Liguo Qin

Sulfated modification and immunomodulatory activity of water-soluble polysaccharides derived from fresh Chinese persimmon fruit

In this study, three kinds of chemically sulfated polysaccharides (PFP-S) were derived from a water-soluble polysaccharide of persimmon fruit with chlorosulfonic acid-pyridine method. Relationship between the degree of substitution and immunomodulatory activity of PFP-S was examined with the splenocytes experiment. The results showed that the splenocytes-activating activity was significantly enhanced by PFP-S in all the groups compared with control group (P<0.01). PFP-SII exhibited the most potent splenocytes-activating activity by increased cytokine production and NO release. It also suggested that the sulfate groups and molecular weight of polysaccharides are key factors to regulate the immunomodulatory activities.

Response of MC3T3-E1 osteoblast cells to the microenvironment produced on Co–Cr–Mo alloy using laser surface texturing

Osteoblast responses to Co–Cr–Mo alloy depend on not only the chemistry of alloy but also the physical properties of alloy surface, such as its microtopography and roughness. This study was undertaken to examine changes in cell adhesion, morphology, differentiation and gene expression during osteoblast interaction with different textured Co–Cr–Mo alloys. With laser surface texturing, three kinds of textured surfaces were fabricated. It showed that the microenvironment processed by laser surface texturing leads to an increase in surface roughness and DMEM contact angles of samples. Adhesion and differentiation tests demonstrated that osteoblast cells can discriminate surfaces with different roughness and surfaces with comparable roughness but different topographies such as triangle, circle and square textures. Morphological characteristics obtained by SEM imaging showed that osteoblast cells are elongated and are in polygonal shape on the textured surface. OPG/RANKL mRNA expression studies showed a significant and marked decrease in RANKL gene expression on the square-textured surface; by contrast, the ratio of OPG/RANKL showed a significant increase. These results indicate that Co–Cr–Mo surface textures affect osteoblast proliferation, morphology and gene expression; the microenvironment of implant should be considered in the future design.

Preparation and bioactive properties of chitosan and casein phosphopeptides composite coatings for orthopedic implants

Using the layer-by-layer deposition method, functional chitosan/casein phospopeptides (CS/CPP) composite coatings were produced on Co-Cr-Mo alloy. The CS/CPP composite coatings had the dendritic topography, and were quite hydrophilic. Zeta potential measurements showed the composite coatings were negative charged at neural pH. XPS results indicated that the CS/CPP composite coatings were covalently bond to the substrate. When MC3T3-E1 cells were seeded on the CS/CPP composite coatings, no cytotoxicity was observed. The bone morphogenetic protein-2 (BMP-2) mRNA expression was significantly up-regulated in MC3T3-E1 cells cultured on the composite coatings and it was twice as much as that of cells cultured on the bare substrate. The expression of osteoprotegerin (OPG) mRNA and the ratio of OPG/receptor activator of nuclear factor-κB ligand (RNAKL) mRNA were increased 5-fold and 55-fold, respectively. These results suggested the CS/CPP composite coatings may have potential application in cobalt matrix orthopaedic implants.

Biotribological application of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) hydrogel as an efficient carrier with slow-release lubrication effect

Excessive wear debris in prosthesis tends to induce loosening, which is a major problem affecting the durability of long-serving implants. Although bionic synovial fluid can be used to improve the lubrication of artificial joints, the fluid is often absorbed easily by the tissues of human body. To enhance the effectiveness of bionic synovial fluid, poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC) hydrogel was prepared as a carrier for the bovine serum albumin (BSA) in synovial fluid. It thus significantly reduces the loss rate of BSA. Experimental results show that the good sustainability and favorable release ability of hydrogel efficiently prevent the rapid outflowing of BSA. Experiments also reveal that the PCEC hydrogel inclines to form a particular structure with BSA and thus give BSA an excellent slow-release performance. Furthermore, friction and wear tests indicate that the released solution from the PCEC hydrogel possesses good lubricating properties. In general, the average friction coefficient of released solution is approximatively 77% lower than that of the normal phosphate-buffered solution. This study furnishes with an effective approach to prolong the lubricating duration of BSA in artificial prostheses.

Fabricating hierarchical micro and nano structures on implantable Co–Cr–Mo alloy for tissue engineering by one-step laser ablation

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co-Cr-Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co-Cr-Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co-Cr-Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants.

A boundary slip region design on journal bearingsunder high speed water lubrication

This paper, based on the two-component slip model, numerically analyzes the tribology performances of journal bearings with boundary slip/no-slip regions on the condition of high speed water lubrication. It is demonstrated that journal bearings with a whole slip sleeve reduce the friction drag and the load carrying capacity. Bearings with a slip/no-slip interval region on sleeve, however, can shorten the cavitation region and enhance the average film pressure, which means the enhancement of load carrying capacity and the reduction of friction drag. When the boundary of the slip and no-slip regions is close to the location between the pressure peak and 180° of the bearing, the load carrying capacity reaches its maximum. Different to loading capacity, friction drag is reduced dramatically with the increase of the slip region. For bearings with small eccentricity ratio, small width and large diameter, the loading capacity and the friction drag can be enhanced and reduced more significantly.

In vivo synthesis of calcium oxalate whiskers on CoCrMo alloy surfaces via biomineralization.

Surface treatments using bio-technology are valuable and fascinating in the sense that such treatments are natural and yield good biocompatibility. Calcium oxalate whiskers for biomedical applications were successfully synthesized on the CoCrMo alloy surfaces implanted in Aloe leaves which consist of many active bio-chemical elements. The effect of surface wettability and surface morphology on the formation of whiskers was investigated using four differently treated CoCrMo surfaces: (i) smoothly polished surface, (ii) electrochemical etched surface, (ii) textured surface with dimples, and (iv) parallel orientated-grooved surface. Results showed that the formed whiskers had a length ranging between 100 μm and 600 μm, and a diameter in the range of 2 μm to 5 μm. Electrochemically etched surfaces had better wettability and were favorably for growing whiskers. Surface morphology with (i) dimple textures or (ii) parallel grooves facilitated the effective control of the size and amount of the grown whiskers.