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- 저자 : Zhiyuan Zheng (검색결과 3 건)
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Meng Zheng,Zhiyuan Zhong,Chunmei Yang,Fenghua Meng,Rui Peng 한국고분자학회 2012 Macromolecular Research Vol.20 No.3
1.8 kDa branched polyethylenimine (PEI) was modified with pH-sensitive degradable acetal containing hydrophobe, 2,4,6-trimethoxybenzylidene-tris(hydroxymethyl)ethane (TMB-THME), to enhance its DNA condensation under extracellular conditions as well as to achieve active DNA release inside cells. PEI-(TMBTHME)n conjugates in the amount of 1.8 kDa were prepared with varying degrees of substitution (DS) from 3.0, 5.7 to 10.1. Notably, dynamic light scattering (DLS) measurements showed that all three 1.8 kDa PEI-(TMB-THME)n conjugates could effectively condense DNA into nano-sized particles (189-197 nm) at N/P ratios ranging from 20/1 to 80/1. The surface charges of PEI-(TMB-THME)n polyplexes depending on DS and N/P ratios varied from +22 to +28 mV,which were comparable to or slightly higher than the unmodified 1.8 kDa PEI counterparts (~+22 to +23 mV). Under a mildly acidic condition mimicking that of endosomes, interestingly, 1.8 kDa PEI-(TMB-THME)n polyplexes were quickly unpacked to release DNA because of the pH-induced acetal degradation that transforms hydrophobic modification into hydrophilic modification. MTT assays demonstrated that all PEI-(TMB-THME)n polyplexes displayed low cytotoxicity (>80%) to 293T, and HeLa cells at N/P ratios ranging from 20/1 to 60/1. The in vitro gene transfection studies showed that the transfection activity of 1.8 kDa PEI was significantly enhanced by modifications with TMBTHME,in which transfection efficiencies increased with increasing DS. For example, 1.8 kDa PEI-(TMBTHME)10.1 polyplexes displayed 250-fold and 80-fold higher transfection efficiencies than those of the unmodified 1.8 kDa PEI counterparts in 293T and HeLa cells, respectively, which were approximately 4-fold and 2-fold higher than that of 25 kDa PEI control. The superior transfection activity of 1.8 kDa PEI-(TMB-THME)10.1 polyplexes was also confirmed by confocal laser scanning microscopy (CLSM), which showed efficient delivery of DNA into the nuclei of 293T cells following 4 h transfection. Modification of low molecular weight PEI with pH-sensitive degradable hydrophobe has appeared to be highly promising in the development of “artificial viruses” for safe and efficient gene transfer.
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Yue Xue,Zhiyuan Zheng,Shuwei Shen,Guangli Liu,Ronald X. Xu 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.2
Electrospun nanofibrous mats (ENM) have been extensively used for removal of suspended particles, cells and bacteria in membrane filtration because of its high porosity and permeability. However, microfiltration process is driven by a certain transmembrane pressure, and the filtration performance of traditional ENM are thereby hindered by its limited mechanical property. In this study, we propose a new strategy that sandwich the ENM between two layers of electrospray-deposited microparticles to enhance the mechanical properties of ENM membrane. Through a suitable thermal treatment, the microparticles stick with each other forming firm networks, while the ENM is rarely influenced. The mechanical tests show that the tensile strength and elastic modulus of the sandwich-structure composite membrane are 5 times and 7 times higher than those of the fibrous membrane, respectively. Meanwhile, the filtration tests show that the rejection rate of the composite membrane is also higher than the fibrous membrane. Our study implies the composite membrane fabricated by layer-by-layer deposition via electrospray and electrospinning has a great potential in microfiltration applications.
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Engineering of a Bacillus subtilis Strain Deficient in Cellulase: Application in Degumming of Ramie
Qi Yang,Shengwen Duan,Lifeng Cheng,Xiangyuan Feng,Ke Zheng,Chunliang Xie,Zhiyuan Liu,Yuande Peng 한국섬유공학회 2019 Fibers and polymers Vol.20 No.1
Degumming is the most important step before ramie fibers are used in textile industry. Conventional chemical degumming technology with alkaline treatment at high temperature causes critical problems in environment. In addition to multiple degumming enzymes (e.g. pectinases and xylanases), Bacillus subtilis strain 168 can also produce cellulase which brings irreversible damage to ramie fibers. In this study, a strain deficient in cellulase was constructed by insertional inactivation of gene eglS to make it suitable for microbial degumming. Results showed that the cellulase activity was not detected in strain ΔeglS, after 25 h of incubation with strain ΔeglS, the weight loss of the ramie fibers was 20.20 %. Though the residual gum content of ramie fibers obtained in microbial degumming process was 19.67 %, microbial intervention followed by diluted alkaline solution treatment showed lower residual gum content (2.73 %) than chemical degumming (2.96 %). The single fiber breaking strength value of ramie fibers from bio-chemical degumming process reached 27.19 cN, which was the highest of three samples. Moreover, bio-chemical degumming process resulted in a 75 % decrease of alkali dosage as compared with chemical degumming process. This study provides a suggestion to genetically modify wild-type strain in order to protect ramie fibers from cellulase damage, and indicates a sustainable alternative for the traditional chemical degumming in the textile industry.
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