Nanostructured Silica Particles Research Articles

Enhancing Antimicrobial Efficacy and Synergistic Effects of Nano-Silica-Based Combinations With Doxycycline, Metronidazole, and Ciprofloxacin Against Enterococcus faecalis Biofilms.

Enterococcus faecalisbiofilm formation within root canals poses a challenging problem in endodontics, often leading to treatment failure. To combat this issue, nanotechnology offers a promising avenue for enhancing antimicrobial efficacy. This study explores the potential synergistic effects of combining nanoscale silica particles with conventional antibiotics, including doxycycline, metronidazole, and ciprofloxacin, against E. faecalis biofilms. The unique characteristics of silica nanoparticles, such as their increased reactivity and ability to be functionalized with other compounds, make them ideal candidates for augmenting antibiotic efficacy. This research investigates the antimicrobial properties of these silica-based combinations and their potential to eliminate or inhibit E. faecalis biofilms more effectively than conventional treatments. Methodology: The methods involved the preparation of nanostructured silica particles and their combination with doxycycline, Flagyl, and ciprofloxacin at subinhibitory concentrations. These combinations were then tested against E. faecalis biofilms using the agar well diffusion technique. Preliminary results suggested that the synergistic interactions between silica nanoparticles and antibiotics can significantly enhance antimicrobial efficacy. The combined treatment exhibited superior inhibitory effects on E. faecalis compared to antibiotics or silica nanoparticles alone (P< 0.05). Conclusions: This study sheds light on the potential of nanoscale silica-based combinations to address the challenges posed by E. faecalis biofilms in endodontics. Understanding the mechanisms of synergy between nanoparticles and antibiotics can pave the way for the development of more effective and targeted strategies for root canal disinfection, ultimately improving the success rates of endodontic treatments.

Synthesis of nanostructured silica particles for controlled release of ascorbic acid: Microstructure features and In Vitro scratch wound assay.

To date, the long term stability of ascorbic acid (AA) under physiological conditions represents a major issue for wound healing and tissue regeneration applications. In this study, ascorbylphosphate (AP) was loaded into silica nanoparticles (SiNPs) through a simple one-step procedure, in which sphericalshaped porous SiNPs were obtained via hydrolysis/condensation of tetraethylorthosilicate (TEOS) in the presence of bicarbonate salt and ammonia. The as-prepared SiNPs were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier Transformer Infrared Spectrophotometer (FTIR). Incorporation of bicarbonate salt resulted in the formation of spherical SiNPs with an average diameter of 460±89nm, while further increase of bicarbonate salt led to the formation of silica sheet-like structures.The AP-loaded SiNPs exhibited high loading efficiency from 92.3- 81.5%, according to AP content and sustained release over 3 days. According to cell viability assay, the obtained AP-enriched SiNPS showed no toxicity and supportive effect to the proliferation of human skin fibroblast cells (HSF) at a concentration less than 200μg/mL. Moreover, it was observed that the wound closure percentage (%) after 24h was also shown to increase to 74.1±3.1% for 20AP-loaded SiNPs compared to control samples (50.1±1.8%). The obtained results clearly demonstrated that the developed SiNPs formulation exhibits optimal microstructure features to maintain a sustained release of AA at wound bed for the healing of skin tissue, including acute and chronic wounds. This article is protected by copyright. All rights reserved.

Thermodynamic Picture of Phase Segregation during the Formation of Bicontinuous Concentric Lamellar (bcl) Silica.

