@article{glomm_moses_brennaman_papanikolas_franzen_2005, title={Detection of adsorption of Ru(II) and Os(II) polypyridyl complexes on gold and silver nanoparticles by single-photon counting emission measurements}, volume={109}, ISSN={["1520-6106"]}, DOI={10.1021/jp049184k}, abstractNote={The present study describes a new application of ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) and osmium(II) tris(bipyridine) (Os(bpy)3(2+)) as phosphorescent labels for the quantification of surface binding of molecules to gold and silver nanoparticles. The fraction of Ru(bpy)3(2+) and Os(bpy)3(2+) that is in solution can be distinguished from the surface-bound fraction by the relative lifetimes and integrated emission yields as determined by time-correlated single-photon counting (TCSPC) spectroscopy. Complementary steady-state measurements were carried out to confirm surface attachment of the phosphorescent label molecules. Although the emission of solutions of Ru(bpy)3(2+) and Os(bpy)3(2+) is quenched proportional to the concentration of 10 nm Au or 20 nm Ag nanoparticles, the quenching is static and not diffusional quenching observed in Stern-Volmer plots. The results demonstrate that time-resolved spectroscopy provides a rapid method for the measurement of surface binding of labeled molecules on metallic nanoparticles. While steady-state measurements require the preparation of a series of samples with varying quencher concentrations and a reference, the method described herein requires a single sample plus reference. The mechanism for phosphorescence quenching on Au and Ag nanoparticles is discussed in terms of energy and electron transfer theories.}, number={2}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Glomm, WR and Moses, SJ and Brennaman, MK and Papanikolas, JM and Franzen, S}, year={2005}, month={Jan}, pages={804–810} }
 @article{tkachenko_xie_liu_coleman_ryan_glomm_shipton_franzen_feldheim_2004, title={Cellular trajectories of peptide-modified gold particle complexes: Comparison of nuclear localization signals and peptide transduction domains}, volume={15}, ISSN={["1520-4812"]}, DOI={10.1021/bc034189q}, abstractNote={Gold nanoparticles modified with nuclear localization peptides were synthesized and evaluated for their subcellular distribution in HeLa human cervical epithelium cells, 3T3/NIH murine fibroblastoma cells, and HepG2 human hepatocarcinoma cells. Video-enhanced color differential interference contrast microscopy and transmission electron microscopy indicated that transport of nanoparticles into the cytoplasm and nucleus depends on peptide sequence and cell line. Recently, the ability of certain peptides, called protein transduction domains (PTDs), to transclocate cell and nuclear membranes in a receptor- and temperature-independent manner has been questioned (see for example, Lundberg, M.; Wikstrom, S.; Johansson, M. (2003) Mol. Ther. 8, 143-150). We have evaluated the cellular trajectory of gold nanoparticles carrying the PTD from HIV Tat protein. Our observations were that (1) the conjugates did not enter the nucleus of 3T3/NIH or HepG2 cells, and (2) cellular uptake of Tat PTD peptide-gold nanoparticle conjugates was temperature dependent, suggesting an endosomal pathway of uptake. Gold nanoparticles modified with the adenovirus nuclear localization signal and the integrin binding domain also entered cells via an energy-dependent mechanism, but in contrast to the Tat PTD, these signals triggered nuclear uptake of nanoparticles in HeLa and HepG2 cell lines.}, number={3}, journal={BIOCONJUGATE CHEMISTRY}, author={Tkachenko, AG and Xie, H and Liu, YL and Coleman, D and Ryan, J and Glomm, WR and Shipton, MK and Franzen, S and Feldheim, DL}, year={2004}, pages={482–490} }
