Introduction

Silica particles are spherical nano and micron silica particles with uniform particle size distribution prepared by St?ber method using ethyl orthosilicate as raw material. The silica particles at the end of Si-OH have hydrophilicity, chemical activity and long-term stability in organic solvents and aqueous solutions. The hydroxyl group on the surface of silica particles can bind a variety of substances to the particle surface, improve the surface state of the particles, and achieve chemical modification. Different functional groups such as COOH and NH2 can be introduced to functionalize the surface. Various biomolecules such as streptavidin, avidin and protein A can be covalently bound to enhance the biological targeting of silica particles.

Biotyscience can supply high-quality silica particles, and can also customize according to the needs of customers. The company's products have been widely used in biomedicine, optics, electronics, catalysis, sensors, drug carriers, jewelry, polymer modification and many other industrial fields[1-7].

Preparation Method

Chemical precipitation method;

Gas phase route;

Sol–gel method (St?ber method)[8].

Application

Biomedical testing[1]: S. aureus aptamer was firstly labelled with fluorescent silica nanoparticles (FNPs), and then introduced into the positive dielectrophoresis (pDEP)-based microfluidic chip after incubation with S. aureus. By applying an appropriate AC frequency to the electrode, the AptS. aureus/FNPs labelled S. aureus moved towards to the strongest electric field region due to pDEP force and enriched between the electrodes, the signal was collected by inverted fluorescence microscope imaging system. This strategy offered several unique advantages included high affinity of aptamer to S. aureus, signal amplification of FNPs, pDEP driven on-line enrichment which was free from washing and separation steps. Based on these features, this assay allowed for detection of as low as 93 and 270 cfu mL-1 S. aureus in deionized water and spiked water samples, respectively. By substituting the aptamer to suit to other pathogenic bacteria, this technique has the potential to develop to a universal method for detecting a wide variety of pathogenic bacteria in biomedical and biotechnological areas.

Pickering emulsions stabilizer[2]: Bare silica particles are generally unable to stabilize Pickering emulsions made with common oils because of the total wetting of silica by water. However, stable O/W Pickering emulsions stabilized by bare silica could be prepared with ‘polar oils, ‘polar oil’meaning organic liquid bearing polar chemical functions but of limited solubility in water for there are two phases coexisting under operative conditions. Successful emulsification has been achieved with bare silica for polar oils having oil–water interfacial tension lower than 15 mN m?1. The surface of silica is easily made hydrophobic by grafting organosilanes. Grafting dichlorodimethylsilane or hexamethyldisilazane to silica leaves hydrophobic dimethylsilyl groups attached at the surface of silica, the grafting degree (surface coverage) controls the hydrophobic character of silica and its wetting by water and oils.

Polymer nanocomposite filler[9]: In case where inorganic fillers are incorporated in the polymer blend materials, inorganic particles (e.g. silica) can be either dispersed in one of the two polymer phases, or adsorbed at the interface between the two phases.   Adsorption at the interface results in a Pickering-like emulsion. Such adsorption contributes to the emulsion morphology and stability; it also influences the mechanical reinforcement of the material by the inorganic fillers.

Sensing[10]: Nanometer sized silica nanoparticles (SiO2-NP) were prepared in water and loaded with two organic compounds, namely perylene and 1,6-diphenyl-1,3,5-hexatriene, which have well-defined and known fluorescence properties.  Differently loaded nanoparticles were characterized by both steady-state and time-resolved spectrofluorimetric techniques. The spectroscopic characterization allowed in the first place to establish where the dye molecules are localized within the particles and, later, to evaluate the sensing capability of the hybrid materials with respect to proteins. In particular, dye molecules resulted to have a bimodal distribution on the particle template, specifically (i) at the particle/water interphase and (ii) in close contact with the silica surface (in the inner particle). To prove the ability of the as-prepared and characterized particles to interact with proteins, BSA and RNA-si were used as models; the particle fluorescence was used as a sensitive tool to monitor the occurrence of such interactions. In all cases, proteins interact very efficiently with the SiO2-NP mainly through static interactions likely determined by electrostatic forces.    A quantitative analysis of the steady-state fluorescence quenching experiments allowed to estimate the interaction radius, which is a useful parameter to sense and to discriminate proteins.

