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Abstract: A new type of acid-labile cationic copolymer consisting of a hydrophilic poly(ethylene glycol) (PEG) block and a polymethacrylamide block bearing tertiary amines linked by acid-labile ortho ester rings in side chains (PAOE), with defined chain length, had been synthesized via RAFT polymerization. The copolymers could efficiently bind and condense plasmid DNA at neutral pH into narrowly dispersed nano-scale polyplexes. The hydrolysis of ortho ester group in the side-chains of PAOE followed a distinct exocyclic mechanism and the rate of hydrolysis was much accelerated at mildly acidic pH, resulting in the accelerated disruption of polyplexes and the release of intact plasmid DNA. The three polymers were not toxic to cultured COS-7 cells as measured by MTT assay. As expected, PEG segments of the PEG-b-PAOE copolymers prevented nonspecific transfection of COS-7 cells. Once conjugated to a targeting ligand to enhance cell-specific entry, PEG-b-PAOE with its pH-triggered DNA release properties may achieve efficient intracellular delivery of DNA or other nucleic acid therapeutics. [Copyright &y& Elsevier]

Abstract: At present, some researchers provide a type of fuzzy risk analysis algorithms for dealing with fuzzy risk analysis problems, where the values of the evaluating items are represented by trapezoidal fuzzy numbers. In those algorithms, the main operations are two: one is arithmetic operators of the trapezoidal fuzzy numbers; the other is the similarity of the trapezoidal fuzzy numbers. However, the arithmetic operators of some algorithms do not satisfy some properties of the trapezoidal fuzzy numbers and the similarity of the trapezoidal fuzzy numbers does not coincide with the intuition of the human being. Due to this situation, in this paper, we present an efficient approach for fuzzy risk analysis based on some new arithmetic operators of the trapezoidal fuzzy numbers and propose a new similarity of the trapezoidal fuzzy numbers to deal with fuzzy risk analysis problems. At the same time, we make an experiment to use 30 sets of trapezoidal fuzzy numbers to compare the experimental results of our proposed approach with the existing similarity measures. At last, we use an example to illustrate the efficiency of the new approach. [Copyright &y& Elsevier]