Spectroscopic and physicochemical characterization of PAMAM dendrimers generation 4.0 and 4.5

D. E. YBARRA; D. E. IGARTUA; M. E. TUTTOLOMONDO; S. DEL V. ALONSO; F. C. ALVIRA

La Plata

Conferencia; XLVII Reunion anual de la sociedad argentina de biofisica; 2018

Theaim of this work is the structural and physicochemical characterization ofpolyamidoamine (PAMAM) dendrimers (D) of generation (G) 4.0 and 4.5, as afunction of the pH. The fluorescence of the PAMAM D is currently a matter ofresearch. It is known that they have two fluorophores, however only one of themis clearly identified. While the second is subject of controversy nowadays.PAMAM D are polymers with a branched structure chemically synthesized from a coreof ethylenediamine with progressive addition (generations) of polyamidoaminegroups. These nanoparticles can have complete G (as DG4.0), which have terminalamino groups; or intermediate G (as DG4.5) with terminal carboxyl groups. Both PAMAMD have interior pockets with tertiary amines and amide bonds. Also, they haveionizable groups in their pockets (tertiary amines) and terminal groups(primary amines or carboxylates) that would allow modifying their conformationdepending on the physicochemical environment. PAMAM D have many biomedicalapplications among them drug- and gene-delivery, theragnostic application. Raman, UV-Vis and fluorescence spectroscopies were used to elucidate structuralcharacteristics. Hydrogen binding constants (pKa) were determinedfor DG4.0 and DG4.5 by potentiometric titration. Raman spectrum showed signalsof tertiary amines and carbonyl of the carboxylic acid and amide bond. On theother hand, transitions corresponding to amides and tertiary amines are foundon UV-Vis spectrum. Tertiary amines absorb in differently according to the pHcondition. In the potentiometric titrations we obtained curves to determine thepKa of the functional groups. The fluorescence emission reinforcesthe idea that the main fluorophore in PAMAM D are the inner tertiary amine.However, we found an unusual behavior of the DG4.0 fluorescence with the pH,while behavior of fluorescence of DG4.5 with the pH are shown for the firsttime. We hope to use these results to obtain a detailed characterization of theinteraction between drugs and PAMAM D, in their internal pockets or theirterminals groups