title: Competitive surface-enhanced Raman scattering assay for the 1,25-dihydroxy metabolite of vitamin D3.
abstract: This paper describes the development and preliminary testing of a competitive surface-enhanced Raman scattering (SERS) immunoassay for calcitriol, the 1,25-dihydroxy metabolite (1,25-(OH)(2)-D(3)) of vitamin D(3). Deficiencies in 1,25-(OH)(2)-D have been linked to renal disease, while elevations are linked to hypercalcemia. Thus, there has been a sharp increase in the clinical demand for measurements of this metabolite. The work herein extends the many attributes of SERS-based sandwich immunoassays that have been exploited extensively in the detection of large biolytes (e.g., DNA, proteins, viruses, and microorganisms) into a competitive immunoassay for the low level determination of a small biolyte, 1,25-(OH)(2)-D(3) (M(w) = 416 g mol(-1)). The assay uses surface modified gold nanoparticles as SERS labels, and has a dynamic range of 10-200 pg mL(-1) and a limit of detection of 8.4 ± 1.8 pg mL(-1). These analytical performance metrics match those of tests for 1,25-(OH)(2)-D(3) that rely on radio- or enzyme-labels, while using a much smaller sample volume and eliminating the disposal of radioactive wastes. Moreover, the SERS-based data from pooled-patient sera show strong agreement with that from radioimmunoassays. The merits and potential utility of this new assay are briefly discussed.
authors.affiliation: Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Dufek
authors.forename: Brian
authors.initials: B
authors.lastname: Ehlert
authors.forename: Michael C
authors.initials: MC
authors.lastname: Granger
authors.forename: Tanya M
authors.initials: TM
authors.lastname: Sandrock
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Legge
authors.forename: Mark G
authors.initials: MG
authors.lastname: Herrmann
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Meikle
authors.forename: Marc D
authors.initials: MD
authors.lastname: Porter
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives / Q000032:analysis* / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay; D015394:Molecular Structure; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties
chemical_list: D002117:Calcitriol