Physico-Chemical nanomaterials science

Proflavin binding to LSMO nanoparticles at temperatures above and below the Сurie point
Dukhopelnikov E. V.,  Blyzniuk I. N.,  Bereznyak E. G.,  Gladkovskaya N. A.
Institute for Radiophysics and Electronics NAS of Ukraine; 12 Akad.Proskury Str., Kharkiv, 61085, Ukraine.
E-mail: dukhopelnikov@gmail.com

Targeted drug delivery by a magnetic field is one of the promising trends in the use of magnetic nanoparticles. Lanthanum strontium manganese oxide nanoparticles (LSMO NPs) have recently been explored for similar use in anti-cancer therapy. The advantage of these nanoparticles is low Curie temperature (20-600C). Therefore, LSMO NPs application makes it possible to combine two types of cancer treatment: drug delivery for chemotherapy and self-controlled hyperthermia.
Changes in the magnetic properties of LSMO NPs above the Curie point can also vary their loading with the drug. In this work, we studied the binding of a positively charged drug proflavine (Pf) with LSMO NPs at temperatures below and above the Curie point by spectrophotometric titration method [1].
The addition of Pf to non-modified LSMO NPs does not change the spectrum of the drug. The lack of binding is explained by the DLS data showing zero zeta potential of the nanoparticles' surface. To charge the surface and increase the colloidal stability of the suspension, we modified the surface of LSMO NPs with sodium citrate. We found that its optimal concentration in solution, which ensures the binding of the maximum amount of Pf, is equal to 2×10-3 M. The coating with sodium citrate creates a surface charge of the NPs equal to -40 (DLS data). By titration of modified LSMO NPs with Pf, the dependencies of the free Pf concentration on the total LSMO NPs concentration were obtained and fitted by the Langmuir equation [1] to determine the Pf-LSMO NPs binding parameters. The binding constant of Pf to LSMO NPs is Кbind=2×104 M-1. The complex formation at a temperature above the Curie point increases the degree of drug loading on the nanoparticle's surface from 110 drugs per one NP at 250C to 150 ones at 600C. It is caused by partial destruction of nanoparticle aggregates in suspension upon LSMO NPs losing their superparamagnetic properties.

1.	Dukhopelnikov E.V., Pesina D.A., Bereznyak E.G. et al. Calculation from Spectrophotometric Data of Binding Parameters of Magnetic Iron Oxide Nanoparticles with Dyes.// J Appl Spectrosc.-2020.-87,-P. 303–308.