Silica-coated Silver Nanoparticles Research Articles

Exploring the effects of silver, silica-coated silver, and gold nanoparticles on lipid vesicles: Insights from LUVs and GUVs

Understanding the interaction between nanoparticles (NP) and lipid membranes is crucial for various biomedical applications. In this study, we investigated the effects of silver nanoparticles (AgNP), silica-coated silver nanoparticles (Ag@SiO2), and gold nanoparticles (AuNP) on 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles. The dynamic light scattering (DLS) and zeta potential measurements were employed to evaluate DOPC large unilamellar vesicles (LUVs) exposed to AgNP, AgNP@SiO2, or AuNP for 180 min. The DOPC giant unilamellar vesicles (GUVs) exposed to the same NP were evaluated by phase-contrast microscopy. The AgNP showed higher reactivity along the exposition time, leading the vesicles to rupture (LUVs and GUVs). The SiO2 coating from Ag@SiO2 decreases the rupture effects compared to uncovered AgNP, showing surface adsorption and, consequently, vesicle morphological changes. The AuNP showed a partial wrapping on the GUVs bilayer and permeation on the LUVs, however the integrity of the bilayer structure is maintained in both GUVs and LUVs. These findings highlight the varying effects of AgNP, Ag@SiO2, and AuNP on lipid vesicles, underscoring the importance of nanoparticle material and coating in their interactions with biological membranes.

Tailoring Mesoporous Silica-Coated Silver Nanoparticles and Polyurethane-Doped Films for Enhanced Antimicrobial Applications.

The global increase in multidrug-resistant bacteria poses a challenge to public health and requires the development of new antibacterial materials. In this study, we examined the bactericidal properties of mesoporous silica-coated silver nanoparticles, varying the core sizes (ca. 28 nm and 51 nm). We also investigated gold nanoparticles (ca. 26 nm) coated with mesoporous silica as possible inert metal cores. To investigate the modification of antimicrobial activity after the surface charge change, we used silver nanoparticles with a silver core of 28 nm coated with a mesoporous shell (ca. 16 nm) and functionalized with a terminal amine group. Furthermore, we developed a facile method to create mesoporous silica-coated silver nanoparticles (Ag@mSiO2) doped films using polyurethane (IROGRAN®) as a polymer matrix via solution casting. The antibacterial effects of silver nanoparticles with different core sizes were analyzed against Gram-negative and Gram-positive bacteria relevant to the healthcare and food industry. The results demonstrated that gold nanoparticles were inert, while silver nanoparticles exhibited antibacterial effects against Gram-negative (Escherichia coli and Salmonella enterica subsp. enterica serovar Choleraesuis) and Gram-positive (Bacillus cereus) strains. In particular, the larger Ag@mSiO2 nanoparticles showed a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 18 µg/mL in the Salmonella strain. Furthermore, upon terminal amine functionalization, reversing the surface charge to positive values, there was a significant increase in the antibacterial activity of the NPs compared to their negative counterparts. Finally, the antimicrobial properties of the nanoparticle-doped polyurethane films revealed a substantial improvement in antibacterial efficacy. This study provides valuable information on the potential of mesoporous silica-coated silver nanoparticles and their applications in fighting multidrug-resistant bacteria, especially in the healthcare and food industries.

Antimicrobial and optical properties of a new biogenic silica-coated silver nanoparticles incorporated into experimental resin.

Evaluate the effects of incorporating silica-coated silver nanoparticles (Ag@SiO2 NPs) into odontological clinic resin materials. Silver nanoparticles coated with silicon dioxide were added to the experimental resin matrix at 1, 3, and 5wt%. Degree of conversion (DC), optical properties (total transmittance and color change), and microstructural analysis were evaluated. Materials were tested for silver ion release, cytotoxicity in dental pulp fibroblasts, Streptococcus mutans biofilm growth by Colony-Forming Unit (CFU) and confocal laser scanning microscopy (CLSM). Groups had a similar DC, despite significant differences observed in transmittance and color change analysis for all groups with NPs. Silver ion release values were below the detection limit after 72h for all groups, and NPs incorporation did not show a statistical difference from the control on pulp fibroblasts assay. After 72h, the CFU count was significantly reduced by 74% from 3wt% of Ag@SiO2NPs. CLSM evaluation on S. mutans colonies showed a dose-dependent decrease in the emitted fluorescence. The application of Ag@SiO2 NPs in a resinous matrix, demonstrates a significant reduction of S. mutans CFU in oral biofilm, at concentrations from 3wt%, without an increase in cytotoxicity. The reduced transmittance values did not affect the DC, although a significant color change was perceived in all concentrations. Key words:Nanoparticles, Silver Compounds, Composite Dental Resin, Anti-Bacterial Agent, Optical Imaging.

