Escherichia coli DH5α functionalised magnetite nanoparticles applied for the magnetic extraction of bacteriophages

The study presents the design of a magnetic nanosystem functionalised with Escherichia coli for bacteriophage isolation. The chitosan-coated nanoparticles (C-MNP) were synthesised by coprecipitation, then functionalised with E. coli cells. Different concentrations of C-MNP and incubation times were tested. The immobilisation kinetics and adsorption isotherm were studied. The kinetics was described with the pseudo-stationary state after 30 min. The isotherm was linearized in the Freundlich model. Thermogravimetric analysis verified the functionalisation of C-MNP with E. coli. The complex was used for the extraction of coliphage, for the analysis of the effect of time and salt concentration on phage desorption, and phage extractions with the reuse of the magnetic nanosystem. Compared with traditional methods, an increase in the phage titre collected with the nanocomplex was achieved. The obtained results suggest that C-MNP/E. coli nanosystem can be used at least three cycles for the phage extraction. The release of the phages from the nanosystem was sensitive to the salt concentration. The use of a designed nano-bio complex allowed a rapid and efficient separation of the phages from the water sample under the application of an external magnetic field, and with the possibility of reusing the magnetic complex.