Immunoassay for foodborne pathogenic bacteria using magnetic composites Ab@Fe 3 O 4 , signal composites Ap@PtNp, and the
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ORIGINAL PAPER
Immunoassay for foodborne pathogenic bacteria using magnetic composites Ab@Fe3O4, signal composites Ap@PtNp, and thermometer readings Shengjun Bu 1 & Kuiyu Wang 2 & Chengyu Wang 1 & Zhongyi Li 1 & Zhuo Hao 1 & Wensen Liu 1 & Jiayu Wan 1 Received: 10 August 2020 / Accepted: 18 November 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract A point-of-care (POC) immunoassay was established for the sensitive and rapid detection of pathogenic Escherichia coli O157:H7, using magnetic Fe3O4 organic-inorganic composites (Ab@Fe3O4) for immunomagnetic separation, nanozyme platinum nanoparticle (PtNp) organic-inorganic composites (Ap@PtNp) for signal amplification, and thermometer readings. Antibodies and Fe3O4 were incubated in Cu2+ phosphate buffer to synthesize the magnetic composite Ab@Fe3O4 with antibodies, to specifically capture E. coli O157:H7. Antimicrobial peptides and PtNp were incubated in Cu2+ 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: Ab@Fe3O4-bacteria-Ap@PtNp for magnetic separation. Ap@PtNp of signal composites catalyzed H2O2 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 101–107 CFU mL−1 and with a detection limit of 14 CFU mL−1. Keywords Foodborne pathogenic bacteria . Point of care . Organic-inorganic composites . Thermal signal
Introduction Foodborne diseases caused by pathogenic bacteria have become a global public health problem, posing a significant threat to human health [1]. It is widely recognized that the rapid, sensitive, and specific detection of pathogens is becoming more important in controlling illness outbreaks [2]. However, access to laboratory tests remains limited in some poor countries, and also in some developing countries [3]. The rapid, sensitive, and specific point-of-care (POC) detection of foodborne pathogenic bacteria can effectively reduce foodand water-borne outbreaks, especially in resource-limited
* Wensen Liu [email protected] * Jiayu Wan [email protected] 1
Institute of Military Veterinary, Academy of Military Medical Sciences, Changchun 130122, China
2
School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
settings [4]. Other common methods of detecting pathogenic bacteria use microbiological plating and counting and the polymerase chain reaction (PCR). Although these approaches are specific and sensitive, their applications in such settings are limited as they are easy to contaminate and generate falsepositive results [5]. Over recent decades, scientists have successfully developed viable POC bioassays, based on immunoassay to detect foodborne pathogenic bacteria [6]. POC testing has the advantage of greater availability in resource-constrain
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