Immunoassay for foodborne pathogenic bacteria using magnetic composites [e-mail].4, signal composites Ap@PtNp, and thermometer readings

• Published in: Mikrochimica acta (1966) 2020-12, Vol.187 (12)
• Main Authors: Bu, Shengjun, Wang, Kuiyu, Wang, Chengyu, Li, Zhongyi, Hao, Zhuo, Liu, Wensen, Wan, Jiayu
• Format: Article
• Language: English
• Subjects: Bacteria; Escherichia coli; Phosphates
• ISSN: 0026-3672
• DOI: 10.1007/s00604-020-04657-1

A point-of-care (POC) immunoassay was established for the sensitive and rapid detection of pathogenic Escherichia coli O157:H7, using magnetic Fe.sub.3O.sub.4 organic-inorganic composites ([e-mail].4) for immunomagnetic separation, nanozyme platinum nanoparticle (PtNp) organic-inorganic composites (Ap@PtNp) for signal amplification, and thermometer readings. Antibodies and Fe.sub.3O.sub.4 were incubated in Cu.sup.2+ phosphate buffer to synthesize the magnetic composite [e-mail].4 with antibodies, to specifically capture E. coli O157:H7. Antimicrobial peptides and PtNp were incubated in Cu.sup.2+ phosphate buffer to synthesize the signal composites Ap@PtNp with antimicrobial peptides (magainin I), recognizing and labeling E. coli O157:H7. In the presence of E. coli O157:H7, magnetic microcomposites targeted bacteria and signal microcomposites to form the sandwich structure: [e-mail].4-bacteria-Ap@PtNp for magnetic separation. Ap@PtNp of signal composites catalyzed H.sub.2O.sub.2 to generate thermo-signals (temperature rise), which were determined by a thermometer. This point-of-care bioassay detected E. coli O157:H7 in the linear range of 10.sup.1-10.sup.7 CFU mL.sup.-1 and with a detection limit of 14 CFU mL.sup.-1.