壳聚糖辐照降解产物涂膜保鲜草莓研究

壳聚糖具有抑菌性与成膜性。将壳聚糖辐照降解得到的一系列不同粘均分子量产物进行涂膜草莓保鲜,研究涂膜液中壳聚糖粘均分子量、浓度、pH值、有机酸、明胶含量对草莓保鲜效果的影响;并设计四因素三水平正交试验。实验结果表明：1％（w／v）7．0×10^4Da壳聚糖、1％（v／v）醋酸、pH5、添加明胶0．5％的涂膜配方具有最好的保鲜效果;在常温（20℃、湿度80％～90％）下可以延长贮藏期2d;低温（3℃-4℃、湿度80％-90％）下可以延长贮藏期3d。     

Effects of chitosan/collagen substrates on the behavior of rat neural stem cells

Spinal cord and brain injuries usually lead to cavity formation. The transplantation by combining stem cells and tissue engineering scaffolds has the potential to fill the cavities and replace the lost neural cells. Both chitosan and collagen have their unique characteristics. In this study, the effects of chitosan and collagen on the behavior of rat neural stem cells (at the neurosphere level) were tested in vitro in terms of cytotoxicity and supporting ability for stem cell survival, proliferation and differentiation. Under the serum-free condition, both chitosan membranes and collagen gels had low cytotoxicity to neurospheres. That is, cells migrated from neurospheres, and processes extended out from these neurospheres and the differentiated cells. Compared with the above two materials, chitosan-collagen membranes were more suitable for the co-culture with rat neural stem cells, because, except for low cytotoxicity and supporting ability for the cell survival, in this group, a large number of cells were observed to migrate out from neurospheres, and the differentiating percentage from neurospheres into neurons was significantly increased. Further modification of chitosan-collagen membranes may shed light on in vivo nerve regeneration by transplanting neural stem cells.     

壳聚糖作为药物缓释控释载体的研究进展

壳聚糖因其具有良好的生物学特性而成为多种药物载体研究的热点。药物经过壳聚糖负载后,不仅能够达到缓释控释的目的,还能够改变药物的给药方式,以此减少给药次数,降低药物不良反应,提高药物生物利用度。本文就壳聚糖和改性壳聚糖作为普通药物和生物大分子药物载体的研究进展作一综述。     

蚯蚓野外采样方法评述

蚯蚓作为土壤生态系统的关键组成部分,不但可以改善土壤结构,而且与许多生物化学养分循环直接相关,对土壤质量改善和土壤生产力提高起到至关重要的作用.然而,蚯蚓野外采样方法的系统研究和评估还比较缺乏,在国内尤其少见.本文综述了目前国内外常见蚯蚓野外采样方法的操作过程、优缺点、有效性以及对蚯蚓种群特征研究结果可能产生的影响,认为在允许扰动土壤的区域,利用驱虫剂与手拣法相结合进行蚯蚓采样能够较为准确地反映蚯蚓种群和生物量的真实特征;在不能扰动土壤的区域异硫氰酸烯丙酯(AITC)溶液方法是最佳选择.     

壳聚糖对大肠杆菌的抑制作用规律及抗菌机理初探

考察了不同分子量壳聚糖对大肠杆菌的抑菌性能,利用壳聚糖的席夫碱反应对其氨基加以保护,探讨了壳聚糖对大肠杆菌的抗菌机理。研究结果表明:壳聚糖分子量越小,对大肠杆菌的抗菌作用越明显;壳聚糖对大肠杆菌的抑菌作用与其氨基的质子化有关。     

Chitosan sponges as tissue engineering scaffolds for bone formation

Rat calvarial osteoblasts were grown in porous chitosan sponges fabricated by freeze drying. The prepared chitosan sponges had a porous structure with a 100-200 microm pore diameter, which allowed cell proliferation. Cell density, alkaline phosphatase activity and calcium deposition were monitored for up to 56 d culture. Cell numbers were 4 x 10(6) (day 1), 11 x 10(6) (day 28) and 12 x 10(6) (day 56) per g sponge. Calcium depositions were 9 (day 1), 40 (day 28) and 48 (day 56) microg per sponge. Histological results corroborated that bone formation within the sponges had occurred. These results show that chitosan sponges can be used as effective scaffolding materials for tissue engineered bone formation in vitro.     

