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A self-contained nanocapsule for nonspecific cytotoxic anticancer drug delivery and release activated by an enzyme and an alternating magnetic field (AMF) is introduced. This specific prodrug-like drug delivery platform is based on an esterase, an oligomer-based separating barrier, and an ester-linked anticancer peptide melittin encapsulated together in the enlarged pore spaces of the mesoporous silica nanoparticles. A superparamagnetic iron oxide nanoparticle core embedded in the center acts as a nanoheater to stimulate a cascade drug release. Each pore space was designed as a reaction nanovial for the activation of the drug release when the solution inside the nanovial is heated. By employing a thermoresponsive separating barrier as a shield of the peptide drug as well as a separator between the ester-containing peptides and the esterase, the nonspecific cytotoxic effect of the drug and off-target drug release are avoided because the drugs remain inactive in the absence of AMF stimulation. When AMF heating actuates the removal of the separating barrier and exposes the peptide drugs to the enzymes, drug release can be activated. In vivo antitumor experiments further revealed that the nanocapsules exhibited excellent biocompatibility and high tumor-targeting/inhibiting efficiency. The selected esterase, which is in close proximity to the ester-containing peptide drug, efficiently cleaves the ester bonds, thereby causing a catalytic release of peptide drugs and intensified anticancer efficacy. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) has become popular these days for their photocatalytic activities of water splitting. Metal-doped hematite materials are interesting as well for the bandgap engineering and for resolving fast charge–hole recombination. In this study, magnetism and ionic behaviors of rare manganese-doped α-Fe2O3/silica nanocomposites are investigated. These nanocomposites are prepared by the impregnation method with a mixture of metal halides, followed by rapid heating (30 °C/min) under air condition. When the molar ratio between FeCl3·6H2O and MnCl2·4H2O is 2.97, wasp-waisted hysteresis and ferromagnetism with the Curie temperatures of 56.1 and 58.0 K are observed for the nanocomposites annealed at 600 °C for the duration of 3 and 7 h, respectively, while dominant spin glass states are observed for the nanocomposites annealed at 500 °C. In x-ray diffraction patterns, mixed phases of α-Fe2O3 are identified, whereas crystalline metallic Mn or Mn oxides are hardly found. Electron energy-loss spectroscopy study indicates that Mn2+ is severely oxidized, and with this oxidation of Mn2+, Si becomes more metallic. When the molar ratio between Fe and Mn halides is 7.32, magnetism is affected by a small amount of γ-Fe2O3, and spin glass states and the competition between ferromagnetism and antiferromagnetism are observed in the long temperature range. [ABSTRACT FROM AUTHOR]

Mesoporous silica nanoparticles (MSNs) functionalized with redox‐sensitive or pH‐sensitive nanovalves for doxorubicin delivery and release by using recombinant human H chain ferritin (HFn) as a cap have been designed and fabricated. In both cases, transmission electron microscope observatory, dynamic light scattering change, Fourier transform infrared spectra examination, thermogravimetric analysis show that HFn can be chemically bonded to MSNs while retaining its ability to target transferrin receptor 1 (TfR1). Cargo loading and release studies demonstrate that HFn is an efficient capping agent, blocking the pores of MSN preventing cargo molecules from diffusing out, and is responsive to redox stimuli or pH changes. More importantly, HFn can not only cap the MSNs, but also enables targeted cargo delivery to malignant cells by binding to the TfR1 that has been overexpressed in various tumors, which can be reflected by the cell viability and fluorescence microscope analysis results comparing with cyclodextrin as the capping agent and TfR1 blocking assay. The in vivo study reveals the excellent efficacy of doxorubicin loaded and HFn capped MSNs on suppression of tumor growth. The new developed drug delivery system features mutually benefit and mutually support, providing strategy for achieving specific‐site therapeutics delivery systems. [ABSTRACT FROM AUTHOR]

We developed a theranostic approach exemplifying a concept called an "exchange method" that controls and "images" drug release from nanoparticles using magnetic resonance imaging-guided high-intensity focused ultrasound. The controllable amount of released drug and therapeutic efficacy can be self-reported by associated MRI contrast changes in solution and in cells. [ABSTRACT FROM AUTHOR]

