different size of crab shell powder through screen separation. The primary element of crab shell is calcium carbonate, chitin as well as protein. The content of protein is a significant indicator of industrial application of crab shell powder. Different size of crab shell powder is processed deproteinizedly,through hot alkali methodenzyme hydrolysis methodhot alkali method assisting microwave respectively. Results: Research result shows that the lower sizes of crab shell powder induce the higher effect of deproteinized processing method. The protein residual amount in crab shell powder of particle size D50 of 8.05 μm being processed in hot alkali for 3 hours is 0.097 %, while time being processed by microwave assisting is significantly reduced, making 20 minutes possible for the same result. Conclusions: Particle size of crab shell powder after superfine pulverizing is small, and deproteinization can be achieved by various methods, while retaining original chitin and biological calcium.

The Research on Deproteinized Techniques of Bio-Calcium Chitin

Firstly, toluenesulfonyl cholesterol was synthesized by the reaction of cholesterol and p-toluenesulfonyl chloride, and then reacted with sodium azide to obtain azido-cholesterol Secondly, propargyl was introduced into the terminal groups of polyethylene glycol (PEG) by the reaction of PEG and bromine propargyl Lastly, cholesterol-(1,2,3-triazole)-PEG oligomer was prepared by the reaction of the azido-cholesterol and propargyl-PEG via click chemistry using CuSO45H2O as a catalyst The structures of the products were characterized by the FTIR and 1H NMR analysis

Chang Ren Zhou

Papers

LBL coating of type I collagen and hyaluronic acid on aminolyzed PLLA to enhance the cell-material interaction

Self-Hardening Calcium Phosphate Composite Scaffold for Bone Tissue Engineering

Rapid biomimetic mineralization of chitosan scaffolds with a precursor sacrificed method in ethanol/water mixed solution

The Research on Deproteinized Techniques of Bio-Calcium Chitin

Synthesis and Characterization of Cholesterol-(1,2,3-triazole)-PEG via Click Chemistry