title: Ultrasensitive electrogenerated chemiluminescence peptide-based method for the determination of cardiac troponin I incorporating amplification of signal reagent-encapsulated liposomes.
abstract: An ultrasensitive electrogenerated chemiluminescence peptide-based (ECL-PB) method for the determination of cardiac troponin I (TnI) incorporating amplification of signal reagent-encapsulated liposome was reported for the first time. A synthesized short linear specific binding peptide (FYSHSFHENWPSK) was employed as a molecular recognition element for TnI, which was a reliable biomarker for detecting cardiac injury. Liposomes assembled using a standard sonication procedure were designed as the carrier of ECL signal reagents [bis(2,2'-bipyridine)-4,4'-dicarboxybipyridine ruthenium-di(N-succinimidyl ester) bis(hexafluorophosphate)] for signal amplification. The magnetic capture peptides for the enrichment of the target protein and magnetic separation were synthesized by covalently attaching the peptides to the surface of magnetic beads via an acylation reaction, and the liposome peptides were synthesized by covalently attaching the peptides to the signal reagent-encapsulated liposomes. In the presence of TnI, sandwich-type conjugates were generated in incubation of the magnetic capture peptides and the liposome peptides. After a magnetic separation, the sandwich-type conjugates were treated with ethanol and, thus, a great number of the ECL reagents were released and measured by the ECL method at a bare glassy carbon electrode with a potential pulse of +1.15 V versus Ag/AgCl in the presence of tri-n-propylamine. The increased ECL intensity has good linearity with the logarithm of the TnI concentration in the range from 10 pg/mL to 5.0 ng/mL, with an extremely low detection limit of 4.5 pg/mL. The proposed ECL-PB method was successfully applied to the detection of TnI in human serum samples. This work demonstrated that the employment of the magnetic capture peptides for the enrichment of the target proteins and magnetic separation and the liposome peptides for the signal amplification and polyvalent binding motifs may open a new door to ultrasensitive detection of proteins in clinical analyses.
authors.affiliation: Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, PR China. honglanqi@snnu.edu.cn
authors.forename: Honglan
authors.initials: H
authors.lastname: Qi
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Qiu
authors.forename: Danping
authors.initials: D
authors.lastname: Xie
authors.forename: Chen
authors.initials: C
authors.lastname: Ling
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.forename: Chengxiao
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D002138:Calibration; D004339:Drug Compounding; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D006801:Humans; D057230:Limit of Detection; D008081:Liposomes / Q000737:chemistry*; D008163:Luminescent Measurements; D059346:Magnets; D008969:Molecular Sequence Data; D009942:Organometallic Compounds / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011485:Protein Binding; D013010:Sonication; D019210:Troponin I / Q000097:blood*
chemical_list: D008081:Liposomes; D009942:Organometallic Compounds; D010455:Peptides; D019210:Troponin I; C511353:bis(2,2'-bipyridine)-4'-methyl-4-carboxybipyridine-ruthenium-N-succinimidyl ester