Types Of Silica Nanoparticles Research Articles

Molecular Dynamics Simulations of the Silica–Cell Membrane Interaction: Insights on Biomineralization and Nanotoxicity

The interaction of silica (SiO2) with biological systems is complex and contradictory. On the one hand, silica is at the basis of several biomineralization processes (e.g., in sponges). On the other hand, silica nanoparticles and dust may lead to silicosis and, at the cellular level, hemolysis. These toxic responses are strongly dependent on the silica polymorph and their root causes are still under debate. Both silica biomineralization and silica-induced nanotoxicity could be related to similar mechanisms of molecular recognition between the cellular membranes and the surface of the SiO2 particles. On the basis of this hypothesis, we employed classical molecular dynamics simulations, coupled to advanced sampling techniques, to achieve an atomistic picture of the interactions between different types of silica nanoparticles and the membrane of erythrocytes. Our predicted free-energy profiles associated with membrane crossing give no evidence for segregation of nanoparticles at the membrane/water interface,...

Mechanistic Modeling of Nanoparticles-Assisted Surfactant Flood

High interfacial tension (IFT) between oil and water brings about high capillarity leading to high residual oil saturation. Surfactants are employed to reduce IFT or modify wettability and mobilize the trapped oil. This paper aims to investigate the interaction of sodium dodecyl sulfate as a surfactant and two types of silica nanoparticles in different particle sizes for the purpose of enhancing oil recovery. Accordingly, the effect of employed nanoparticles on the critical micelle concentration (CMC) of the surfactant was investigated by the use of electrical conductivity measurements. Phase behavior studies were also carried out to examine the solubilizing ability of the surfactant and nanoparticles assembly. Based on the analysis of solubilization curves, an ultra-low IFT chemical formulation for the target reservoir crude oil was identified and the stability of the optimum solutions was examined through visual observation, optical absorption, and zeta potential measurements. The oil recovery experiments were performed in a quarter five-spot transparent pore network model saturated with crude oil to observe the displacement behavior of the injectant and its influence on oil recovery. Phase behavior tests indicated that the silica nanoparticles smaller in size are more effective in terms of IFT reduction since they can achieve ultra-low IFT level, and the conductivity measurements showed they relatively reduce the CMC of the surfactant. The results of stability tests demonstrated the optimum solutions are stable for more than 1 week. The micromodel experiments displayed that oil recovery increased by 4% during nanoparticles-assisted surfactant flood in comparison with surfactant flood.

Morphology and molecular dynamics investigation of low molecular weight PDMS adsorbed onto Stöber, fumed, and sol-gel silica nanoparticles

Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto three types of silica nanoparticles, namely Stöber, fumed-pyrogenic, and silica gel, were studied employing scanning electron microscopy (SEM), isothermal nitrogen adsorption–desorption, calorimetry (DSC) and broadband dielectric spectroscopy (BDS) techniques. The initial Stöber particles (specific surface area SBET ∼240 m2/g) form a quite loose silica network with mainly textural pores of ∼12 nm in size. Fumed silica (SBET ∼260 m2/g) demonstrates denser aggregation and increased textural porosity (∼11 nm), while silica gel (SBET ∼850 m2/g) exhibits tremendous intraparticle porosity (tubular-like pores of ∼6 nm). On adsorption of PDMS (at ∼20 and ∼30 wt%), the glass transition temperature (Tg) decreases as compared to the bulk, while the glass transition step broadens. Results suggest loosened molecular packing of the polymer chains accompanied by a broadening of the range of relaxation times in the composites as compared to the neat polymer. On the other hand, the heat capacity step at glass transition is significantly suppressed in the composites, suggesting the formation of a rigid polymer fraction (RAF) at the interfaces with nanoparticles due to strong physical interaction (hydrogen bonding). RAF increases in the order Stöber < fumed (A300) < silica gel, this increase following that of SBET, in agreement with results in previous work on silica/PDMS systems. Next to the segmental dynamics (α relaxation) of the bulk-like polymer related to the glass transition, BDS allowed the detection of a separate segmental-like relaxation of the polymer in the interfacial silica-PDMS zone. In terms of timescale the interfacial relaxation is almost identical for Stöber and A300, and slightly faster for silica gel. Comparison of the results of the present work with previous results obtained with similar nanocomposites based on low molecular weight PDMS and silica, provides additional support to recently proposed ‘SBET–interfacial dynamics’ and ‘chain packing–polymer dynamics’ correlations.