Periodic high-intensity focused ultrasound modulation of a nanoparticle generates reversible MRI T1 relaxivity changes at the 1.5 mm3 focal point causing periodic T1-weighted signal changes. Fourier analysis extracts signal changes at the modulation frequency, and a modulation enhancement map spotlights the precise region of interest by increasing contrast almost 100-fold. [ABSTRACT FROM AUTHOR]

Triapine (3-AP), is an iron-binding ligand and anticancer drug that is an inhibitor of human ribonucleotide reductase (RNR). Inhibition of RNR by 3-AP results in the depletion of dNTP precursors of DNA, thereby selectively starving fast-replicating cancer cells of nucleotides for survival. The redox-active form of 3-AP directly responsible for inhibition of RNR is the Fe(II)(3-AP)2 complex. In this work, we synthesize 12 analogs of 3-AP, test their inhibition of RNR in vitro, and study the electronic properties of their iron complexes. The reduction and oxidation events of 3-AP iron complexes that are crucial for the inhibition of RNR are modeled with solution studies. We monitor the pH necessary to induce reduction in iron complexes of 3-AP analogs in a reducing environment, as well as the kinetics of oxidation in an oxidizing environment. The oxidation state of the complex is monitored using UV–Vis spectroscopy. Isoquinoline analogs of 3-AP favor the maintenance of the biologically active reduced complex and possess oxidation kinetics that allow redox cycling, consistent with their effective inhibition of RNR seen in our in vitro experiments. In contrast, methylation on the thiosemicarbazone secondary amine moiety of 3-AP produces analogs that form iron complexes with much higher redox potentials, that do not redox cycle, and are inactive against RNR in vitro. The catalytic subunit of human Ribonucleotide Reductase (RNR), contains a tyrosyl radical in the enzyme active site. Fe(II) complexes of 3-AP and its analogs can quench the radical and, subsequently, inactivate RNR. The potency of RNR inhibitors is highly dependent on the redox properties of the iron complexes, which can be tuned by ligand modifications. Complexes are found to be active within a narrow redox window imposed by the cellular environment. [ABSTRACT FROM AUTHOR]

Interference effects in electronic absorption spectra caused by coupling between excited states are calculated and interpreted by using numerical integration of the time-dependent Schrödinger equation and the time-dependent theory of electronic spectroscopy. The interference between nearby spin-forbidden doublet and spin-allowed quartet states of chromium (III) and vanadium (II) metal complexes causes sharp decreases of intensity or dips in the envelopes of absorption bands. The states are coupled by spin–orbit coupling. The origin of the dips is explained in terms of interference between wave packets moving on potential energy surfaces representing the states. The importance of curve crossing and amplitude transfer between the states is analyzed quantitatively. The theory is applied to the absorption spectrum of a chromium (III) complex. [ABSTRACT FROM AUTHOR]

We describe biodegradable mesoporous hybrid nanoparticles (NPs) in the presence of proteins and their applications for drug delivery. We synthesized oxamide phenylene-based mesoporous organosilica nanoparticles (MON) in the absence of a silica source which had remarkably high organic content and high surface areas. Oxamide functions provided biodegradability in the presence of trypsin model proteins. MON displayed exceptionally high payloads of hydrophilic and hydrophobic drugs (up to 84 wt %), and a unique zero premature leakage without the pore capping, unlike mesoporous silica. MON were biocompatible and internalized into cancer cells for drug delivery. [ABSTRACT FROM AUTHOR]

Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min−1) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1−xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature. [ABSTRACT FROM AUTHOR]

Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co-condensation of TEOS with variable amounts (2-5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on-demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans-to- cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on-command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin-loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not. [ABSTRACT FROM AUTHOR]

