Biomaterials Research Group
We work at the interface of biophysics and materials science to develop novel nanostructures and devices that seamlessly integrate biological molecules with electronic circuits. Our goal is to develop versatile interfaces that allow seamless bidirectional information exchange between biological organisms and electronic devices and open new paradigms in bioengineering, medicine and nanotechnology.
Research Areas
High-speed in-situ atomic force microscopy of biological processes
Bionanoelectronics
Our lives, health, and public safety are increasingly dependent on our interactions with devices, sensors, and other man-made objects. We are working on developing new concepts for efficient bi-directional interfaces between living and artificial systems with the focus on efficient integration of electronic circuits with chemical signaling that is characteristic of biological systems. To build these structures at the scale commensurate with biomolecule dimensions we use hierarchical assembly of biological and nanoelectronic components. Currently our efforts are centered on developing 1D lipid bilayer devices that incorporate natural and artificial pores and demonstrating their integration with live cells and cell cultures.
DNA transport through carbon nanotube porins Schematic showing the translocation of single-stranded DNA through a CNT porin in the lipid bilayer (see text for details). Symbols in circles indicate ground electrode (top) and reference electrode (bottom). b, Current trace showing multiple transient blockades caused by 81-nt ssDNA translocation through the CNT channel (middle) with magnified view (bottom). The top trace shows the control trace recorded in absence of ssDNA. The applied voltage was −50 mV. c, d, Histograms of conductance blockade levels (c) and dwell times (d) for 806 ssDNA translocation events.
Carbon nanotube nanofluidics
Mesoscale phenomena bridge the divide between atomic-level and bulk-level behavior and one of the most interesting and striking examples of mesoscale behavior is fast transport in carbon nanotube channels. Narrow hydrophobic inner pores of carbon nanotubes can be so small that they force water into a single hydrogen bonded chains, a conformation that does not exist in bulk state. Extreme degree of molecular confinement and smooth surfaces of these nanotube pores enable nearly frictionless flow of water, ions and small molecules through them. One-dimensional hydrogen-bonded water conformation also help to relay protons through the nanotube pore extremely fast. We are studying the fundamentals of these fast transport phenomena using carbon nanotube porins -- short carbon nanotubes that mimic the architecture and the functionality of biological membrane proteins. We are also incorporating these porin structures into bioelectronic interfaces and artificial membranes to take advantage of their fast transport characteristics and robust mechanical properties.
(RIGHT) Proton Kinetics a, Schematic of the proton conductance measurement. b, Normalized pyranine dye fluorescence intensity changes (I/I0) as a function of time. Inset: Magnified initial region of pH gradient dissipation kinetics for 0.8- and 1.5-nm-diameter CNTPs in DOPC liposomes. Solid lines are a linear fit to the data in pH range from 7.5 to 6.9. (LEFT) Small CNTp characterization, Schematics showing CNTPs inserted into a liposome. b,c, Molecular models showing water molecules in the inner pores of two CNTPs of different diameters: 1.5 nm (b), and 0.8 nm (c). d,e, 3D fluorescence spectra of the uncut (d) and cut (e) 0.8-nm-diameter CNTs showing predominance of (8,4) CNT species after sonication cutting. f, Histogram showing the lengths of the CNTPs inserted into liposomes as measured from cryogenic TEM images. The red solid line indicates a fit to a log-normal distribution (mean value: 10.6 ± 0.9 nm). The insets show representative cryogenic TEM images of CNTPs in liposomes. Red frames outline locations of CNTPs. g, Raman spectrum of the CNTP/lipid suspension after 16 h of sonication-assisted cutting for 0.8-nm-diameter porins. The broad DOPC lipid signal peak between 1,000–3,000 cm–1 indicates that CNTPs are sufficiently solubilized by the lipid. Inset: Magnified view of the radial breathing mode (RBM) region of the spectrum (100–350 cm–1).
High-speed in-situ atomic force microscopy of biological processes
Atomic force microscopy (AFM) can image surfaces of materials and biological objects in-situ with nanometer scale resolution. A recent development of fast-scanning AFM instrumentation gave us the capability to image surfaces at nanometer scale resolution at near-video rates enabling them for the first time to track and image the motion of biological molecules. We are exploring the unique capabilities of high-speed AFM to capture and analyze nanometer-scale dynamics of biological and non-biological objects assembled on surfaces and surface templates in aqueous environments.