Poly(carboxybetaine methacrylate)-grafted silica nanoparticle: A novel carrier for enzyme immobilization

Polymer-coated nanoparticles are favorable carriers for enzyme immobilization for their advantages of high specific surface area, small mass transfer resistance and a large number of active groups for covalent bonding of enzymes. Of the various polymers, zwitterionic polymers have been found to work as protein stabilizers. Inspired by the literature outcomes, we have herein developed a novel nanoparticle-based carrier modified by grafting a highly hydrophilic zwitterionic polymer, poly(carboxybetaine methacrylate) (pCBMA), on silica nanoparticles (SNPs), which was denoted as SNPs-pCBMA. For comparison, an uncharged polymer, poly(glycidyl methacrylate) (pGMA), was also grafted onto SNPs to prepare SNPs-pGMA. The two types of polymer-grafted SNPs were extensively characterized and used for the covalent bonding of two enzymes, catalase and lipase (pGMA-CAT, pCBMA-CRL, pGMA-CRL and pCBMA-CRL). The results revealed that both the immobilized enzymes on SNPs-pCBMA exhibited higher thermal and storage stabilities than those on SNPs-pGMA, due to protective effects of the zwitterionic polymer. For example, by incubation at 50 °C for 20 min, the residual activities of pCBMA-CAT and pCBMA-CRL kept 60.5% and 60.3% of their initial activities, respectively, higher than those of pGMA-CAT and pGMA-CRL (55.6% and 48.3%, respectively). The immobilized enzymes on SNPs-pCBMA also exhibited higher stability under neutral and alkaline conditions and good reusability. Taken together, the research proved that pCBMA-grafted materials were promising support for enzyme immobilizations.

Organosilica Nanoparticles and Medical Imaging.

Medical imaging technology using nanoparticles has several advantages from it varies functional properties. As we described previous chapters, mesoporous silica nanoparticles demonstrated great contribution for nanomedicine progress and it has been expected to cause an innovation in medical field. Recently we developed a novel type of silica nanoparticles, organosilica nanoparticles. Organosilica nanoparticles are both structurally and functionally different from common silica nanoparticles by including mesoporous silica nanoparticles. The organosilica nanoparticles are inherent organic-inorganic hybrid nanomaterials. The interior and exterior functionalities of organosilica nanoparticles are effective for their internal and surface functionalization. Medical imaging using organosilica nanoparticles is making a new field of nano-medical imaging. Multifunctionalizations peculiar to organosilica nanoparticles enable to construct novel medical imaging system. In this chapter we will introduce organosilica nanoparticles, and its applications on advanced medical imaging.

Silica-based nanoparticles are efficient delivery systems for temoporfin.

Drug targeting using functionalized nanoparticles to advance their transport to the dedicated site became a new standard in novel anticancer methods Anticancer photodynamic therapy also takes benefit from using nanoparticles by means of increasing targeting efficiency and decreased side effect. With this in mind, the silica-based nanoparticles, as drug delivery systems for the second-generation photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl) chlorin (temoporfin) were developed. In order to determine the stability and therapeutic performance of the selected nanomaterials in physiological fluids, their physicochemical properties (i.e. size, polydispersity, zeta potential) were measured by dynamic light scattering technique and the diameter and the morphology of the individual particles were visualized by a transmission electron microscopy. Their efficacy was compared with commercial temoporfin formulation in terms of in vitro phototoxicity in 4T1 (murine mammary carcinoma) and of in vivo anticancer effect in Nu/Nu mice bearing MDA-MB-231 tumors. The two types of silica nanoparticles, porous and non-porous and with different surface chemical modification, were involved and critically compared within the study. Their efficacy was successfully demonstrated and was shown to be superior in comparison with commercial temoporfin formulation in terms of in vitro phototoxicity and cellular uptake as well as in terms of in vivo anticancer effect on human breast cancer model. Temoporfin-loaded silica nanoparticles also passed through the blood-brain barrier showing potential for the treatment of brain metastases.

