Binding properties of polyamidoamine dendrimers

Abstract

Dendrimers are globular, hyperbranched polymers possessing a high concentration of surface functional groups and internal cavities. These unique features make them good host molecules for small ligands. To reveal relationships between dendrimer size and its encapsulating properties, the interactions of the fourth and the sixth generations of polyamidoamine dendrimers (PAMAM G4 and PAMAM G6) with a fluorescent dye 1-anilinonaphthalene-8-sulfonate (ANS) were studied. Because ANS is a fluorescent molecule and its fluorescence is very sensitive to changes in its microenvironment, it was possible to use spectrofluorometric methods to evaluate the interactions with dendrimers. A double fluorometric titration method was used to estimate a binding constant and the number of binding centers. There were two types of dendrimer binding centers characterized by different affinity towards ANS. For PAMAM G4, the values of K b and n for low-affinity and high-affinity sites equaled to 2.6 Â 10 5 , 0.60 and 3.70 Â 10 6 , 0.34, respectively, whereas in the case of PAMAM G6, these values equaled to 1.2 Â 10 5 , 76.34 and 1.38 Â 10 6 , 22.73. It was observed that the size of the dendrimer had a strong impact on the number of ANS molecules that interacted with dendrimers and their location within the macromolecule.

Fluorescence-Based Comparative Binding Studies of the Supramolecular Host Properties of PAMAM Dendrimers Using Anilinonaphthalene Sulfonates: Unusual Host-Dependent Fluorescence Titration Behavior

“…In the case of 1,8-ANS in G6, the double reciprocal plot was linear, as shown in Figure 6c ); the fit results are listed in Table 3 . The value of K b obtained falls between the two values reported for 1,8-ANS in G6 in buffer solution by Bryszewska et al [ 25 ] for the low and high affinity binding centers. However the value of n obtained here is very small, and is expected to be much greater than 1 for this very large dendrimer [ 25 ].…”

“…The results for the fits to Equation 3 are shown in Table 3 . For 1,8-ANS with G4, Bryszewska et al reported K b values of 5.6 × 10 4 M −1 [ 23 ], 2.6 × 10 5 M −1 (low affinity binding centers) and 3.7 × 10 6 M −1 (high affinity binding centers) [ 25 ] and n values of 0.31 [ 23 ], 0.60 (low affinity binding centers) and 0.34 (high affinity binding centers) [ 25 ] in buffer solution. Our value of K b of 1.8 ± 0.5 × 10 5 in nanopure water is in best agreement with that reported for the low affinity (surface) binding centers, however our value of n is slightly lower than that reported.…”

“…They used a double fluorometric titration technique, in which the fluorescence is studied both as a function of host concentration at fixed guest concentration and as a function of guest concentration at fixed host concentration [ 23 – 26 ], and found that binding of 1,8-ANS in these dendrimers is very complex. They found that there are two distinctive types of binding centers for G4 and G6 PAMAM dendrimers, which they referred to as low affinity and high affinity, and which correspond to surface and core cavities, respectively [ 25 ]. However, in a previous publication they observed only one type of binding site for G4 [ 23 ].…”

Specific vapor sorption properties of phosphorus-containing dendrimers

“…The selectivity of dendrimers may be high because of their ability to sorb different substrates in different binding sites. Being derived from structural considerations [5], the presence of different binding sites in dendrimers was directly proved by 1 H NMR [6] and fluorescent [7] titration in solution. For dendrimers in solid state, this feature was concluded from dependence of guest uptake on their generation number [8] and from different adsorption kinetics for different substrates [9].…”

The interaction mechanism between lipopeptide (daptomycin) and polyamidoamine (PAMAM) dendrimers

“…Changes in fluorescence emission characteristics of fluorescence probes, e.g. 1‐anilinonapthalene‐8‐sulfonic acid, have been used to estimate binding constants . Several factors have been shown to influence the formation of dendrimeric complexes such as pH, molecular size, and surface structure [].…”