Selective Detection of Shiga-like Toxin 1 from Complex Samples Using Pigeon Ovalbumin Functionalized Gold Nanoparticles as Affinity Probes

Abstract

Escherichia coli O157:H7 is a foodborne pathogen. This bacterial strain can generate Shiga-like toxins (SLTs), which can cause serious sickness and even death. Thus, it is important to develop effective and sensitive methods that can be used to rapidly identify the presence of SLTs from complex samples. Pigeon egg white (PEW) contains abundant glycoproteins, including pigeon ovalbumin (POA) (∼60%). POA possesses Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini, which can recognize the B subunits in SLT type 1 (SLT-1B). Thus, POA is a suitable probe for trapping SLT-1B. In this work, we used PEW proteins as starting materials to react with aqueous tetrachloroauric acid for generation of PEW-protein-immobilized gold nanoparticles (AuNPs@PEW) via one-pot reactions. We demonstrated that the generated AuNPs@PEW were mainly dominated by POA-immobilized Au NPs. The as-prepared AuNPs@PEW were used as affinity probes to selectively probe SLT-1B from complex cell lysates derived from E. coli O157:H7. The selective trapping step can be completed within ∼90 s under microwave heating (power = 450 W) to enrich sufficient SLT-1B for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric analysis. Furthermore, this approach can be used to detect SLT-1B at a concentration as low as ∼40 pM. The feasibility of using the proposed method to selectively detect SLT-1B from ham contaminated by E. coli O157:H7 was also demonstrated.

Inhibition of the lethality of Shiga-like toxin-1 by functional gold nanoparticles

“…The maximum absorption band appeared at the wavelength of $520 nm (Figure 1(A)), and the generated POA-Au NPs had red color (inset photograph in Figure 1(A)). The generated POA-Au NPs have similar UV-Vis absorption spectrum and color to that in the previous reported [40]. Figure 1(B) shows the transmission electron microscope (TEM) image of the generated POA-Au NPs.…”

“…Characterization of POA-Au NPs POA-Au NPs were prepared according to the method reported previously [40]. The generated POA-Au NPs were first characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy.…”

“…The resultant lyophilized PEW was stored in a freezer (À20 C). POA-Au NPs were generated based on the method reported previously [40]. When preparing POA-Au NPs, PEW proteins were denatured first.…”

“…POA is a glycoprotein and contains Gala(1!4)-Gal-b(1!4)-GlcNAc termini [32], and it has been used to target SLT-1B [27]. In addition, POA contains three cysteines [33], which can serve as reducing/capping agents [34][35][36][37][38][39] for generation of Au NPs by reacted with aqueous tetrachloroauric acid through one-pot reactions [40]. Furthermore, the POA immobilized Au NPs (POA-Au NPs) possessed selective targeting capacity toward SLT-1B [40].…”

“…In addition, POA contains three cysteines [33], which can serve as reducing/capping agents [34][35][36][37][38][39] for generation of Au NPs by reacted with aqueous tetrachloroauric acid through one-pot reactions [40]. Furthermore, the POA immobilized Au NPs (POA-Au NPs) possessed selective targeting capacity toward SLT-1B [40]. Herein, POA-Au NPs are explored to have the capability to neutralize the toxicity of SLT-1 in the SLT-1 infected cells.…”