Fluorescence resonance energy transfer between phenanthrene and PAMAM dendrimers

Abstract

We describe herein an adsorption-induced energy transfer between phenanthrene, a major environmental pollutant, and a fluorescently labeled dendrimer acting as a host molecule. We find experimentally that such energy transfer is the most efficient at a solvent pH of 8 and for a phenanthrene:dendrimer molar ratio of 1:2. Using molecular dynamics simulations we show that the strongest binding interactions occur between phenanthrene and the primary amines of the dendrimer. The simulations provide evidence that at low pH, phenanthrene-phenanthrene interactions are favorable and compete with phenanthrene-dendrimer binding. This study offers a new scheme for detecting dendrimer molecular assembly and a physical basis for exploiting dendrimer nanotechnologies for water purification and environmental remediation.

Multiscale Modeling for Host-Guest Chemistry of Dendrimers in Solution

“…The types of guest molecules considered in this review will include low molecular weight organic molecules [24,29,50,51], and nucleic acids [38,[69][70][71][72][73]. The review of interactions of dendrimers with lipid membrane has been clearly explained in Reference [37].…”

“…Thus, these simulations are routinely used to investigate conformational changes of a single dendrimer in explicit solvent with respect to dendrimer generation (size) and process conditions, such as temperature and solvent pH [52][53][54][55]62,63]. All-atom simulations may also be used to investigate the dynamics of binding between of a single dendrimer and one or more ligands in explicit solvent [24,38,39,64].…”

“…The breadth across applications is attributed to dendrimers being well-defined, monodisperse nanostructures with tunable critical nanoscale design parameters [15,16], such as size, shape, rigidity, surface functionality, and solvent affinity. For this reason, dendrimers have been studied as hosts for a number of guest species: drugs [1][2][3][4], gene [17][18][19], contrast agents [7,20,21], metal ions [9][10][11][12][13][14], polymers [22], and organic pollutants [23,24]. Astruc and coworkers have written an exceptionally comprehensive review on dendrimers functioning as hosts [25].…”

“…For this reason, the FMO approach is most effective when it is coupled with methods such as docking or classical molecular dynamics to model the interaction of dendrimers with guest molecules. At the next higher scales of calculation, all-atom and mesoscale simulations have been widely applied to study the binding mechanism of dendrimers with guest molecules [24,38,39,[48][49][50][51]. There are two main approaches for mesoscale simulations: coarse-grained "particle-based" simulations and statistical field theories.…”

“…Detailed conformations of dendrimers interacting with guest molecules have been studied by nuclear magnetic resonance(NMR) [34][35][36] and the size of the dendrimer-guest complexes has been measured by dynamic light scattering (DLS) [22,31]. For instance, supramolecular assemblies of polyamidoamine (PAMAM) dendrimers and phenanthrene, an organic pollutant, have been studied using fluorescence resonance energy transfer (FRET) to understand the interaction between dendrimers and guest molecules in aqueous solution [24]. Using FRET experiments, the most stable state for PAMAM-phenanthrene binding was observed at a pH of 8 and 1:2 molar ratio of phenanthrene to PAMAM.…”