Preparation of immunomagnetic nanoparticles for the separation and enrichment of Alicyclobacillus spp. in apple juice

- The recognition capacity of different IMPs was evaluated.
- The best protocol for preparation of IMPs was optimized.
- The immunocapture conditions for bacteria were assayed.
- Specificity of IMS for different bacteria was evaluated.
- Apple juice samples contaminated with Alicyclobacillus spp. were detected.

Specific anti-Alicyclobacillus IgG antibody was immobilized on the surface of magnetic nanoparticles for the development of immunomagnetic nanoparticles (IMPs), which will be used for the immunocapture of Alicyclobacillus spp. The immunobinding efficacy of oxidized antibody using oriented immobilization was evaluated by comparing its Alicyclobacillus acidoterrestris (A. acidoterrestris) capturing capacity with that of a randomly immobilized system and physical adsorption. The results indicated that oriented immobilization of oxidized antibody onto the (3-aminopropyl) triethoxysilane coated magnetic nanoparticles exhibited better recognition capacity than others. In the process, the sugar moiety in the CH2 domain of the antibody's fragment crystallizable region (Fc region) was oxidized and translated into aldehyde group. The reactions between the aldehyde groups of antibody and amine groups of magnetic nanoparticles could prompt the accurate orientation of antibody binding at the Fc region. At optimum condition, the maximum antibody adsorption capacity of magnetic nanoparticles could arrive to 75.6 μg/mg and the separation efficiency for A. acidoterrestris could be up to 80% or more. The results showed that the obtained IMPs and optimized protocol exhibited a higher recognition ability for Alicyclobacillus spp. and a lower nonspecific adsorption of others. Based on the specific binding affinity of the oriented immobilization process, the immobilization approach proposed here may be an attractive strategy for the preparation of IMPs for immunocapture and rapid detection of Alicyclobacillus spp. in apple juice.