Unveiling the effect of the crystalline phases of iron oxyhydroxide for highly sensitive and selective detection of dopamine.

Electrocatalysis is key to the development of several important energy and biosensing applications. In this regard, the crystalline phase-dependent electrocatalytic activity of materials has been extensively studied for reactions such as hydrogen evolution, oxygen reduction, etc. But such comprehensive studies for evaluating the phase-dependence of electrochemical biosensing have not been undertaken. Herein, three crystalline phases (α-, ß-, and γ-) of iron oxyhydroxide (FeOOH) have been synthesized and characterized by spectroscopic and microscopy techniques. Electrochemical studies revealed their high sensitivity and selectivity towards dopamine (DA) detection. Amongst the three electrocatalysts, ß-FeOOH shows the highest sensitivity (337.15 µA mM-1 cm-2) and the lowest detection limit (0.56 µM). The enhanced electrocatalytic activity of ß-FeOOH, as compared to that of α- and γ-FeOOH, was attributed to its higher active site percentage and facile electrode kinetics. Furthermore, theoretical studies probed into the DA-FeOOH interactions by evaluating the charge transfer characteristics and hydrogen adsorption energies of the three phases to support the experimental findings.

Electronic structures and spectroscopic signatures of diiron intermediates generated by O2 activation of nonheme iron(II)-thiolate complexes.

The activation of O2 at thiolate-ligated iron(II) sites is essential to the function of numerous metalloenzymes and synthetic catalysts. Iron-thiolate bonds in the active sites of nonheme iron enzymes arise from either coordination of an endogenous cysteinate residue or binding of a deprotonated thiol-containing substrate. Examples of the latter include sulfoxide synthases, such as EgtB and OvoA, that utilize O2 to catalyze tandem S-C bond formation and S-oxygenation steps in thiohistidine biosyntheses. We recently reported the preparation of two mononuclear nonheme iron-thiolate complexes (1 and 2) that serve as structural active-site models of substrate-bound EgtB and OvoA (Dalton Trans. 2020, 49, 17745-17757). These models feature monodentate thiolate ligands and tripodal N4 ligands with mixed pyridyl/imidazolyl donors. Here, we describe the reactivity of 1 and 2 with O2 at low temperatures to give metastable intermediates (3 and 4, respectively). Characterization with multiple spectroscopic techniques (UV-vis absorption, NMR, variable-field and -temperature Mössbauer, and resonance Raman) revealed that these intermediates are thiolate-ligated iron(III) dimers with a bridging oxo ligand derived from the four-electron reduction of O2. Structural models of 3 and 4 consistent with the experimental data were generated via density functional theory (DFT) calculations. The combined experimental and computational results illuminate the geometric and electronic origins of the unique spectral features of diiron(III)-µ-oxo complexes with thiolate ligands, and the spectroscopic signatures of 3 and 4 are compared to those of closely-related diiron(III)-µ-peroxo species. Collectively, these results will assist in the identification of intermediates that appear on the O2 reaction landscapes of iron-thiolate species in both biological and synthetic environments.

Radio frequency plasma assisted surface modification of Fe3O4 nanoparticles using polyaniline/polypyrrole for bioimaging and magnetic hyperthermia applications.

Surface modification of superparamagnetic Fe3O4 nanoparticles using polymers (polyaniline/polypyrrole) was done by radio frequency (r.f.) plasma polymerization technique and characterized by XRD, TEM, TG/DTA and VSM. Surface-passivated Fe3O4 nanoparticles with polymers were having spherical/rod-shaped structures with superparamagnetic properties. Broad visible photoluminescence emission bands were observed at 445 and 580 nm for polyaniline-coated Fe3O4 and at 488 nm for polypyrrole-coated Fe3O4. These samples exhibit good fluorescence emissions with L929 cellular assay and were non-toxic. Magnetic hyperthermia response of Fe3O4 and polymer (polyaniline/polypyrrole)-coated Fe3O4 was evaluated and all the samples exhibit hyperthermia activity in the range of 42-45 °C. Specific loss power (SLP) values of polyaniline and polypyrrole-coated Fe3O4 nanoparticles (5 and 10 mg/ml) exhibit a controlled heat generation with an increase in the magnetic field.

