Design of Organic Macrocycle-Modified Iron Oxide Nanoparticles for Drug Delivery

Nitroreductase-sensitive fluorescent covalent organic framework for tumor hypoxia imaging in cells

Covalent organic frameworks (COFs) have been used in cell imaging, but very rarely for imaging specific cell conditions. Herein, a β-ketoenamine-based fluorescent COF was post-synthetically modified to incorporate a hypoxia-targeting molecule. Fluorescence microscopy imaging shows that the material discriminates between HeLa cells grown under hypoxia and those cultured under normoxia.

KLVFF oligopeptide-decorated amphiphilic cyclodextrin nanomagnets for selective amyloid beta recognition and fishing

Recognition and capture of amyloid beta (Aβ) is a challenging task for the early diagnosis of neurodegenerative disorders, such as Alzheimer's disease. Here, we report a novel KLVFF-modified nanomagnet based on magnetic nanoparticles (MNP) covered with a non-ionic amphiphilic β-cyclodextrin (SC16OH) and decorated with KLVFF oligopeptide for the self-recognition of the homologous amino-acids sequence of Aβ to collect Aβ (1-42) peptide from aqueous samples. MNP@SC16OH and MNP@SC16OH/Ada-Pep nanoassemblies were fully characterized by complementary techniques both as solid powders and in aqueous dispersions. Single domain MNP@SC16OH/Ada-Pep nanomagnets of 20-40 nm were observed by TEM analysis. DLS and ζ-potential measurements revealed that MNP@SC16OH nanoassemblies owned in aqueous dispersion a hydrodynamic radius of about 150 nm, which was unaffected by Ada-Pep decoration, while the negative ζ-potential of MNP@SC16OH (-40 mV) became less negative (-30 mV) in MNP@SC16OH/Ada-Pep, confirming the exposition of positively charged KLVFF on nanomagnets surface. The ability of MNP@SC16OH/Ada-Pep to recruit Aβ (1-42) in aqueous solution was evaluated by MALDI-TOF and compared with the ineffectiveness of undecorated MNP@SC16OH and VFLKF scrambled peptide-decorated nanoassemblies (MNP@SC16OH/Ada-scPep), pointing out the selectivity of KLVFF-decorated nanohybrid towards Aβ (1-42). Finally, the property of nanomagnets to extract Aβ in conditioned medium of cells over-producing Aβ peptides was investigated as proof of concept of effectiveness of these nanomaterials as potential diagnostic tools.

1,3-Diketone Calix[4]arene Derivatives-A New Type of Versatile Ligands for Metal Complexes and Nanoparticles

The present review is aimed at highlighting outlooks for cyclophanic 1,3-diketones as a new type of versatile ligands and building blocks of the nanomaterial for sensing and bioimaging. Thus, the main synthetic routes for achieving the structural diversity of cyclophanic 1,3-diketones are discussed. The structural diversity is demonstrated by variation of both cyclophanic backbones (calix[4]arene, calix[4]resorcinarene and thiacalix[4]arene) and embedding of different substituents onto lower or upper macrocyclic rims. The structural features of the cyclophanic 1,3-diketones are correlated with their ability to form lanthanide complexes exhibiting both lanthanide-centered luminescence and magnetic relaxivity parameters convenient for contrast effect in magnetic resonance imaging (MRI). The revealed structure–property relationships and the applicability of facile one-pot transformation of the complexes to hydrophilic nanoparticles demonstrates the advantages of 1,3-diketone calix[4]arene ligands and their complexes in developing of nanomaterials for sensing and bioimaging.

Selective Identification of Phenylalanine Using Cucurbit[7,8]uril-Based Fluorescent Probes

The interactions of two host–guest inclusion complexes comprised of cucurbit[7]uril (Q[7]) and cucurbit[8]uril (Q[8]) with a derivative of toluidine blue O (TB) have been investigated using 1H NMR and fluorescence spectroscopy. The experimental results revealed that the Q[7] host interacts with a TB molecule to form a 1:1 inclusion complex and the Q[8] host interacts with two TB guest molecules to form a 1:2 inclusion complex. The inclusion of the TB guest molecule within the Q[7] host gave rise to significant fluorescence enhancement, whereas the inclusion of the TB guest molecule within the Q[8] host resulted in significant fluorescence quenching. Further recognition experiments involving a series of l-α-amino acids revealed that the TB@Q[7] inclusion fluorescence probe exhibits high selectivity for the recognition of phenylalanine via significant fluorescence quenching in an aqueous solution, whereas the TB@Q[8] inclusion fluorescence probe also exhibited high selectivity for phenylalanine recognition via fluorescence enhancement in an aqueous solution.