A Study on Polyurethane Hybrid Nanocomposite Foams Reinforced with Multiwalled Carbon Nanotubes and Silica Nanoparticles

ABSTRACTMultifunctional polyurethane foams reinforced with multiwalled carbon nanotubes and silica nanoparticles enhanced specific properties. We studied the effects of nanoparticle addition into polyurethane on mechanical properties and thermal stability by means of tensile, Charpy impact, hardness tests, and thermogravimetric analysis. Nanoparticles added to polyurethane are multiwalled carbon nanotubes, two types of silica nanoparticles, and multiwalled carbon nanotube/spherical silica as hybrid filler. Hybrid polyurethane/spherical silica/multiwalled carbon nanotube nanocomposite with the constant overall content of 0.75 wt% showed higher tensile strength, hardness, and thermal stability than either of nanoparticles at this content, which approves a synergistic effect between multiwalled carbon nanotubes and silica nanoparticles.

Fabrication of silica-coated hollow particles by using ultrasonically generated microbubbles

Particles that have a hollow structure have attracted considerable attention owing to their high performance in thermal insulation and soundproofing, as well as various other applications. Makuta et al. previously reported the fabrication of hollow particles with a cyanoacrylate (CA) shell by blowing CA vapor into water in the form of microbubbles under ultrasonic oscillation. In this study, we succeeded in the fabrication of hollow particles coated with silica nanoparticles, by generating CA hollow particles in the silica nanoparticle-dispersed aqueous solution. The applications of silica-coated hollow particles can be extended by adding diverse features to the silica nanoparticles, including electric insulation, corrosion resistance, and heat resistance. In addition, the stability of the dispersion and yield of the silica-coated hollow particles depended on the type of silica nanoparticles and the flow rate of the supplied gas. Moreover, we confirmed that aggregation of the fabricated particles was suppressed by using acid-stabilized silica nanoparticles. In addition, an increase in the flow rate of the supplied gas led to an increase in the number of generated microbubbles, thus enhancing the yield of the fabricated particles.

Functional Group Coverage and Conversion Quantification in Nanostructured Silica by 1H NMR

Silica nanostructured materials are important in many fields, including catalysis, imaging, and drug delivery, mainly due to the versatility of surface functionalization that can bestow a huge variety of chemical and physical properties. With most applications requiring precise control over this surface modification, characterization of surface composition and reactivity have become of extreme importance. We present a novel approach to track silica surface modification and quantify functional group coverage using only solution NMR. We test the method using different types of silica nanoparticles and surface modifications, to show that after dissolving the silica matrix, the 1H NMR spectra can be resolved for every single component of the mixture. By using an internal standard, we are able to quantify the density of ligands and follow their sequential modification. Our work presents a fast, accurate, and straightforward method for surface characterization of silica nanostructures, using widely available NMR spectroscopy and small amounts of sample.

A temperature-controlled method to produce Janus nanoparticles using high internal interface systems: Experimental and theoretical approaches

This work presents a unique method to produce large amounts of very small Janus nanoparticles (<50nm) using Pickering emulsions of paraffin-in-water, known as desymmetrization process in high internal interface systems. Unlike other similar works, applying a thermal shock in cooling stage allowed surfactants to be not used in the process besides stabilizing nanoparticles. This provided better modification efficiency after coverage of solid paraffin droplets with small nanoparticles as well as controlling limited and partial coalescences. Two types of silica nanoparticles with different size (<50nm) were used and (3-aminopropyl)triethoxysilane was also applied in order to modify their exposed surface after preparation of stabilized emulsion. Besides SEM images, some other new experimental/analytical procedures are proposed in order to investigate the presence of nanoparticles on the surface of provided solid paraffin droplets. Produced Janus nanoparticles were characterized using FTIR, TGA and EDX tests in order to confirm the chemical modification. Furthermore, a chloroform/water mixture was used to demonstrate the differences of Janus nanoparticles with similar uniformly modified nanoparticles. The results revealed the amphiphilic properties of Janus nanoparticles which led them to be placed at the interface while uniformly modified particles were placed in chloroform phase.

Toxic and adjuvant effects of silica nanoparticles on ovalbumin-induced allergic airway inflammation in mice.