Interactions of Chemically Synthesized Ferrihydrite Nanoparticles with Human Serum Transferrin: Insights from Fluorescence Spectroscopic Studies.

Human serum transferrin (HST) is a glycoprotein involved in iron transport that may be a candidate for functionalized nanoparticles to bind and target cancer cells. In this study, the effects of the simple and doped with cobalt (Co) and copper (Cu) ferrihydrite nanoparticles (Fh-NPs, Cu-Fh-NPs, and Co-Fh-NPs) were studied by spectroscopic and molecular approaches. Fluorescence spectroscopy revealed a static quenching mechanism for all three types of Fh-NPs. All Fh-NPs interacted with HST with low affinity, and the binding was driven by hydrogen bonding and van der Waals forces for simple Fh-NPs and by hydrophobic interactions for Cu-Fh-NPs and Co-Fh-NPs binding, respectively. Of all samples, simple Fh-NPs bound the most to the HST binding site. Fluorescence resonance energy transfer (FRET) allowed the efficient determination of the energy transfer between HST and NPs and the distance at which the transfer takes place and confirmed the mechanism of quenching. The denaturation of the HST is an endothermic process, both in the case of apo HST and HST in the presence of the three types of Fh-NPs. Molecular docking studies revealed that Fh binds with a low affinity to HST (Ka = 9.17 × 103 M-1) in accord with the fluorescence results, where the interaction between simple Fh-NPs and HST was described by a binding constant of 9.54 × 103 M-1.

Theranostic two-dimensional superparamagnetic maghemite quantum structures for ROS-mediated cancer therapy.

In this work, size- and shape-controlled two-dimensional (2D) superparamagnetic maghemite (γ-Fe2O3) quantum flakes (MQFs) with high surface area and mesoporosity were prepared by facile hydrothermal synthesis for biological applications. These quantum flakes exhibited superparamagnetic behaviours over a wide temperature range of 75-950 K with high saturation magnetization of Ms - 23 emu g-1 and a lower coercivity of Hc - 6.1 Oe. MQFs also demonstrated a good colloidal stability and a positively charged flake surface. Selective toxicity dependent upon selective ROS scavenging/generation and cellular MQF uptake towards non-malignant human keratinocyte (HaCaT) and malignant melanoma (A357) and human breast cancer (MDA-MB 231) cell lines were witnessed. An increased ROS concentration resulted due to the peroxidase-like activity of MQFs in malignant cells. In contrast, ROS scavenging was observed in non-malignant cells due to dominant catalase-like activity. In vitro fluorescence properties added the diagnostic ability to the ambit of MQFs. Furthermore, the therapeutic efficiency could be significantly enhanced by the hyperthermic (25-47 °C) ability of MQF in cancerous cells. Our findings reveal the novel theranostic MQF structure with immense cancer therapeutic potential via augmentation of ROS generation by hyperthermia in a selective microenvironment.

Synthesis of magnetic chitosan biopolymeric spheres and their adsorption performances for PFOA and PFOS from aqueous environment.

Due to numerous applications and excellent environmental stability, long-chain perfluorinated chemicals (PFCs) are ubiquitous in water across the world and adversely affect the living organisms. Thus, this study focused on the mitigation of the most frequently used long-chain PFCs namely perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) from water using reduced graphene oxide modified zinc ferrite immobilized chitosan beads (rGO-ZF@CB) as an adsorbent. The results from the adsorption isotherm and kinetic studies revealed that the adsorption data fitted well to the Langmuir and the pseudo-second-order models. According to the Langmuir isotherm, the rGO-ZF@CB possessed the maximum adsorption capacity of 16.07 mg/g for PFOA and 21.64 mg/g for PFOS. Both the electrostatic attractions and hydrophobic interactions have driven the removal of PFOA and PFOS by prepared rGO-ZF@CB. Eventually, the rGO-ZF@CB could be considered as an efficient adsorbent for the effective removal of PFOA and PFOS molecules from the aqueous environment.

Designing biopolymer-based artificial peroxidase for oxidative removal of dibenzothiophene from a model diesel fuel.

