Interaction of polymer-coated silicon nanocrystals with lipid bilayers and surfactant interfaces

Abstract

We use photoluminescence (PL) microscopy to measure the interaction between PEGylated silicon nanocrystals (SiNCs) and two model surfaces; lipid bilayers and surfactant interfaces. By characterizing the photostability, transport, and size-dependent emission of the PEGylated nanocrystal clusters, we demonstrate the retention of red PL suitable for detection and tracking with minimal blueshift after a year in an aqueous environment. The predominant interaction measured for both interfaces is short-range repulsion, consistent with the ideal behavior anticipated for PEGylated phospholipid coatings. However, we also observe unanticipated attractive behavior in a small number of scenarios for both interfaces. We attribute this anomaly to defective PEG coverage on a subset of the clusters, suggesting a possible strategy for enhancing cellular uptake by controlling the homogeneity of the PEG corona. In both scenarios, the shape of the apparent potential is modeled through the free or bound diffusion of the clusters near the confining interface.

Silicon Nanocrystals and Their Composites: Syntheses, Fluorescence Mechanisms, and Biological Applications

“…The photostability of Si NCs can also be greatly improved with a polymer coating. Recently, Elbaradei et al 55 used ethylene glycol-coated silicon nanocrystals to prepare an ultrahigh stability composite, which retained red fluorescence intensity after one year.…”

First-Principles Study of Fluorescence in Silver Nanoclusters

“…Biological applications requiring fluorophores, such as biolabels and biosensors, typically use either organic dyes or metal-chalcogenide quantum dots. In these applications, quantum dots offer superior photostability when compared to organic dyes, yet consist primarily of toxic materials such as lead and cadmium. − Aside from the toxicities, quantum dots are typically large and cumbersome for transport through biological membranes. ,, AgNCs on the other hand, with core diameters of 1 nm or less, can be readily transported throughout the body, while the relatively benign nature of silver addresses potential concerns about nanotoxicity. − Furthermore, AgNCs have demonstrated highly efficient photoemission with quantum yields as high as 90% in some cases …”

“…2−6 Aside from the toxicities, quantum dots are typically large and cumbersome for transport through biological membranes. 1,7,8 AgNCs on the other hand, with core diameters of 1 nm or less, can be readily transported throughout the body, while the relatively benign nature of silver addresses potential concerns about nanotoxicity. 9−17 Furthermore, AgNCs have demonstrated highly efficient photoemission with quantum yields as high as 90% in some cases.…”