A "signal-off" electrochemiluminescence immunosensor based on electron transfer between core-shell emitter Ag@SiO2 and quencher CeO2

Silver nanoparticles (Ag·NPs) show promising advantages in electrochemiluminescence (ECL) owing to their favorable optical properties and biocompatibility. However, their susceptibility to oxidation and degradation in the presence of air adversely affects ECL intensity. In this study, we employed a sandwich sensing platform using silica-coated silver nanoparticles (Ag@SiO2) as a novel luminescent material and cerium dioxide (CeO2) as an ECL signal quencher for sensitive neuro-specific enolase (NSE) detection. The core-shell structure protected Ag NPs within the silica (SiO2) layer, enhancing their ECL luminescence properties by reducing external environmental influence and preventing Ag NPs aggregation. Amino-functionalized CeO2 efficiently diminished Ag@SiO2 ECL emission through electron transfer, resulting in a "signal-off" detection mode with high sensitivity and accuracy. The detection limit reached 1.66 fg/mL, and the detection range spanned from 100 fg/mL to 500 ng/mL, showcasing a powerful biomolecule detection strategy.

Three in-one fenestrated approaches of yolk-shell, silver-silica nanoparticles: A comparative study of antibacterial, antifungal and anti-cancerous applications

Yolk-shell-based silica-coated silver nanoparticles are prominently used in the biomedical field aas well as bare silver nanoparticles for various biological applications. The present work narrates the synthesis and silica coating of metallic silver nanoparticles and investigates their antibacterial, antifungal, and anticancerous activity. Both synthesized nanoparticles were characterized by TEM, and SEM-EDX. The average size of silver nanoparticles was 50 nm, while after coating with silica, the average size of silica-coated silver nanoparticles was 80 nm. The nanoparticles' antibacterial, antifungal, and anticancer properties were comparatively examined in vitro. Agar well diffusion method was employed to explore the antibacterial activity against gram-positive bacteria (Bacillus cereus) and gram-negative bacteria (Escherichia coli) at different concentrations and antifungal activity against Candida Albicans. To understand the minimum concentration of both nanoparticles, we employed the minimum inhibitory concentration (MIC) test, against bacterial and fungal strains, which was dose dependent. We learned that bare silver nanoparticles showed high antibacterial activity, whereas silica-coated silver nanoparticles surpassed their antifungal capability over bare silver nanoparticles against Candida albicans. The anticancer activity of the as-prepared nanoparticles was executed in opposition to the prostate cancer cell (PC-3) line by MTT assay, which showed meaningful activity. Following this, flow cytometry was also effectuated to learn about the number of apoptotic and necrotic cells. The results of this study demonstrate the dynamic anti-cancerous, antibacterial, and antifungal activities of bare silver nanoparticles and silica-coated silver nanoparticles for a long-lasting period.

Synthesis and in vivo evaluation of three fluid spray dried hybrid ciprofloxacin microparticles in Sprague Dawley rats

