Photostability of quantum dots with amphiphilic polymer-based passivation strategies

Abstract

Quantum dots (QDs) have many appealing properties for biological fluorescence imaging, but exhibit photostabilities that are dependent upon surface passivation to minimize susceptibility to oxygen and light. Here, through spectroscopy and imaging techniques, we compare the photostability of micelle-encapsulated QDs with QDs passivated with either crosslinked amphiphilic polymers or crosslink-free amphiphilic polymers. Both crosslinked and crosslink-free amphiphilic polymer passivation strategies produced QDs with high photoluminescence stability for exposure to light under ambient conditions. In contrast, micelle encapsulation resulted in QDs with photoluminescence emission levels that were highly sensitive to both light exposure and oxygen, exhibiting a reduction of up to 70% in photoluminescence intensity within twenty minutes of exposure. With the addition of reducing agents, the photoluminescence level of the micelle-encapsulated QDs was significantly stabilized. We conclude that amphiphilic polymers provide coatings with considerably higher integrity and stability than micelle encapsulation, reducing the QDs' sensitivities to oxygen and light, both of which are relevant factors in biological imaging applications.

Stability of fluorescent labels in PLGA polymeric nanoparticles: Quantum dots versus organic dyes

“…Quantum dots are synthesized highly monodisperse crystalline cadmium selenide fluorescent nanoparticles whose stability and quantum yield have been dramatically increased by epitaxial growth of a semiconductor shell mostly composed of zinc sulfide (Murray et al, 1993;Hines et al, 1996;Smith et al, 2006). They are emerging as attractive alternatives to the small organic fluorescent dyes for many biological and biomedical applications because of their unique optical properties including narrow tunable emission spectra, high photoluminescence quantum efficiency and excellent photostability (Nida et al, 2008). They also exhibit broad absorption spectra allowing exciting several colors of QDs simultaneously with single excitation wavelength thus minimizing auto-fluorescence and sample bleaching (Wu et al, 2003).…”

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique

“…chloroform) treatment that leads to localized electronic states, called surface state, which are able to act as electron or hole traps, and as a result, fluorescence emission is decreased. In order to reduce the number of surface states, as reported in recent literature [19], the surface atoms should be optimally reconstructed and passivated with different absorbates, e.g. polymers that can occupy the vacant coordinate sites on the QD surface.…”

Amphipol-encapsulated CuInS2/ZnS quantum dots with excellent colloidal stability

“…40 The photostability of QDs passivated with amphipols has been shown to be significantly improved in comparison to those encapsulated in micelles. 41 In general, stability in the aqueous environment is achieved 45 through either the presence of polyethylene glycol (PEG) chains or chargeable polar groups. Both methods are effective, yet recent studies have suggested that a zwitterionic surface provides an excellent alternative to PEG since a much lower molecular weight is required in order to achieve good stability.…”