Aging Process of Polyamidoamine Dendrimers: Effect of pH and Shaking in the Fluorescence Emission and Aggregation-State

In the last years, it has been discovered and intensely studied the non-traditional intrinsic fluorescence of PAMAM dendrimers. Nevertheless, their aging process in aqueous suspension is scarcely studied, being unknown the causes of the observed changes in their fluorescence properties. Hence, this work aims to characterize the PAMAM dendrimers of generation 4.0 (DG4.0) and 4.5 (DG4.5) through the aging process at three different pH conditions, stored with or without shaking. We studied, up to 16 days, the UV-Vis absorption, the fluorescence emission, and the size of dendrimers/aggregates. In a different way than the already published work, we demonstrated that there is no chemical change in dendrimers through the aging process, even though changes in fluorescence emission were observed. Besides, we have put in evidence that changes in the agglomeration patterns of dendrimers would not be related to change in the fluorescence emission thought aging. Moreover, we demonstrated that DG4.5 formed large aggregates in water that need to be disrupted by shaking previous to an in vivo administration.