The thermodynamic picture describing the formation mechanism of bicontinuous concentric lamellar (bcl) nanostructured silica particles, bcl silica, was investigated thoroughly. A series of classical kinetics of bcl silica by varying the synthesis time were employed to observe the morphological evolution of bcl silica. The formation mechanism of bcl silica is proposed as the hydrolysis and condensation reactions in the reverse micelle, followed by the phase segregation process. The images of the whole part and the cross-section of bcl silica reveal that bcl silica can be obtained just 30 min after the synthesis starts. The particle morphology evolves from bicontinuous lamellar (bl) morphology, with the absence of the dense part in the center of the particle, to bicontinuous concentric lamellar (bcl) morphology. The theoretical part of this study is focused on the phase segregation process of the mixture. This process is divided thermodynamically into several reversible processes based on the reduced Helmholtz free energy state function. The type of the lamellar orientation (i.e., parallel or perpendicular orientation) changed as the stacked lamellae changed in thickness and was followed by the decrease in the free energy. It was merely shown that the segregation of the thin slab of the lamellar polysiloxane stack favors the perpendicular orientation. In contrast, the thick slab of the lamellar polysiloxane stack yields a complex lamellar structure consisting of perpendicular and parallel orientations. A lamellar polymer confined between two planar substrates can experience a topological transformation into a sphere due to an unfavorable environment, i.e., high surface tension. After the topological transformation, lamellae with a perpendicular orientation form bicontinuous lamellae, whereas the complex lamellar structure transforms into a bicontinuous concentric lamellar morphology.

Morphological Effects of Various Silica Nanostructures on the Mechanical Properties of Printed Parts in Digital Light Projection 3D Printing

Nanostructured silica particles are common additives in polymer-based coating applications and therefore of great interest to obtain better properties of light-curable three-dimensional (3D) printe...

Textural control of bicontinuous concentric lamellar nanostructured mesoporous silica via low-pressure solvothermal method

KCC-1 with bicontinuous concentric lamellar (bcl) morphology provides plenty of functional characteristics, such as open channel structure, excellent accessibility, and large surface area. KCC-1 is commonly synthesized via the less favorable high-pressure solvothermal method due to the upscaling difficulties. This paper reports a simple process for producing the bcl nanostructured silica particles via a lower-pressure solvothermal route in a PFA bottle. This work has demonstrated the textural properties, covering particle size, particle morphology, and pore characteristics of bcl nanostructured silica, which can be effectively controlled by varying the surfactant-to-silica-precursor and water-to-oil molar ratios. The average particle size of bcl nanostructured silica can be adjusted from 303 to 971 nm, which can be controlled by the varied molar ratios of CTAB/TEOS 0.10–0.65 and Water/Toluene 2.17–10.87. The optimal molar ratio of CTAB/TEOS was 0.40, and the optimal molar ratio of Water/Toluene was 6.04. The sample synthesized under optimal conditions exhibits well-defined morphology and uniform bcl size. The sample synthesized under optimal condition provides a BET surface area of 782 m2/g with pore volume and pore size up to 1.12 cm3/g and 5.1 nm, respectively.

Nanostructured silica particles from Cymbopogon flexuosus (Nees ex Steud.): extraction, characterization and study of their blend with osteoporotic drugs

Cymbopogon flexuosus (lemongrass) is one of the potential herbaceous sources for the extraction of silica. Silica plays a vital role in formation of bone and its maintenance by improving the quality of the bone matrix and facilitating bone mineralization. This work presents the extraction of silica nanoparticles from different parts of lemongrass such as root, stem and leaf. IR spectra of all the three extracts confirmed the presence of siloxane and silanol linkage. The SEM analysis revealed the SiNPs from root, stem and leaves to be aggregates of tubular, fibrous and spherical structures, respectively. Significant differences were observed in elemental composition of SiNPs as determined by EDAX. Optimization of the acid leaching process further enhanced the yield by around 30% from leaves. EDAX revealed significant differences in the elemental composition. The DLS histogram showed a size distribution of 62.4 nm validating Zetasizer evaluation having PdI of 0.127. The work also reports the screening of drugs through in silico approach wherein the drug risedronate showed ideal parameters satisfying the Lipinski’s rule of 5. Further, the cytotoxicity of SiNPs and SiNPs with risedronate (drug) was tested on HUVEC and Saos-2 cell lines. The SiNPs showed lesser IC50 value in comparison with risedronate and SiNPs with risedronate tested on both the cell lines. LDH assay elaborated prominent cell leakage by risedronate-anchored SiNPs which is found significant in comparison with bare SiNPs. Treatment of the osteoporotic cells with risedronate/silica blend (1:1000) revealed efficient deposition of calcium and drug in the cells as determined by microscopic observations. Drug release studies of SiNPs with risedronate were performed. FTIR indicated the presence of siloxane (Si–O–Si) and silanol (Si–OH) functional groups. In vitro study of different ratios of risedronate with silica on Saos-2 cell lines was performed to determine the mineralization potential of the combinatorial drug. It was found that the cells incubated with 0.6 mg/ml and 0.8 mg/ml of risedronate with silica showed efficient deposition of calcium inside the cells. The wild variety of Cymbopogon flexuosus could be a potential source for the extraction of SiNPs, which finds much use in biomedical applications.

