Abstract
The aim of our study was to develop a novel method for nanocarriers’ preparation as a fluorine magnetic resonance imaging (19F MRI)-detectable drug delivery system. The novelty of the proposed approach is based on the application of fluorinated polyelectrolyte Nafion as a contrast agent since typical MRI contrast agents are based on paramagnetic gadolinium or ferro/superparamagnetic iron oxide compounds. An advantage of using an 19F-based tracer comes from the fact that the 19F image is detected at a different resonance frequency than the 1H image. In addition, the close to zero natural concentration of 19F nuclei in the human body makes fluorine atoms a promising MRI marker without any natural background signal. That creates the opportunity to localize and identify only exogenous fluorinated compounds with 100% specificity. The nanocarriers were formed by the deposition of polyelectrolytes on nanoemulsion droplets via the layer-by-layer technique with the saturation approach. The polyelectrolyte multilayer shell was composed of Nafion, the fluorinated ionic polymer used for labeling by 19F nuclei, and poly-l-lysine (PLL). The surface of such prepared nanocarriers was further pegylated by adsorption of pegylated polyanion, poly-l-glutamic acid (PGA). The 19F MRI-detectable hydrophobic nanocarriers with an average size of 170 nm and a sufficient signal-to-noise ratio have been developed and optimized to be used for passive tumor targeting and drug delivery.
Highlights
Nafion, developed by the DuPont in the late 1960s, is a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer produced by copolymerization of a perfluorinated vinyl ether comonomer with tetrafluoroethylene, resulting in the Teflonlike backbone bearing hydrophilic sulfonic acid groups.[1]
It has been applied as the material for biosensors, for controlled drug release, and for the formation of antimicrobial coatings.[8−11] Since Nafion possesses 19F nuclei, it can be used for fluorine magnetic resonance imaging (19F MRI)
Typical MRI contrast agents are based on paramagnetic gadolinium or ferro/superparamagnetic iron oxide compounds, producing positive or negative contrast in the 1H MR image[12−14] due to the change of relaxation times T1 or T2 (T2*) caused by local disturbances of the magnetic field experienced by water molecules in the imaged object in the surrounding of the contrast agent
Summary
Nafion, developed by the DuPont in the late 1960s, is a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer produced by copolymerization of a perfluorinated vinyl ether comonomer with tetrafluoroethylene, resulting in the Teflonlike backbone bearing hydrophilic sulfonic acid groups.[1] Nafion was the first synthetic polymer ever developed with ionic properties, and it started an entirely new class of polymers called ionomers.[2] It combines the physical and chemical properties of its Teflon base material with ionic characteristics, which results in specific properties: resistance to chemicals, relatively high working temperatures compared to other polymers, high ion conductivity (a cation exchange polymer), and very selective and high permeability for water.
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