Silica-based Nanostructures Research Articles

Engineered mesoporous silica-based nanoparticles as smart chemotherapy nanodevice for bortezomib administration

Engineered mesoporous silica-based nanostructures for selective and pH-sensitive release of the anticancer drug bortezomib. The developed “smart chemotherapy” showed higher efficacy in vivo compared to traditional free bortezomib administration.

Silica- and Silicon-Based Nanostructures

As depicted in Figure 1, studies on silicon and silica-based nanostructures first appeared in the early 1990s, and their numbers grew until the mid-2010s [...]

Optimized antibody immobilization on natural silica-based nanostructures for the selective detection of E. coli.

This study reports for the first time the surface modification of fluorescent nanoparticles derived from geothermal silica precipitate with Escherichia coli (E. coli) antibody. The immobilization of biomolecules on the inorganic surface has been carried out using two different pathways, namely the silanization and hydrosilylation reactions. The former applied (3-aminopropyl)triethoxysilane (APTES) as the crosslinker, while the latter used N-hydroxysuccinimide coupled with N-ethyl-N′-(3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC/NHS). Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), and fluorescence spectroscopy were used to confirm the chemical, physical, and optical properties of the surface-modified fluorescent silica nanoparticles (FSNPs). Based on the results of the FTIR, fluorescence spectroscopy and stability tests, the modified FSNPs with EDC/NHS with a ratio of 4 : 1 were proven to provide the optimum results for further conjugation with antibodies, affording the FSNP-Ab2 sample. The FSNP-Ab2 sample was further tested as a nanoplatform for the fluorescence-quenching detection of E. coli, which provided a linear range of 102 to 107 CFU mL−1 for E. coli with a limit of detection (LoD) of 1.6 × 102 CFU mL−1. The selectivity of the biosensor was observed to be excellent for E. coli compared to that for P. aeruginosa and S. typhimurium, with reductions in the maximum fluorescence intensity at 588 nm of 89.22%, 26.23%, and 54.06%, respectively. The inorganic nanostructure–biomolecule conjugation with optimized coupling agents showed promising analytical performance as a selective nanoplatform for detecting E. coli bacteria.

Characterization and Cytotoxicity Comparison of Silver- and Silica-Based Nanostructures.

Core-shell structures are the most common type of composite material nanostructures due to their multifunctional properties. Silver nanoparticles show broad antimicrobial activity, but the safety of their utilization still remains an issue to tackle. In many applications, the silver core is coated with inorganic shell to reduce the metal toxicity. This article presents the synthesis of various materials based on silver and silica nanoparticles, including SiO2@Ag, Ag@SiO2, and sandwich nanostructures—Ag@SiO2@Ag—and the morphology of these nanomaterials based on transmission electron microscopy (TEM), UV-Vis spectroscopy, and FT-IR spectroscopy. Moreover, we conducted the angle measurements due to the strong relationship between the level of surface wettability and cell adhesion efficiency. The main aim of the study was to determine the cytotoxicity of the obtained materials against two types of human skin cells—keratinocytes (HaCaT) and fibroblasts (HDF). We found that among all the obtained structures, SiO2@Ag and Ag@SiO2 showed the lowest cell toxicity and very high half-maximal inhibitory concentration. Moreover, the measurements of the contact angle showed that Ag@SiO2 nanostructures were different from other materials due to their superhydrophilic nature. The novel approach presented here shows the promise of implementing core-shell type nanomaterials in skin-applied cosmetic or medical products.

Effect of water nanoconfinement on the dynamic properties of paramagnetic colloidal complexes.

The anomalous behavior of confined water at the nanoscale has remarkable implications in a number of nanotechnological applications. In this work, we analyze the effect of water self-diffusion on the dynamic properties of a solvated gadolinium-based paramagnetic complex, typically used for contrast enhancement in magnetic resonance imaging. In particular, we examine the effect of silica-based nanostructures on water behavior in the proximity of the paramagnetic complex via atomistic simulations, and interpret the resulting tumbling dynamics in the light of the local solvent modification based on the Lipari-Szabo formalism and of the fractional Stokes-Einstein relation. It is found that the local water confinement induces an increased "stiffness" on the outer sphere of the paramagnetic complex, which eventually reduces its tumbling properties. These model predictions are found to explain well the relaxivity enhancement observed experimentally by confining paramagnetic complexes into porous nanoconstructs, and thus offer mechanistic guidelines to design improved contrast agents for imaging applications.

