Now showing 1 - 3 of 3
  • Publication
    Magnetic Nanoparticle Composites in Complex Matrices: The Role of Particle Dispersion in Providing Controlled Stimulus Response
    (University College Dublin. School of Chemistry, 2022) ;
    0000-0003-2685-4592
    Magnetic nanoparticles (MNPs) have potential biomedical applications as efficient mediators for AC-magnetic field hyperthermia and as contrast agents for magnetic resonance imaging (MRI) due to their strong responses to applied magnetic fields. However, several challenges are associated with the use of MNPs for in vivo biomedical applications that must be addressed to realise these technologies. The surface chemistry of MNPs must be engineered to prevent nanoparticle aggregation and reduce their rate of interaction with biomolecules. This work focuses on the development of synthetic strategies to address the longstanding challenges of maintaining the in vivo magnetic efficiency of MNPs as theragnostic agents and as magnetic components in responsive nanocomposite materials. Multicore iron oxide nanoparticles, nanoflowers (NFs), display strong magnetic responses arising from complex internal magnetic ordering. A catechol-derived grafting approach is described to strongly bind polyethylene glycol (PEG) to NFs and provide stable hydrogen-bonded hydrated layers that ensure exceptional long-term colloidal stability in buffers and media even at clinical MRI field strength and high concentration. The approach enables the first comprehensive study into the MRI (relaxivity) and hyperthermic (SAR) efficiencies of fully dispersed NFs. The predominant role of internal magnetization dynamics in providing high relaxivity and SAR that are unaffected by PEG molecular weight or corona formation in biological environments is identified. The PEGylated NF suspensions exhibited intra-tumour stability and promising retention of relaxivity in vivo due to the strongly anchored PEG layer. For magnetic-polymer nanocomposites, NF dispersion ensures that SAR is fully retained despite their immobilization in the polymer matrix. The retention of SAR in bulk polymers is exploited for further biomedical functionality by utilising their heating capabilities for triggered therapeutic drug release stimulated by increased local temperature. The polymer formulation is also shown to be suitable for two-photon polymerization and dynamic light processing printing techniques enabling high resolution 3D fabrication of magnetic composites. Finally, the magnetic polymer nanocomposites were investigated as magnetically retrievable adsorbents for the removal of micropollutants from aqueous solution. This multifunctional approach demonstrates practical synthetic methods for the preparation of nanomaterials for therapeutic, diagnostic, and environmental applications, while also contributing to the understanding of the fundamental magnetic and chemical mechanisms enabling these applications.
      14
  • Publication
    Graphene oxide modulates inter-particle interactions in 3D printable soft nanocomposite hydrogels restoring magnetic hyperthermia responses
    Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications.
      226Scopus© Citations 5
  • Publication
    Spatiotemporally Resolved Heat Dissipation in 3D Patterned Magnetically Responsive Hydrogels
    Multifunctional nanocomposites that exhibit well-defined physical properties and encode spatiotemporally controlled responses are emerging as components for advanced responsive systems, for example, in soft robotics or drug delivery. Here an example of such a system, based on simple magnetic hydrogels composed of iron oxide magnetic nanoflowers and Pluronic F127 that generates heat upon alternating magnetic field irradiation is described. Rules for heat-induction in bulk hydrogels and the heat-dependence on particle concentration, gel volume, and gel exposed surface area are established, and the dependence on external environmental conditions in “closed” as compared to “open” (cell culture) system, with controllable heat jumps, of ∆T 0–12°C, achieved within ≤10 min and maintained described. Furthermore the use of extrusion-based 3D printing for manipulating the spatial distribution of heat in well-defined printed features with spatial resolution <150 µm, sufficiently fine to be of relevance to tissue engineering, is presented. Finally, localized heat induction in printed magnetic hydrogels is demonstrated through spatiotemporally-controlled release of molecules (in this case the dye methylene blue). The study establishes hitherto unobserved control over combined spatial and temporal induction of heat, the applications of which in developing responsive scaffold remodeling and cargo release for applications in regenerative medicine are discussed.
      159Scopus© Citations 12