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Open Positions
   
Postdocs
 
We are always looking for talented and motivated postdoctoral researchers to join the group! Interested applicants, please send a copy of your CV to Prof. Xu.
 
Graduate Students
 
We are also always looking for talented and motivated students to join the group. We have open positions for those who have been admitted into Berkeley graduate programs. Please feel free to contact Prof. Xu for further information.
 
 
Project 1
   
Directed Nanoparticle Assemblies
 
Nanoparticles with controlled size, shape, and chemical composition can be readily synthesized and have demonstrated various new phenomena due to quantum confinement. Hierarchical assemblies of nanoparticles with different composition and sizes lead to new functionalities due to coupling effects. Rationally designed nanocomposites based on nanoparticles and supramolecules can not only combine the properties from parent constituents but also exhibit new ones unseen before. Our group's long-term goal is to generate hierarchically structured, functional nanocomposites with tunable optical, electronic and mechanical properties, thus enabling the creation of next-generation photovoltaic, optoelectronic, and data storage devices.
 
Selected Publications
 
S.N. Raja, A.C. Olsen, A. Limaye, K. Thorkelsson, A. Luong, L. Lin, R.O. Ritchie, T. Xu, A.P. Alivisatos. Influence of three-dimensional nanoparticle branching on the Young's modulus of nanocomposites: Effect of interface orientation, PNAS, 2015, 112 (21), 6533-6538

J. Kao and T. Xu. Nanoparticle Assemblies in Supramolecular Nanocomposite Thin Films: Concentration Dependence, JACS, 2015, 137 (19), 6356-6365

K. Thorkelsson, P. Bai and T. Xu. Self-Assembly and Applications of Anisotropic Materials: A Review, Nano Today, 2015, 10 (1), 48-66

J. Kao, K. Thorkelsson, P. Bai, Z. Zhang, C. Sun and T. Xu. Rapid Fabrication of Hierarchically Structured Supramolecular Nanocomposite Thin Films in One Minute, Nature Communications, 2014, 5, 4053

P. Bai, J. Kao, J. H. Chen, W. Mickelson, A. Zettl, and T. Xu. Nanostructures on Graphene using Supramolecule and Supramolecular Nanocomposites, Nanoscale, 2014, 6, 4503-4507

K. Thorkelsson, J. H. Nelson, A. P. Alivisatos, and T. Xu. End-to-End Alignment of Nanorods in Thin Films, Nano Letters, 2013, 13 (10), 4908-4913

J. Kao, P. Bai, J. M. Lucas, A. P. Alivisatos, and T. Xu, Size-Dependent Assemblies of Nanoparticle Mixtures in Thin Films, Journal of the American Chemical Society, 2013, 135 (5), 1680-1683

J. Kao, P. Bai, V. P. Chuang, Z. Jiang, P. Ercius, and T. Xu, Nanoparticle Assemblies in Thin Films of Supramolecular Nanocomposites, Nano Letters, 2012, 12 (5), 2610-2618

B.J. Rancatore, C.E. Mauldin, S.H. Tung, C. Wang, A. Hexemer, J. Strzalka, J.M.J. Fréchet and T. Xu, Nanostructured Organic Semiconductors via Directed Supramolecular Assembly, ACS Nano, 2010, 4 (5), 2721-2729

Y. Zhao, K. Thorkelsson, A.J. Mastroianni, T. Schilling, J.M. Luther, B.J. Rancatore, K. Matsunaga, H. Jinnai, Y. Wu, D. Poulsen, J.M.J. Fréchet, A.P. Alivisatos, T. Xu, Small-molecule-directed nanoparticle assembly towards stimuli-responsive nanocomposites, Nature Materials, 2009, 8, 979-985
 
Project 2
   
Peptide-Polymer Conjugate Micelles for Drug Delivery
 
Despite rapid developments in cancer therapeutic drugs, ~40% of the emerging small molecule drugs have poor aqueous solubility and short tissue half-lives and require development of drug carriers to improve their solubility, stability, pharmacokinetics, biodistribution, toxicity profile and efficacy. To this end, a balance must be struck between optimizing blood residence time, tumor penetration, targeted internalization and clearance pathway to minimize toxicity. Current FDA-approved Doxil (~100 nm) and Abraxane (~130 nm) have provided only modest survival benefits presumably due to inefficient transport of the chemotherapeutic drug into the tumor. There is increasing evidence that a drug's limited penetration and distribution within a tumor, which results in insufficient elimination of malignant cells, may contribute to tumor repopulation after treatment.

Our group has developed a new family of nanocarriers, called "3-helix micelles" that are ~15 nm in size as a new class of nanocarriers for drug delivery. The 3-helix micelle has a blood circulation half life of 29 hrs with minimal cargo leakage and deep tumor penetration and has demonstrated great potential for drug formulation.
 
