Synthesis of novel hybrid mesoporous gold iron oxide nanoconstructs for enhanced catalytic reduction and remediation of toxic organic pollutants

The development of highly efficient, rapid, and recyclable nanocatalysts for effective elimination of toxic environmental contaminants remains a high priority in various industrial applications. Herein, we report the preparation of hybrid mesoporous gold-iron oxide nanoparticles (Au-IO NPs) via the nanocasting “inverse hard-templated replication” approach. Dispersed Au NPs were anchored on amine-functionalized iron oxide incorporated APMS (IO@APMS-amine), followed by etching of the silica template to afford hybrid mesoporous Au-IO NPs. The obtained nanoconstructs were fully characterized using electron microscopy, N2 physisorption, and various spectroscopic techniques. Owing to their magnetic properties, high surface areas, large pore volumes, and mesoporous nature (SBET = 124 m2 g−1, Vpore = 0.33 cm3 g−1, and dpore = 4.5 nm), the resulting Au-IO mesostructures were employed for catalytic reduction of nitroarenes (i.e. nitrophenol and nitroaniline), two of the most common toxic organic pollutants. It was found that these Au-IO NPs act as highly efficient nanocatalysts showing exceptional stabilities (>3 months), enhanced catalytic efficiencies in very short times (∼100% conversions within only 25-60 s), and excellent recyclabilities (up to 8 cycles). The kinetic pseudo-first-order apparent reaction rate constants (kapp) were calculated to be equal to 8.8 × 10−3 and 23.5 × 10−3 s−1 for 2-nitrophenol and 2-nitroaniline reduction, respectively. To our knowledge, this is considered one of the best and fastest Au-based nanocatalysts reported for the catalytic reduction of nitroarenes, promoted mainly by the synergistic cooperation of their high surface area, large pore volume, mesoporous nature, and enhanced Au-NP dispersions. The unique mesoporous hybrid Au-IO nanoconstructs synthesized here make them novel, stable, and approachable nanocatalyst platform for various catalytic industrial processesThe authors acknowledge funding by the Arab Fund for Economic and Social Development (AFESD) – Arab Fund Fellowship Award Program. The authors thank Drs Nawal The authors acknowledge funding by the Arab Fund for Economic and Social Development (AFESD) – Arab Fund Fellowship Award Program. The authors thank Drs Nawa

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe₃O₄ Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe3O4 phases, high saturation magnetizations (Ms = ~40 emu·g−1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm2/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τR = 5.41 × 10−7 s), which was compared to the Brownian relation time value (τB = 11 × 10−7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe3O4 MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications

Enhanced Enzymatic Activity of OPH in Ammonium-Functionalized Mesoporous Silica: Surface Modification and Pore Effects

Organophosphorus hydrolase (OPH) is an enzyme capable of rapidly degrading organophosphorus toxins, such as phosphorus-based nerve agents and pesticides. In these studies, OPH was immobilized within the pores of spherical mesoporous silica particles and the rate of hydrolysis of diethyl-4-nitrophenyl phosphate (paraoxon) was correlated to surface functionalization (acid, amine, or ammonium) and pore diameter. Conversion rates were measured by using a novel ³¹P NMR method developed by our group. After immobilization within ammonium-modified particles, OPH was more active for paraoxon degradation than free OPH, while amine- or acid-modified particles led to decreased activities. OPH immobilized within the pores of intermediate diameter (6 nm) also showed the highest activities. We also varied the amount of ammonium coverage and found that 14–20% w/w of the ammonium organosilane per particle was sufficient to observe enhancement of OPH activity

Heating efficiency of Gd- and Co-doped γ-Fe2O3 nanoparticles measured by AC magnetometer for magnetic-mediated hyperthermia