Biomimetic Colorants and Coatings Designed with Cephalopod-Inspired Nanocomposites.

Brilliant and dynamic colors in nature have stimulated the design of dyes and pigments with broad applications ranging from electronic displays to apparel. Inspired by the nanostructured pigment granules present in cephalopod chromatophore organs, we describe the design and fabrication of biohybrid colorants containing the cephalopod-specific pigment, xanthommatin (Xa), encased within silica-based nanostructures. We employed a biomimetic approach to encapsulate Xa with amine-terminated polyamidoamine (PAMAM) dendrimer templates, which helped stabilize the pigment during encapsulation. Depending on the concentration of Xa used in the reaction, the resultant biohybrid nanomaterials generated a range of neutral colors of differing hues. When applied as coatings, these colorants can be triggered to change color from yellow/gold to red in the presence of a chemical reducing agent, as we leverage the natural redox-dependent color change of Xa. Altogether, these capabilities demonstrated the ability to process biochromes like Xa as nanomaterials that can be applied as coatings with a tunable and dynamic range.

Recent advances on silica-based nanostructures in photocatalysis

Development of highly efficient photocatalysts has emerged as a research hotspot because of their crucial role in affecting the conversion efficiency of solar energy for applications in resource exploitation and environmental purification. The photocatalytic performance of the photocatalysts basically depends on the behaviors of light absorption, charge generation and separation, surface property and structural stability. Owing to its unique advantages (high surface area, tunable porosity, modifiable surface), porous silica provides an interesting platform to construct well-defined nanostructures such as core-shell, yolk-shell and other specific structures which effectively improved one or more of the above behaviors for photocatalysis. Typically, the structure with hollow morphology favors the light scattering and enlargement of surface area, while coating or binding with silica can modify the surface property of a photocatalyst to enhance the surface adsorption of reactants and physicochemical stability of catalysts. This review discusses the recent advances in the design, synthesis, formation mechanism of well-defined silica-based nanostructures, and the achievements of desired physicochemical properties for regulating the photocatalytic performance.

Recent advances in the synthesis and applications of anisotropic carbon and silica-based nanoparticles

Colloidal nanoparticles with anisotropic architectures have attracted a variety of interest and attention due to different physical and chemical properties compared with the isotropic counterparts, making them promising candidates in many fundamental studies and practical applications. Particularly, carbon and silica-based anisotropic nanoparticles can be one stand out by combing both intrinsic merits of carbons and silica, such as structural stability, biocompatibility, large surface area, and ease of functionalization with the anisotropic structural complexity. In this review, we aim to provide an updated summary of the research related to the anisotropic carbon and silica-based nanostructures, covering both their synthesis and applications.

Luminescent Silica-Based Nanostructures from in Vivo Iridium-Doped Diatoms Microalgae

A novel biotechnological approach to the preparation of Ir-doped luminescent silica-based nanostructures is proposed availing use of diatoms microalgae which generate highly nanostructured biosilica shells (frustules) by in vivo biomineralization of orthosilicic acid. After the in vivo incorporation of a phosphorescent organometallic complex (Ir-1) in Thalassiosira weissflogii diatom frustules (DFs), bulk functionalized phosphorescent silica-based nanostructures are obtained by isolation and proper ultrafine processing of Ir-1-doped DFs. High-resolution characterization reveals the presence of phosphorescent hybrid organic/inorganic clusters composed of biogenic silica NPs intimately trapped within the diatom organic residual matter. The biofactory strategy investigated herein can be a sustainable, cost-effective, and scalable route to transition metal-doped silica nanomaterials and can pave the way to a great variety of heavy-metal and rare-earth metal doped silica nanostructures, whose applications rang...

Chitosan Composites Synthesized Using Acetic Acid and Tetraethylorthosilicate Respond Differently to Methylene Blue Adsorption.