Selected Publications
 
J.W. Seo, J.C. Ang, L.M. Mahakian, S. Tam, B. Fite, E.S. Ingham, J. Beyer, J. Forsayeth, K.S. Bankiewicz, T. Xu, K.W. Ferrara. Self-assembled 20-nm 64Cu-micelles enhance accumulation in rat glioblastoma, Journal of Controlled Release, 2015, 220, 51-60

H. Dong, R. Lund and T. Xu. Micelle Stabilization via Entropic Repulsion: Balance of Force Directionality and Geometric Packing of Subunits, Biomacromolecules, 2015, 16 (3), 743-747

N. Dube, J. W. Seo, H. Dong, J. Y. Shu, R. Lund, L. M. Mahakian, K. W. Ferrara and T. Xu. Effect of Alkyl Length of Peptide-Polymer Amphiphile on Cargo Encapsulation Stability and Pharmacokinetics of 3-Helix Micelles, Biomacromolecules, 2014, 15(8), 2963-2970

E. A. Salegio, H. Streeter, N. Dube, P. Hadaczek, L. Samaranch, A. Kells, W. San Sebastian, Y. Zhai, J. Bringas, T. Xu, J. Forsayeth, and K. S. Bankiewicz Distribution of nanoparticles throughout the cerebral cortex of rodents and non-human primates: Implications for gene and drug therapy, Frontiers in Neuroanatomy, 2014, 8 (9), 1-8

N. Dube, J. Y. Shu, H. Dong, J. W. Seo, E. Ingham, A. Kheirolomoom, P.-Y. Chen, J. Forsayeth, K. Bankiewicz, K. W. Ferrara, and T. Xu. Evaluation of Doxorubicin-Loaded 3-Helix Micelles as Nanocarriers, Biomacromolecules, 2013, 14 (10), 3697-3705

R. Lund, J. Y. Shu, and T. Xu. A Small-angle X-ray Scattering Study of alpha-Helical Bundle-Forming Peptide-Polymer Conjugates in Solution: Chain Conformations, Macromolecules, 2013, 46 (4), 1625-1632.

H. Dong, J. Y. Shu, N. Dube, Y. Ma, M. V. Tirrell, K. H. Downing, and T. Xu, 3-Helix Micelles Stablized by Polymer Springs, Journal of the American Chemical Society, 2012, 134 (28), 11807-11814.

J. Y. Shu, R. Lund, and T. Xu, Solution Structural Characterization of Coiled-Coil Peptide-Polymer Side-Conjugates, Biomacromolecules, 2012, 13 (6), 1945-1955.

H. Dong, N. Dube, J. Y. Shu, J. W. Seo, L. M. Mahakian, K. W. Ferrara, and T. Xu, Long-Circulating 15 nm Micelles Based on Amphiphilic 3-Helix Peptide-PEG Conjugates, ACS Nano, 2012, 6 (6), 5320-5329.
 
Project 3
   
Subnanometer Porous Membranes for Gas Separation
 
Nature routinely produces membranes containing oriented channels with molecularly defined size, topology and surface chemistry. However achieving this with "man-made" materials remains a significant challenge. This project focuses on fabricating polymeric membranes containing sub-nanometer channels that are vertically aligned which make them useful for various applications such as carbon capture and different separation processes in both gaseous phase and solution phase.
 
Selected Publications
 
C. Zhang and T. Xu. Co-assembly of cyclic peptide nanotubes and block copolymers in thin films: controlling the kinetic pathway, Nanoscale, 2015, 7, 15117-15121

R. Hourani, C. Zhang, R. van der Weegen, L. Ruiz, C. Li, S. Keten, B. A. Helms, and T. Xu, Processible Cyclic Peptide Nanotubes With Tunable Interiors, Journal of the American Chemical Society, 2011, 133 (39), 15296-15299.

T. Xu, N. Zhao, F. Ren, R. Hourani, M.T. Lee, J.Y. Shu, S. Mao, and B.A. Helms, Subnanometer Porous Thin Films by the Co-assembly of Nanotube Subunits and Block Copolymers, ACS Nano, 2011, 5 (2), 1376-1384.
 
Project 4
   
Protein-Polymer Biomaterials
 
Development of functional hybrid biomaterials has the potential to impact a variety of fields, including work done in catalysis, medical therapeutics, energy, and molecular sensing. Synergistic integration of protein and synthetic polymer is of particular interest as the breadth of functionalities accessible by proteins compliments the nature of synthetic polymers. However, it remains a significant challenge to produce protein-based functional materials without compromising native protein structure and their inherent functionality. We are looking for great minds to join and help us overcome these barriers, paving a new path towards the generation of protein-based functional materials.
 
Selected Publications
 
A.D. Presley, J. Chang, and T. Xu, Directed co-assembly of heme proteins with amphiphilic block copolymers toward functional biomolecular materials, Soft Matter, 2011, 7, 172-179.
 

The Ting Xu Group