title: Optimization of SERS tag intensity, binding footprint, and emittance.
abstract: Nanoparticle surface enhanced Raman scattering (SERS) tags have attracted interest as labels for use in a variety of applications, including biomolecular assays. An obstacle to progress in this area is a lack of standardized approaches to compare the brightness of different SERS tags within and between laboratories. Here we present an approach based on binding of SERS tags to beads with known binding capacities that allows evaluation of the average intensity, the relative binding footprint of particles in a SERS tag preparation, and the size-normalized intensity or emittance. We tested this on four different SERS tag compositions and show that aggregated gold nanorods produce SERS tags that are 2-4 times brighter than relatively more monodisperse nanorods, but that the aggregated nanorods are also correspondingly larger, which may negate the intensity if steric hindrance limits the number of tags bound to a target. By contrast, SERS tags prepared from smaller gold nanorods coated with a silver shell produce SERS tags that are 2-3 times brighter, on a size-normalized basis, than the Au nanorod-based tags, resulting in labels with improved performance in SERS-based image and flow cytometry assays. SERS tags based on red-resonant Ag plates showed similarly bright signals and small footprint. This approach to evaluating SERS tag brightness is general, uses readily available reagents and instruments, and should be suitable for interlab comparisons of SERS tag brightness.
authors.affiliation: La Jolla Bioengineering Institute Suite 210 3535 General Atomics Court San Diego, California 92121, United States.
authors.forename: John P
authors.initials: JP
authors.lastname: Nolan
authors.forename: Erika
authors.initials: E
authors.lastname: Duggan
authors.forename: Danilo
authors.initials: D
authors.lastname: Condello
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001360:Avidin / Q000737:chemistry / Q000378:metabolism; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism; D004396:Coloring Agents / Q000737:chemistry / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry*; D008863:Microspheres; D043942:Nanotubes; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism; D012834:Silver / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D020349:Surface Plasmon Resonance; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D001360:Avidin; D004396:Coloring Agents; D005456:Fluorescent Dyes; D006046:Gold; D018719:Erb-b2 Receptor Tyrosine Kinases; D012710:Serum Albumin, Bovine; D012834:Silver; D000068878:Trastuzumab; C093483:neutravidin