title: Enhanced sandwich immunoassay using antibody-functionalized magnetic iron-oxide nanoparticles for extraction and detection of soluble transferrin receptor on a photonic crystal biosensor.
abstract: Iron deficiency anemia (IDA) has detrimental effects on individuals and societies worldwide. A standard sandwich assay (SA) for the detection of soluble transferrin receptor (sTfR), a biomarker of IDA, on a photonic crystal (PC) biosensor was established, but it was susceptible to non-specific signals from complex matrixes. In this study, iron-oxide nanoparticles (fAb-IONs) were used as magnetic immuno-probes to bind sTfR and minimize non-specific signals, while enhancing detection on the PC biosensor. This inverse sandwich assay (IA) method completely bound sTfR with low variability (<4% RSD) in buffer and allowed for its accurate and precise detection in sera (Liquichek™ control sera) on the PC biosensor using two certified ELISAs as reference methods. A linear dose-response curve was elicited at the fAb-IONs concentration in which the theoretical binding ratio (sTfR:fAb-IONs) was calculated to be <1 on the IA. The LoDs for sTfR in the SA and IA were similar (P>0.05) at 14 and 21 μg/mL, respectively. The inherent imprecision of the IA and reference ELISAs was σ(δ)=0.45 µg/mL and the mean biases for Liquichek™ 1, 2 and 3 were 0.18, 0.19 and -0.04 µg/mL, respectively. Whereas the inherent imprecision of the SA and reference ELISAs was σ(δ)=0.52 µg/mL and the biases for Liquichek™ 1, 2 and 3 were 0.66, 0.14 and -0.67 µg/mL, respectively. Thus, unlike the SA, the IA method measures sTfR with the same bias as the reference ELISAs. Combined magnetic separation and detection of nutrition biomarkers on PC biosensors represents a facile method for their accurate and reliable quantification in complex matrixes.
authors.affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Ross D
authors.initials: RD
authors.lastname: Peterson
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Weili
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Cunningham
authors.affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States. Electronic address: jandrade@illinois.edu.
authors.forename: Juan E
authors.initials: JE
authors.lastname: Andrade
mesh_terms: D000906:Antibodies / Q000737:chemistry; D015415:Biomarkers / Q000737:chemistry; D015374:Biosensing Techniques; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D053768:Metal Nanoparticles / Q000737:chemistry*; D011990:Receptors, Transferrin / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D000906:Antibodies; D015415:Biomarkers; D005290:Ferric Compounds; D011990:Receptors, Transferrin; C000499:ferric oxide
keywords: Biosensor; Iron deficiency; Iron-oxide nanoparticles; Magnetic separation; Photonic crystal; Soluble transferrin receptor