Intrinsic Fluorescence of PAMAM Dendrimers—Quenching Studies

Abstract

Intrinsic, non-traditional fluorescence of polyamidoamine (PAMAM) dendrimers that do not possess classical fluorophores has been attracting considerable interest for the last decade. Many hypotheses regarding the source of the fluorescence have appeared, but some of them are still disputable. In order to shed new light on the nature of the phenomenon, we applied quenchers that are normally used to study intrinsic fluorescence of proteins (i.e., KI, CsCl, and acrylamide). KI and acrylamide efficiently quenched steady state fluorescence of PAMAM G2, PAMAM G3, and PAMAM G4 dendrimers. Stern-Volmer plots exhibited a downward curvature that has been elucidated by heterogenous emission. We assume that there are two distinct fluorescent moieties in the dendrimer structure that are characterized by different accessibility to the quenchers.

Clusterization-triggered emission: Uncommon luminescence from common materials

“…The emission is described as clusteroluminescence and the chromophores responsible for it are classified as clusteroluminogens [68] . More recently, Tomalia, Klajnert-Maculewicz et al have described the phenomenon using the term 'non-traditional intrinsic luminescence' (NTIL) [69][70][71][72] . In essence, the photophysical characteristics of NTIL are similar to CTE.…”

New insights into the blue intrinsic fluorescence of oxidized PAMAM dendrimers considering their use as bionanomaterials

“…35 Also, a recent work devoted to the study of fluorescence quenching in pristine PAMAM dendrimers points out that there are two distinct fluorescent moieties in their structure with the emission maxima separated by 40 nm. 42 It is therefore reasonable to assume that the amide and tertiary amine groups that exist in the dendrimer scaffold constitute two distinct HASLs with photoluminescence properties that are dependent on the pH environment which is in turn strongly affected by the APS treatment. However, it seems that the APS treatment does not exert its effect to the same extent in both HASLs as it causes a red shift in the maximum wavelength of fluorescence.…”

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

“…Dendrimers are highly branched, three-dimensional molecules, 1–10 nm in size, with unique physiochemical properties, such as: (1) very low cytotoxicity, (2) capacity to penetrate cells with high efficiency, and (3) an “autofluorescence ability” that allows the investigation of their fate in the cell and the living organism [ 52 , 53 , 54 ]. The main methods of dendrimer synthesis include the divergent growth method, convergent method, hypercore and branched method, and double and mixed exponential growth method [ 55 ], but the most commonly used methods are divergent and convergent [ 56 ].…”