Naturally occurring peroxidases are important for living organisms and have manifold utility in industries. However, lack of stability in harsh reaction conditions hinders wide applicability of such enzymes. Thus, suitable alternative is vital which can endure severe reaction conditions. As a substitute of natural peroxidase, herein, biopolymer-based polyelectrolyte complexes (PECs) coordinated with Fen+ is proposed as macromolecular peroxidase mimicking systems. Three PECs were engineered via complexation of protonated chitosan and alginate with Fe2+ (Fe2+-PEC), Fe3+ (Fe3+-PEC), and Fe3O4 (Fe3O4-PEC), respectively. Computational study showed the Fe3+-PEC was highly stable with abundant electrostatic and intramolecular hydrogen bonding interactions. The versatility of the Fe-PECs as artificial peroxidase biocatalysts was probed by two types of peroxidase assays - ABTS oxidation in buffer systems (pH 4.0 and 7.0) and pyrogallol oxidation in organic solvents (acetonitrile, ethyl acetate and toluene). Overall, Fe3+-PEC showed remarkably high peroxidase activity both in aqueous buffers and in organic solvents, whereas, Fe3O4-PEC showed least catalytic activity. Finally, as a proof of concept, the ability of the biocatalyst to carry out deep oxidative desulphurization was demonstrated envisaging removal of dibenzothiophene from model fossil fuel in a sustainable way.

Green Synthesis of Iron Oxides and Phosphates via Thermal Treatment of Iron Polyphenols Synthesized by a Camellia sinensis Extract.

Iron oxide nanoparticles (FeONPs) prepared with plant extracts have been emerging as green and sustainable materials. FeONPs are usually amorphous due to the chelation of the tea polyphenols (TPs) to the iron, and the real nature of the iron compounds is not completely understood. The main goal of this study was to investigate the behavior of the green FeONPs synthesized from an Fe3+ salt and Cammelia sinensis (black tea) extract upon thermal treatment, in order to remove TPs and enable the formation of crystalline materials suitable for a thorough characterization and with the potential for diverse applications. The as-prepared FeONPs were assigned as mixed-valence Fe(III) oxyhydroxides and Fe(II)/Fe(III) ions bound to TPs. A detailed description of the phase transformation upon heating revealed the formation of the rare nano ß-Fe2O3 phase at 400 °C, followed by a transformation to α-Fe2O3 as the temperature increased. Above 600 °C, the unprecedented formation of FePO4 and Fe3PO7 was observed, produced from the reaction of Fe2O3 and free phosphate ions present in the black tea leaves, Fe3PO7 being the major phase obtained at 900 °C. Finally, the catalytic potential of the FeONPs to treat the azo dye methyl orange through a heterogeneous Fenton-like system was investigated.

Synthesis of a Nitrogenase PN -Cluster Model with [Fe8 S7 (µ-Sthiolate )2 ] Core from the All-Ferric [Fe4 S4 (Sthiolate )4 ] Cubane Synthon.

Constructing synthetic models of the nitrogenase PN -cluster has been a long-standing synthetic challenge. Here, we report an optimal nitrogenase PN -cluster model [{(TbtS)(OEt2 )Fe4 S3 }2 (µ-STbt)2 (µ6 -S)] (2) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl] that is the closest synthetic mimic constructed to date. Of note is that two thiolate ligands and one hexacoordinated sulfide are connecting the two Fe4 S3 incomplete cubanes similar to the native PN -cluster, which has never been achieved. Cluster 2 has been characterized by X-ray crystallography and relevant physico-chemical methods. The variable temperature magnetic moments of 2 indicate a singlet ground state (S=0). The Mössbauer spectrum of 2 exhibits two doublets with an intensity ratio of 3:1, which suggests the presence of two types of iron sites. The synthetic pathway of the cluster 2 could indicate the native PN -cluster maturation process as it has been achieved from the Fe4 S4 cubane Fe4 S4 (STbt)4 (1).

Iron(III) Complex-Functionalized Gold Nanocomposite as a Strategic Tool for Targeted Photochemotherapy in Red Light.

