SOD Antioxidant Nanoreactors: Influence of Block Copolymer Composition on the Nanoreactor Efficiency

Abstract

The bioavailability limitations of proteins make them difficult to be directly delivered, particularly in diseases caused by insufficient amounts or inactive variants of those proteins. Nanoreactors represent a new promising approach to overcome these limitations because they serve both to protect the protein in their aqueous interior, and simultaneously to allow the protein to act in situ. Here we examine an antioxidant nanoreactor based on SOD encapsulated in amphiphilic block copolymer nanovesicles, and analyze its behavior as a function of the copolymer composition. The membrane of the triblock copolymer nanovesicles plays a double role, both to shield the sensitive protein and selectively to let superoxide and dioxygen penetrate to its inner space. The encapsulation efficiency for different triblock copolymer vesicles was quantified by fluorescence correlation spectroscopy using a fluorescently labeled SOD. Pulse radiolysis experiments and an enzymatic assay were used to compare the permeability of the wall-forming membranes towards superoxide anions. While the encapsulation efficiency mainly depends on the vesicle dimensions, the membrane permeability is mainly affected by the length of the hydrophobic PDMS middle blocks of our polymers. For polymers with very long PDMS chains superoxide anion transport across the membranes was too slow to be detected by our experiments.

Functionalization of Block Copolymer Vesicle Surfaces

“…Polymersomes that have assembled from amphiphilic block copolymers have proven to be useful tools as drug delivery systems [8,[20][21][22], nanoreactors and sensors [13,17,[23][24][25][26][27][28]. The attachment of targeting ligands or enzymes to the polymersomes, as well as the immobilization of polymer vesicles on surfaces, is of crucial importance in most of the previously mentioned applications.…”

Enzyme Immobilization by Microencapsulation: Methods, Materials, and Technological Applications

“…23.4 kDa for PMOXA 65 -PDMS 165 -PMOXA 65 (45) vs 760 Da for POPC), the resulting nano-or microscale vesicles are often larger aggregates than liposomes and exhibit membranes of increased thickness. The thickness in turn depends on the molecular mass of the hydrophobic part of the polymers (46).…”

Engineered nanomaterial uptake and tissue distribution: from cell to organism

“…10 Approaches to test dye leakage are centrifugation, sodiumdodecyl sulfate polyacrylamide gel electrophoresis (PAGE), or fluorescence correlation spectroscopy (FCS). [17][18][19] Special care should be taken when choosing an appropriate dye since lipophilic dyes may partition from the particulate structure into the lipid membranes of the cell. To circumvent dye leakage, intrinsic fluorescence of nanoparticles is an attractive alternative, as has been described for gold.…”