Point-of-care detection of pathogenic bacteria based on pregnancy test strips and metal–organic frameworks

Abstract

Presently, pregnancy test strip (PTS) is one of the most widely used and advanced biomedical testing products. In this study, a portable, sensitive, and low-cost biosensor based on PTS was developed for detecting pathogenic bacteria. In the present study, PTS combined with metal–organic frameworks (MOFs) and hybridization chain reaction (HCR) was used for visual point-of-care (POC) detection of Escherichia coli O157:H7. A single-stranded capture probe (CP) was immobilized onto the surface of magnetic beads (MBs). The CP and an E. coli O157:H7-specific aptamer (AP) formed a double-stranded structure on the surface of MBs. The AP preferentially bound to E. coli O157:H7, thereby exposing some CP and causing their release. Subsequently, the single-stranded CP hybridized with biotin-labeled double-stranded DNA polymers by HCR through the 5ʹ-end sequence of the reporter probe (RP). Numerous MOFs encapsulated with human chorionic gonadotropin (hCG) and modified streptavidin (SA) were then introduced and could be directly and visually detected by PTSs. Under optimal conditions, the method can detect E. coli O157:H7 with a detection limit of 530 CFU/mL. Thus, this method has a high potential for cost-effective, portable, and rapid determination of E. coli O157:H7, especially in resource-limited environments.