Mechanistic Analysis of Ion Association between Dendrigraft Poly-l-lysine and 8-Anilino-1-naphthalenesulfonate at Liquid|Liquid Interfaces

Abstract

Molecular association between biocompatible dendritic polymers, dendrigraft poly-l-lysines (DGLs), and an anionic fluorescent probe, 8-anilino-1-naphthalenesulfonate (ANS), was studied at the polarized water|1,2-dichloroethane (DCE) interface. The fluorescence intensity of ANS measured in aqueous solution was enhanced by the coexistence of DGLs over a wide pH range (2 < pH < 10), where ANS and DGL exist as a monoanionic form and a polycation, respectively. The voltammetric responses indicated that the positively charged DGLs were adsorbed at the water|DCE interface, whereas ANS was transferred across the interface accompanied by the adsorption process. The interfacial behavior of the DGL-ANS associates was analyzed by potential-modulated fluorescence (PMF) spectroscopy. The PMF results demonstrated that the ion association between DGLs and ANS at the water|DCE interface is strongly affected by the applied potential and the dendritic generation of DGL. By applying appropriate potentials, the ANS anion was dissociated from its ion associate with DGLs at the interface and transferred into the organic phase, whereas DGLs remained in the aqueous phase. The Gibbs free energy of ion association (Δ G) was estimated for the second-fourth generation DGLs (DGL-G2-G4) and the G4 polyamidoamine (PAMAM) dendrimer as a control. The highest stability of the DGL-G4-ANS associate manifested itself through Δ G: DGL-G4-ANS (>G4 PAMAM dendrimer-ANS) > DGL-G3-ANS > DGL-G2-ANS. The results elucidated the efficient anion-binding ability of higher generation DGLs and its potential dependence at the liquid|liquid interface.

Transfer Mechanism of Anthracycline Antibiotics and Their Ion Association with PAMAM Dendrimer at Liquid|Liquid Interfaces**

“…The ion association energies between dendritic polymers and guest ions have been reported at liquid|liquid interfaces, and multivalent ions tend to form relatively stable ion associates [49,57] . The Δ G assoc values determined for the G3.5 PAMAM dendrimer‐anthracycline derivative system are of the same order of magnitude as those of the cationic dendritic polymer‐monoanion systems [56] . In contrast to small anionic species encapsulated into the positively charged interior of the G3.5 PAMAM dendrimer, the cationic anthracycline derivatives will locate closer to the negatively charged periphery region.…”

“…The shift of transfer potential is described as a function of the ion‐association energy (Δ G assoc ) at given pH [Eq. ]: [49,56–57] …”

“…The shift of transfer potential ðDðD w o � tr ÞÞ is described as a function of the ion-association energy (ΔG assoc ) at given pH [Eq. ( 4)]: [49,[56][57]…”

“…[49,57] The ΔG assoc values determined for the G3.5 PAMAM dendrimer-anthracycline derivative system are of the same order of magnitude as those of the cationic dendritic polymer-monoanion systems. [56] In contrast to small anionic species encapsulated into the positively charged interior of the G3.5 PAMAM dendrimer, the cationic anthracycline derivatives will locate closer to the negatively charged periphery region. The anthracycline derivatives possibly interact with the interior of the dendrimer via hydrogen bonding, [53,58] and it may also contribute to the stable ion association.…”

Highly Branched Polymers Based on Poly(amino acid)s for Biomedical Application

“…More recently, highly branched PAAs gained attention for their ability to (i) mimic globular proteins, so called ‘proteinoids’, which can be studied as mock proteins or peptides for their interaction with various environments [ 6 , 7 , 8 , 9 ] and were mentioned as early as 1958 in this capacity by Fox and Harada [ 10 ], and (ii) interact with biologically relevant molecules. The latter one has become the more intensely researched area as PAAs lend themselves to a multitude of biomedical applications, including the delivery of drugs [ 11 , 12 , 13 ] and nucleotides, for a review see Kataoka [ 14 ], and as imaging reagents, [ 15 , 16 ] and tissue adhesives [ 17 , 18 ] and most recently in the development of theranostics [ 19 , 20 ].…”