The sol-gel and cross-linking processes have been used by researchers to synthesize silica-based nanostructures and optimize their size and morphology by changing either the material or the synthesis conditions. However, the influence of the silica nanostructures on the overall physicochemical and mechanistic properties of organic biopolymers such as chitosan has received limited attention. The present study used a one-step synthetic method to obtain chitosan composites to monitor the uptake and release of a basic cationic dye (methylene blue) at two different pH values. Firstly, the composites were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) to ascertain their chemical identity. Adsorption studies were conducted using methylene blue and these studies revealed that Acetic Acid-Chitosan (AA-CHI), Tetraethylorthosilicate-Chitosan (TEOS-CHI), Acetic Acid-Tetraethylorthosilicate-Chitosan (AA-TEOS-CHI), and Acetic Acid-Chitosan-Tetraethylorthosilicate (AA-CHI-TEOS) had comparatively lower percentage adsorbances in acidic media after 40 h, with AA-CHI adsorbing most of the methylene blue dye. In contrast, these materials recorded higher percentage adsorbances of methylene blue in the basic media. The release profiles of these composites were fitted with an exponential model. The R-squared values obtained indicated that the AA-CHI at pH ~ 2.6 and AA-TEOS-CHI at pH ~ 7.2 of methylene blue had steady and consistent release profiles. The release mechanisms were analyzed using Korsmeyer-Peppas and Hixson-Crowell models. It was deduced that the release profiles of the majority of the synthesized chitosan beads were influenced by the conformational or surface area changes of the methylene blue. This was justified by the higher correlation coefficient or Pearson’s R values (R ≥ 0.5) computed from the Hixson-Crowell model. The results from this study showed that two of the novel materials comprising acetic acid-chitosan and a combination of equimolar ratios of acetic acid-TEOS-chitosan could be useful pH-sensitive probes for various biomedical applications, whereas the other materials involving the two-step synthesis could be found useful in environmental remediation of toxic materials.

Effects of silica-based nanostructures with raspberry-like morphology and surfactant on the interfacial behavior of light, medium, and heavy crude oils at oil-aqueous interfaces

Any efficient exploitation of new petroleum reservoirs necessitates developing methods to mobilize the crude oils from such reservoirs. Here silicon dioxide nanoparticles (SiO2 NPs) were used to improve the efficiency of the chemical-enhanced oil recovery process that uses surfactant flooding. Specifically, SiO2 NPs (i.e., 0, 0.001, 0.005, 0.01, 0.05, and 0.1 wt%) and Tween®20, a nonionic surfactant, at 0, 0.5, and 2 critical micelle concentration (CMC) were varied to determine their effect on the stability of nanofluids and the interfacial tension (IFT) at the oil–aqueous interface for 5 wt% brine-surfactant-SiO2 nanofluid-oil systems for West Texas Intermediate light crude oil, Prudhoe Bay medium crude oil, and Lloydminster heavy crude oil. Our study demonstrates that SiO2 NPs may either decrease, increase the IFT of the brine-surfactant-oil systems, or exhibit no effects at all. For the brine-surfactant-oil systems, the constituents of the oil and aqueous substances affected the IFT behavior, with the nanoparticles causing a contrast in IFT trends according to the type of crude oil. For the light oil system (0.5 and 2 CMC Tween®20), the IFT increased as a function of SiO2 NP concentration, while a threshold concentration of SiO2 NPs was observed for the medium (0.5 and 2 CMC Tween®20) and heavy (2 CMC Tween®20) oil systems in terms of IFT trends. Concentrations below the SiO2 NP threshold concentration resulted in a decrease in IFT, and concentrations above this threshold resulted in an increase in IFT. The IFT decreased until the NP concentration reached a threshold concentration where synergetic effects between nonionic surfactants and SiO2 NPs are the opposite and result in antagonistic effects. Adsorption of both SiO2 NPs and surfactants at an interface caused a synergistic effect and an increased reduction in IFT. The effectiveness of the brine-surfactant-SiO2 nanofluids in decreasing the IFT between the oil-aqueous phase for the three tested crude oils were ranked as follows: (1) Prudhoe Bay > (2) Lloydminster > and (3) West Texas Intermediate. The level of asphaltenes and resins in these crude oil samples reflected these rankings. A decrease in the IFT also indicated the potential of the SiO2 NPs to decrease capillary pressure and induce the movement and recovery of oil in original water-wet reservoirs. Conversely, an increase in IFT indicated the potential of SiO2 NPs to increase capillary pressure and oil recovery in reservoirs subject to wettability reversal under water-wet conditions. Raspberry-like morphology particles were discovered in 5 wt% brine-surfactant-SiO2 nanofluid-oil systems. The development of raspberry-like particles material with high surface area, high salt stability, and high capability of interfaces alteration and therefore wettability changes offers a wide range of applications in the fields of applied nanoscience, environmental engineering, and petroleum engineering.

