Key Engineering Materials Vols. 645-646

Abstract: The objective of this study was to develop a novel silica modified large-sized hydroxyapatite whiskers with improved properties for use in bone repair applications. Large-sized whiskers with a mean length of 250μm were obtained by a hydrothermal co-precipitation method at 150°C, 7.5Mpa in high-pressure reactor. Silica modified hydroxyapatite whiskers were prepared by dissolving TEOS in ethanol solution, then sintering with hydroxyapatite. The compositional and morphological properties of prepared whiskers were studied by means of x-ray diffraction (XRD), Fouier transform infrared (FT-IR), scanning electron microscopy (SEM). The results indicated the evidence of nanosilicon dioxide particles on the surface of HAP whiskers. The size of nanosilicon dioxide particles depends on dropping and stirring rate. Hence, this new type of silica modified large-sized hydroxyapatite whiskers is a valuable candidate for biomedical applications.Key words: hydroxyapatite, hydrothermal co-precipitation, surface modified, whiskers

Abstract: Microfluidic chips have been widely used in various of areas, such as biology, chemistry, medical science and so on. As one of the key techniques of microfluidic chips, the technique of micro driven of the water has been studied by experts all around the world for years. Of all kinds of the driven methods, the power costed by bionic driven is lowest. Moreover, as xylem is the main channel to transport the water in a tree, the mechanism of water transportation has been always an important issue in the study of physiological plant ecology. In this paper, the models of a single vessel element with different pit numbers (5 pits, 10 pits and 20 pits) or diameters(4µm and 7µm) were established according to the xylem and the pits’ structure. The 3-dimensional flow distribution was analyzed by ANSYS 12.0 calculating by realizable κ-ε algorithm. The pressure distribution contours and the velocity distribution contours of a single vessel element could be obtained after calculated by the software. According to the results, the flow field in a single vessel element of the xylem was studied. In addition, the influence of pits on the pressure and velocity were analyzed. The results showed that the influence on pressure and velocity is less when the diameter is smaller. As the number of pits on the vessel increased, the influence on the distribution of pressure and velocity is greater. Based on the result of numerical simulation of vessel element, a bionic structural microfluidic chip was designed and then analyzed by ANSYS 12.0.

Abstract: The forming process of denture preparation based micro-flow extrusion was researched. The dental ceramic materials having health care function was preparation. Through analysis and calculation, the rheological properties of the ceramic slurry confirmed to be pseudo-plastic fluid . The extrusion head as a key part was designed. The pressure distribution and velocity distribution of the internal flow field of extrusion head were simulated by using START-CD software ,the analysis result can used to guide the optimal design of extrusion head.

Abstract: In this paper, an effective, simple and universal method for cell immobilization was developed. A self-polymerization nanofilm of poly (dopamine) was used to fix yeast cells in microfluidic channels. The surface morphology of the poly (dopamine) film was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Water contact angles (WCA) was also used to characterize the surface property of the poly (dopamine) nanofilm. The WCA on the PDMS substrates rapidly decreased from 105° to 59.8° with an increase in poly (dopamine) coating time. The interfacial process of dopamine self-polymerization and the cell immobilization were measured in a label-free and real-time mode by a surface plasmon resonance (SPR) instrument. Finally the immobilized yeast cells were observed by using a light microscope. From the experimental results, the yeast cells can be easily immobilized on the microfluidic channels modified with the nanofilm of poly (dopamine), which will hold great potential for the immobilization, detection and further analysis of other suspension cells, such as blood cells.

Abstract: This paper presents a silicon-based ultrasonic scalpel for minimally invasive surgery. Starting from the fundamental theory, the micro ultrasonic scalpel using triangular silicon horn chip is designed and fabricated in detail. It is found that the magnification of the composed horn keeps 5.8 when size changes. A micro scalpel has been fabricated by MEMS technology. The test results show that a good performance in vibration and fit for puncturing biological tissues at the micro/nanoscale are obtained in the micro ultrasonic scalpel.

Abstract: Currently, the developed electrospinning technique is capable of producing sub-micron diameter fibers, has better bionic of the extracellular matrix (ECM) on the size and morphology. Joining the nanofiber network into the porous macro scaffolds by the association of electrospinning with 3D printing technology can effectively support bionic microenvironment and improve the cell compatibility of scaffolds. We prepared the GE/CA-PCL scaffold by the composite approach, and characterized the morphology, cell compatibility and mechanical properties of scaffolds compared to the GE/CA scaffold prepared by single 3D printing technology. The composite molding process of 3D printing and electrospinning is a promising technique used for preparing scaffolds for tissue engineering and clinical medicine.

Abstract: Huperzine A (HupA), an alkaloid isolated from the Chinese club moss, is a reversible inhibitor of cholinesterases which cross the blood-brain barrier and show high specificity for acetylcholinesterase (AChE). However, HupA induces unwanted side effects in an effective dose against nerve agent poisoning. In the present study, HupA–loaded poly (lactide-co-glycolide) nanoparticles (HupA-PLGA-NP) were prepared using the O/W emulsion solvent evaporation method. The results of SEM demonstrated that HupA-PLGA-NP had an spherical shape and a smooth surface without pores. It’s mean diameter and PDI were 208.5±3.6nm and 0.09±0.01 respectively. The Zeta potential was-35.3±1.8mV and the drug loading was 2.86±0.6%. In vitro drug release studies showed that HupA-PLGA-NP had a sustained-release behavior in phosphate buffer solution, The accumulated amount of HupA was about 72.1% at 48h with a low burst release within 30min. The LD₅₀ values of HupA and HupA-PLGA-NP were 1.40 and 4.85mg/kg respectively, showing that the toxicity of HupA was reduced by 3.5 times. We evaluated the protective efficacy for different doses of HupA or HupA-PLGA-NP against 1.0×LD₉₅(143.0μg/kg) soman toxicity. The results confirmed that HupA (0.3~0.5mg/kg) or HupA-PLGA-NP (0.5~1.5mg/kg) could ensure animals survive. However, about 10% of the animals injected with HupA (0.8mg/kg) died, while no animals died when injected with HupA-PLGA-NP (1.5mg/kg). Aim to 100% survival rate, the effective protective time (12h) of HupA-PLGA-NP (0.5mg/kg,iv) against 1.0×LD₉₅ soman toxicity in mice was significantly prolonged compared with that of HupA (4h). The study of AChE activity showed that whole-blood and supernatant of brain diluted by 80-fold and 10-fold respectively were optimum in this study. AChE inhibition after administration of HupA and HupA-PLGA-NP (0.5mg/kg,iv) was recorded and analyzed, The peak values of AChE inhibition in whole-blood and brain by HupA-PLGA-NP (17.6% and 21.8%) were lower than those by HupA (33.7% and 31.9%) and AChE inhibition time by HupA-PLGA-NP was longer than that by HupA. These data confirmed that HupA-PLGA-NP had less toxic and more longer time than HupA against 1.0×LD₉₅ soman poisoning and warrant further development as a potent medical countermeasure against chemical warfare nerve agents (CWNAs) poisoning.