Iron(III)-phenolate/carboxylate complexes exhibiting photoredox chemistry and photoactivated reactive oxygen species (ROS) generation at their ligand-to-metal charge-transfer (LMCT) bands have emerged as potential strategic tools for photoactivated chemotherapy. Herein, the synthesis, in-depth characterization, photochemical assays, and remarkable red light-induced photocytotoxicities in adenocarcinomic human immortalized human keratinocytes (HaCaT) and alveolar basal epithelial (A549) cells of iron(III)-phenolate/carboxylate complex of molecular formula, [Fe(L1)(L2)] (1), where L1 is bis(3,5 di-tert-butyl-2-hydroxybenzyl)glycine and L2 is 5-(1,2-dithiolan-3-yl)-N-(1,10-phenanthroline-5-yl)pentanamide, and the gold nanocomposite functionalized with complex 1 (1-AuNPs) are reported. There was a significant red shift in the UV-visible absorption band on functionalization of complex 1 to the gold nanoparticles (λmax: 573 nm, 1; λmax: 660 nm, 1-AuNPs), rendering the nanocomposite an ideal candidate for photochemotherapeutic applications. The notable findings in our present studies are (i) the remarkable cytotoxicity of the nanocomposite (1-AuNPs) to A549 (IC50: 0.006 µM) and HaCaT (IC50: 0.0075 µM) cells in red light (600-720 nm, 30 J/cm2) while almost nontoxic (IC50 > 500 µg/mL, 0.053 µM) in the dark, (ii) the nontoxicity of 1-AuNPs to normal human diploid fibroblasts (WI-38) or human peripheral lung epithelial (HPL1D) cells (IC50 > 500 µg/mL, 0.053 µM) both in the dark and red light signifying the target-specific anticancer activity of the nanocomposite, (iii) localization of 1-AuNPs in mitochondria and partly nucleus, (iv) remarkable red light-induced generation of reactive oxygen species (ROS: 1O2, •OH) in vitro, (v) disruption of the mitochondrial membrane due to enhanced oxidative stress, and (vi) caspase 3/7-dependent apoptosis. A similar cytotoxic profile of complex 1 was another key finding of our studies. Overall, our current investigations show a new red light-absorbing iron(III)-phenolate/carboxylate complex-functionalized gold nanocomposite (1-AuNPs) as the emerging next-generation iron-based photochemotherapeutic agent for targeted cancer treatment modality.

Microwave assisted synthesis of Fe3O4 stabilized ZrO2 nanoparticles - Free radical scavenging, radiolabeling and biodistribution in rabbits.

AIMS: In vivo biodistribution of radio labeled ZrO2 nanoparticles is addressed for better imaging, therapy and diagnosis. Nanoparticles are synthesized by microwave assisted sol-gel technique using Fe3O4 as a stabilizer. Antioxidant assay, hemolytic activity in human blood and biodistribution in rabbits was explored to study the therapeutical as well as in vivo targeted diagnostic applications of as synthesized nanoparticles. MAIN METHODS: Fe3O4 stabilized zirconia nanoparticles are synthesized using microwave assisted sol-gel method. Microwave (MW) powers are varied in the range of 100 to 1000 W. As synthesized nanoparticles are evaluated using different characterizations such as X-ray diffractometer, scanning electron microscope, Raman spectroscopy, impedance analyzer, Vickers micro hardness indenter, FTIR, and UV-Vis spectroscopy. In vitro activity of synthesized nanoparticles is checked in freshly extracted human blood serum. To study biodistribution of Fe3O4 stabilized zirconia nanoparticles in rabbit, technetium-99 m was used for labeling purpose. The labeling efficacy and stability of labeled nanoparticles are also measured with instant thin layer chromatography (ITLC) method. Intravenous injection of 99mTc-Fe3O4 stabilized zirconia nanoparticles (0.2 ml), containing 110 MBq of radioactivity, is performed to study the biodistribution; nanoparticles are injected into the ear vein of animal (rabbit). KEY FINDINGS: Zirconia (ZrO2) nanoparticles (NPs) are stabilized using Fe3O4 that were prepared by means of microwave assisted sol-gel method. Crystallite size (~20 nm) agrees well with the values required to stabilize tetragonal zirconia (t-ZrO2). Volume shrinkage results in high value of hardness (~1369). Dielectric constant values, compatible for biomedical application, are observed for tetragonally stabilized samples. Low value of hemolytic response is observed for Fe3O4 stabilized ZrO2 NPs. 99mTc radio labeled ZrO2 NPs proved to be potential candidate to study biodistribution. Biodistribution studies show stability of radiolabeled NPs in the original suspension as well as in blood serum. CT scan of rabbit is performed for several times to check the biodistribution of NPs with time and survival of rabbit. Results suggest that these NPs can also be used as targeted nanoparticles as well as variants of drug payload carrier. SIGNIFICANCE: Results signify that Fe3O4 stabilized ZrO2 nanoparticles synthesized by microwave assisted sol-gel method may be considered as "all-rounder" nanoplatform and are safe enough to be used in diagnostic as well as therapeutic purposes.

