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Silica nanoparticles coencapsulating gadolinium oxide and horseradish peroxidase for imaging and therapeutic applications

Authors Gupta N, Shrivastava A, Sharma RK

Received 25 April 2012

Accepted for publication 15 June 2012

Published 3 December 2012 Volume 2012:7 Pages 5491—5500


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Nikesh Gupta,1 Anju Shrivastava,2 Rakesh K Sharma1

Nanotechnology and Drug Delivery Research Lab, Department of Chemistry, 2Department of Zoology, University of Delhi, Delhi, India

Abstract: Mesoporous silica nanoparticles coencapsulating gadolinium oxide and horseradish peroxidase (HRP) have been synthesized in the aqueous core of sodium bis-(2-ethylhexyl)sulfosuccinate (AOT)–hexane–water reverse micelle. The average diameter of these silica particles is around 25 nm and the particles are spherical and highly monodispersed as depicted using transmission electron microscopy. The entrapment efficiency of HRP was found to be as high as 95%. Practically, the entrapped enzyme shows zero leachability up to 90 days. The enzyme entrapped in these silica nanoparticles follows Michaelis–Menten kinetics. Peroxidase entrapped in silica nanoparticles shows higher stability towards temperature and pH change as compared to free enzymes. The gadolinium oxide-doped silica nanoparticles are paramagnetic as observed from the nuclear magnetic resonance line-broadening effect on the proton spectrum of the surrounding water molecule. The entrapped enzyme, HRP, has been used to convert a benign prodrug, indole-3-acetic acid (IAA), to a toxic oxidized product and its toxic effect has been tested on cancerous cell lines through thiazolyl blue tetrazolium blue (MTT) assay. In vitro studies on different cancerous cell lines show that the enzyme has been entrapped and retains its activity inside the silica nanoparticles. IAA alone has no cytotoxic effect and it becomes active only after oxidative decarboxylation by HRP.

Keywords: indole-3-acetic acid, HRP, free radical, cytotoxicity, MRI

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