Surfactant-assisted selective etching strategy for generation of rattle-like mesoporous silica nanoparticles

Tuning Mesoporous Silica Nanoparticles in Novel Avenues of Cancer Therapy

The global menace of cancer has led to an increased death toll in recent years. The constant evolution of cancer therapeutics with novel delivery systems has paved the way for translation of innovative therapeutics from bench to bedside. This review explains the significance of mesoporous silica nanoparticles (MSNs) as delivery vehicles with particular emphasis on cancer therapy, including novel opportunities for biomimetic therapeutics and vaccine delivery. Parameters governing MSN synthesis, therapeutic agent loading characteristics, along with tuning of MSN toward cancer cell specificity have been explained. The advent of MSN in nanotheranostics and its potential in forming nanocomposites for imaging purposes have been illustrated. Additionally, various hurdles encountered during the bench to bedside translation have been explained along with potential avenues to circumvent them. This also opens up new horizons in drug delivery, which could be useful to researchers in the years to come.

Enhanced Doxorubicin Delivery in Folate-Overexpressed Breast Cancer Cells Using Mesoporous Carbon Nanospheres

Nanoparticle-based drug delivery reveals the safety and effectiveness and avoids premature drug release from the nanocarrier. These nanoparticles improve the bioavailability and stability of the drug against chemical and enzymatic degradation and facilitate targeted drug delivery. Herein, targeted folic acid-conjugated oxidized mesoporous carbon nanospheres (Ox-MPCNPs) were successfully fabricated and developed as antitumoral doxorubicin delivery for targeted breast cancer therapy. Fourier transform infrared spectroscopy studies confirmed that the doxorubicin was successfully bound on the Ox-MPCNP through hydrogen bonding and π-π interactions. X-ray diffraction studies showed that the synthesized doxorubicin-loaded Ox-MPCNP is semi-crystalline. The surface morphology of the synthesized doxorubicin-loaded Ox-MPCNP (DOX/Ox-MPCNP-Cys-PAsp-FA) was studied by scanning electron microscopy and high-resolution transmission electron microscopy, which demonstrates a sphere-shaped morphology. The cytotoxic effects of DOX/Ox-MPCNP-Cys-PAsp-FA were studied in MCF-7 breast cancer cells using the CytoTox96 assay kit. The study confirmed the cytotoxic effects of the synthesized nanospheres in vitro. Moreover, DOX/Ox-MPCNP-Cys-PAsp-FA-treated cells displayed efficient cell apoptosis and cell death in flow cytometry analysis. The mitochondrial fragmentation and nucleus damages were further confirmed by fluorescence microscopy. Thus, the approach used to construct the DOX/Ox-MPCNP-Cys-PAsp-FA carrier provides excellent opportunities for the targeted treatment of breast cancer.

Preparation and Properties of Organic-Inorganic Hybrid Antireflection Films Made by a Low-Temperature Process Using Hollow Silica Nanoparticles

Layers made of hollow silica nanoparticles have potential applications as antireflection films with lower refractive index values compared with existing materials such as silica glass (1.50) and magnesium fluoride (1.38). The advantages of such nanoparticles result from interactions between the solid shell, the cavity phase core, and the voids between particles. To obtain practical antireflection films, it is necessary to control the number of layers of these hollow silica nanoparticles and to fill the gaps between particles with a solid. In the present study, antireflection films were prepared by applying a coating of hollow silica nanoparticles dispersed in a UV-curable monomer solution onto plastic substrates. After film formation and exposure to UV light, the voids between the nanoparticles were completely filled with a polymer matrix. Tuning the particle concentration in the coating solution allowed the formation of antireflection films comprising one to three layers of the hollow silica nanoparticles. The reflectance of the films was dependent on the number of layers, and a 100 nm thick film in which two layers of hollow silica nanoparticles were precisely arranged showed the lowest reflectance of 0.92% at 550 nm wavelength, equivalent to a refractive index of 1.23. Because the voids between particles were filled with the polymer, these films resisted contamination during manual handling and so would be expected to maintain low reflectance during practical applications. This work demonstrates that nanosized inorganic-organic hybrid films composed of hollow silica nanoparticles and a UV-curable resin can exhibit optical properties and structural integrity that cannot be achieved by either substance alone.

Renaissance of Stöber method for synthesis of colloidal particles: New developments and opportunities

Colloidal silica particles have received a widespread interest because of their potential applications in adsorption, ceramics, catalysis, drug delivery and more. Among many approaches towards fabrication of these colloidal particles, Stöber, Fink and Bohn (SFB) method, known as Stöber synthesis is an effective sol-gel strategy for production of uniform, monodispersed silica particles with highly tailorable size and surface properties. This review, after a brief introduction showing the importance of colloidal chemistry, is focused on the Stöber synthesis of silica spheres including discussion of the key factors affecting their particle size, porosity and surface properties. Next, further developments of this method are presented toward fabrication of polymer, carbon, and composite spheres.

The Synthesis of Hollow/Porous Cu2O Nanoparticles by Ion-Pairing Behavior Control

Owing to the properties of low density, large surface areas, excellent loading capacity, high permeability, and interstitial hollow spaces, hollow nanostructures have been widely applied in many important research fields, such as catalysis, drug-controlled release, confined synthesis, optics and electronics, and energy storage. This work provided a simple platform for hollow Cu2O nanostructure synthesis based on the surfactant controlling methodology, which is under the supposed mechanism of ion-pairing behavior at the initial nucleation stage. Thus here, we explore our system in two different directions: (1) we get different types of hollow Cu2O nanoparticles by controlling the surfactant concentration during the synthesis step in colloids, which is critical to the novel structure design and potential application in many different areas and (2) we explore the method to Cu2O hollow particle synthesis to test the hypothesis of the ion-pairing behavior during the initial nucleation by tuning the solvent ratio, cation concentration (such as NH4NO3 addition amount difference in the synthetic step), and selective etching. By tuning the synthetic conditions as well as designing control experiments, we hope to provide a solid understanding of the crystal growth mechanism. Our improved understanding in similar systems (both Cu2O and ZnO systems) will make it easier for interpreting nanostructure formation in new discoveries and, more importantly, in rationally designing various complex nanostructures based on a bottom-up strategy.

Rational design of yolk–shell nanostructures for photocatalysis

Yolk–shell structures provide an ideal platform for the rational regulation and effective utilization of charge carriers because of their void space and large surface areas. Furthermore, the efficiency of charge behavior in every step can be further improved by many strategies. This review describes the synthesis of yolk–shell structures and their effect for the enhancement of heterogeneous photocatalysis.

Synthesis and Application of Dendritic Fibrous Nanosilica/Gold Hybrid Nanomaterials

Morphologically unique silica nanoparticles can be used as effective templates to prepare silica-metal hybrid nanomaterials, which are highly applicable in a variety of areas. Mesoporous silica nanoparticles, which have high surface areas and an abundance of pores, can be used to synthesize mesoporous silica core-metal shell nanostructures with catalytically active sites. In this work, dendritic fibrous nanosilica (DFNS) with a high surface area is successfully employed as a template to synthesize DFNS/Au hybrid nanomaterials. Au nanodots are initially synthesized through the selective reduction of Au ions on the surface of the DFNS after surface modification to form DFNS/Au dots. A seed-mediated growth method is used to controllably grow Au nanoparticles on the DFNS/Au dots to generate DFNS core-Au nanoparticles shell nanohybrids (DFNS/Au NPs) and DFNS core-Au layer shell nanohybrids (DFNS/Au layers). The catalytic activities of DFNS/Au NPs and DFNS/Au layers in the 4-nitrophenol reduction reaction are compared.