Fusion processes of liposomes mediated by magnetic nanoparticles and regulated by external magnetic field

RAQUEL V. VICO; FRANCESCA GIUDICE; MARTÍN E. VILLANUEVA

CABA, Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias.; 2017

Sociedad Argentina de Biofísica

Functionalized magnetic iron oxide nanoparticles areone of the best choices for biological and biomedical applications, primarilybecause of their biocompatibility, superparamagnetic behavior and also for thechemical stability that the corresponding capping agent can attribute to them.It has been studied that oleic acid (a commonly used surfactant to stabilizenanoparticles) have the ability to intervene and regulate vital mechanisms ofgreat implication in many cellular processes such is the membrane fusion, aphenomenon that continues to be the object of innumerable investigations today.To further investigate the event of fusion, in thiswork we have synthesized magnetic nanoparticles coated by OA (MNPs@OA) throughthe well known co-precipitation method and characterized the interaction ofthis NPs with Large Unilamellar Vesicles (LUVs) composed of-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with an average size of100 nm. Liposomes represent a widely used model of biomembranes to provide keyinsights into the characteristics and dynamics of substrate-membraneinteractions. Volumes of MNPs@OA were added to a volume of LUVs and measuredalong the time through dynamic light scattering (DLS) in order to know theprofile of the process.Once these measures concluded that the nanoparticlesinduce some kind of effect on the size of the lipidic structures, we proceededto study the event through fluorescence spectroscopy by the means of thestandard Tb/DPA assay. In the corresponding assay separate vesicle (LUVs)populations are loaded with TbCl3 or DPA, if fusion occurs Tb3+/DPAcomplex takes place yielding enhancement of the fluorescence intensity (If).We monitored the increment of the If along the time (Time Driveprogram) after adding different volumes (2,5-5 μL) of MNPs@OA dispersed in THF,to a mixture of 125 μL of each LUVs population. Fluorescence emission of vesiclesloaded with the Tb3+/DPA complex pre-formed were also measured in away to know the total If attributed to the complete formation of thecomplex in the medium and therefore calculate an approximated percentage offusion1.         In addition we have evaluated the effect of applying variablepotential fields to the NPs-LUVs system by placing an electromagnet (directlyconnected to a potential source) parallel to the fluorescence cuvette. It wasfound that the acceptable percentages obtained with the NPs in absence ofexternal magnetic field were considerably improved as a consequence of applysuch stimulus.   With the purpose of access some extra informationregarding the morphology of the NP-LUVs system after the incubation of bothcomponents, we performed Transmission Electronic Microscopy (TEM) and also aturbidimetric experiment that allows to determine the changes in the opticaldensity by means of UV-Visible.