Solvothermal synthesis of α-Fe2O3 polyhedrons and its application in an immunochromatographic strip test for the detection of foodborne pathogen Listeria monocytogenes.

The immunochromatographic strip test (ICST) is a powerful on-site detection technology due to its unique advantages of simplicity, rapidity, and readability by the naked eye. Here we illustrate the potential of α-Fe2O3 polyhedrons as a novel visual label, which exhibit advantages of high stability and economy, for the detection of Listeria monocytogenes (L. monocytogenes) as a model foodborne pathogen. A low-cost and simple one-step solvothermal approach was developed for the synthesis of α-Fe2O3 polyhedrons; the average diameter of the α-Fe2O3 polyhedrons is about 200 nm. The crystal structure and morphology of α-Fe2O3 polyhedrons were characterized by x-ray diffraction and transmission electron microscope. α-Fe2O3 polyhedrons were immunized with anti-L. monocytogenes antibody to prepare an antibody-colloidal α-Fe2O3 polyhedron ICST. Visual detection can be obtained directly by the naked eye within 10 min. The detection limit of L. monocytogenes by α-Fe2O3 polyhedron ICST assay was 3.8 × 106 and 5.6 × 106 CFU/ml of pure culture and artificially spiked orange juice drink sample, respectively. Results indicated that the antibody-colloidal α-Fe2O3 polyhedron ICST is a rapid, simple, and low-cost assay. This approach showed great potential in the application of foodborne pathogen detection concerning food safety.

Non-hydrolytic synthesis of caprylate capped cobalt ferrite nanoparticles and their application against Erwinia carotovora and Stenotrophomonas maltophilia.

Magnetic cobalt Ferrite nanoparticles capped with caprylate groups, CH3(CH2)6CO2-, have been synthesized using a novel non-hydrolytic coprecipitation method under inert conditions. Particle diameter was characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). The spinel ferrite crystal phase was verified using X-ray diffraction (XRD), and the presence of the capping agent was confirmed using Fourier Transform Infrared spectroscopy (FTIR). Bactericidal effects of the particles were tested against broth cultures of Erwinia carotovora and Stenotrophomonas maltophilia. The final particles had an average diameter of 3.81 nm and readily responded to a neodymium magnet. The particles did have a significant effect on the OD600 of both broth cultures.

A new type of magnetic molecular imprinted material combined with ß-cyclodextrin for the selective adsorption of zearalenone.

In this paper, a new magnetic molecular imprinted polymer-cyclodextrin (MMIP-CD) material was prepared by connecting ß-cyclodextrin (CD) on the surface of a magnetic molecular imprinted polymer (MMIP) and used for the rapid and specific adsorption of zearalenone (ZEN). By using warfarin as the virtual template molecule, tetraethyl orthosilicate (TEOS) as the crosslinking agent, and (3-aminopropyl) triethoxysilane (APTES) as the functional monomer, a MMIP was produced by surface imprinting technology. Sulfobutyl ether-ß-cyclodextrin attached to the surface of the MMIP under heating conditions produced a new specific adsorption material with exceptional adsorption capacity and excellent selectivity for ZEN. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and TEM-mapping results showed that the prepared MMIP-CD had a uniform particle size of about 480 nm, and the molecularly imprinted layer was successfully wrapped on the surface of the nanoparticles with a thickness of about 50 nm, whereby the cyclodextrin was effectively attached to the surface of the MMIP. The adsorption mechanism of MMIP-CD was confirmed by kinetic adsorption and thermodynamic adsorption experiments, the maximum adsorption capacity was found to be about 30 mg g-1, and the adsorption equilibrium could be reached within 20 min. The value of IF (QMMIP-CD/QMNIP) is 4.642. This showed that compared with MNIP, MMIP-CD showed a greatly improved specific adsorption capacity of ZEN. Selective experiments proved that MMIP-CD effectively combined the advantages of MMIP and CD, enhancing the adsorption capacity together with reducing the disadvantages that MMIP cannot distinguish structural analogs and CD cannot identify hydrophobic compounds effectively. In actual sample testing, the limit of quantification (LOQ) and limit of detection (LOD) were 0.1 ng kg-1 and 0.3 ng kg-1, respectively. The stability and detection precision of this method were 0.98-2.76% and 1.67-3.88%, respectively. The results proved that MMIP-CD had good development potential in the field of selective adsorption of ZEN, and laid the foundation for follow-up research.

