The diffusion coefficients of small nitroxide probes as guests in aqueous solutions of the triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) EO13PO30EO13 (Pluronic L64) were measured at 300 K by one-dimensional electron spin resonance imaging (1D ESRI). The method is based on encoding the spatial distribution of the probes as a function of time in ESR spectra recorded in the presence of magnetic field gradients and simulation of these spectra in order to extract the diffusion coefficient, D. The rate of transport of each probe as a function of polymer content in the various phases (micellar, hexagonal, lamellar, and reverse micellar) of aqueous L64 depends on the probe location in the self-assembled system. The probe site was deduced from the analysis of the ESR spectra; the isotropic hyperfine splitting, a N, from the 14N nucleus of the >NO fragment in the probes was the polarity sensitive parameter. D values for the cationic probe 4-(N,N,N-trimethyl)ammonium-2,2,6,6-tetramethyl-piperidine-1-oxyl iodide that is known to reside in the water domains follow the expression D = D 0 exp(−aw 2), where D 0 is the diffusion coefficient in the neat solvent and w 2 is the weight fraction of the polymer. For the hydrophobic probe 5DSE, the methyl ester of doxylstearic acid where 5 indicates the carbon atom to which the doxyl group is attached, D is significantly lower and almost constant for w 2 in the range 0.20−0.80. For the probe perdeuterio-2,2‘,6,6‘-tetramethyl-piperidone-N-oxide that is located at the interface between water and the EO domains, D decreases with increase in the polymer content, but the decrease is more prominent for w 2 in the range 0.10−0.30; at w 2 = 0.90, D is similar to that of the polymer chains. The method of 1D ESRI enables the measurement of D values for guests present in small concentrations, typically ≤2 × 10-3 mol/L. This method and the results obtained in this study are relevant for assessing both the rate of transport of drugs in drug delivery systems and the partitioning of various guests in complex systems, for instance in biological membranes.

No abstract

No abstract

Magnetic nanosystems (MNSs) consisting of magnetic iron oxide nanoparticles (IONPs) coated by human serum albumin (HSA), commonly used as a component of hybrid nanosystems for theranostics, were engineered and characterized. The HSA coating was obtained by means of adsorption and free radical modification of the protein molecules on the surface of IONPs exhibiting peroxidase-like activity. The generation of hydroxyl radicals in the reaction of IONPs with hydrogen peroxide was proven by the spin trap technique. The methods of dynamic light scattering (DLS) and electron magnetic resonance (EMR) were applied to confirm the stability of the coatings formed on the surface of the IONPs. The synthesized MNSs (d ~35 nm by DLS) were intraarterially administered in tumors implanted to rats in the dose range from 20 to 60 μg per animal and studied in vivo as a contrasting agent for computed tomography. The long-term (within 14 days of the experiment) presence of the MNSs in the tumor vascular bed was detected without immediate or delayed adverse reactions and significant systemic toxic effects during the observation period. The peroxidase-like activity of MNSs was proven by the colorimetric test with o-phenylenediamine (OPD) as a substrate. The potential of the synthesized MNSs to be used for theranostics, particularly, in oncology, was discussed.