Research Description:

 

(I) Understanding influences of valence state on material properties of noble metal nanoparticles and explore their biomedical applications

 



Valence-State Effects in noble metal nanoparticles

Material properties of noble metal NPs are strongly dependent on the number of free electrons in the particles, therefore, valence states of metal atoms are expected to have a significant influence on material properties of gold nanoparticles, which, however, is still far from full understanding. We recently created a class of ~2nm gold nanoparticles with nearly 50% Au(I) and 50% Au(0) by utilizing the self-dissociation process of glutathione-gold(I) polymers in aqueous solution. These small gold nanoparticles exhibit bright luminescence and more interestingly, we found that singlet and triplet excited states involving the emission are degenerate in energy by measuring luminescence lifetimes excitation wavelengths. These luminescent nanoparticles can be considered an intermediate state between luminescent gold(I) complexes and reduced nonluminescent gold nanoparticles. We are currently unraveling the quantitative relationships between valence states and luminescent property.


Renal Clearable luminescent gold nanoparticles for cancer imaging

Developing functional nanomaterials with efficient renal clearance to minimize the nanotoxicity is of fundamental importance to their in vivo biomedical applications. Recently, we found that the renal clearance of ~2 nm glutathione-coated luminescent NPs was more than 10 to 100 times better than those of the similar sized AuNPs coated by bis(p-sulfonatophenyl)-phenylphosphine and cysteine respectively. The efficient renal clearance of the luminescent particles results from the very small particle size and glutathione ligand, which not only enables the majority of the luminescent AuNPs to be cleared out of the body through kidney filtration, but also stabilizes the luminescent AuNPs during the blood circulation. In addition, the particle size can influence renal clearance efficiency through changing the interactions between ligands and serum proteins.

Recent Publications:
 

(1) M. Yu,† C. Zhou,† J. Liu, J. D. Hankins, J. Zheng, “Luminscent Gold Nanoparticles with pH De-pendent Membrane Adsorption”, J. Am. Chem. Soc., 2011, 133(29), 11014-11017.

 

(2) C. Zhou, C. Sun, M. Yu, Y. Qin, J. Wang, M. Kim, J. Zheng “Luminescent Gold Nanoparticles with Mixed Valence States Generated from Dissociation of Polymeric Au (I) Thiolates” J. Phys. Chem. C, 2010, 114(17), 7727-7732.

 

(3) C. Zhou, M. Long, Y. Qin, X. Sun, J. Zheng “Luminescent Gold Nanoparticles with Efficient Renal Clearance” Angew. Chem. Int. Ed., 2011, 50(14), 3168-3172.

 

(4) C. Ratanatawanate, J. Yu, C. Zhou, J. Zheng, K. J. Balkus “Synthesis of Gold Nanoclusters: A Fluorescent Marker for Water-soluble TiO2 Nanotubes” Nanotechnology, 2011, 22(6): 065601.
   
(II) Developing novel nanobiotechnology with luminescent metal NPs
 


1. Integration of Fluorescence and Raman Microscopy for Bioimaging.

Both fluorescence and Raman based imaging techniques have greatly advanced our fundamental understanding of cell biology. However, these two techniques are often used to address different biological problems and have their own limitations: fluorescence based imaging tools can track biomolecules but can not directly  image interactions of biomolecules at the chemical-bond level. Raman based imaging techniques can offer chemical information of biomolecules but can not directly track biomolecules inside live cells. Combining the strengths of fluorescence and Raman imaging techniques will allow us to simultaneously track biomolecules and real-time image their interactions with other biomolecules at the chemical level. To achieve this objective, we are currently integrating our fluorescent and Raman active metal nanoparticles with a fluorescence-Raman microscope; so that cellular dynamics of biomolecules and their interactions with others inside live cells can be reported in real-time.
   
2. Imaging entry pathways and interactions of metal NPs in live cells

Metal NPs hold great promise in diagnostic-cancer imaging, photothermal therapy and targeted drug delivery. Real-time imaging of cellular entry pathways and interactions of metal NPs is challenging because metal NPs are difficult to be detected using routine fluorescence microscope. Although conjugation of fluorescent dyes to the metal NPs can partially overcome this limitation, entry pathways of metal NPs are often interfered by fluorescent dyes. To address this challenge, we are applying luminescent metal NPs and investigating how the size, surface chemistry as well as valence states of metal atoms affect the entry pathways and interactions.

[Contact us]

2.440 NSERL Building, The University of Texas at Dallas
Tel: 972-883-5768 (Dr. Zheng), 972-883-5769 (Lab)