Core-shell FePt-cube@covalent organic polymer nanocomposites: a multifunctional nanocatalytic agent for primary and metastatic tumor treatment.

Metastasis and spread are currently the main factors leading to high mortality of cancer, so developing a synergetic antitumor strategy with high specificity and hypotoxicity is in urgent demand. Based on the design concept of "nanocatalytic medicine", multifunctional nanotherapeutic agent FePt@COP-FA nanocomposites (FPCF NCs) are developed for cancer treatment. Specifically, in the tumor microenvironment (TME), FePt could catalyze intracellular over-expressed H2O2 to generate highly active hydroxyl radicals (˙OH), which could not only induce the apoptosis of tumor cells, but also activate the "ferroptosis" pathway resulting in the lipid peroxide accumulation and ferroptotic cell death. Moreover, owing to the excellent photothermal effect, the FPCF NCs could effectively ablate primary tumors under near-infrared (NIR) laser irradiation and produce numerous tumor-associated antigens in situ. With the assistance of a checkpoint blockade inhibitor, anti-CTLA4 antibody, the body's specific immune response would be initiated to inhibit the growth of metastatic tumors. In particular, such synergistic therapeutics could produce an effective immunological memory effect, which could prevent tumor metastasis and recurrence again. In summary, the FPCF NC is an effective multifunctional antitumor therapeutic agent for nanocatalytic/photothermal/checkpoint blockade combination therapy, which exhibits great potential in nanocatalytic anticancer therapeutic applications.

Synthesis of heteronanostructures for multimodality molecular imaging-guided photothermal therapy.

Combining photothermal therapy (PTT) and multimodality molecular imaging into one nanotheranostic can improve the diagnostics and therapeutics outcome of malignant tumors significantly. Herein, a heteronanostructure (named Au-Fe3O4@PDA-PEG-DTPA-Gd) has been synthesized for multimodality molecular imaging-guided PTT by conjugation of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) on a polydopamine (PDA) coated Au-Fe3O4 heterodimeric via a polyethylene glycol (PEG) crosslinker. Au-Fe3O4@PDA-PEG-DTPA-Gd exhibits reasonable biocompatibility, high photothermal conversion efficiency (η = 41.3%), integration of excellent T1-/T2-weighted magnetic resonance imaging (MRI, the molar longitudinal relaxivity rate (r1) = 6.14 mM-1 s-1/transverse relaxation rate (r2) = 71.88 mM-1 s-1) and X-ray computed tomography imaging (CT, approximately 1.94 times higher than that of the commercial CT contrast agent ioversol) contrast functionality. The theranostic capability of Au-Fe3O4@PDA-PEG-DTPA-Gd has been verified on the triple negative breast tumor cell (MDA-MB-231 cell) and MDA-MB-231 tumor-bearing mouse model. From MR/CT imaging, Au-Fe3O4@PDA-PEG-DTPA-Gd shows remarkable PTT efficacy, which completely inhibits MDA-MB-231 tumor growth in vivo with a single treatment.

Iron-based nano-structured surfaces with antimicrobial properties.

Bactericidal nanopillar arrays on cicada wings represent a non-toxic antimicrobial technology as they work through physical cell rupture instead of a chemical mechanism. Here, we reported iron-based nanopillar arrays (FeOOH and Fe2O3) that can grow on various substrates by a simple solution method. These surfaces showed good structure-based antimicrobial activity. Even more simply, we have prepared urchin-type FeOOH and Fe2O3 particles, which can be easily coated onto various substrates to create structure-based disinfection surfaces. This work provides a simple and general methodology to apply this killed-by-structure technology for real world uses.