The aim of this study is to prepare and characterise mucoadhesive silica-coated silver nanoparticles loaded with ciprofloxacin (S-AgNPs-CSCFX), and investigate serum biochemical, haematological, and histopathological effects in Sprague Dawley rats upon oral administration. S-AgNPs-CSCFX microparticles were prepared using three fluid nozzle spray drying and characterised by scanning electron microscopy (SEM), X-ray dispersive spectrometry (EDX), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), zeta potential and particles size measurements and X-ray powder diffraction (XRPD). Adult male Sprague Dawley rats were randomly divided between six-treated groups, including blank S-AgNPs and S-AgNPs-CSCFX (LD: Low dose; MD: Median Dose; HD: High Dose) and control group. Each group was treated daily to evaluate the effect of the prepared particles on the lipid profile, serum biochemical, hormonal level, haemogram, and vital organ histopathology. The results showed successful encapsulation of silver nanoparticles which resulted in spherical-shaped S-AgNPs-CSCFX with an average size of 1–5 μm and surface charge of 25.2 ± 5.52 mv. The in-vivo results showed that different doses of blank S-AgNPs and S-AgNPs-CSCFX had no significant toxic effects on the physiological, biochemical, and haematological parameters. There were no marked histopathological alterations in the vital organs of the treated rats with blank and loaded particles.

Color Transferability from Solution to Solid Using Silica Coated Silver Nanoparticles.

The interpretation of color change in sensors and tests can be linked to incorrect conclusions if the intrinsic color changes are not accounted for. In this work, we study the intrinsic color change associated with the process of embedding nanoparticles in a polymer to create nanocomposite films. We present a safer, faster method to coat silver nanoparticles with silica and employ a seven-factor Plackett-Burman design to identify critical factors in the synthesis. Silver nanodisks with increasing thicknesses of the silica shell showed a decreasing sensitivity of their localized surface plasmon resonance (LSPR) toward changes in the refractive index surrounding the nanoparticle. A color shift of up to 72 nm was observed when bare nanoparticles were embedded in poly(vinyl alcohol), but no color change was perceived when nanoparticles were coated with a 25-nm-thick silica shell. Understanding the origin of color changes intrinsic to the preparation of polymeric nanocomposites aids in the design and correct use of plasmonic sensors.

Antifungal nanosuspensions with surfactants and silver for the treatment of onychomycosis

Fungal nail infection (Onychomycosis) often requires prolonged treatment and is associated with a high risk of resistance to treatment. Here in this contribution, we introduce a novel approach to enhance penetration and antifungal activity of the antifungal drug griseofulvin (GF). Solid dispersions were prepared with hydroxypropyl methylcellulose acetate succinate (HPMCAS) and combined with surfactant (either sodium dodecyl sulphate (SDS), dodecyl trimethylammonium bromide (DTAB), or Pluronic F127) using mechanochemical activation. The prepared powders were then suspended with spray-dried silica-coated silver nanoparticles and applied onto infected bovine hooves to assess permeability and antifungal activity. The results showed that the prepared nanosuspensions significantly suppressed fungal activity causing disruption of fungal biofilms. Raman mapping showed enhanced permeation while dynamic vapor sorption (DVS), and particle size measurements showed varied effects depending on the type of surfactant and milling conditions. The prepared nanosuspensions displayed enhanced solubility of the poorly soluble drug reaching approximately 1.2 mg/mL. The results showed that the dispersions that contained DTAB displayed maximum efficacy while the inclusion of colloidal silver did not seem to significantly improve the antifungal activity compared to other formulations.

Mesoporous silica-coated silver nanoparticles as ciprofloxacin/siRNA carriers for accelerated infected wound healing

The colonization of bacterial pathogens is a major concern in wound infection and becoming a public health issue. Herein, a core–shell structured Ag@MSN (silver core embedded with mesoporous silica, AM)-based nanoplatform was elaborately fabricated to co-load ciprofloxacin (CFL) and tumor necrosis factor-α (TNF-α) small interfering RNA (siTNF-α) (AMPC@siTNF-α) for treating the bacterial-infected wound. The growth of bacterial pathogens was mostly inhibited by released silver ions (Ag+) and CFL from AMPC@siTNF-α. Meanwhile, the loaded siTNF-α was internalized by macrophage cells, which silenced the expression of TNF-α (a pro-inflammatory cytokine) in macrophage cells and accelerated the wound healing process by reducing inflammation response. In the in vivo wound model, the Escherichia coli (E. coli)-infected wound in mice almost completely disappeared after treatment with AMPC@siTNF-α, and no suppuration symptom was observed during the course of the treatment. Importantly, this nanoplatform had negligible side effects both in vitro and in vivo. Taken together, this study strongly demonstrates the promising potential of AMPC@siTNF-α as a synergistic therapeutic agent for clinical wound infections.Graphical

