α,β-poly [(N-hydroxypropyl/aminoethyl)-DL-Aspartamide-co-L-Lysine]: Potential Non-viral Vector For Gene Delivery

Polyaminoacid materials are widely researched as non-viral gene vectors because of the advantages, such as biodegradation, low cytotoxicity and so on. Polylysine, poly(aspartic acid), polyornithine and polyglutamide of them are researched in a lot of articles. Polylysine and polyornithine have positively charge in the physiological condition and can condense DNA by the static force. Poly(aspartic acid) has the structure of the imide ring and can be grafted with the functional side chains of condensing DNA by ring-opening with alkaline reagents. According to the advantages of many sites recognized by enzymes and high speed of degradation of copolyaminoacid materials, a new type of gene vector material, copolymers of aspartic acid and lysine, is synthesized by thermal copolycondensation with phosphoric acid catalysis. Now the similar researches are little. A series of Poly[Aspartic acid-co-L-lysine](PAL) are copolycondensed by DL-aspartice acid and L-lysine with different ratios in different conditions and their constructions are affirmed by the spectra of 'H-NMR, FT-IR, X-Ray, TGA. Characteristic viscosity of the series of PAL are measured with the method of capillary viscosity, αβ -poly [(N-hydroxypropyl/aminoethyl)-DL-Aspartamide-co-L-Lysine] (PHAAL) is synthesized by ring-opening poly[aspartic acid-co-lysine](PAL) with the alkaline n-propanolamine and ethylene diamine. PHAAL performed good degradability in the phosphoric acid buffer solution(PBS)(0.01M, ph=7.4) and in the solution of enzyme(Papain, Trypsine) at 37?.1 by GPC experiment. After degradation in PBS for four days, the mean molecule of PHAAL fell to the 70% of origin. After degradation in the solution of Papain for 12 hours, the mean molecule of PHAAL dropped 32% and degradation was complete in 24 hours. Moreover PHAAL degraded completely in the solution of Trypsin in 12 hours. PHAAL appeared less cytotoxicity than poly(ethylenimine)(25KDa) and poly-L-lysine(15.7KDa) in Hela, E.C.V-304, Bcap37 cell lines, which was quantified by MTT assay. Furthermore PHAAL didn't perform distinct cytotoxicity up to 40ug/ml. The combination ability of PHAAL and plasmid DNA was evaluated by agarose gel electrophoresis with agarose gel(1.0% w/v) containing ethidium bromide(0.25ug/ml). The PHAAL with higher ratios of lysine in the copolymers have higher ability of condensing DNA. Among them, the PHAAL-T25(DL-aspartic acid: L-lysine=5:5, mol/mol) can condense and regard DNA completely. In a word, the polyaminoacid materials, PHAAL, is the kind of macromolecule materials as the non-viral gene vector.