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

Abstract

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. Electronic supplementary material The online version of this article (10.1186/s12951-019-0469-z) contains supplementary material, which is available to authorized users.

Microbe‐Mediated Extracellular and Intracellular Mineralization: Environmental, Industrial, and Biotechnological Applications

“…[ 328 ] These genetically engineered magnetosomes with fused protein A bind antibodies automatically, and are inexpensive, ecofriendly alternatives to the use of commercial immunomagnetic beads for pathogen detection. [ 353 ] Apart from using harvested and purified magnetosomes, MO‐1 MTB has also been decorated with rabbit anti‐MO‐1 cell polyclonal antibodies to become magnetic‐guiding, auto‐propelling microrobots for detection and separation of S. aureus . [ 354 ] After binding of the polyclonal antibody‐coated MO‐1 MTB to protein A on the surface of S. aureus (e.g., in an infected wound), the bacteria are mechanically injured and eliminated via the application of a swinging magnetic field ( Figure ).…”

A Versatile Toolkit for Controllable and Highly Selective Multifunctionalization of Bacterial Magnetic Nanoparticles

“…[ 17,24 ] The latter was furthermore used as single anchor protein for magnetosome display of protein A, thereby generating magnetic beads that were capable of binding the F C region of mammalian antibodies. [ 27,28 ] However, it so far remained unexplored if these Mam proteins can be utilized for simultaneous magnetosome expression of more complex, multimeric (enzyme) proteins.…”

Magnetic Actuation Methods in Bio/Soft Robotics

“…Regarding magnetosomes, their highly desirable single domain magnetic domain, the ability to functionalize their lipid membrane, and their biocompatibility has allowed their usage in several fields such as contrast agents for Magnetic Resonance Imaging (MRI), [ 196,197 ] separation of biomolecules, [ 198–200 ] cellular homeostasis disorder, [ 201 ] hyperthermia therapy, [ 202,203 ] photothermia therapy, [ 204 ] immunoassays, [ 205 ] drug delivery, [ 206 ] biosensing (Peroxidase‐like activity), [ 207 ] and stain removal. [ 208 ]…”