Enhancement of nitrogen release properties of urea–kaolinite fertilizer with chitosan binder

The use of controlled release fertilizer (CRF) has become a new trend to minimize environmental pollution. In this study, urea–kaolinite containing 20 wt% urea after one hour dry grinding was mixed with different concentrations of chitosan as a binder to prepare nitrogen-based CRF. Fourier transform infrared spectroscopy confirmed the hydrogen bonding between urea and kaolinite. Covalent interaction between urea–kaolinite and chitosan make the granules stronger. The nitrogen release was measured in 5 days interval using a diacetylmonoxime calorimetric method at a wavelength of 527 nm. The results illustrated that by increasing the chitosan concentration from 3 to 7.5%, nitrogen release decreased from 41.23 to 25.25% after one day and from 77.31 to 59.27% after 30 days incubation in water. Compressive stress at break tests confirmed that granules with chitosan 6% had the highest resistance and were chosen for ammonia volatilization tests. Ammonia volatilization was carried out using the forced-draft technique for a period of 10 weeks. The results showed that the total amount of ammonia loss for conventional urea fertilizer and urea–kaolinite–chitosan granules was 68.63 and 56.75%, respectively. This controlled release product could be applied in agricultural crop production purpose due to its controlled solubility in the soil, high nutrient use efficiency and potential economic benefits.     

Kupffer Cell Isolation for Nanoparticle Toxicity Testing

The large majority of in vitro nanotoxicological studies have used immortalized cell lines for their practicality. However, results from nanoparticle toxicity testing in immortalized cell lines or primary cells have shown discrepancies, highlighting the need to extend the use of primary cells for in vitro assays. This protocol describes the isolation of mouse liver macrophages, named Kupffer cells, and their use to study nanoparticle toxicity. Kupffer cells are the most abundant macrophage population in the body and constitute part of the reticulo-endothelial system (RES), responsible for the capture of circulating nanoparticles. The Kupffer cell isolation method reported here is based on a 2-step perfusion method followed by purification on density gradient. The method, based on collagenase digestion and density centrifugation, is adapted from the original protocol developed by Smedsrød et al. designed for rat liver cell isolation and provides high yield (up to 14 x 10⁶ cells per mouse) and high purity (>95%) of Kupffer cells. This isolation method does not require sophisticated or expensive equipment and therefore represents an ideal compromise between complexity and cell yield. The use of heavier mice (35-45 g) improves the yield of the isolation method but also facilitates remarkably the procedure of portal vein cannulation. The toxicity of functionalized carbon nanotubes f-CNTs was measured in this model by the modified LDH assay. This method assesses cell viability by measuring the lack of structural integrity of Kupffer cell membrane after incubation with f-CNTs. Toxicity induced by f-CNTs can be measured consistently using this assay, highlighting that isolated Kupffer cells are useful for nanoparticle toxicity testing. The overall understanding of nanotoxicology could benefit from such models, making the nanoparticle selection for clinical translation more efficient.     

In vitro study of alginate–chitosan microcapsules: an alternative to liver cell transplants for the treatment of liver failure

The application of alginate–chitosan (AC) microcapsules to liver cell transplantation has not been previously investigated. In the current in vitro study, we have investigated the potential of AC microcapsules for the encapsulation of liver cells and show that the AC membrane supports the survival, proliferation and protein secretion by entrapped hepatocytes. The AC membrane provides cell immuno-isolation and has the potential for cell cryopreservation. The AC microcapsule has several advantages compared to more widely used alginate–poly-L-lysine (APA) microcapsules for the application of cell therapy.