Enhancing Singlet Oxygen Photocatalysis with Plasmonic Nanoparticles

Photocatalysts able to trigger the production of singlet oxygen species are the topic of intense research efforts in organic synthesis. Yet, challenges still exist in improving their activity and optimizing their use. Herein, we exploited the benefits of plasmonic nanoparticles to boost the activity of such photocatalysts via an antenna effect in the visible range. We synthesized silica-coated silver nanoparticles (Ag@SiO2 NPs), with silica shells which thicknesses ranged from 7 to 45 nm. We showed that they served as plasmonically active supports for tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+, and demonstrated an enhanced catalytic activity under white light-emitting diode (LED) irradiation for citronellol oxidation, a key step in the commercial production of rose oxide fragrance. A maximum enhancement of the plasmon-mediated reactivity of approximately 3-fold was observed with a 28 nm silica layer along with a 4-fold enhancement in the emission intensity of the photocatalyst. Using electron energy loss spectroscopy (EELS) and boundary element method simulations, we mapped the decay of the plasmonic signal around the Ag core and provided a rationale for the observed catalytic enhancement. This work provides a systematic analysis of the promising properties of plasmonic NPs used as catalysis-enhancing supports for common homogeneous photocatalysts and a framework for the successful design of such systems in the context of organic transformations.

Pinhole-Free Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy for Interference-Free Probing of Electrochemical Reactions.

Investigating the behavior of analytes at the electrode surface is crucial in understanding the electrochemical and electrocatalytic reactions. Although Surface Enhanced Raman Scattering (SERS) is sensitive to minor chemical changes in the analyte, it is not widely used to study the reaction mechanisms on nonplasmonic surfaces because of the interference from plasmonic SERS substrates. In this study, we have investigated the redox reaction of Nile Blue A on a glassy carbon surface using pinhole-free silica-coated silver nanoparticles for Raman signal enhancement. The silver nanostructures were synthesized by a chemical reduction method, and the quality of the silica layer was confirmed using microscopic and electrochemical method. The in situ spectroelectrochemical data reveals the catalytic interference from silver which considerably alters the native reaction mechanism. The pinhole-free silica layer prevents the hot electron transfer and yields an interference-free enhancement to the Raman signals.

Surface plasma enhanced fluorescence combined aptamer sensor based on silica modified silver nanoparticles for signal amplification detection of cholic acid

Cholic acid (CA), as an important gut bacterial metabolite in humans, would cause DNA damage when its level increases. Determination of CA is extremely significant and necessary in human because of its importance in medical and clinical diagnose. Herein, aptamer-modified fluorescence sensor combined surface plasmon resonance (SPR) enhanced fluorescence for signal amplification detection of CA was firstly developed. Silica-coated silver nanoparticles (Ag@SiO2) as SPR materials were decorated with CdTe quantum dots (QDs) to obtain enhancement of fluorescent signal. Then CA aptamer was modified to the surface of the CdTe QDs (Ag@SiO2@QDs-Apt) through the covalent binding for specific recognition of CA. The maximum fluorescent enhancement was obtained with 36 nm of Ag nanoparticle. Compared with aptamer-modified QDs (QDs-Apt), Ag@SiO2@QDs-Apt showed super sensitivity with the linear range of 0.1–500 μM. Finally, the as-prepared nanosensor was applied to the detection of CA in human urine and serum with the recovery rate of 95.00–110.39%.

