Antioxidant Nanoreactor Based on Superoxide Dismutase Encapsulated in Superoxide-Permeable Vesicles

Abstract

We designed and tested an antioxidant nanoreactor based on encapsulation of Cu,Zn superoxide dismutase in amphiphilic copolymer nanovesicles, the membranes of which are oxygen permeable. The nanovesicles, made of poly(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline), successfully encapsulated the protein during their self-assembling process, as proved by confocal laser-scanning microscopy and fluorescence-correlation spectroscopy. Electron paramagnetic resonance spectroscopy and circular dichroism analyses showed that no structural changes appeared in the protein molecules once inside the inner space of the nanovesicles. The function of this antioxidant nanoreactor was tested by pulse radiolysis, which demonstrated that superoxide dismutase remains active inside the nanovesicles and detoxifies the superoxide radical in situ. The membrane of our triblock copolymer nanovesicles plays a double role, both to shield the sensitive protein and to selectively let superoxide and dioxygen penetrate to its inner space. This simple and robust hybrid system provides a selective shielding of sensitive enzymes from proteolytic attack and therefore a new direction for developing drug delivery applications.

Self‐Assembled Block Copolymer Aggregates: From Micelles to Vesicles and their Biological Applications

“…[125] Vesicles with responses to pH stimulus also exhibit applications for the rapid and non-cytotoxic cellular delivery of DNA sequences, which opens the possibilities for efficient gene-delivery for the treatment of specific genetic diseases. [100,101] The use of polymer vesicles as synthetic nano-reactors [140] has also been reported with several biological connotations. [137] Vesicles that can successfully convert ADP into the biochemical fuel ATP have been prepared, [135] alongside multi-step cascade reactions that utilize vesicles with three different incorporated enzymes.…”

“…[135][136][137] Several pioneering reports based on PMOXA-PDMS-PMOXA triblock copolymer vesicles have demonstrated a wide variety of potential biological applications. [137][138][139][140] Significant reduction in the cytotoxicity of anti-cancer drugs has been reported by encapsulating prodrugs within the vesicular interior, whereby the active (hence cytotoxic) compound is only generated when exposed to the specific conditions found within tumourous tissues. [138] Functionalization of these vesicles with membrane channel proteins coupled with encapsulation of prodrug-activating enzymes also show some promise for cancer treatment.…”

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.…”

Bio-Decorated Polymer Membranes: A New Approach in Diagnostics and Therapeutics

“…While offering the advantage of a more stable carrier compared to liposomes, the use of polymersomes to release the loaded compounds represents the conventional approach of drug delivery with well known drawbacks, such as an uncontrolled release, or possible degradation in other compartments than the desired ones. A step further was marked by the introduction of polymeric nanoreactors based on polymersomes serving as cages for enzymes/proteins that act in situ without being released [68]. To allow the enzyme to act inside the inner cavity, these nanoreactors possess a membrane permeable in specific molecules, such as to ions, which can penetrate from the environment and arrive at the enzyme location.…”