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.     

Effect of chitosan‐alginate nanoparticles and ultrasound on the efficiency of gene transfection of human cancer cells

Background

Gene therapy has been used to treat a variety of health problems, but transfection inefficiency and the lack of safe vectors have limited clinical progress. Fabrication of a vector that is safe and has high transfection efficiency is crucial for the development of successful gene therapy. The present study aimed to synthesize chitosan‐alginate nanoparticles that can be used as carriers of the pAcGFP1‐C1 plasmid and to use these nanoparticles with an ultrasound protocol to achieve high efficiency gene transfection.

Methods

Chitosan was complexed with alginate and the pAcGFP1‐C1 plasmid at different charge ratios to create chitosan‐alginate‐DNA nanoparticles (CADNs). The average particle size and loading efficiency were measured. Plasmid DNA retardation and integrity were analysed on 1% agarose gels. The effect of CADNs and ultrasound on the efficiency of transfection of cells and subcutaneous tumors was evaluated.

Results

In the CADNs, the average size of incorporated plasmid DNA was 600–650 nm and the loading efficiency was greater than 90%. On the basis of the results of the plasmid DNA protection test, CADNs could protect the transgene from DNase I degradation. The transgene product expression could be enhanced efficiently if cells or tumor tissues were first given CADNs and then treated with ultrasound.

Conclusions

The use of CADNs combined with an ultrasound regimen is a promising method for safe and effective gene therapy. Copyright © 2009 John Wiley & Sons, Ltd.

     

Synthesis and characterization of a novel MPEG–chitosan diblock copolymer and self-assembly of nanoparticles

In this paper, a simple and novel method based on free-radical polymerization initiated by potassium persulfate (KPS) was developed to synthesize the MPEG–chitosan diblock copolymer (MPEG–CS). The obtained MPEG–CS diblock copolymer was characterized by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (¹H NMR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The MPEG–CS copolymer could self-assemble into nanoparticles in aqueous solution. A typical TEM photography indicated that the well-spherical nanoparticles with diameter at about 200 nm were obtained. In vitro cell culture assay indicated that MPEG–CS nanoparticles are non-toxic and cell-compatible as the polymer concentration was smaller than 0.6 mg/ml. In conclusion, the obtained MPEG–CS nanoparticles might have great potential application in drug-delivery system.     

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.     

萘普生缓释微球制备工艺及性能研究

本文利用壳聚糖和海藻酸钠通过复凝聚法将萘普生制成微球,研究成球的最佳制备工艺条件及载药微球性能,制备了可生物相容,自然降解无毒的载药微球。实验中,以微球的药物包封率为制备工艺优化指标,通过正交实验得出微球的最佳制备工艺条件为:壳聚糖浓度∶海藻酸钠浓度为1:1,pH值为4.0,搅拌速度为300rpm,反应温度为35℃。以最佳制备工艺条件制备的含药微球,重现性好,工艺稳定,同时体外溶出实验表明,该微球具有较好的缓释作用。     

绿色木霉粗纤维素酶液水解壳聚糖的研究

利用自制绿色木霉粗纤维素酶液降解壳聚糖制备低聚壳聚糖.采用粘度法、乙酰丙酮法和还原糖浓度分析,研究了温度、pH值及反应时间等因素对壳聚糖水解程度和产物相对分子质量的影响,并采用质谱法对水解产物进行定性分析.结果表明,粗纤维素酶液水解壳聚糖作用的最适pH为5.0、最适反应温度为50 ℃、最适反应时间为12 h.粗纤维素酶...     

N-酰化低聚壳聚糖衍生物还原能力的研究

对低聚壳聚糖进行N-酰化改性,制得取代度相同的N-马来酰低聚壳聚糖(NMCOS),N-琥珀酰低聚壳聚糖(NSCOS),N-邻苯二甲酰低聚壳聚糖(NPCOS),其中NMCOS1、NSCOS1、NPCOS1的取代度均为0.25;NMCOS2、NSCOS2、NPCOS2的取代度均为0.49。考察了6种N-酰化低聚壳聚糖衍生物的还原能力。结果表明:当取代度相同时,N-邻苯二甲酰低聚壳聚糖的还原能力最强,其次是N-马来酰低聚壳聚糖,N-琥珀酰低聚壳聚糖的还原能力最差。这可能是由取代基的性质不同所致。     

胞外ATP对壳聚糖诱导的ROS和PAL活性变化的影响

以烟草BY-2悬浮细胞为材料,探讨了胞外ATP对壳聚糖引起的活性氧(reactive oxygen species,ROS)水平和苯丙氨酸解氨酶(phenylalanine ammonia-lyase,PAL)活性变化的影响。结果表明,5~20μg·mL^-1壳聚糖处理导致了烟草悬浮细胞细胞内ROS水平逐渐增加;壳聚糖也导致了PAL活性的增加,其活性在15μg·mL^-1壳聚糖处理下达到峰值,此后有所降低。10~40μmol·L^-1外源ATP处理未引起烟草悬浮细胞内ROS水平和PAL活性的显著变化。细胞外ATP水平则随壳聚糖浓度的增加而逐渐下降。本文进一步分析了细胞外ATP对壳聚糖引起的ROS水平和PAL活性变化的影响。结果显示,外源施加20μmol·L^-1ATP可以有效降低壳聚糖诱导的烟草悬浮细胞ROS水平上升,同时外源ATP也明显减缓了壳聚糖所诱导的PAL活性的上升。上述结果表明,细胞外ATP水平能够影响壳聚糖引起的ROS水平和PAL活性的变化。     

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.     

A miniaturized nebulization catheter for improved gene delivery to the mouse lung

BACKGROUND: The available methods for administration of gene delivery systems to the lungs of small animals via nebulization have several drawbacks. These include lack of control over the delivered dose and a negative impact on the stability of the formulation. This paper describes a new nebulization catheter device for the administration of plasmid-based gene delivery systems (polyplexes) as aerosols to the mouse lung in vivo. METHODS: The physical stability of naked pDNA and polyplexes formulated with chitosan oligomers and PEI was examined following nebulization with the catheter device. We also examined the in vitro transfection efficiency of the polyplexes recovered after nebulization. Lung distribution and gene expression after administration of the selected gene delivery systems to the mouse lung were also investigated. RESULTS: In contrast to previously described nebulization methods, the structural integrity of the unprotected naked pDNA was maintained following nebulization by the catheter device, which indicates relatively mild nebulization conditions. In addition, the nebulization procedure did not affect the physical stability of the formulated polyplexes. Small volumes of the pDNA aerosol (10-20 microl) were delivered in a highly controlled and reproducible manner. The aerosol droplet size varied with the molecular weight of the polycations. Aerosol delivery via this method resulted in improved lung distribution of pDNA polyplexes and a six-fold increase in the efficiency of gene delivery in vivo over that seen with the commonly used intratracheal instillation method. CONCLUSION: The use of the nebulization catheter device provides a promising alternative for aerosol gene delivery to the mouse lung.