Synthesis, Characterization and Magnetic Hyperthermia of Monodispersed Cobalt Ferrite Nanoparticles for Cancer Therapeutics.

Magnetic nanoparticles such as cobalt ferrite are investigated under clinical hyperthermia conditions for the treatment of cancer. Cobalt ferrite nanoparticles (CFNPs) synthesized by the thermal decomposition method, using nonionic surfactant Triton-X100, possess hydrophilic polyethylene oxide chains acting as reducing agents for the cobalt and iron precursors. The monodispersed nanoparticles were of 10 nm size, as confirmed by high-resolution transmission electron microscopy (HR-TEM). The X-ray diffraction patterns of CFNPs prove the existence of cubic spinel cobalt ferrites. Cs-corrected scanning transmission electron microscopy-high-angle annular dark-field imaging (STEM-HAADF) of CFNPs confirmed their multi-twinned crystallinity due to the presence of atomic columns and defects in the nanostructure. Magnetic measurements proved that the CFNPs possess reduced remnant magnetization (MR/MS) (0.86), which justifies cubic anisotropy in the system. Microwave-based hyperthermia studies performed at 2.45 GHz under clinical conditions in physiological saline increased the temperature of the CFNP samples due to the transformation of radiation energy to heat. The specific absorption rate of CFNPs in physiological saline was 68.28 W/g. Furthermore, when triple-negative breast cancer cells (TNBC) in the presence of increasing CFNP concentration (5 mg/mL to 40 mg/mL) were exposed to microwaves, the cell cytotoxicity was enhanced compared to CFNPs alone.

Ferric Ion Driven Assembly of Catalase-like Supramolecular Photosensitizing Nanozymes for Combating Hypoxic Tumors.

A facile approach to assemble catalase-like photosensitizing nanozymes with a self-oxygen-supplying ability was developed. The process involved Fe3+ -driven self-assembly of fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids. By adding a zinc(II) phthalocyanine-based photosensitizer (ZnPc) and the hypoxia-inducible factor 1 (HIF-1) inhibitor acriflavine (ACF) during the Fe3+ -promoted self-assembly of Fmoc-protected cysteine (Fmoc-Cys), the nanovesicles Fmoc-Cys/Fe@Pc and Fmoc-Cys/Fe@Pc/ACF were prepared, which could be disassembled intracellularly. The released Fe3+ could catalyze the transformation of H2 O2 enriched in cancer cells to oxygen efficiently, thereby ameliorating the hypoxic condition and promoting the photosensitizing activity of the released ZnPc. With an additional therapeutic component, Fmoc-Cys/Fe@Pc/ACF exhibited higher in vitro and in vivo photodynamic activities than Fmoc-Cys/Fe@Pc, demonstrating the synergistic effect of ZnPc and ACF.

Superior antibacterial activity of Fe3O4@copper(ii) metal-organic framework core-shell magnetic microspheres.

With the rapid evolution of antibiotic resistant bacteria, it has become more and more difficult to treat bacterial infection with traditional antibiotics. Therefore, new strategies with high antibacterial efficiency are urgently needed to combat bacteria effectively. Herein, Fe3O4@copper(ii) metal-organic framework Cu3(BTC)2 (Cu-BTC) core-shell structured magnetic microspheres were prepared via a layer by layer growth process. The as-prepared Fe3O4@Cu-BTC possessed a unique broad-spectrum antibacterial potency against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The slowly released copper ions and enhanced reactive oxygen species (ROS) generation by facilitating the effective separation and transfer of photoexcited electron-hole pairs played a role in the antibacterial activity of Fe3O4@Cu-BTC. Copper ions released from Fe3O4@Cu-BTC adhered to the negatively charged bacterial cell, interacted with the bacterial membrane, destroyed the integrity of the membrane which resulted in leakage of bacterial content and then generated ROS to damage DNA, thus leading to cell death. Accordingly, this study provides a competitive strategy for preparing recyclable antibacterial materials that are endowed with targeted antibacterial therapy.