title: Conformation-sensitive antibody-based point-of-care immunosensor for serum Ca(2+) using two-dimensional sequential binding reactions.
abstract: To assess the homeostasis of Ca(2+) metabolism, we have developed a rapid immunosensor for ionic calcium using a membrane chromatographic technique. As calcium-binding protein (CBP) is available for the recognition and undergone conformation change upon Ca(2+) binding, a monoclonal antibody sensitive to the altered structure of CBP has been employed. The sequential binding scheme was mathematically simulated and shown to match with the experimental results. At the initial stage, the rapid analytical system using lateral flow was constructed by immobilizing the antibody on the immuno-strip nitrocellulose membrane and labeling CBP with colloidal gold as a tracer. A major problem with this system in measuring ionic calcium levels was retarded migration of the gold tracer along the immuno-strip. It was conceivable that the divalent cation at a high concentration caused a change in the physical properties of the tracer, resulting in a non-specific interaction with the membrane surface. This problem was circumvented by first eluting a sample containing biotinylated CBP along the immuno-strip and then supplying the gold coupled to streptavidin across the signal generation pad of the strip. The color signal was then generated via biotin-SA linkage and measured using a smartphone-based detector developed in our laboratory. This two-dimensional chromatographic format completed the Ca(2+) analysis within 15min, the analytical performance covered the clinical dynamic range (0.25-2.5mM) and highly correlated with that of the reference system, i-STAT. These results inspired us to eventually investigate a dual-immunoassay system that measures simultaneously ionic calcium and parathyroid hormone, which regulates the ionic calcium level in serum. This will significantly simplify the current diagnostic protocols, which involve separate devices.
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Ji-Na
authors.initials: JN
authors.lastname: Park
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Sung-Ho
authors.initials: SH
authors.lastname: Paek
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Dong-Hyung
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Seo
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea; Devices and Materials Laboratory, LG Electronics Advanced Research Institute, Seocho-Gu, Seoul 06763, Republic of Korea.
authors.forename: Guei-Sam
authors.initials: GS
authors.lastname: Lim
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Ju-Hee
authors.initials: JH
authors.lastname: Kang
authors.affiliation: College of Information and Communications, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea.
authors.forename: Sung-Pil
authors.initials: SP
authors.lastname: Paek
authors.affiliation: Department of Biomedical Laboratory Science, College of Health Science, Eulji University, Seongnam 13135, Republic of Korea.
authors.forename: Il-Hoon
authors.initials: IH
authors.lastname: Cho
authors.affiliation: Department of Bio-Microsystem Technology, Korea University, 145 Anam-Ro, Sungbuk-Gu, Seoul 02841, Republic of Korea; Department of Biotechnology and Bioinformatics, Korea University, 2511 Sejong-Ro, Sejong 30019, Republic of Korea. Electronic address: shpaek@korea.ac.kr.
authors.forename: Se-Hwan
authors.initials: SH
authors.lastname: Paek
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D015374:Biosensing Techniques / Q000191:economics / Q000295:instrumentation*; D019921:Biotinylation; D002118:Calcium / Q000097:blood* / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D002846:Chromatography, Affinity / Q000191:economics / Q000295:instrumentation*; D004867:Equipment Design; D006046:Gold / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000191:economics / Q000295:instrumentation; D057230:Limit of Detection; D019095:Point-of-Care Systems; D011485:Protein Binding; D011487:Protein Conformation; D000068997:Smartphone; D019809:Streptavidin / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D006046:Gold; D019809:Streptavidin; D002118:Calcium
keywords: Conformation-specific antibody; Conformational change of calcium-binding protein; Highly resolved dynamic range; Point-of-care immunosensor for Ca(2+); Smartphone-based immunosensor