Improving the Cellular Uptake of Biomimetic Magnetic Nanoparticles

Abstract

Magnetococcus marinus magnetosome-associated protein MamC, expressed as recombinant, has been proven to mediate the formation of novel biomimetic magnetic nanoparticles (BMNPs) that are successful drug nanocarriers for targeted chemotherapy and hyperthermia agents. These BMNPs present several advantages over inorganic magnetic nanoparticles, such as larger sizes that allow the former to have larger magnetic moment per particle, and an isoelectric point at acidic pH values, which allows both the stable functionalization of BMNPs at physiological pH value and the molecule release at acidic (tumor) environments, simply based on electrostatic interactions. However, difficulties for BMNPs cell internalization still hold back the efficiency of these nanoparticles as drug nanocarriers and hyperthermia agents. In the present study we explore the enhanced BMNPs internalization following upon their encapsulation by poly (lactic-co-glycolic) acid (PLGA), a Food and Drug Administration (FDA) approved molecule. Internalization is further optimized by the functionalization of the nanoformulation with the cell-penetrating TAT peptide (TATp). Our results evidence that cells treated with the nanoformulation [TAT-PLGA(BMNPs)] show up to 80% more iron internalized (after 72 h) compared to that of cells treated with BMNPs (40%), without any significant decrease in cell viability. This nanoformulation showing optimal internalization is further characterized. In particular, the present manuscript demonstrates that neither its magnetic properties nor its performance as a hyperthermia agent are significantly altered due to the encapsulation. In vitro experiments demonstrate that, following upon the application of an alternating magnetic field on U87MG cells treated with BMNPs and TAT-PLGA(BMNPs), the cytotoxic effect of BMNPs was not affected by the TAT-PLGA enveloping. Based on that, difficulties shown in previous studies related to poor cell uptake of BMNPs can be overcome by the novel nanoassembly described here.

Enhanced Cytotoxic Effect of TAT–PLGA-Embedded DOXO Carried by Biomimetic Magnetic Nanoparticles upon Combination with Magnetic Hyperthermia and Photothermia

“…In the context of surface properties, TAT–PLGA(DOXO-BMNPs) nanoassemblies displayed a ζ-potential at pH 7.4 of −3.8 ± 0.2 mV. At this identical pH, the ζ-potential values of PLGA(BMNPs) and TAT–PLGA(BMNPs) were −32 ± 3 mV and −13 ± 5 mV, respectively [ 22 ]. This negative net charge at physiological pH, added to the superparamagnetic character of biomimetic magnetic nanoparticles, avoids the aggregation of the magnetic nanoassemblies in the absence of an external magnetic field due to electrostatic or magnetic dipole–dipole interactions [ 3 , 9 ].…”

“…The encapsulation protocol for the BMNPs and DOXO-BMNP nanoassemblies is based on the single emulsion-evaporation method [ 22 , 31 ]. To prevent the oxidation of the magnetic particles, all buffers and aqueous solutions were degassed under vacuum.…”

“…The TAT–PLGA(DOXO-BMNPs) nanoassembly was characterized by nanoparticle tracking analysis (NTA) using a Malver NanoSight NS300 instrument on diluted samples (1:1000) at 25 °C. For simplicity, the results obtained for this nanoassembly were compared to those obtained from PLGA(BMNPs), as previous results demonstrated that the TAT peptide did not significantly increase the size of the nanoassembly compared to that of PLGA(BMNP) by ~7% [ 22 ]. For each sample, three sequences of 30 s with 25 FPS were recorded.…”

“…A way to improve such an internalization is to embed the nanoassembly in liposomes or polymeric nanoparticles [ 21 , 22 ]. Among them, the use of poly(lactic- co -glycolic acid) (PLGA) is particularly interesting due to its biocompatibility and biodegradability.…”

“…PLGA has also been used in the recent past to encapsulate MNPs [ 29 ], as well BMNPs [ 22 ]. In this second study, we demonstrated that PLGA and/or TAT–PLGA covering of BMNPs does improve the cell uptake of the nanoparticles, does not shelter the magnetic properties of the BMNPs, and maintains their ability to behave as hyperthermic agents.…”