Hydrophilic-Oleophobic Membranes Based on Hydrolysis Products of Methoxytrimethylsilane with Additions of Silica Particles

The authors have shown the possibility of obtaining hydrophilic-oleophobic membranes through the application of an oleophobizing compound to a membrane base presented by meshes from stainless steels 100, 200, and 400. The oleophobizing compound is methoxytrimethylsilane from whose hydrolysis oleophobic methyl groups and hydrophilic silanol ones develop which form the type of wettability of a membrane. It has been shown that adding nanostructured silica particles creates surface roughness with an enormous number of pores and channels, which considerably enhances the oleophobicity of synthesized membranes. The resulting membranes exhibit high oleophobicity to organic liquids, letting water pass through their structure. This is promising for their use in the sphere of low-cost gravity separation of water and organic liquids.

Expanding the Horizon of Mechanochromic Detection by Luminescent Shear Stress Sensor Supraparticles

AbstractNovel sensor particles have been developed that expand the variety of today's mechanochromic systems. The developed supraparticles consist of several different components to enable the sensor function. First, a luminescence‐quenching core material is coated with silica nanoparticles. Second, this structure is surrounded by raspberry‐like nanostructured silica particles, which host luminophore moieties. Upon shear stress, components spatially separated in the original supraparticles, namely quencher and luminophore components, come into contact. This causes an irreversible quenching of the luminescence (sensor turn‐off). Different options to select core, quencher, and luminophore components allow to drive the sensors to different sensing options regarding response time, sensitivity, and operation time. The sensors can be sensitive and rapid in response or generated to monitor the influence of shear stress over longer periods of time. Thus, a rapid, visible, “on‐the‐fly” sensing of shear stress is possible as well as monitoring the impact of prolonged shear stress. The particles are assembled by spray‐drying. This affords flexibility when choosing the type of quencher and luminophore moiety. As such, the sensitivity of this robust, particle‐based shear stress sensor system can be deliberately configured. Furthermore, the supraparticle sensor can be integrated in surfaces to create interactive, communicating materials.

Extracellular versus Intracellular Degradation of Nanostructured Silica Particles.

Silica nanoparticles appear as promising drug carriers for intracellular delivery. However, the mechanisms by which they are degraded within cells remain largely unknown. In this context, we have prepared three types of PEGylated fluorescent silica nanoparticles with various internal structures (core-shell biocomposite, multilayered, and hollow mesoporous) and studied their degradation in a buffer, in a culture medium, and in contact with human dermal fibroblasts. All particles were prone to dissolve in solution, leading to an increase of porosity and/or the precipitation of new colloids and eventually fragmentation, with a faster rate in the medium compared to that in the buffer. All particles were also uptaken by the cells without significant cytotoxic effect. Their intracellular degradation occurred faster than in suspension, but following almost similar dissolution mechanisms. These results strongly suggest that in these conditions, silica nanoparticles must be primarily considered as hydrolytically degraded and not biodegraded, a point of importance for their future applications in drug delivery.

