Xiao Yan Lin

Evaluation of Bioactivity and Cytocompatibility of Nano-Hydroxyapatite/Collagen Composite In Vitro

A nano-hydroxyapatie/collagen composite was fabricated by an in situ synthesis technique. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analyses for the composite indicated crystals on the collagen fibril matrix exhibited certain orientation. Bioactivity of the composite was investigated through in vitro tests in a sterile simulated body fluid (SBF) system. Scanning electron microscopy and energy-dispersive X-ray analysis of the composite showed that the composite had the ability to induce the formation of calcium phosphate crystals on the surface of the composite in SBF. The cytocompatibility of the composite was evaluated by in vitro cytotoxicity test. Both the results from MTT assay and scanning electron microscope (SEM) observations indicated that the composite had no adverse impact on cell proliferation and morphology. The results imply the composite is high bioactive and has good cytocompatibility.

Preparation and Characterization of Collagen by Hydrogel Formation Method

A kind of medical collagen was prepared by hydrogel formation method. Chemical and physical properties were investigated by FTIR, amino acid analysis, SDS-PAGE, carbohydrate content analysis, heavy metal content analysis. Degradation experiments in vivo and subsequent histological investigations were carried out to evaluate the biological performance. The results suggested that the collagen achieved is promising in tissue engineering scaffold materials for a long-term (more than 12 weeks) implantation application.

In Vitro and In Vivo Biocompatibility of Nano-Hydroxyapatite/Collagen Composites

A nano-grade hydroxyapatite/collagen composite was prepared by an in situ synthesis technique from calcium nitrate, diammoniun hydrogen phosphate, and a cowhide collagen sol at low temperature. XRD and TEM analyses of the composite indicated that crystals formed in the collagen fibril matrix were nanohydroxyapatite with low crystallinity. Biocompatibility of the composite was evaluated by in vitro cytotoxicity test and in vivo genotoxicity and sensitization test. No mutagenic activity of the composite was observed in mouse micronucleus tests. No evidence of dermal sensitization of the composite was found in guinea pig maximization tests. The results from a filter diffusion test indicated that the composite did not induce a cytotoxic behavior. All these results suggest that the composite has excellent biocompatibility.

Mesoscale Simulation of Drug Molecules Distribution in the Matrix of Konjac Glucomannan (KGM) at Varying Drug Concentrations

Dissipative particle dynamics (DPD) is used in this work to simulate the distribution of carmustine (BCNU) molecules in konjac glucomannan (KGM) as potential drug carrier. It is shown from DPD simulation that the aggregated morphology of KGM differs at varying BCNU concentration levels. At 1 mol % of BCNU the phase aggregates as spherical particles, and at 5 mol% of BCNU, some BCNU molecules were partially uncovered by KGM molecules due to high drug concentration. However, even at higher concentration, most of the BCNU molecules are distributed in the inner area of the matrix, indicating that KGM interacts with BCNU well and it is a promising drug carrier for BCNU in water. DPD simulations may provide a powerful tool for designing drug delivery systems.

Collagen-Calcium Phosphate Hybrids for Bone Grafts: A Novel Route Leading to High Initial Strengths

An organic/inorganic composite hydrogel route was used to prepare collagen-calcium phosphate hybrids with high mechanical strengths, via in-situ mineral synthesis during collagen fibrillogenesis followed by dehydration. An array of characterization techniques including X-ray diffraction and Fourier transform infrared spectroscopy analyses confirmed that the final products are analogous to natural bone. A three-point bending strength of 70 MPa, much higher than the values reported in the literature, was recorded in the present case, due to the three dimensional network structure achieved between inorganic and organic phases. This innovative method provides an efficient route to produce bone grafts with the desirable mechanical properties which are dependent upon the actual inorganic/organic ratio and water content.