Ag@mSiO2@Ag core–satellite nanostructures enhance the antibacterial and anti-inflammatory activities of naringin

Bacterial infections have caused many human diseases, so effective treatment of bacterial infections is an urgent problem that needs to be solved. In this work, a multifunctional therapeutic core–satellite nanoplatform (ASAN NPs) with antibacterial and anti-inflammatory properties was designed and synthesized. First, mesoporous silica-coated silver nanoparticles (Ag NPs) with different sizes were synthesized via a simplified method that improved the stability and drug-carrying capacity of the Ag NPs. Then, the NPs were loaded with anti-inflammatory and antibacterial naringin. The characterization results showed that the ASAN NPs were successfully synthesized, with an average particle size of 110 ± 15 nm. In vitro antibacterial test results showed that the synergistic effect of Ag NPs and naringin enhanced the antibacterial activity in a dose-dependent manner. The ASAN NPs achieved high-efficiency antibacterial activity by increasing the permeability of the cell membrane, destroying the integrity of the bacteria, and significantly increasing the level of bacterial reactive oxygen species. The in vivo antibacterial results showed that the ASAN NPs had highly effective anti-infective and anti-inflammatory activities and did not show obvious side effects. Thus, ASAN NPs appear to be promising antimicrobial agents with good biocompatibility, potent antibacterial activity, and anti-inflammatory activity.

A novel hemocompatible core@shell nanosystem for selective targeting and apoptosis induction in cancer cells

Synthesis, characterization and evaluation of transferrin-decorated mesoporous silica-coated silver nanoparticles as a novel hemocompatible core@shell nanosystem for selective targeting and apoptosis induction in cancer cells.

Scalable and stable silica-coated silver nanoparticles, produced by electron beam evaporation and rapid thermal annealing, for plasmon-enhanced photocatalysis

This study demonstrates an easy, scalable way to fabricate stable plasmonic photocatalysts for gas-phase photocatalysis. Silver nanoparticles, coated with silica for improved stability, were fabricated via electron beam evaporation and rapid thermal annealing, modeled via finite difference time domain simulations, and characterized. Catalytic performance was evaluated by monitoring total volatile organic compound concentration from toluene degradation in a gas-phase recirculating batch reactor. Results of cycled experiments demonstrate 5-fold increase in apparent quantum yield and 18% increase in reaction rate constant over TiO2. This approach may enable plasmonic photocatalysis by offering a simple, scalable fabrication method more reliable than colloidal synthesis.

Facile preparation of core-shell Ag@SiO2 nanoparticles and their application in spectrally splitting PV/T systems

Several researchers have demonstrated that plasmonic nanofluids based filters can potentially enhance hybrid solar photovoltaic/thermal (PV/T) systems performance. In this work, we report a facile process for achieving silica-coated silver (Ag) nanoparticles using dimethylamine (DMA) as a basic solvent to induce tetraethyl orthosilicate (TEOS) hydrolysis. Then, the prepared Ag@SiO2 nanoparticles which have a controllable silica shell thickness are suspended in propylene glycol-CoSO4 hybrid fluid. Finally, the characteristics of the PV/T system filtered by the Ag@SiO2/CoSO4-PG nanofluids are evaluated based on the indoor test and photo-thermal conversion model. The results show that the nanoparticles prepared under optimized conditions, i.e., pH value of 8–9, water: ethanol volume ratio of 1:4, temperature of 25 °C, TEOS volume of 0.05 mL, and reaction time of 12 h, exhibit an absorption peak at 474 nm. Further, this study reveals that Ag@SiO2/CoSO4-PG nanofluid filter with concentration of 25.4 mg/L gives a reasonable spectral match with silicon concentrator solar cell according to the measured optical transmittance and the calculated filtering efficiency of 39.3%. The use of 25.4 mg/L Ag@SiO2/CoSO4-PG nanofluid filter produces a higher total efficiency of 63.3% and yields economic value enhancement of 67.8% compared to the PV only system when worth factor (w) is 3.

Silica-Coated Silver Nanoparticles Decorated with Fluorescent CdTe Quantum Dots and DNA Aptamers for Detection of Tetracycline

An aptamer-labelled fluorescent nanoprobe-integrated shell-isolated nanoparticle-enhanced fluorescence spectroscopy (SHINEFs) had been proposed for selective and sensitive detection of Tc. In the s...