Amorphous Silica Particles Relevant in Food Industry Influence Cellular Growth and Associated Signaling Pathways in Human Gastric Carcinoma Cells.

Nanostructured silica particles are commonly used in biomedical and biotechnical fields, as well as, in cosmetics and food industry. Thus, their environmental and health impacts are of great interest and effects after oral uptake are only rarely investigated. In the present study, the toxicological effects of commercially available nano-scaled silica with a nominal primary diameter of 12 nm were investigated on the human gastric carcinoma cell line GXF251L. Besides the analysis of cytotoxic and proliferative effects and the comparison with effects of particles with a nominal primary diameter of 200 nm, emphasis was also given to their influence on the cellular epidermal growth factor receptor (EGFR) and mitogen-activated protein kinases (MAPK) signaling pathways—both of them deeply involved in the regulation of cellular processes like cell cycle progression, differentiation or proliferation. The investigated silica nanoparticles (NPs) were found to stimulate cell proliferation as measured by microscopy and the sulforhodamine B assay. In accordance, the nuclear level of the proliferation marker Ki-67 was enhanced in a concentration-dependent manner. At high particle concentrations also necrosis was induced. Finally, silica NPs affected the EGFR and MAPK pathways at various levels dependent on concentration and time. However, classical activation of the EGFR, to be reflected by enhanced levels of phosphorylation, could be excluded as major trigger of the proliferative stimulus. After 45 min of incubation the level of phosphorylated EGFR did not increase, whereas enhanced levels of total EGFR protein were observed. These results indicate interference with the complex homeostasis of the EGFR protein, whereby up to 24 h no impact on the transcription level was detected. In addition, downstream on the level of the MAP kinases ERK1/2 short term incubation appeared to affect total protein levels without clear increase in phosphorylation. Depending on the concentration range, enhanced levels of ERK1/2 phosphorylation were only observed after 24 h of incubation. Taken together, the present study demonstrates the potential of the tested silica particles to enhance the growth of gastric carcinoma cells. Although interference with the EGFR/MAPK cascade is observed, additional mechanisms are likely to be involved in the onset of the proliferative stimulus.

Outset of the Morphology of Nanostructured Silica Particles during Nucleation Followed by Ultrasmall-Angle X-ray Scattering.

Nucleation and growth of SBA-15 silica nanostructured particles with well-defined morphologies has been followed with time by small-angle X-ray scattering (SAXS) and ultrasmall-angle X-ray scattering (USAXS), using synchrotron radiation. Three different morphologies have been compared: platelets, toroids, and rods. SEM observations of the particles confirm that two key physical parameters control the morphology: the temperature and the stirring of the solution. USAXS curves demonstrate that primary particles with a defined shape are present very early in the reaction mixture, immediately after a very fast nucleation step. This nucleation step is detected at 10 min (56 °C) or 15 min (50 °C) after the addition of the silica precursor. The main finding is that the USAXS signal is different for each type of morphology, and we demonstrate that the difference is related to the shape of the particles, showing characteristic form factors for the different morphologies (platelet, toroid, and rod). Moreover, the size of the mesocrystal domains is correlated directly with the particle dimensions and shape. When stirred, aggregation between primary particles is detected even after 12 min (56 °C). The platelet morphology is promoted by constant stirring of the solution, through an oriented aggregation step between primary particles. In contrast, toroids and rods are only stabilized under static conditions. However, for toroids, aggregation is detected almost immediately after nucleation.