BackgroundSilica nanoparticles (SNPs) can easily enter in respiratory system via inhalation because of their low molecular weight and ease of dispersion. Toxicity and adverse effects of SNPs vary according to the physical characteristics of the particle.MethodsTo evaluate the toxic and adjuvant effects of 3 types of SNPs in the airway system, six-week-old female BALB/c mice were intranasally administered 3 types of SNPs (spherical [S-SNP], mesoporous [M-SNP], and polyethylene glycol-conjugated [P-SNP]) alone or SNPs/ovalbumin (OVA), three times weekly for 2 weeks. Airway hyper-responsiveness (AHR), bronchoalveolar lavage fluid (BALF), cytokine levels, and histology of the lungs were analyzed.ResultsThe S-SNPs/OVA group and M-SNPs/OVA group showed significant AHR, compared to the control group. Among all SNP-treated groups, the group administered SNPs/OVA showed greater inflammatory cell infiltration in BALF, extensive pathological changes, and higher cytokine levels (IL-5, IL-13, IL-1β, and IFN-γ) than those administered SNPs alone or saline/OVA.ConclusionExposure to SNPs alone and SNPs/OVA induced toxicity in the respiratory system. SNPs alone showed significant toxic effects on the airway system. Meanwhile, SNPs/OVA exerted adjuvant effects to OVA of inducing allergic airway inflammation. In particular, M-SNPs showed the most severe airway inflammation in both direct toxicity and adjuvant effect assays. P-SNPs induced less inflammation than the other types of SNPs in both models.

Mesoporous Silica Materials in Drug Delivery System: pH/Glutathione- Responsive Release of Poorly Water-Soluble Pro-drug Quercetin from Two and Three-dimensional Pore-Structure Nanoparticles

Quercetin (Quer) is one of natural products (pro-drugs), presenting pharmacological properties such as: anti-oxidant, anti-inflammatory and anti-cancer activities. However, poor solubility of the Quer causes its poor bioavailability, and consequently reduces its therapeutic efficiency. To manage this problem, different actions are undertaken, among other drug delivery systems (DDSs) are investigated. The objective of present work was to evaluate potential applications of silica nanoparticles as quercetin nanocarriers and to investigate the influence of pH conditions and glutathione (GSH, as non-redox process) concentrations on quercetin release. Two types of mesoporous silica nanoparticles: MCM-41 (2D arrangement of pores) and KCC-1 (3D arrangement of pores) were synthesized and then functionalized by amino-groups. Immersion-evaporation method was used to load the Quer in nanoparticles. Several analysis techniques were used (e.g. electron microscopy, X-Ray diffraction, Zeta potential, simultaneous thermal analysis-connected to FTIR and many more). Obtained results indicated that both types of silica nanoparticles were successfully loaded with quercetin, and that the Quer present in silica mesopores had a non-crystalline structure. Loading capacity of functionalized MCM-41 was slightly higher than functionalized KCC-1 (29.11 wt% and 26.49 wt%, respectively). This difference could be attributed to the differences in the morphology structures such as surface area and pore volume property. From in vitro release and kinetics studies, the results showed that quercetin release from both materials was pH-GSH-silica type nanoparticles-dependent. In summary, it can be stated that pH/GSH-stimuli release of quercetin was achieved using MCM-41 and KCC-1 amine-functionalized mesoporous silica nanoparticles as a drug carriers. Therefore both investigated nanomaterials could be beneficial for long-term release

Effect of Silica Surface Properties on the Formation of Multilayer or Submonolayer Protein Hard Corona: Albumin Adsorption on Pyrolytic and Colloidal SiO2 Nanoparticles

The adsorption of bovine serum albumin (BSA) on two types of silica nanoparticles (NPs), one pyrolytic (P-SiO2; namely, AOX50 by Evonik) and the other colloidal (lab-made by using inverse micelles microemulsion, M-SiO2), is studied. Both materials are characterized in terms of size of primary particles (by transmission electron microscopy); amounts (by thermogravimetry) and distribution of silanols (infrared spectroscopy in controlled atmosphere, augmented by H/D isotopic exchange and reaction with VOCl3, to distinguish silanols actually located at the surface of nanoparticles); water contact angle; ζ-potential; and dispersion state in water, PBS buffer, and BSA solutions in PBS (by dynamic light scattering, DLS). Proteins are found to act as dispersing agent toward the large aggregates formed by both types of NPs in PBS buffer, although monodispersion was not attained in the conditions investigated. The problem of the determination of the silica surface actually available in NP agglomerates for protein a...