Biogenic synthesis and antimicrobial activity of silica-coated silver nanoparticles for esthetic dental applications

Objectivesthis study aimed to synthesize AgNPs from green tea (GT) extract, forming GT-AgNPs, and to coat their surfaces with silica, resulting in light-colored Ag@SiO2 nanoparticles. Materials and Methodsparticles were characterized and tested for minimal inhibitory concentration (MIC), biofilm formation against Streptococcus mutans and cytotoxicity evaluation on dental pulp fibroblasts. ResultsX-ray diffraction (XRD) confirmed the formation of pure AgNPs, whereas energy dispersive X-ray spectroscopy (EDS) mapped their elemental atoms. Dynamic light scattering (DLS) demonstrated formation of particles at nanoscale, with moderate polydispersity and negative zeta potential, in agreement with nanoparticle tracking analysis (NTA) size measurements. Fourier-transformed infrared (FTIR) spectroscopy confirmed the successful condensation of silica, which significantly increased surface area by 50%, as assayed by surface area analysis (BET). Thermogravimetric analysis showed a 18%-mass of silica on the surface of Ag@SiO2NPs. Transmission electron microscopy (TEM) displayed the spherical shape of nanoparticles and average size of 11 nm for GT-AgNPs and Ag@SiO2NPs. Ag@SiO2NPs demonstrated potent antimicrobial action against S. mutans, with MIC determined as 600 μg/mL, and inhibition of approximately 44% (p < 0.05) of biofilm formation. At the MIC concentrations, both NPs did not exhibit cytotoxicity. ConclusionAg@SiO2NPs might have a useful application in dental materials. Clinical significanceThe possibility of incorporating antimicrobial properties in restorative materials without compromising esthetics makes the AgNPs@SiO2 NPs promising agents against S. mutans biofilm formation, hence the prevention of dental caries. This represents a great step towards the development of more interactive biomaterials in dentistry to overcome clinical problems.

Monitoring forced degradation of drugs using silica coated AgNPs with surface-enhanced Raman scattering

Potential degradation products (DPs), even in small concentrations, can cause changes in pharmacological and toxicological properties of a drug with a significant impact on product quality and safety. Thus, their stability and understanding of possible degradation mechanisms have a significant importance. Although liquid chromatography is the conventional technique used for forced degradation studies with excellent accuracy and reproducibility, the main disadvantages of the technique are being expensive and time-consuming. As a powerful technique, surface-enhanced Raman scattering (SERS) can be an alternative with its high sensitivity, easy sample preparation and low cost. In this study, the degradation of both tofacitinib (TOF), a Janus kinase inhibitor, and methotrexate (MTX), an inhibitor of tetrahydrofolate dehydrogenase, are studied using SERS under hydrolytic, oxidative and thermal conditions using mesoporous silica coated silver nanoparticles (Si@AgNPs) as SERS substrates. The study demonstrated that the degradation of the tested drugs using Si@AgNPs as SERS substrates could be monitored through the spectral changes on SERS spectra of drugs under several degradation conditions.

Highly sensitive metal-enhanced fluorescence biosensor prepared on electrospun fibers decorated with silica-coated silver nanoparticles

A new metal-enhanced fluorescence (MEF)-based biosensor platform was prepared on fibrous substrates. First, polycaprolactone (PCL) fibers were obtained via electrospinning process. PCL fibers were decorated with photoreduced silver nanoparticles followed by silica coating, generating silver-decorated PCL fibers with a silica layer (Ag@SiO2-PCL). The silica layer acted as a spacer between the silver nanoparticles and the fluorescent molecules to optimize the MEF effect. The MEF was obtained from the silver-decorated PCL fibers, the extent of which could be controlled by the thickness of the silica layer. The fibrous structure of Ag@SiO2-PCL had higher protein loading capacity than conventional two-dimensional glass slides due to its large surface area, while the presence of silica-coated silver nanoparticles resulted in higher fluorescence intensity than silica-coated PCL fibers (SiO2-PCL) without silver nanoparticles via the MEF effect. Both features of Ag@SiO2-PCL were combined to produce combined effects in improving the performance of fluorescence-based biosensing. According to immunobinding assays between fluorescently labeled anti-IgG and IgG immobilized onto different substrates, Ag@SiO2-PCL had much better sensing performance in terms of sensitivity and detection limit than glass slides and SiO2-PCL due to the combined effects of a large surface area and the MEF effect.