Modulating Release of Metoprolol Tartrate with Nanostructured Silica Particles

To develop a kind of gastrointestinal timed-release preparation for Metoprolol Tartrate, nanostructured silica particles were chose for the purpose. Briefly, MCM-41 type mesoporous silica nanospheres with a size of 100-200 nm were synthesized through the reaction of tetraethyl orthosilicate (TEOS) in the water medium at 353 K, with introducing some cetyltrimethyl ammonium bromide (CTAB) as porogens. Various analytical methods, including FT-IR, XRD, TEM, N2 physisorption and thermal analysis, were applied to characterize the final products. Metoprolol Tartrate was then loaded into the mesoporous silica nanospheres by soaking. Results of the release of the drug in simulated gastric juice indicated that the drug can release up to 24 h and its maximum released amount was 4.5%. In the simulated intestinal juice the maximum cumulative released amount of metorprolol was 10.8%.In vitro release behavior revealed that the mesoporous silica were appropriate used as drug delivery system.

Sol-Gel Synthesized Nanostructured Silica Particles for Application in Gas Transport Properties of PU-PDMS Based Mixed-Matrix Membranes

New Silicon based nanostructures particles were successfully synthesized by tetraethoxysilane (TEOS) as silica precursor, mixture of two copolymers of PPG-b-PPE-b-PPG and PEO-b-PPG-b-PEO (Plutonic) as templates. PU-PDMS and PU-PDMS/silica composite membranes were prepared by solution casting technique. Synthesized mesoporus silica particles and hybrid membranes were characterized using Nitrogen adsorption-desorption (BET), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). As confirmed by BET analysis, the mean pore diameters of SPB1,2 Silicon particles are around 9 nm. The SEM micrographs confirmed the nanoscale distribution of silica particles in the polymer matrix. Gas permeation of PU-PDMS/silica hybrid membranes with silica contents of 5, 10 and 20 wt.% was studied for N2, CO2 and He single gases at8 bar. The obtained results suggest a significant increase in permeability of all gases upon increasing the silica particles content. The possible reasons for such behavior were stated and discussed.

Antibacterial activity by nanosilver particles

ABSTRACTThe antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO2 nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction. The antibacterical activity of these composite samples was investigated for a constant composite particle concentration. The highest activity was observed for the higher silver content particles.

Antibacterial Activity of Nanosilver Ions and Particles

The antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO(2) nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction the exposed Ag surface area was measured qualitatively by O(2) chemisorption. Furthermore, the fraction of dissolved nanosilver was determined by measuring the released (leached) Ag(+) ion concentration in aqueous suspensions of such Ag/SiO(2) particles. The antibacterial effect of Ag(+) ions was distinguished from that of nanosilver particles by monitoring the growth of E. coli populations in the presence and absence of Ag/SiO(2) particles. The antibacterial activity of nanosilver was dominated by Ag(+) ions when fine Ag nanoparticles (less than about 10 nm in average diameter) were employed that release high concentrations of Ag(+) ions. In contrast, when relatively larger Ag nanoparticles were used, the concentration of the released Ag(+) ions was lower. Then the antibacterial activity of the released Ag(+) ions and nanosilver particles was comparable.

Universal Correlation and Mechanism for the Antibacterial Activity of Silver Nanoparticles

AbstractSilver clusters (4-150 nm) anchored on nanostructured silica particles (300-400 m2/g) with closely controlled Ag content and size were made in one-step by scalable flame spray pyrolysis of Ag-nitrate and hexamethyldisiloxane containing solutions. Composite Ag/SiO2 nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction, N2 adsorption. The activity of such nanoparticles against the Gram negative bacterium Escherichia coli was investigated by monitoring the recombinantly synthesized green fluorescent protein. It is shown that higher Ag content particles exhibit a stronger antibacterial effect.