Most research groups, including us, utilize calorimetric methods to determine the heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF). Herein, we report the heating efficiencies of γ-Fe2O3 and doped γ-Fe2O3 NPs using AC magnetometry, which allows us to directly calculate the AC hysteresis loop area from which the heating abilities can be deduced. First, all NPs were prepared and thoroughly characterized both structurally (XRD, Rietveld, and TEM) and magnetically (DC and AC magnetization measurements). Structural analysis indicated the phase purity (γ-Fe2O3) and crystallite sizes (∼10 nm) of the as-prepared γ-Fe2O3 NPs. Both DC and AC measurements indicated the superparamagnetic behavior for γ-Fe2O3 and Gd-doped γ-Fe2O3(Gd-5%) NPs, while Co-doped γ-Fe2O3(Co-5%) NPs exhibited ferrimagnetic nature. The heating abilities and specific absorption rate (SAR) values were then analyzed at frequency, f = 132 kHz and several AC field amplitudes (µ0HAC) ranging from 0 to 88 mT. From AC magnetometry calculations, the SAR values were found to be 20 W/g and 17 W/g for γ-Fe2O3 and γ-Fe2O3(Gd-5%) NPs, respectively, while that of γ-Fe2O3(Co-5%) NPs reached SAR of 120 W/g, almost 6 times higher. This high heating efficiency of γ-Fe2O3(Co-5%) sample is attributed to their higher effective anisotropy and saturation magnetization where the heat release is mainly dominated by Neel relaxation. Finally, a viability assay against metastatic breast cancer cells was conducted, indicating the biocompatibility and low toxicity of the as-synthesized γ-Fe2O3 and doped γ-Fe2O3 NPs. These results strongly suggest the promising utilization of γ-Fe2O3 NPs, particularly Co-doped, as a potential candidate for magnetic-mediated hyperthermia

Preparation and characterization of various PVPylated divalent metal-doped ferrite nanoparticles for magnetic hyperthermia

There is an incessant demand to keep improving on the heating responses of polymeric magnetic nanoparticles (MNPs) under magnetic excitation, particularly in the pursuit for them to be utilized for clinical hyperthermia applications. Herein, we report the fabrication of a panel of PVP-capped divalent metal-doped MFe2O4 (M ≅ Co, Ni, Zn, Mg, and Sn) MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology and assess their magneto-thermal abilities. The physiochemical, structural, morphological, compositional, and magnetic properties of the doped ferrites were fully characterized using various techniques mainly TEM, XRD, EDX, FTIR, and VSM. The obtained doped MNPs exhibited stabilized quasi-spherical sized particles (10–17 nm), pure well-crystallized cubic spinel phases, and high saturation magnetizations (Ms = 26–81 emu g−1). In response to a clinically-safe alternating magnetic field (AMF) (f = 332.8 kHz and H = 170 Oe), distinctive heating responses of these doped ferrites were attained. Hyperthermia temperatures of 42 °C can be reached very fast in only ∼5 min, with heating temperatures slowly increasing to reach up to 55 °C. The highest heating performance was observed for PVP-NiFe2O4 and the lowest for PVP-Sn-doped NPs (SAR values: PVP-NiFe2O4 > PVP-CoFe2O4 > PVP-ZnFe2O4 > PVP-MgFe2O4 > PVP-SnFe2O4). This trend was found to be directly correlated to their observed magnetic saturation and anisotropy. Heating efficiencies and specific SAR values as functions of concentration, frequency, and amplitude were also systematically investigated. Finally, cytotoxicity assay was conducted on aqueous dispersions of the doped ferrite NPs, proving their biocompatibility and safety profiles. The PVPylated metal-doped ferrite NPs prepared here, particularly Ni- and Co-doped ferrites, are promising vehicles for potential combined magnetically-triggered biomedical hyperthermia applications

Maghemite (γ-Fe2O3) and γ-Fe2O3-TiO2 Nanoparticles for Magnetic Hyperthermia Applications: Synthesis, Characterization and Heating Efficiency

