uri physics colloquium

Optical Properties of Biopolymer-Carbon Nanotube Hybrids: From Fundamentals to Biomedical Applications

Daniel E. Roxbury, Ph.D., Assistant Professor, Department of Chemical Engineering, University of Rhode Island

abstract

The intrinsic band-gap photoluminescence of single-walled carbon nanotubes (SWCNTs) exhibits exceptional photostability, narrow bandwidth, near-infrared (nIR) tissue-penetrating emission, and microenvironmental sensitivity, which enables their usage in a variety of biomedical imaging and sensing applications. Amphiphilic biopolymers, such as single-stranded DNA or peptides, are capable of singly-dispersing SWCNTs, enabling photoluminescence in aqueous solutions, in addition to increasing the biocompatibility of the hybrid. A DNA sequence-dependent scheme for SWCNT species (chirality) separation has been observed that highly correlated with DNA-SWCNT binding strengths.  Using all-atom replica exchange molecular dynamics simulations (REMD), equilibrium structures confirmed that a variety of novel DNA secondary structures form when confined to the exterior surface of the SWCNT in a DNA-sequence and SWCNT-chirality-dependent fashion. In biological applications, DNA-encapsulated SWCNTs were found to enter primary mammalian endothelial cells by means of an energy-dependent endocytosis mechanism and remain in the endosomal pathway. A novel hyperspectral fluorescence imaging approach was able to spatially resolve over a dozen chiralities of single SWCNTs in live cells, in excised mouse tissue, and in live zebrafish.  Additionally, in the endosomes of live cells, the SWCNT’s ability to sense perturbations in its microenvironment, via modulations in emission intensity and peak center wavelength, was exploited as a non-destructive and long-term monitoring nIR optical reporter of cholesterol accumulation. Again using REMD simulation, there was observed correspondence between the optical signals of the SWCNT and the nanostructured analytes and solvent molecules

Bio-Sketch: Dr. Roxbury is currently an Assistant Professor of Chemical Engineering at the University of Rhode Island where he is an investigator for the Rhode Island IDeA Network for Excellence in Biomedical Research (RI-INBRE) and leads an interdisciplinary research team. Prof. Roxbury received his B.S. and Ph.D. degrees in chemical engineering from Lehigh University (Bethlehem, PA). Prior to attaining a faculty position, Prof. Roxbury conducted his postdoctoral work at Memorial Sloan Kettering Cancer Center (New York, NY), where he was externally funded through an American Cancer Society Postdoctoral Fellowship.