Biomedical subjects

James M Tsay

Publications and source records attributed to James M Tsay.

6 recordsLinked to original sources

PubMed2006

Rotational and translational diffusion of peptide-coated CdSe/CdS/ZnS nanorods studied by fluorescence correlation spectroscopy.

CdSe/CdS/ZnS nanorods (NRs) of three aspect ratios were coated with phytochelatin-related peptides and studied using fluorescence correlation spectroscopy (FCS). Theoretical predictions of the NRs' rotational diffusion contribution to the correlation curves were experimentally confirmed. We monitored rotational and translational diffusion of NRs and extracted hydrodynamic radii from the extracted diffusion constants. Translational and rotational diffusion constants (D(trans) and D(rot)) for NRs were in good agreement with Tirado and Garcia de la Torre's as well as with Broersma's theories when accounting for the ligand dimensions. NRs fall in the size range where rotational diffusion can be monitored with higher sensitivity than translational diffusion due to a steeper length dependence, D(rot) approximately L(-)(3) versus D(trans) approximately L(-)(1). By titrating peptide-coated NRs with bovine serum albumin, we monitored (nonspecific) binding through rotational diffusion and showed that D(rot) is an advantageous observable for monitoring binding. Monitoring rotational diffusion of bioconjugated NRs using FCS might prove to be useful for observing binding and conformational dynamics in biological systems.

Amino Acid Sequence↗

PubMed2005

Advances in fluorescence imaging with quantum dot bio-probes.

After much effort in surface chemistry development and optimization by several groups, fluorescent semiconductor nanocrystals probes, also known as quantum dots or qdots, are now entering the realm of biological applications with much to offer to biologists. The road to success has been paved with hurdles but from these efforts has stemmed a multitude of original surface chemistries that scientists in the biological fields can draw from for their specific biological applications. The ability to easily modulate the chemical nature of qdot surfaces by employing one or more of the recently developed qdot coatings, together with their exceptional photophysics have been key elements for qdots to acquire a status of revolutionary fluorescent bio-probes. Indeed, the unique properties of qdots not only give biologists the opportunity to explore advanced imaging techniques such as single molecule or lifetime imaging but also to revisit traditional fluorescence imaging methodologies and extract yet unobserved or inaccessible information in vitro or in vivo.

Chromogenic Compounds↗

PubMed2005

Comparison of photophysical and colloidal properties of biocompatible semiconductor nanocrystals using fluorescence correlation spectroscopy.

A number of different surface chemistries have been developed in recent years to render semiconductor nanocrystals (NCs) stable in water and biocompatible. However, most of these surface modifications affect NCs' photophysical properties, calling for a method to simultaneously monitor colloidal and fluorescence properties. Fluorescence correlation spectroscopy (FCS) combined with ensemble spectroscopic methods and Monte Carlo simulations were used to interpret and derive photophysical as well as colloidal properties of four different NC surface treatments. Using a novel FCS scheme with alternating laser excitation at two different intensities, we first ruled out influences from optical gradient forces (optical trapping). We then compared concentration of emitting particles, brightness per particle, saturation intensity, blinking (intermittency), hydrodynamic radius, and propensity for aggregation of the different bioconjugated NCs. This approach was successfully applied during the development and optimization of peptide-coated NCs.

Biocompatible Materials↗

PubMed2005

Enhancing the photoluminescence of peptide-coated nanocrystals with shell composition and UV irradiation.

The composition and structure of inorganic shells grown over CdSe semiconductor nanocrystal dots and rods were optimized to yield enhanced photoluminescence properties after ligand exchange followed by coating with phytochelatin-related peptides. We show that, in addition to the peptides imparting superior colloidal properties and providing biofunctionality in a single-step reaction, the improved shells and pretreatment with UV irradiation resulted in high quantum yields for the nanocrystals in water. Moreover, peptide coating caused a noticeable red-shift in the absorption and emission spectra for one of the tested shells, suggesting that exciton-molecular orbital (X-MO) coupling might take place in these hybrid inorganic-organic composite materials.

Cadmium Compounds↗

PubMed2005

New light on quantum dot cytotoxicity.

As quantum dots are beginning to be used for in vivo imaging, the question of their long-term effect on cell viability is becoming critical. In this issue of Chemistry & Biology, Lovrić and colleagues examine the likely role of reactive oxygen species in quantum dot cytotoxicity .

Animals↗

PubMed2004

Hybrid approach to the synthesis of highly luminescent CdTe/ZnS and CdHgTe/ZnS nanocrystals.

We report the synthesis of highly luminescent CdTe/ZnS and CdHgTe/ZnS core/shell semiconductor nanocrystals (NCs). A hybrid of two synthesis routes leads to novel nanocrystal compositions and small core/shell sizes (4-5 nm) that emit in the far-red and near-infrared regions. These particles exhibit higher resistance to oxidation and photobleaching, have high quantum yields, and could be used for biological labeling and imaging.

Cadmium Compounds↗