In this report, the heating efficiencies of γ-Fe2O3 and hybrid γ-Fe2O3-TiO2 nanoparticles NPs under an alternating magnetic field (AMF) have been investigated to evaluate their feasible use in magnetic hyperthermia. The NPs were synthesized by a modified sol-gel method and characterized by different techniques. X-ray diffraction (XRD), Mössbauer spectroscopy and electron microscopy analyses confirmed the maghemite (γ-Fe2O3) phase, crystallinity, good uniformity and 10 nm core sizes of the as-synthesized composites. SQUID hysteresis loops showed a non-negligible coercive field and remanence suggesting the ferromagnetic behavior of the particles. Heating efficiency measurements showed that both samples display high heating potentials and reached magnetic hyperthermia (42 °C) in relatively short times with shorter time (~3 min) observed for γ-Fe2O3 compared to γ-Fe2O3-TiO2. The specific absorption rate (SAR) values calculated for γ-Fe2O3 (up to 90 W/g) are higher than that for γ-Fe2O3-TiO2 (~40 W/g), confirming better heating efficiency for γ-Fe2O3 NPs. The intrinsic loss power (ILP) values of 1.57 nHm2/kg and 0.64 nHm2/kg obtained for both nanocomposites are in the range reported for commercial ferrofluids (0.2–3.1 nHm2/kg). Finally, the heating mechanism responsible for NP heat dissipation is explained concluding that both Neel and Brownian relaxations are contributing to heat production. Overall, the obtained high heating efficiencies suggest that the fabricated nanocomposites hold a great potential to be utilized in a wide spectrum of applications, particularly in magnetic photothermal hyperthermia treatments

Development of Multifunctional Hyaluronan-Coated Nanoparticles for Imaging and Drug Delivery to Cancer Cells

Currently, there is high interest in developing multifunctional theranostic platforms for cancer monitoring and chemotherapy. Herein, we report hyaluronan (HA)-coated superparamagnetic iron oxide nanoparticles (HA-SPION) as a promising system for targeted imaging and drug delivery. When incubated with cancer cells, HA-SPIONs were rapidly taken up and the internalization of HA-SPION by cancer cells was much higher than the NPs without HA coating. The high magnetic relaxivity of HA-SPION coupled with enhanced uptake enabled magnetic resonance imaging of cancer cells. Furthermore, doxorubicin (DOX) was attached onto the nanoparticles through an acid responsive linker. While HA-SPION was not toxic to cells, DOX-HA-SPION was much more potent than free DOX to kill not only drug-sensitive but also multi-drug-resistant cancer cells. This was attributed to differential uptake mechanisms and cellular distributions of free DOX and DOX-HA-SPION in cancer cells

Magnetic Fluorescent Nanoformulation for Intracellular Drug Delivery to Human Breast Cancer, Primary Tumors, and Tumor Biopsies: Beyond Targeting Expectations

We report the development of a chemotherapeutic nanoformulation made of polyvinyl­pyrrolidone-stabilized magneto­fluorescent nanoparticles (Fl-PMNPs) loaded with anticancer drugs as a promising drug carrier homing to human breast cancer cells, primary tumors, and solid tumors. First, nanoparticle uptake and cell death were evaluated in three types of human breast cells: two metastatic cancerous MCF-7 and MDA-MB-231 cells and nontumorigenic MCF-10A cells. While Fl-PMNPs were not toxic to cells even at the highest concentrations used, Dox-loaded Fl-PMNPs showed significant potency, effectively killing the different breast cancer cells, albeit at different affinities. Interestingly and superior to free Dox, Dox-loaded Fl-PMNPs were found to be more effective in killing the metastatic cells (2- to 3-fold enhanced cytotoxicities for MDA-MB-231 compared to MCF-7), compared to the normal noncancerous MCF-10A cells (up to 8-fold), suggesting huge potentials as selective anticancer agents. Electron and live confocal microscopy imaging mechanistically confirmed that the nanoparticles were successfully endocytosed and packaged into vesicles inside the cytoplasm, where Dox is released and then translocated to the nucleus exerting its cytotoxic action and causing apoptotic cell death. Furthermore, commendable and enhanced penetration in 3D multilayered primary tumor cells derived from primary lesions as well as in patient breast tumor biopsies was observed, killing the tumor cells inside. The designed nanocarriers described here can potentially open new opportunities for breast cancer patients, especially in theranostic imaging and hyperthermia. While many prior studies have focused on targeting ligands to specific receptors to improve efficacies, we discovered that even with passive-targeted tailored delivery system enhanced toxic responses can be attained