In Vivo Evaluation of Nano-HA/PDLLA Composite

The purpose of this study was to evaluate the behavior of nano-hydroxyapatite/ poly(D,L)lactide (n-HA/PDLLA) composite in vivo. The composite rods containing about 40wt% n-HA and control HA rods with a diameter of 2mm and a length of 6mm were implanted into the femora of 16 New Zealand rabbits. Composite wafers with a diameter of 5mm and a thickness of 1mm were implanted into the dorsal subcutis of 18 Wistar Albino rats. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The histological analysis showed no obvious difference between n-HA /PDLLA composite and pure HA that had good biocompatibility and osteoconductivity. SEM analysis of the surface and cross section of the samples showed that the degradation of the composite started from surface, then into the inner gradually and formed multiple pores at surface. The pore size and porosity gradually increased along with time and a porous network may be formed.

Effect of Lignin and RLDPE Soil Amendments on Water Holding Capacities of Desert

The influence of recycled low density polyethylene (RLDPE) with different sizes and lignin soil amendments on dry bulk density (BD), water holding capacities (WHC) including saturated soil moisture content (SSMC), and moisture content at wilting point (MCWP) of desert was investigated. Results obtained show that BD decreased with the lignin and RLDPE added in desert. Lignin could significantly improve SSMC of desert soil. SSMC increased with the addition of RLDPE when the weight of RLDPE was less than 20 wt%, while its content was more than 20%, SSMC appeared a sharp decline. As for MCWP (5, 10, 15 and 20 wt%), it showed that the lignin presented dramatically positive effect, while RLDPE with different sizes presented slightly negative effect. Smaller particle sizes of RLDPE showed apparently the impact on soil properties in comparison with larger ones. It is hopeful that both lignin and RLDPE may be potential soil amendments for improving WHC of desert.

Thermocatalytic Degradation of Low Density Polyethylene Films at Artificial Aging Treatment under Lower Temperature

Low density polyethylene (LDPE) films added thermal catalyst were investigated at artificial aging time of 0, 10, 20, and 30 days, respectively. The samples obtained were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), gel permeation chromatograph (GPC) and fourier transform infrared spectroscopy (FT-IR). It shows that the surface of film was destroyed via thermocatalytic reactions at lower temperature. In addition, the changes of chemical groups were also observed in the thermocatalytic degradation process. Thus, the validation to the thermocatalytic route has been confirmed over lower temperature excitation. It is hoped that our work may provide a new insight into the degradation of polymeric films at lower temperature.

Biosorption of Strontium Ions by Low-Cost Sunflower Stem and Leaf

Low cost agricultural by-products are potential materials for water pollution treatment such as removal of radionuclide. This paper deals with removal of strontium ions from aqueous solution using sunflower stem (SFS) and leaf (SFL). Batch sorption experiments were performed as a function of initial solution pH, adsorbent dosage and initial strontium (II) concentration. The removal efficiency of strontium (II) increased with initial pH and achieved maximum values at a pH range of 4.0-7.0 both for SFS and SFL. The isotherm adsorption data was modeled best by the nonlinear Langmuir-Freundlich equation. The maximum sorption capacity of SFS and SFL were observed to be 17.87 and 22.31 mg/g under optimal conditions, respectively.

Study on Aqueous Viscosity Behaviors of Hydroxypropyl Methylcellulose Hydrosol and Konjac Glucomanan Hydrosol

In this work, the viscosity behavior of hydroxypropyl methylcellulose (HPMC) and konjac glucomanan (KGM) hydrosol was studied. Effects of mass fractions, water quality and sodium chloride (NaCl) on the viscosity of hydrosol were investigated by rotating viscometer. The results indicated that the viscosity of KGM and HPMC apparently increased with the increasing of mass fraction. HPMC could always maintain high viscosity in various kinds of water, whereas the viscosity of KGM reduced in tap water. The salt resistance experiments shown that the viscosities of the two kinds of hydrosol with 0.9% NaCl appeared a little decrease, hence, all hydrosols have a good salt resistance.