Fluorescence correlation spectroscopy for diffusion of mobile quantum dots in dilute solutions

Designing a better theranostic nanocarrier for cancer applications

Nanocarriers show incredible potential in theranostic applications as they offer diagnostic capabilities along with the ability to encapsulate and protect drugs from degradation, be functionalized with targeting moieties and be designed with controlled release mechanisms. Most clinically approved nanocarrier drugs are liposomal formulations. As such, considerable research has been directed towards designing liposomal carriers that can release their payloads via exogenous or endogenous triggers. For triggered release to effectively increase drug bioavailability, nanocarriers must first accumulate at the tumor site via the enhanced retention and permeability effect. It has been demonstrated in the chicken embryo chorioallantoic membrane and murine xenografted models that nanoparticle surface charge and geometry, with respect to vascular endothelium fenestration size, drive this accumulation in angiogenic tissue.

Influence of the length and grafting density of PNIPAM chains on the colloidal and optical properties of quantum dot/PNIPAM assemblies

Structural and optical characterization of water soluble, thermo-responsive quantum dot/poly(N-isopropyl acrylamide) (QD/PNIPAM) hybrid particles using fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements performed at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM is reported. By increasing the temperature above the LCST, the signature of the PNIPAM chain collapse covering the QDs is revealed by FCS measurements. Despite the significant structural change, the TCSPC measurements show that the fluorescence lifetimes remain of the same order of magnitude at T > LCST. Such QD/PNIPAM hybrid particles with water solubility and robust thermo-responsive behavior at physiologically relevant temperatures are potentially useful for (bio)molecular sensing and separation applications.