 @article{xie_tkachenko_glomm_ryan_brennaman_papanikolas_franzen_feldheim_2003, title={Critical flocculation concentrations, binding isotherms, and ligand exchange properties of peptide-modified gold nanoparticles studied by UV-visible, fluorescence, and time-correlated single photon counting spectroscopies}, volume={75}, ISSN={["0003-2700"]}, DOI={10.1021/ac034578d}, abstractNote={Protocols for modifying gold nanoparticles with peptide-bovine serum albumin (BSA) conjugates are described within. The resulting constructs were characterized using a number of techniques including static fluorescence spectroscopy and time-correlated single photon counting spectroscopy (TCSPC) in order to quantify peptide-BSA binding isotherms, exchange rates, critical flocculation concentrations, and the composition of mixed peptide-BSA monolayers on gold nanoparticles. TCSPC has proven to be a powerful technique for observing the microenvironment of protein-gold nanoparticle conjugates because it can distinguish between surface-bound and solution-phase species without the need for separation steps. Full characterization of the composition and stability of peptide-modified metal nanoparticles is an important step in their use as intracellular delivery vectors and imaging agents.}, number={21}, journal={ANALYTICAL CHEMISTRY}, author={Xie, H and Tkachenko, AG and Glomm, WR and Ryan, JA and Brennaman, MK and Papanikolas, JM and Franzen, S and Feldheim, DL}, year={2003}, month={Nov}, pages={5797–5805} }
 @article{tkachenko_xie_coleman_glomm_ryan_anderson_franzen_feldheim_2003, title={Multifunctional gold nanoparticle-peptide complexes for nuclear targeting}, volume={125}, ISSN={["0002-7863"]}, DOI={10.1021/ja0296935}, abstractNote={The ability of peptide-modified gold nanoparticles to target the nucleus of HepG2 cells was explored. Five peptide/nanoparticle complexes were investigated, particles modified with (1) the nuclear localization signal (NLS) from the SV 40 virus; (2) the adenovirus NLS; (3) the adenovirus receptor-mediated endocytosis (RME) peptide; (4) one long peptide containing the adenovirus RME and NLS; and (5) the adenovirus RME and NLS peptides attached to the nanoparticle as separate pieces. Gold nanoparticles were used because they are easy to identify using video-enhanced color differential interference contrast microscopy, and they are excellent scaffolds from which to build multifunctional nuclear targeting vectors. For example, particles modified solely with NLS peptides were not able to target the nucleus of HepG2 cells from outside the plasma membrane, because they either could not enter the cell or were trapped in endosomes. The combination of NLS/RME particles (4) and (5) did reach the nucleus; however, nuclear targeting was more efficient when the two signals were attached to nanoparticles as separate short pieces versus one long peptide. These studies highlight the challenges associated with nuclear targeting and the potential advantages of designing multifunctional nanostructured materials as tools for intracellular diagnostics and therapeutic delivery.}, number={16}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Tkachenko, AG and Xie, H and Coleman, D and Glomm, W and Ryan, J and Anderson, MF and Franzen, S and Feldheim, DL}, year={2003}, month={Apr}, pages={4700–4701} }
 @article{franzen_folmer_glomm_r o'neal_2002, title={Optical properties of dye molecules adsorbed on single gold and silver nanoparticles}, volume={106}, ISSN={["1520-5215"]}, DOI={10.1021/jp025536g}, abstractNote={Despite the well-known relationship between the resonance Raman excitation profile and the absorption line shape, there is scant experimental evidence for effects in absorption or fluorescence spectroscopy related to the observations of surface-enhanced Raman scattering (SERS). On the other hand, numerous Raman studies have been done on the SERS phenomenon, where large enhancement factors have been determined. In this work, the absorption properties of molecules adsorbed on single gold and silver nanoparticles (monomers) have been investigated, with particular emphasis on an examination of the effect on the spectrum of the adsorbate. A number of the adsorbates studied are similar to those reported in SERS studies. The adsorbates can be divided into two classes according to the nature of the interaction with the adsorbent. Class I shows little change in the absorption spectrum. Class II shows a large reduction in absorption. The only examples of an increase in absorption arise from solvatochromic effects. ...}, number={28}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Franzen, S and Folmer, JCW and Glomm, WR and R O'Neal}, year={2002}, month={Jul}, pages={6533–6540} }