Acute exposure to silica nanoparticles aggravate airway inflammation: different effects according to surface characteristics.

Silica nanoparticles (SNPs) are widely used in many scientific and industrial fields despite the lack of proper evaluation of their potential toxicity. This study examined the effects of acute exposure to SNPs, either alone or in conjunction with ovalbumin (OVA), by studying the respiratory systems in exposed mouse models. Three types of SNPs were used: spherical SNPs (S-SNPs), mesoporous SNPs (M-SNPs), and PEGylated SNPs (P-SNPs). In the acute SNP exposure model performed, 6-week-old BALB/c female mice were intranasally inoculated with SNPs for 3 consecutive days. In the OVA/SNPs asthma model, the mice were sensitized two times via the peritoneal route with OVA. Additionally, the mice endured OVA with or without SNP challenges intranasally. Acute SNP exposure induced significant airway inflammation and airway hyper-responsiveness, particularly in the S-SNP group. In OVA/SNPs asthma models, OVA with SNP-treated group showed significant airway inflammation, more than those treated with only OVA and without SNPs. In these models, the P-SNP group induced lower levels of inflammation on airways than both the S-SNP or M-SNP groups. Interleukin (IL)-5, IL-13, IL-1β and interferon-γ levels correlated with airway inflammation in the tested models, without statistical significance. In the mouse models studied, increased airway inflammation was associated with acute SNPs exposure, whether exposed solely to SNPs or SNPs in conjunction with OVA. P-SNPs appear to be relatively safer for clinical use than S-SNPs and M-SNPs, as determined by lower observed toxicity and airway system inflammation.

Effect of the functionalization of silica nanoparticles as a reinforcing agent on dental composite materials

The present study evaluated the effect of silica nanoparticle aggregation state on the reflectance and crystallinity of dental composite materials. Two types of silica nanoparticles (ca. 10 nm): Aerosil 200 non-funcionalized and Aerosil DT4 funcionalized with 3-methacryloxypropyltrimethoxysilane. Nanoparticles were dispersed in a monomer mix composed by Urethane Dimethacrylate (UDMA) and Ethylene glycol Dimethacrylate (EGDMA) in a 80:20 mass ratio. The particle size of silica and their aggregation state were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing that the Aerosil DT4O has dense aggregates with sizes higher than 1 µm; on the other hand the Aerosil 200O showed a particle gel-like structure. The functionalization degree of the Aerosil DT4O was determined by thermogravimetric analysis (TGA), obtaining a value of 7.57% w/w. The composite materials were evaluated by Differencial Scanning Calorimerty (DSC) to determine their crystallinity. The composite material reinforced by Aerosil DT4 showed lower cristallinity than the system with Aerosil 200 due to higher interaction of the polymeric matrix with the funcionalized surface of the Aerosil DT4. The effect of the aggregation state of silica nanoparticles on the optical properties of the composite mateial was determined by reflectance analysis. The Aerosil 200 sample showed a lower degree of nanoparticle aggregation and higher reflectance than the system with Aerosil DT4. The functionalization of the Aerosil DT4 induced nanoparticle aggregation diminishing the optical properties of the composite material.

Effect of particle hydrophobicity on CO2 foam generation and foam flow behavior in porous media

Studies of CO2 foam stabilized with silica nanoparticles at reservoir conditions were carried out for CO2 foam enhanced oil recovery (EOR) application. In the study described in this paper, three types of silica nanoparticles with varied wettability were employed to study the effects of particle hydrophobicity on CO2 foam generation at reservoir conditions. The results showed that nanoparticle surface hydrophobicity played an important role in CO2 foam generation. More CO2 foam was generated as the particle surface changed from strongly hydrophilic to somewhat hydrophobic. The bubble size of the CO2 foam decreased noticeably as the particle surface became more hydrophobic. Nanosilica particle-stabilized CO2 foam demonstrated a significant effect on the reduction of the CO2 mobility at a phase ratio between 2 and 11. The particle-stabilized CO2 foam also improved the apparent viscosity of the CO2 as the mixture flowed through a capillary tube.

