title: Effect of conformation and drop properties on surface-enhanced Raman spectroscopy of dried biopolymer drops.
abstract: Biofluids are complex solutions consisting of small ions and large biopolymers such as DNA, proteins, or proteoglycans. Biopolymers affect fluid properties but their effect on drop deposition has not been examined. Hyaluronic acid (HA), an important component in synovial fluid, was chosen as a model biopolymer, and examined using surface-enhanced Raman spectroscopy (SERS). Nanoliter volumes of HA solutions were dried onto a patterned SERS substrate and spectra were collected from the dried hyaluronic acid drops with a near-infrared Raman microscope. Characteristic hyaluronic acid bands were examined. Capillary viscometry measured properties of HA solutions, and entanglement behavior was also modeled using scaling theory principles. Viscosity measurements were incorporated into models of suspended particle droplets to account for the effect of inter-chain attraction on droplet formation. Microscope images were used to evaluate the shape of the dried drop. Relative drop thickness was estimated from concentric rings found at drop edges using established models of light interference by thin films. We found SERS spectra were sensitive not only to polymer conformation, but also to type of deposition (ring versus uniform), and the thickness of the resulting deposition. These data suggest an approach to elucidate the effects of biopolymers and dehydrated biofluids on SERS analysis.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, USA.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Esmonde-White
authors.forename: Stephanie V
authors.initials: SV
authors.lastname: Le Clair
authors.forename: Blake J
authors.initials: BJ
authors.lastname: Roessler
authors.forename: Michael D
authors.initials: MD
authors.lastname: Morris
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D002197:Capillary Action; D004247:DNA / Q000737:chemistry; D003890:Desiccation; D006820:Hyaluronic Acid / Q000737:chemistry; D008968:Molecular Conformation; D011506:Proteins / Q000737:chemistry; D011509:Proteoglycans / Q000737:chemistry; D012996:Solutions; D013059:Spectrum Analysis, Raman; D014783:Viscosity
chemical_list: D001704:Biopolymers; D011506:Proteins; D011509:Proteoglycans; D012996:Solutions; D006820:Hyaluronic Acid; D004247:DNA