title: Investigating the colloidal stability of fluorescent silica nanoparticles under isotonic conditions for biomedical applications.
abstract: Fluorescent silica nanoparticle (NP) labels are of great interest in biomedical diagnostics, however, when used in bioassays under physiological conditions they rapidly agglomerate and precipitate from solution leading to high levels of non-specific binding. In this work, using size and zeta-potential data obtained from Dynamic and Electrophoretic Light Scattering analysis, the improvement in colloidal stability of silica NPs under physiological conditions was correlated with an increase in the concentration of three additives: (1) a protein, bovine serum albumin (BSA); (2) a neutral surfactant, Tween 20®; and (3) a charged surfactant, sodium dodecyl sulfate (SDS). The number of BSA molecules present in the NP corona at each concentration was calculated using UV-Vis spectroscopy and a bicinchoninic acid protein assay (BCA). The optimal concentration of each additive was also effective in stabilizing antibody labeled fluorescent nanoparticles (αNPs) under physiological conditions. Using a fourth additive, trehalose, the colloidal stability of αNPs after freeze-drying and long-term storage also significantly improved. Both as-prepared and freeze-dried αNPs were tested in a standard fluorescence immunoassay for the detection of human IgG. The as-prepared assay showed a higher sensitivity at low concentration and a lower limit of detection when compared to a free dye assay. Assays performed with freeze dried αNPs after 4 and 22 days also showed good reproducibility.
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: robert.nooney@dcu.ie.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Nooney
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: angela.white26@mail.dcu.ie.
authors.forename: Angela
authors.initials: A
authors.lastname: White
authors.affiliation: Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA 30332-0400, USA. Electronic address: christyc@gmail.com.
authors.forename: Christy
authors.initials: C
authors.lastname: O'Mahony
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: claire.oconnell57@mail.dcu.ie.
authors.forename: Claire
authors.initials: C
authors.lastname: O'Connell
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: susan.kelleher@dcu.ie.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Kelleher
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: stephen.daniels@dcu.ie.
authors.forename: Stephen
authors.initials: S
authors.lastname: Daniels
authors.affiliation: Biomedical Diagnostic Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Collins Avenue, Glasnevin, Dublin 9, Ireland. Electronic address: colette.mcdonagh@dcu.ie.
authors.forename: Colette
authors.initials: C
authors.lastname: McDonagh
mesh_terms: D003102:Colloids / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D005612:Freeze Drying; D006801:Humans; D007118:Immunoassay; D007074:Immunoglobulin G / Q000737:chemistry; D008027:Light; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011136:Polysorbates / Q000737:chemistry; D011804:Quinolines / Q000737:chemistry; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D003102:Colloids; D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D011136:Polysorbates; D011804:Quinolines; D013501:Surface-Active Agents; D012710:Serum Albumin, Bovine; D012967:Sodium Dodecyl Sulfate; D012822:Silicon Dioxide; C047117:bicinchoninic acid
keywords: Colloidal stability; Fluorescence; Immunoassay; Proteins; Silica nanoparticles; Surfactants