Despite the worldwide interest generated by periodic mesoporous organosilica (PMO) bulk materials, the design of PMO nanomaterials with controlled morphology remains largely unexplored and their properties unknown. In this work, we describe the first study of PMO nanoparticles (NPs) based on meta-phenylene bridges, and we conducted a comparative structure-property relationship investigation with para-phenylene-bridged PMO NPs. Our findings indicate that the change of the isomer drastically affects the structure, morphology, size, porosity and thermal stability of PMO materials. We observed a much higher porosity and thermal stability of the para-based PMO which was likely due to a higher molecular periodicity. Additionally, the para isomer could generate multipodal NPs at very low stirring speed and upon this discovery we designed a phenylene-ethylene bridged PMO with a controlled Janus morphology. Unprecedentedly high payloads could be obtained from 40 to 110 wt % regardless of the organic bridge of PMOs. Finally, we demonstrate for the first time the co-delivery of two cargos by PMO NPs. Importantly, the cargo stability in PMOs did not require the capping of the pores, unlike pure silica, and the delivery could be autonomously triggered in cancer cells by acidic pH with nearly 70 % cell killing. [ABSTRACT FROM AUTHOR]

A facile, reproducible, and scalable method was explored to construct uniform Au@poly(acrylic acid) (PAA) Janus nanoparticles (JNPs). The as-prepared JNPs were used as templates to preferentially grow a mesoporous silica (mSiO2) shell and Au branches separately modified with methoxy-poly(ethylene glycol)-thiol (PEG) to improve their stability, and lactobionic acid (LA) for tumor-specific targeting. The obtained octopus-type PEG-Au-PAA/mSiO2-LA Janus NPs (PEG-OJNP-LA) possess pH and NIR dual-responsive release properties. Moreover, DOX-loaded PEG-OJNP-LA, upon 808 nm NIR light irradiation, exhibit obviously higher toxicity at the cellular and animal levels compared with chemotherapy or photothermal therapy alone, indicating the PEG-OJNP-LA could be utilized as a multifunctional nanoplatform for in vitro and in vivo actively-targeted and chemo-photothermal cancer therapy. [ABSTRACT FROM AUTHOR]

A facile, reproducible, and scalable method was explored to construct uniform Au@poly(acrylic acid) (PAA) Janus nanoparticles (JNPs). The as-prepared JNPs were used as templates to preferentially grow a mesoporous silica (mSiO2) shell and Au branches separately modified with methoxy-poly(ethylene glycol)-thiol (PEG) to improve their stability, and lactobionic acid (LA) for tumor-specific targeting. The obtained octopus-type PEG-Au-PAA/mSiO2-LA Janus NPs (PEG-OJNP-LA) possess pH and NIR dual-responsive release properties. Moreover, DOX-loaded PEG-OJNP-LA, upon 808 nm NIR light irradiation, exhibit obviously higher toxicity at the cellular and animal levels compared with chemotherapy or photothermal therapy alone, indicating the PEG-OJNP-LA could be utilized as a multifunctional nanoplatform for in vitro and in vivo actively-targeted and chemo-photothermal cancer therapy. [ABSTRACT FROM AUTHOR]

We report a two-photon-actuated cancer cell killing system that kills the cancer cells via drug delivery through multifunctional mesoporous silica nanogates. Two-photon-sensitive mesoporous organosilica (M2PS) nanocarriers were synthesized via the co-condensation of a silica precursor and a two-photon electron donor. The nanogates were constructed using a fast one-pot process at room temperature on the drug-loaded M2PS nanoparticles (NPs) with the bis(3-triethoxysilylpropyl)disulfide precursor. One and two-photon-actuated cargo releases from the M2PS nanogates were successfully monitored in aqueous solutions. Furthermore, the cellular uptake in MCF-7 cells was demonstrated via two-photon fluorescence imaging of the NPs, which were then applied successfully for drug delivery in cells. [ABSTRACT FROM AUTHOR]

A series of magnetically active ferrite nanoparticles (NPs) are prepared by using Mn oxide NPs as seeds. A Verwey transition is identified in Fe3O4 NPs with an average diameter of 14.5 nm at 96 K, where a sharp drop of magnetic susceptibility occurs. In MnFe2O4 NPs, a spin glass-like state is observed with the decrease in magnetization below the blocking temperature due to the disordered spins during the freezing process. From these MnFe2O4 NPs, MnFe2O4@MnxFe1−xO core–shell NPs are prepared by seeded growth. The structure of the core is cubic spinel (Fd3̅m), and the shell is composed of iron–manganese oxide (MnxFe1−xO) with a rock salt structure (Fm3̅m). Moiré fringes appear perpendicular to the 〈110〉 directions on the cubic shape NPs through the plane-matched epitaxial growth. These fringes are due to the difference in the lattice spacings between MnFe2O4 and MnxFe1−xO. Exchange bias is observed in these MnFe2O4@MnxFe1−xO core–shell NPs with an enhanced coercivity, as well as the shift of hysteresis along the field direction. [ABSTRACT FROM AUTHOR]

