Journal Article

Engineered magnetosomes fused to functional molecule (protein A) provide a highly effective alternative to commercial immunomagnetic beads

Liu, Lingzi, Li, Shuli, Tian, Jiesheng, Li, Ying, Ma, Shijiao, Wen, Ying, Jiang, Wei, Li, Feng, He, Jinxin, Wang, Zhanhui, Xu, Junjie, Xu, Ting

2019

Overview

Background Magnetosomes (also called bacterial magnetic nanoparticles; BMPs) are biomembrane-coated nanoparticles synthesized by magnetotactic bacteria (MTB). Engineered BMPs fused to protein A (termed ∆F-BMP-FA) bind antibodies (Abs) automatically, and thus provide a series of potential advantages. However, no report so far has systematically evaluated functional applicability of genetically engineered BMPs. Results We evaluated properties of ∆F-BMP-FA, and developed/optimized culture methods for host strain Magnetospirillum gryphiswaldense ΔF-FA, ∆F-BMP-FA extraction conditions, conditions for Ab conjugation to ∆F-BMP-FA surface, and procedures for antigen detection using ∆F-BMP-FA/Ab complexes (termed BMP-A-Ab). Fed-batch culture for 36 h in a 42-L fermentor resulted in yields (dry weight) of 2.26 g/L for strain ΔF-FA and 62 mg/L for ∆F-BMP-FA. Optimal wash cycle number for ∆F-BMP-FA purification was seven, with magnetic separation following each ultrasonication step. Fusion of protein A to BMPs resulted in ordered arrangement of Abs on BMP surface. Linkage rate 962 μg Ab per mg ∆F-BMP-FA was achieved. BMP-A-Ab were tested for detection of pathogen ( Vibrio parahaemolyticus ; Vp) surface antigen and hapten (gentamicin sulfate). Maximal Vp capture rate for BMP-A-Ab was 90% (higher than rate for commercial immunomagnetic beads), and detection sensitivity was 5 CFU/mL. ∆F-BMP-FA also bound Abs from crude mouse ascites to form complex. Lowest gentamicin sulfate detection line for BMP-A-Ab was 0.01 ng/mL, 400-fold lower than that for double Ab sandwich ELISA, and gentamicin sulfate recovery rate for BMP-A-Ab was 93.2%. Conclusion Our findings indicate that engineered BMPs such as ∆F-BMP-FA are inexpensive, eco-friendly alternatives to commercial immunomagnetic beads for detection or diagnostic immunoassays, and have high Ab-conjugation and antigen-adsorption capacity.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Adsorption / Aminoglycosides / Antibodies / Antigens / Ascites / Bacteria / Bacterial magnetic nanoparticles / Bacterial proteins / Batch culture / Beads / Biotechnology / Bone morphogenetic proteins / Chemistry / Chemistry and Materials Science / Conjugation / Culture / Diagnostic systems / Displays (Marketing) / Enzyme-linked immunosorbent assay / Enzymes / Fed-batch culture / Fermentation / Fusion protein / Genetic engineering / Genetically modified organisms / Gentamicin / Gentamicin sulfate / Immunoassay / Immunoassays / Magnetic separation / Methods / Microorganisms / Molecular Medicine / Nanomaterials / Nanoparticles / Nanotechnology / Physiological aspects / Properties / Protein A / Proteins / Sulfates / Surface display technique / Vibrio parahaemolyticus / Waterborne diseases / Weight