Pore size-controlled synthesis and characterization of nanostructured silica particles

Silica nano-materials with meso- and macroporosity are of great interest due to their variety of potential applications. For the application as a catalytic supporter, nanostructured spherical silica particles having both mesopores and macropores were prepared by using an aerosol templating method with colloidal mixtures of polystyrene latex (PSL) particles and silica nanoparticles. The as-prepared particles showed bimodal size distribution consisting of mesopores ranging 2–20 nm and macropores ranging 60–160 nm. As the PSL size decreased, mesopore size increased due to a reduction in packing rates of primary SiO 2 nanoparticles composing the walls of nanostructured porous particles. With an increment of the weight ratio of PSL/SiO 2, mesopores size increased but mesopore volume decreased due to the broken structure of particles and reduction in packing rates. Mesopores disappeared when the furnace temperature was 900 °C. The residuals of organic template were detected when furnace temperature and flow rate of carrier gas were below 600 °C and above 3 l/min, respectively.

Nanostructure Evolution: From Aggregated to Spherical SiO2 Particles Made in Diffusion Flames

AbstractThe formation of nanostructured silica particles by oxidation of hexamethyldisiloxane (HMDSO) in co‐annular diffusion flames is investigated by in‐situ small‐angle X‐ray scattering (SAXS). This enabled the nonintrusive monitoring of the mass fractal dimension, the aggregate size, and the number of primary particles per aggregate, along with the silica volume fraction, the primary particle diameter, the geometric standard deviation, and the number density along the flame axis. Parallel to this, thermophoretic sampling (TS) of the particles and analysis by transmission electron microscopy (TEM) allowed for direct comparison of particle morphology to that obtained from the above SAXS analysis, which were compared also to the ultra‐small‐angle X‐ray scattering (USAXS) data for product particles collected from the filter. The flame temperature was measured by in‐situ Fourier transform infrared (FTIR) spectroscopy. By increasing the oxygen flow rate, the laminar diffusion flame changed to a turbulent, premixed‐like flame. Non‐aggregated, spherical particles were formed in the former, while aggregates were formed in the latter flame. The relatively long high‐temperature particle residence times in the laminar diffusion flame facilitated sintering of the aggregates formed earlier into compact spherical particles at later stages of the flame.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)

Preparation of Micrometer‐ to Sub‐micrometer‐Sized Nanostructured Silica Particles Using High‐Energy Ball Milling

Nanostructured porous silica particles with sizes in the micrometer to sub‐micrometer range are of great interest due to their potential applications as catalyst supports and nanocomposite materials. However, if these particles are to be used in industry, a process must be developed to affordably produce them on a large scale. This paper reports on a high‐energy ball‐milling process that has been used to create micrometer‐ to sub‐micrometer‐sized mesoporous silica particles starting from a silica xerogel prepared by a surfactant self‐assembly sol–gel process. We have studied various milling conditions such as milling media (zirconia, stainless steel, or steel‐centered nylon balls), milling time, and the presence of surfactants during milling and the resulting effect on particle size and pore structure. Results from transmission electron microscopy, scanning electron microscopy, X‐ray diffraction, light scattering, and nitrogen adsorption demonstrate the feasibility of producing large quantities of nanostructured particles by this simple milling process.

Control of the morphology of nanostructured particles prepared by the spray drying of a nanoparticle sol

The control of the morphology of nanostructured particles prepared by the spray drying of nanoparticle sol was investigated experimentally and the results are qualitatively explained based on available theory. A theoretical analysis indicates that the structural stability of the droplet and the hydrodynamic effects during the drying process play important roles in controlling the morphology of the resulting particles. The size of the sol in the droplet, droplet size, viscosity of droplet, drying temperature, gas flow rate, and addition of surfactant are all crucial parameters that affect the morphology of particles. Experimentally, nanostructured silica particles were prepared from a nanosize silica sol under various preparation conditions. Doughnut-shaped particles can be produced when the droplet size is large, in conjunction with high temperature, high gas flow rate and in the presence of an added surfactant. Appropriate choice of the spray drying method permits control of the particle size and shape, ranging from spheres to ellipsoids as well as doughnut-shaped particles by varying the preparation conditions. The results open a new route to controlling the formation of a wide variety of nanostructured particles.