Synthesis, functionalization, and applications of morphology-controllable silica-based nanostructures: A review

Abstract Morphology-controllable silica-based nanostructures (MC SiO 2 Ns) have been comprehensively studied because of their potential practical applications in various fields, such as biological chemistry. The superior properties of these nanostructures, including low density, biocompatibility, thermal stability, and high mechanical strength, have been the focus of research to improve their current performance. In this review, experimental parameters, morphology, and formation mechanism of MC SiO 2 Ns (including vesicle-like mesoporous silica, rod-like mesoporous silica, and silica mesoporous nanospheres) are discussed. Moreover, current progress in functionalization and performance improvement of MC SiO 2 Ns is presented. Applications of MC SiO 2 Ns in immobilization techniques, biological catalysis, and drug delivery are also provided.

Smart Biodecorated Hybrid Nanoparticles

The preparation and decoration of smart composite nanoparticles have been reported. The noble metal nanomaterials, quatum dots, silica-based nanostructures and their nanoconjugates possess physical and chemical properties that strongly deviated from those typical for bulk materials. The structure of composits consists of a core and is usually coated with a shell. The shell acts as an external envelop which enhances the colloidal stability of nanoconjugates and photoluminescence properties of the QDs and renders protection to the core of the nanocrystal from photo-initiated degradation. The preparation and modification of the smart nanostructures are described. Biodecorated hybrid nanostructures with different functional ligands used for various bioanalytical applications have been also reported. The composite nanoparticles coated by organic shells with functional groups were considered to govern the covalent immobilization of biomolecules. The hybrid nano(bio)materials namely silica- and noble metal- based nanomaterials have recently been explored and are used for imaging and therapeutic applications. The enhanced cellular drug delivery to cancer cell lines via nanoconjugates revealed that PEG-covered gold nanoparticles are an effective tool for transporting and delivering platinum-bassed drugs. Biodecorated nanoparticles provide opportunities for designing various types of therapeutics with novel properties that are not possible to obtain with traditional therapeutics. Keywords: Composite and hybrid nanoparticles, biomolecules, biodecoration, application, cancer treatment.

Role of Host–Guest Interactions in Tuning the Optical Properties of Coumarin Derivatives Incorporated in MCM-41: A TD-DFT Investigation

The encapsulation of organic dye molecules in silica-based nanostructures leads to composite materials with novel optical properties and a wide range of applications in the field of nanotechnology. The design of new dye-doped silica-based devices requires a deep understanding of how host–guest interactions affect the optical properties and stability of the dye/silica assembly. In this work, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the effect of the host–guest interactions on the structural, optical, and electronic properties of two 7-aminocoumarin dyes (labeled C339 and C340) incorporated into MCM-41. Our calculations show that the interaction of the carbonyl groups of the coumarin molecules with the silanol groups on the silica surface is responsible for the dye stabilization and is strengthened upon photoexcitation. As a result, the computed absorption and emission spectra of the incorporated dyes are red-shifted compared to those in ...

A new high-throughput method utilizing porous silica-based nano-composites for the determination of partition coefficients of drug candidates

We show that highly porous silica-based nanoparticles prepared via micro-emulsion and sol-gel techniques are stable colloids in aqueous solution. By incorporating a magnetic core into the porous silica nano-composite, it is found that the material can be rapidly separated (precipitated) upon exposure to an external magnetic field. Alternatively, the porous silica nanoparticles without magnetic cores can be equally separated from solution by applying a high-speed centrifugation. Using these silica-based nanostructures a new high-throughput method for the determination of partition coefficient for water/n-octanol is hereby described. First, a tiny quantity of n-octanol phase is pre-absorbed in the porous silica nano-composite colloids, which allows an establishment of interface at nano-scale between the adsorbed n-octanol with the bulk aqueous phase. Organic compounds added to the mixture can therefore undergo a rapid partition between the two phases. The concentration of drug compound in the supernatant in a small vial can be determined by UV-visible absorption spectroscopy. With the adaptation of a robotic liquid handler, a high-throughput technology for the determination of partition coefficients of drug candidates can be employed for drug screening in the industry based on these nano-separation skills. The experimental results clearly suggest that this new method can provide partition coefficient values of potential drug candidates comparable to the conventional shake-flask method but requires much shorter analytical time and lesser quantity of chemicals.

Catalytically active self-assembled silica-based nanostructures containing supported nanoparticles

Self-assembled tubular silica-based nanostructures can be prepared using a simple, low-energy intensive and benign protocol under mild conditions (<100 °C) using microwave irradiation and conventional heating. These nanotubes were found to contain metal nanoparticles that are catalytically active in the microwave-assisted homocoupling of terminal alkynes.