Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) and core-shell type nanoparticles, consisting of SPIONs coated with mesoporous silica and/or lipid, were synthesised and tested for their potential theranostic applications in drug delivery, magnetic hyperthermia and as a contrast agent. Transmission Electron Microscopy (TEM) confirmed the size of bare and coated SPIONs was in the range of 5–20 nm and 100–200 nm respectively. The superparamagnetic nature of all the prepared nanomaterials as indicated by Vibrating Sample Magnetometry (VSM) and their heating properties under an AC field confirm their potential for hyperthermia applications. Scanning Column Magnetometry (SCM) data showed that extrusion of bare-SPION (b-SPION) dispersions through a 100 nm polycarbonate membrane significantly improved the dispersion stability of the sample. No sedimentation was apparent after 18 h compared to a pre-extrusion estimate of 43% settled at the bottom of the tube over the same time. Lipid coating also enhanced dispersion stability. Transversal relaxation time (T2) measurements for the nanoparticles, using a bench-top relaxometer, displayed a significantly lower value of 46 ms, with a narrow relaxation time distribution, for lipid silica coated SPIONs (Lip-SiSPIONs) as compared to that of 1316 ms for the b-SPIONs. Entrapment efficiency of the anticancer drug, Doxorubicin (DOX) for Lip-SPIONs was observed to be 35% which increased to 58% for Lip-SiSPIONs. Moreover, initial in-vitro cytotoxicity studies against human breast adenocarcinoma, MCF-7 cells showed that % cell viability increased from 57% for bSPIONs to 82% for Lip-SPIONs and to 87% for Lip-SiSPIONs. This suggests that silica and lipid coatings improve the biocompatibility of bSPIONs significantly and enhance the suitability of these particles as drug carriers. Hence, the magnetic nanomaterials prepared in this work have potential theranostic properties as a drug carrier for hyperthermia cancer therapy and also offer enhancement of contrast agent efficacy and a route to a significant increase in dispersion stability.
Highlights
Cancer is one of the most devastating diseases in the world, causing millions of fatalities every year
The magnetization curves for the prepared magnetic nanoparticles obtained from Vibrating Sample Magnetometry (VSM) measurements are presented in figure 2
Composite drug carrier systems comprising of core SPIONs coated with silica and/or lipids have been developed with promising theranostic properties
Summary
Cancer is one of the most devastating diseases in the world, causing millions of fatalities every year. The limitations associated with T1 contrast agents are poor detection sensitivity, short blood circulation and toxicity concerns (Estelrich et al 2015) whereas the major drawback of T2 agents is in its contrast mechanism, which produces a signal-decreasing effect (Pellico et al 2019) To overcome these limitations, there is a need to enhance the properties of current contrast agents or search for a dual or all-in-one contrast agent. The coating may fully cover one individual particle or relatively small multi-cores rather than larger agglomerates of variable size and shape Such surface modification enhances the stability of the suspension and aids in controlling the size of the NPs, both of which are important parameters for in-vivo applications of SPIONs in hyperthermia drug delivery and MRI applications (Hola et al 2015, Patil et al 2016)
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