Magnetic nanoparticles (MNPs) are increasingly attracting the attention of scientists. Over the past few years, magnetic nanoparticles have become known as an important class of nanomaterials finding their application in many fields of science. The greatest interest of scientists is attracted by the use of MNPs in the field of biomedicine: hyperthermia, targeted drug delivery, tissue engineering, theranostics, magnetic resonance imaging, stimulation of cell growth, etc. Of particular interest is the magnetic properties of nanoparticles, which make it possible to manipulate a biological object using an external magnetic field.
In this work, we developed a method for the synthesis of dopamine-functionalized rod-shaped MNPs based on iron oxide. The synthesized nanoparticles were used in combination with a low-frequency alternating magnetic field to study the lysis of E. coli cells under the action of Lys 394, for which the outer membrane of the cell wall is normally impermeable. We studied the lysis of the cell suspension with particles in the presence and absence of an external field under the action of the enzyme (Lys394 endolysin). It was shown that MNPs in the absence of a magnetic field do not affect the cell lysis. In the work, particles with a length of 40 to 70 nm and a width of 20 to 40 nm were used. For each particle size, different magnetic field parameters were tested. The highest efficiency of the cell lysis was achieved with particles 56±13 nm long and 13±3 nm wide, and with a magnetic field intensity of 68.5 mT. According to the experimental data, cell lysis under the action of endolysin in the presence of MNPs and a low-frequency alternating magnetic field increases almost 2-fold. The possibility of manipulating a biological membrane with MNPs under the action of a magnetic field was additionally demonstrated by two independent experiments: the use of a hydrophobic Nile red (NR) dye and an assessment of the yield of the periplasmic protein β-lactamase. In one of them, disordering leads to the release of more than 80% of the periplasmic enzyme β-lactamase, and in the other, to a significant change in the fluorescence of the hydrophobic dye NR.
Thus, we have shown that it is possible in principle to remotely enhance the efficiency of the enzyme in the lysis of the bacterial cell wall as a result of the disordering of its structure under the action of rod-like MNPs driven into oscillatory motion by an external non-heating low frequency magnetic field. The study demonstrates the prospects for using an external low-frequency magnetic field to enhance the action of bacteriophage antibacterial endolysins against gram-negative pathogens.