Wrapping Nanocrystals with an Amphiphilic Polymer Preloaded with Fixed Amounts of Fluorophore Generates FRET-Based Nanoprobes with a Controlled Donor/Acceptor Ratio

Abstract

Colloidal nanocrystal (NC) donors wrapped with a polymer coating including multiple organic acceptor molecules are promising scaffolds for fluorescence resonance energy transfer (FRET)-based nanobiosensors. Over other self-assembling donor-acceptor configurations, our preloaded polymers have the virtue of producing compact assemblies with a fixed donor/acceptor distance. This property, together with the possibility of stoichiometric polymer loading, allowed us to directly address how the FRET efficiency depended on the donor/acceptor. At the population level, nanoprobes based on commercial as well as custom CdSe/ZnS donors displayed the expected dose-dependent rise in transfer efficiency, saturating from about five ATTO dyes/NC. However, for a given acceptor concentration, both the intensity and lifetime of single-pair FRET data revealed a large dispersion of transfer efficiencies, highlighting an important heterogeneity among nominally identical FRET-based nanoprobes. Rigorous quality check during synthesis and shell assembly as well as postsynthesis sorting and purification are required to make hybrid semiconductor-organic nanoprobes a robust and viable alternative to organic or genetically encoded nanobiosensors.

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

“…Thus, models describing the different parts of the ligand shell would need to consider distributions of respective different layers. Fortunately, distributions are not as smeared out as one may expect, as for example indicated by fluorescence resonance energy transfer measurements which revealed a relatively narrow distribution of fluorophores attached to the polymer shell around fluorescent NPs [123]. Different layers of the ligand shell can also interact in different manners with ions.…”

In vitro interaction of colloidal nanoparticles with mammalian cells: What have we learned thus far?

“…However, due to the fact that specific targeting still is possible [84], enough ligands still are biologically active. For highly defined NPs, such as nearly monodisperse NPs overcoated with a shell of an amphiphilic polymer [135], the corona formed by special model proteins can be surprisingly well organized. By using fluorescence correlation spectroscopy (FCS), Röcker et al investigated the adsorption of human serum albumin onto FePt NPs and found clear evidence that the proteins formed a monolayer on the surface of the NP [136].…”

Ion and pH Sensing with Colloidal Nanoparticles: Influence of Surface Charge on Sensing and Colloidal Properties

“…quantum dots) it can be used for the optical excitation of the ion-sensitive fluorophore via fluorescence energy transfer (FRET). [29][30][31][32][33] For metallic-carrier NPs, the emission of the (ion-sensitive) fluorophore can be quenched, when the fluorophore comes close to the metal surface. [34][35][36][37][38] In either case the fluorescence is influenced by the distance between the NP and the ion-sensitive fluorophore.…”