β-Cyclodextrin-Silica Hybrid: A Spatially Controllable Anchoring Strategy for Cu(II)/Cu(I) Complex Immobilization

The development of new strategies for spatially controllable immobilization has encouraged the preparation of novel catalysts based on the organic-inorganic hybrid concept. In the present paper, a Cu-based multi-structured silica catalyst has been prepared and fully characterized. The inclusion of Cu(II) in β-cyclodextrins has been exploited with the double aim to stabilize the metal and to act as a source of Cu(I) catalytic sites. Multi-technique characterization by infrared, UV-visible, electron microscopy and X-ray absorption spectroscopies of the fresh and exhaust catalysts provided information on the local structure, redox properties and stability of the investigated hybrid systems. The catalytic system showed that copper nanospecies were dispersed on the support and hardly affected by the catalytic tests, confirming the stabilizing effect of β-CD, and likely of the N1-(3-Trimethoxysilylpropyl) diethylenetriamine spacer, as deduced by X-ray absorption spectroscopy analysis. Overall, we demonstrate a feasible approach to efficiently anchor Cu(II) species and to obtain a reusable single-site hybrid catalyst well suited for Cu(I)-catalyzed alkyne-azide cycloaddition.

Chemical Synthesis of Magnetic Nanoparticles for Permanent Magnet Applications

Permanent magnets are a class of critical materials for information storage, energy storage, and other magneto-electronic applications. Compared with conventional bulk magnets, magnetic nanoparticles (MNPs) show unique size-dependent magnetic properties, which make it possible to control and optimize their magnetic performance for specific applications. The synthesis of MNPs has been intensively explored in recent years. Among different methods developed thus far, chemical synthesis based on solution-phase reactions has attracted much attention owing to its potential to achieve the desired size, morphology, structure, and magnetic controls. This Minireview focuses on the recent chemical syntheses of strongly ferromagnetic MNPs (H_c >10 kOe) of rare-earth metals and FePt intermetallic alloys. It further discusses the potential of enhancing the magnetic performance of MNP composites by assembly of hard and soft MNPs into exchange-coupled nanocomposites. High-performance nanocomposites are key to fabricating super-strong permanent magnets for magnetic, electronic, and energy applications.

Synthesis, physical characterization, and antifungal and antibacterial activities of oleic acid capped nanomagnetite and cobalt-doped nanomagnetite

Nanoparticles, 10–14 nm, consisting of either Fe3O4 or Co0.2Fe2.8O4 stabilized with oleic acid, were prepared using solution combustion. Their structural and magnetic properties were examined using X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, and Fourier-transform infrared spectroscopy. The properties of both sets of materials are similar, except that the cobalt-doped particles are considerably less magnetic. The in vitro inhibitory activities of the nanoparticles were assessed against pathogenic bacteria Shigella dysenteriae, Klebsiella pneumoniae, Acinetobacter baumannii, Streptococcus pyogenes, and pathogenic fungi and molds Candida albicans, Fusarium oxysporum, and Aspergillus fumigatus. The magnetite nanoparticles were moderately effective against all tested pathogens, but the activity of the cobalt-doped nanoparticles was significantly lower, possibly due to an interruption of the Fenton reaction at the bacterial membrane. This work suggests that potentially doping magnetite with stronger metal oxidants may instead enhance their antimicrobial effects.

Tuning the surface coating of IONs toward efficient sonochemical tethering and sustained liberation of topoisomerase II poisons

Background

Iron oxide nanoparticles (IONs) have been increasingly utilized in a wide spectrum of biomedical applications. Surface coatings of IONs can bestow a number of exceptional properties, including enhanced stability of IONs, increased loading of drugs or their controlled release.

Methods

Using two-step sonochemical protocol, IONs were surface-coated with polyoxyethylene stearate, polyvinylpyrrolidone or chitosan for a loading of two distinct topo II poisons (doxorubicin and ellipticine). The cytotoxic behavior was tested in vitro against breast cancer (MDA-MB-231) and healthy epithelial cells (HEK-293 and HBL-100). In addition, biocompatibility studies (hemotoxicity, protein corona formation, binding of third complement component) were performed.

Results

Notably, despite surface-coated IONs exhibited only negligible cytotoxicity, upon tethering with topo II poisons, synergistic or additional enhancement of cytotoxicity was found in MDA-MB-231 cells. Pronounced anti-migratory activity, DNA fragmentation, decrease in expression of procaspase-3 and enhancement of p53 expression were further identified upon exposure to surface-coated IONs with tethered doxorubicin and ellipticine. Moreover, surface-coated IONs nanoformulations of topo II poisons exhibited exceptional stability in human plasma with no protein corona and complement 3 binding, and only a mild induction of hemolysis in human red blood cells.

Conclusion

The results imply a high potential of an efficient ultrasound-mediated surface functionalization of IONs as delivery vehicles to improve therapeutic efficiency of topo II poisons.

