Research Interests: Biomolecule-nanoparticle hybrids
Current Focus: Biomolecules, such as proteins and DNA, are extremely versatile building blocks which fulfill myriad functions in living systems. Nanotechnology has co-opted many of these molecules, taking advantage of their structural versatility to bind and manipulate nanoparticles. For example, hydrophobic single-wall carbon nanotubes (SWCNTs) become water soluble when wrapped helically with single-stranded DNA. This technique has led to many advances in the purification and manipulation of CNTs (see websites of Xiaomin Tu and Ming Zheng). To understand SWCNT purification (one of the goals of the Nanotube Metrology project), and, more generally, to understand how a biological molecule can have such elegant interaction with a nanoparticle, it is necessary to develop a method for measuring the structure of the hybrid DNA-SWCNT. This method should answer questions including whether DNA bases stack to each other (as they do in nature) or to the nanotube surface (as theory predicts); how the structure of the hybrid depends on the sequence of DNA and structural conformation of the SWCNT.
To this end, we are developing an x-ray diffraction (XRD) structural measurement method. The biggest challenge is creating a sample: DNA-SWCNT must be in a globally ordered nematic liquid crystalline phase for XRD to work - something which has never been achieved. An additional challenge is the removal of impurities which interfere with liquid crystal formation. The Complex Fluids group is uniquely positioned to solve such colloidal science problems. Thus far, using osmotic pressure and centrifugal methods, we have been able to create such ordered phases which display characteristic fluorescence anisotropy (see Figure); the next step is to perform XRD measurements on such samples.
Other Interests: Self-assembly of DNA-SWCNT into clusters and into 2D and 3D nematic phases; quantitative measurements of SWCNT properties using our pure SWCNT samples; molecular combing of DNA-SWCNT to generate arrays of aligned SWCNT on a substrate; other biomolecule-nanoparticle systems, such as protein condensation of silica nanoparticles; techniques of atomic force microscopy and fluorescence correlation spectroscopy, as they pertain to SWCNT measurement.
Honors and Awards
National Research Council Postdoctoral Fellowship at NIST, 2011
Elizabeth V. Stout Dissertation Award, P.C. Rossin College of Engineering and Applied Science, Lehigh University, 2008
Steuber Prize for Excellence in Writing, University of Wisconsin, 2001
Selected Recent Publications
1. C Khripin, D Pristinski, D R Dunphy, C J Brinker, B Kaehr “Protein -Directed Assembly of Arbitrary Three-Dimensional Nanoporous Silica Architectures” ACS Nano 2011 5(2) 1401–1409
2. C Khripin, C J Brinker, B Kaehr “Mechanically tunable multiphoton fabricated protein hydrogels investigated using atomic force microscopy” Soft Matter, 2010 6 2842-2848
3. C Khripin, S Manohar, M Zheng, A Jagota “Measurement of electrostatic properties of DNA-carbon nanotube hybrids by capillary electrophoresis” Journal of Physical Chemistry C 2009 113 13616–13621
4. C Khripin, M Zheng, A Jagota “Deposition and meniscus alignment of DNA-CNT on a substrate” Journal of Colloid and Interface Science 2009 330 255–265
5. C Khripin “Random sequential adsorption of line segments with a finite jamming limit” Journal of Colloid and Interface Science 2008 323 213–215
6. C Khripin, T Tang and A Jagota “Deformation of a sheet with coupling between elasticity and concentration” Journal of Physical Chemistry B 2008 112 722–726
1. C Khripin, M Zheng, A Jagota “Molecular Combing of DNA and Carbon Nanotubes” in Nanoscale Liquid Interfaces; Eds.: T Ondarçuhu, J P Aimé; Pan Stanford Publishing, Chicago, IL (in press)
Selected Recent Presentations
1. “Simultaneous measurement of length, concentration and brightness of single-walled carbon nanotubes with fluorescence correlation spectroscopy” (Contributed talk) APS Meeting, Dallas, TX 2011
2. “Investigating the Mechanical Properties of Multiphoton Fabricated Protein Hydrogels Using Atomic Force Microscopy” (Contributed talk) MRS Spring Meeting, San Francisco, CA 2010
3. “Cell formation of silica-lipid shells for enhanced viability” (Contributed poster) ACS Fall Meeting, Washington, DC 2009
4. “Deposition and Meniscus Alignment of DNA-CNT on a Substrate (Contributed talk) MRS Fall Meeting, Boston, MA 2007
2010-2011 Postdoc, Polymers Division, NIST
2008-2010 Postdoc, Brinker group, Sandia Nat. Lab.
Ph.D., Chemical Engineering, Lehigh University, 2008