Calcination of hydrated iron salts in the pores of both spherical and rod-shaped mesoporous silica nanoparticles (NPs) changes the internal structure from an ordered 2D hexagonal structure into a smaller number of large voids in the particles with sizes ranging from large hollow cores down to ten nanometer voids. The voids only form when the heating rate is rapid at a rate of 30 °C min−1. The sizes of the voids are controlled reproducibly by the final calcination temperature; as the temperature is decreased the number of voids decreases as their size increases. The phase of the iron oxide NPs is α-Fe2O3 when annealed at 500 °C, and Fe3O4 when annealed at lower temperatures. The water molecules in the hydrated iron (III) chloride precursor salts appear to play important roles by hydrolyzing SiOSi bonding, and the resulting silanol is mobile enough to affect the reconstruction into the framed hollow structures at high temperature. Along with hexahydrates, trivalent Fe3+ ions are assumed to contribute to the structure disruption of mesoporous silica by replacing tetrahedral Si4+ ions and making FeOSi bonding. Volume fraction tomography images generated from transmission electron microscopy (TEM) images enable precise visualization of the structures. These results provide a controllable method of engineering the internal shapes in silica matrices containing superparamagnetic NPs. [ABSTRACT FROM AUTHOR]

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Mesoporous silica nanoparticles (MSNPs) are functionalized with molecular-recognition sites by anchoring a triazine or uracil fragment on the surface. After loading these MSNPs with dyes (propidium iodide or rhodamine B) or with a drug (camptothecin, CPT) they are capped by the complementary fragments, uracil and adenine, respectively, linked to the bulky cyclodextrin ring. These MSNPs are pH-sensitive and indeed, the dye release was observed at acidic pH by continuously monitored fluorescence spectroscopy studies. On the other hand, no dye leakage occurred at neutral pH, hence meeting the non-premature requirement to minimize side effects. In vitro studies were performed and confocal microscopy images demonstrate the internalization of the MSNPs and also dye release in the cells. To investigate the drug-delivery performance, the cytotoxicity of CPT-loaded nanoparticles was tested and cell death was observed. A remarkably lower amount of loaded CPT in the MSNPs (more than 40 times less) proved to be as efficient as free CPT. These results not only demonstrate the drug release after pore opening under lysosomal pH, but they also show the potential use of these MSNPs to significantly decrease the amount of the administered drug. [ABSTRACT FROM AUTHOR]

Mesoporous silica nanoparticles with a cubic ( Ia3 d) pore structure are derivatized with light-activated nanoimpellers to control the release of loaded guest molecules under external photo-control. The nanoimpellers consist of azobenzene derivatives that are attached to the interiors of the three-dimensional interconnected pores, and undergo photoisomerization that results in dynamic wagging motions of the unbound termini and drives the expulsion of molecules from the pores. Stimulated release experiments monitored by fluorescence spectroscopy demonstrate that the nanoimpeller-functionalized MCM-48 particles are able to trap and release both hydrophilic and hydrophobic cargo molecules under external photocontrol in aqueous, non-aqueous, and intracellular environments. [ABSTRACT FROM AUTHOR]

The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6-trioxytriphenyl-amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The second is provided by the three oxygen atoms, each of which bridges two adjacent aryl groups. There are two bands in the visible region of the optical absorption spectrum; their assignment and the interpretation of the contributing orbitals and electronic states are described in terms of the neighboring orbital model that explains the effects of the two types of coupling. The bonding changes that take place in the excited electronic states are probed by resonance Raman spectroscopy intensities and analyzed using the time-dependent theory of resonance Raman spectroscopy. The optical absorption spectrum was fit using the measured vibrational frequencies and excited state distortions. The distortions correlate well with the bonding changes predicted by the neighboring orbital model. The resonance Raman data and neighboring orbital model analysis reveal that the two optical absorption bands correspond to charge transfers from aryl groups with different nodal structures in their pi orbitals. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]