Self-assembly of stimuli-responsive imine-linked calix[4]arene nanocapsules for targeted camptothecin delivery

Here we report template-free synthesis of imine-linked calix[4]arene hollow nanocapsules and their utility in the effective delivery of a poorly soluble cancer drug into tumor cells.

Precise supramolecular control of surface coverage densities on polymer micro- and nanoparticles

We report herein the controlled surface functionalization of micro- and nanoparticles by supramolecular host-guest interactions. Our idea is to exploit the competition of two high-affinity guests for binding to the surface-bound supramolecular host cucurbit[7]uril (CB7). To establish our strategy, surface azide groups were introduced to hard-sphere (poly)methylmethacrylate particles with a grafted layer of poly(acrylic acid), and a propargyl derivative of CB7 was coupled to the surface by click chemistry. The amount of surface-bound CB7 was quantified with the high-affinity guest aminomethyladamantane (AMADA), which revealed CB7 surface coverage densities around 0.3 nmol cm-2 indicative of a 3D layer of CB7 binding sites on the surface. The potential for surface functionalization was demonstrated with an aminoadamantane-labeled rhodamine (Ada-Rho) as a second high-affinity guest. Simultaneous incubation of CB7-functionalized particles with both high-affinity guests, AMADA and Ada-Rho, revealed a simple linear relationship between the resulting surface coverage densities of the model fluorescent dye and the mole fraction of Ada-Rho in the incubation mixture. This suggests a highly modular supramolecular strategy for the stable immobilization of application-relevant molecules on particle surfaces and a precise control of their surface coverage densities.

4-Sulfocalix[4]arene/Cucurbit[7]uril-Based Supramolecular Assemblies through the Outer Surface Interactions of Cucurbit[n]uril

Upon mixing of aqueous solutions of the freely soluble building blocks cucurbit[7]uril (Q[7]) and 4-sulfocalix[4]arene (SC[4]A), white microcrystals instantly separate in near-quantitative yield. The driving force for this assembly is suggested to be the outer-surface interaction of the Q[n]. Dynamic light scattering, scanning electron microscopy, and NMR (diffusion-ordered NMR spectroscopy) analyses have confirmed the supramolecular aggregation of Q[7] and SC[4]A. Titration ¹H NMR spectroscopy and isothermal titration calorimetry have shown that the interaction ratio of Q[7] and SC[4]A is close to 3:1. Moreover, the Q[7]/SC[4]A-based supramolecular assembly can accommodate molecules of some volatile compounds or luminescent dyes. Thus, this work offers a simple and highly efficient means of preparing adsorbent or solid fluorescent materials.

Iron nanostructured catalysts: design and applications

This review is focused on the recent advances in the design of iron nanostructures and their catalytic applications.

Sequential Delivery of Doxorubicin and Zoledronic Acid to Breast Cancer Cells by CB[7]-Modified Iron Oxide Nanoparticles

Drug-loaded magnetic nanoparticles were synthesized and used for the sequential delivery of the antiresorptive agent zoledronic acid (Zol) and the cytotoxic drug doxorubicin (Dox) to breast cancer cells (MCF-7). Zol was attached to bare iron oxide nanoparticles (IONPs) via phosphonate coordination to form Z-NPs. The unbound imidazole of Zol was then used to complex the organic macrocycle CB[7] to obtain CZ-NPs. Dox was complexed to the CZ-NPs to form the fully loaded particles (DCZ-NPs), which were stable in solution at 37 °C and physiological pH (7.4). Fluorescence spectroscopy established that Dox is released in solution from DCZ-NPs suddenly (i) when the particles are subjected to magnetically induced heating to 42 °C at low pH (5.0) and (ii) in the presence of glutathione (GSH). Mass spectrometry indicated that Zol is released slowly in solution at low pH after Dox release. Magnetic measurements with a magnetic reader revealed that DCZ-NPs are internalized preferentially by MCF-7 cells versus nonmalignant cells (HEK293). Zol and Dox acted synergistically when delivered by the particles. DCZ-NPs caused a decrease in the viability of MCF-7 cells that was greater than the net decrease caused when the drugs were added to the cells individually at concentrations equivalent to those delivered by the particles. MCF-7 cells were treated with DCZ-NPs and subjected to an alternating magnetic field (AMF) which, with the nanoparticles present, raised the temperature of the cells and triggered the intracellular release of Dox, as indicated by fluorescence activated cell sorting (FACS). The cytotoxic effects of the DCZ-NPs on MCF-7 cells were enhanced 10-fold by AMF-induced heating. DCZ-NPs were also able to completely inhibit MCF-7 cell adhesion and invasion in vitro, indicating the potential of the particles to act as antimetastatic agents. Together these results demonstrate that DCZ-NPs warrant development as a system for combined chemo- and thermo-therapeutic treatment of cancer.