| Dendrimers are highly branched and symmetrical macromolecules with specificchemical composition, precise molecular weight, and well-definedcore-interior-periphery architecture. The empty interior cavity could be used forphysical encapsulation of different drugs. Various ligands can be conjugated to thedendrimer periphery via surface engineering. These smart features enable theapplication of dendrimers in many fields.In this essay, The themo-sensitive functional structure units (N-propylpiperazin-1-yl)-4-oxo-butanoic acid (NPPOBA), which are considered to playan important role in their temperature sensitive behavior were introduced to thesurface of the relatively lower generation polyamidoamine (PAMAM) dendrimer andendowed the dendrimer with pH and temperature sensitive property. In the presentstudy, G2.5and G3.5PAMAM were synthesized, and in order to increase the densityof the terminal groups of PAMAM dendrimer, the ester-terminated groups ofPAMAM dendrimer were converted into the hydroxyls by the addition oftrihydroxymethyl amino methane (Tris). The functional structure units wereconjugated to the surface of PAMAM-Tris dendrimer by using EDC·HCl as acoupling agent. The obtained PAMAM-Tris-NPPOBA was connected withfluorescein isothiocyanate (FITC) to get fluorescently labeled dendrimer for cellexperiments.The result showed that the PAMAM-Tris-NPPOBA exhibited temperature andpH sensitive, and the lower critical solution temperature (LCST) was affected by thesolvent, the carrier concentration, and the encapsulated drugs.Finally, human breast cancer cells (MCF-7) was selected to examine thedendrimer’s cytotoxicity and endosomal escape behavior, preliminary resultsconfirmed our hypothesis that the pH, temperature sensitive dendrimer has the abilityof endosomal escape behavior with negligible cytotoxicity.The results indicate that the modified dendrimers with pH and temperaturesensitive property might be a promising carrier for drug delivery systems. |
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