title: T4 bacteriophage conjugated magnetic particles for E. coli capturing: Influence of bacteriophage loading, temperature and tryptone.
abstract: This work demonstrates the use of bacteriophage conjugated magnetic particles (Fe3O4) for the rapid capturing and isolation of Escherichia coli. The investigation of T4 bacteriophage adsorption to silane functionalised Fe3O4with amine (NH2), carboxylic (COOH) and methyl (CH3) surface functional groups reveals the domination of net electrostatic and hydrophobic interactions in governing bacteriophage adsorption. The bare Fe3O4and Fe3O4-NH2with high T4 loading captured 3-fold more E. coli (∼70% capturing efficiency) compared to the low loading T4 on Fe3O4-COOH, suggesting the significance of T4 loading in E. coli capturing efficiency. Importantly, it is further revealed that E. coli capture is highly dependent on the incubation temperature and the presence of tryptone in the media. Effective E. coli capturing only occurs at 37°C in tryptone-containing media with the absence of either conditions resulted in poor bacteria capture. The incubation temperature dictates the capturing ability of Fe3O4/T4, whereby T4 and E. coli need to establish an irreversible binding that occurred at 37°C. The presence of tryptophan-rich tryptone in the suspending media was also critical, as shown by a 3-fold increase in E. coli capture efficiency of Fe3O4/T4 in tryptone-containing media compared to that in tryptone-free media. This highlights for the first time that successful bacteria capturing requires not only an optimum tailoring of the particle's surface physicochemical properties for favourable bacteriophage loading, but also an in-depth understanding of how factors, such as temperature and solution chemistry influence the subsequent bacteriophage-bacteria interactions.
authors.affiliation: School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Ayu Ekajayanthi
authors.initials: AE
authors.lastname: Liana
authors.affiliation: School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: c.marquis@unsw.edu.au.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Marquis
authors.affiliation: School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia; ithree Institute, University of Technology Sydney, Sydney, NSW 2007, Australia. Electronic address: cindy.gunawan@uts.edu.au.
authors.forename: Cindy
authors.initials: C
authors.lastname: Gunawan
authors.affiliation: School of Chemistry and Australian Centre for NanoMedicine, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: J Justin
authors.initials: JJ
authors.lastname: Gooding
authors.affiliation: School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Rose
authors.initials: R
authors.lastname: Amal
mesh_terms: D000327:Adsorption; D017122:Bacteriophage T4 / Q000737:chemistry / Q000502:physiology*; D003198:Computer Simulation; D004926:Escherichia coli / Q000187:drug effects / Q000821:virology*; D005290:Ferric Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D008280:Magnetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010461:Peptones / Q000737:chemistry*; D012542:Scattering, Radiation; D012821:Silanes / Q000737:chemistry; D055672:Static Electricity; D013499:Surface Properties; D013696:Temperature
chemical_list: D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; D010461:Peptones; D012821:Silanes; C000499:ferric oxide; C001830:tryptones
keywords: Adsorption; Bacteria capture; Bacteriophages; Magnetic particles; Surface modifications