Gellified ionic liquid based composite electrolytes—Influence of different silica as filler materials on electrical and mechanical properties of the electrolyte

The electrical and mechanical properties of N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfon)imide (BMP-TFSI) lithium electrolyte with 15wt.% LiTFSI as conducting salt are reported. The conductivity and the viscosity for the neat electrolyte as well as for IL/solid dispersions with different types of silica nanoparticles (commercially available silica nanoparticles, mesoporous KIT-6 silica and surface-modified silica nanoparticles) as second phase are reported. Systematic conductivity and viscosity data are presented, and their correlation suggests that the partial conductivity of at least one ion is enhanced. It is concluded that an interface effect is indeed responsible for this effect.

Influence of various types of silica nanoparticles on permeation properties of polyurethane/silica mixed matrix membranes

The transport performances of carbon dioxide (CO2) and methane (CH4) gases were investigated in polyesterurethane mixed matrix membranes (MMMs), in separate tests, containing different fumed silica nanoparticles. Non-modified and commercially-modified silica (with octylsilane and polydimethylsiloxane) were used as fillers. The structural characteristics of the membranes were studied by scanning electron microscopy, infrared spectroscopy, X-ray diffraction and differential scanning calorimetry to confirm some interactions between the PU and nanoparticles and the changes induced in PU microphase in the presence of silica. Surface treatment of silica filler with long hydrophobic chains reduced the aggregation of nanoparticles and improved dispersion in MMMs. Addition of silica nanoparticles into PU matrix increased both separation factor and CO2 permeation in the membranes. The fumed silica disrupted chain packing and increased dynamic free volume to improve CO2 permeation regardless of silica type. The results revealed that among silica nanoparticles, the unmodified particles with OH groups on their surface showed better performance for CO2/CH4 separation. In our current research, a new model for prediction of gas permeation through PU/silica membranes was proposed considering the presence of filler aggregation in the matrix as well as free volume at the interface layer.

Biomedical applications of organosilica nanoparticles toward theranostics

AbstractNanoparticles for biomedical applications have several advantages as multifunctional agents. Among various types of nanoparticles for biomedical applications, silica nanoparticles have characteristic positioning due to their inherent property. The recent development of silica nanoparticles is creating a new trend in nanomedicine. A novel type of silica nanoparticle, organosilica nanoparticle, is both structurally and functionally different from the common (inorgano)silica nanoparticle. The organosilica nanoparticles are inherent organic-inorganic hybrid nanomaterials. The interior and exterior functionalities of organosilica nanoparticles are useful for their multifunctionalization. Biomedical applications of organosilica nanoparticles are leading to a wide range of nanomedical fields such as basic biomedical investigations and clinical applications. Multifunctionalizations peculiar to organosilica nanoparticles enable the creation of novel imaging systems and therapeutic applications. In this review, I will introduce differences between (inorgano)silica nanoparticles and organosilica nanoparticles, and then focus on biomedical applications of organosilica nanoparticles toward theranostics.

Influence of various loadings of hydrophilic or hydrophobic silica nanoparticles on water uptake and porosity of a polyurethane coating

AbstractIn this paper, water uptake, porosity and corrosion behaviours of two‐pack polyurethane coatings separately loaded with two types of silica nanoparticles (i.e. hydrophilic and hydrophobic silica nanoparticles) are presented. Water uptake of such coatings was measured by the aid of electrochemical impedance spectroscopy whereas porosity of the coatings was determined according to the ASTM D 6583 standard. Transmission electron microscopy and Fourier transform infrared spectroscopy were also utilised to examine morphology and chemical structure of the nanoparticles filled coatings. These techniques show that the hydrophobic SiO2 nanoparticles could be easily dispersed throughout the polyurethane matrix while negatively influence the curing process of the coatings. The results reveal that the incorporation of both hydrophilic and hydrophobic silica nanoparticles into the polyurethane matrix, generally, reduces the percent porosity of the resultant coatings. However, obtained results show that the type and content of silica nanoparticles influence the capacitance and therefore water uptake of the coatings to various extents.