Imaging[11]: The synthesis and characterization of organically modified silica (ORMOSIL) nanoparticles has been reported, covalently incorporating the fluorophore rhodamine-B, and surface-functionalized with a variety of active groups. The synthesized nanoparticles are of ultralow size (diameter～20 nm), highly monodispersed, stable in aqueous suspension, and retain the optical properties of the incorporated fluorophore. The surface of the nanoparticles can be functionalized with a variety of active groups such as hydroxyl, thiol, amine, and carboxyl. The carboxyl groups on the surface were used to conjugate with various bioactive molecules such as transferrin, as well as monoclonal antibodies such as anti-claudin 4 and anti-mesothelin, for targeted delivery to pancreatic cancer cell lines. In vitro experiments have revealed that the cellular uptake of these bioconjugated (targeted) nanoparticles is significantly higher than that of the nonconjugated ones. The ease of surface functionalization and incorporation of a variety of biotargeting molecules, combined with their observed noncytotoxicity, makes these fluorescent ORMOSIL nanoparticles potential candidates as efficient probes for optical bioimaging, both in vitro and in vivo.

Drug delivery[12]: Mesoporous silica nanoparticles (MSNs) have the potential of targeted drug delivery. Specifically, due to the large surface area and the controllable surface functionality of MSNs, they can be controllably loaded with large amounts of drugs and coupled to homing molecules to facilitate active targeting, simultaneously carrying traceable (fluorescent or magnetically active) modalities, also making them highly interesting as theragnostic agents. The increased relative surface area and small size, and flexible surface functionalization which is beneficially exploited in nanomedicine.

Nucleic acid carrier[13]: Surface-functionalized mesoporous silica nanoparticles (MSNP) can be used as an efficient and safe carrier for bioactive molecules. By noncovalently attaching polyethyleneimine (PEI) polymer to the particle surface, the cellular uptake of MSNP is enhanced, and a cationic surface is generated, allowing for nucleic acid delivery in addition to traditional drug delivery.

Light trapping[5]: A highly efficient light-scattering layer, composed of quasi-periodic discrete silica nanoparticles directly deposited onto polymer substrates to produce bendable organic solar cells (OSCs) with enhanced light absorption. A silica nanoparticle layer (SNL) underwent self-assembly on a highly flexible and heat-sensitive polymer at room temperature during fabrication, which employed a unique plasmaenhanced chemical vapour deposition technique. Such efficient light-scattering SNLs have not been realizable by conventional solution-based coating techniques. SNLs were optimized by precisely controlling dimensional parameters, specifically, the nanoparticle layer thickness and interparticle distance. The optimized SNL exhibited an improved transmission haze of 16.8% in the spectral range of 350–700 nm, where reduction of the total transmission was suppressed to 2%. Coating light-scattering SNLs onto polymer substrates is a promising method for improving the light harvesting abilities of OSCs by enhancing the light absorption of photoactive polymer layers. This SNL-based flexible OSC exhibited a record power conversion efficiency (PCE) of 7.4%, representing a 13% improvement, while reducing the thickness of the photoactive polymer layer by 30%.

Advantages

Highly uniform particle size;

Extremely stable;

Good dispersion.

Reference

1 Shangguan J., Li Y., He D., et al. (2015). A combination of positive dielectrophoresis driven on-line enrichment and aptamer-fluorescent silica nanoparticle label for rapid and sensitive detection of Staphylococcus aureus. Analyst. 140(13), 4489–4497. https://doi.org/10.1039/C5AN00535C

2 Chevalier Y., Bolzinger M.A. (2013). Emulsions stabilized with solid nanoparticles: pickering emulsions. Colloids Surf. A. 439, 23–34. https://doi.org/10.1016/j.colsurfa.2013.02.054

3 Shahabi S., Treccani L., Dringen R., et al. (2015). Modulation of silica nanoparticle uptake into human osteoblast cells by variation of the ratio of amino and sulfonate surface groups: effects of serum. ACS Appl. Mater. Interfaces. 7(25), 13821–13833. https://doi.org/10.1021/acsami.5b01900

4 Zhu M., Zhu Y., Zhang L., et al. (2016). Preparation of chitosan/mesoporous silica nanoparticle composite hydrogels for sustained co-delivery of biomacromolecules and small chemical drugs. Sci. Technol. Adv. Mater. 14(4), 045005. https://doi.org/10.1088/1468-6996/14/4/045005)

5 Yun J., Wang W., Kim S.M., et al. (2015). Light trapping in bendable organic solar cells using silica nanoparticle arrays. Energy Environ. Sci. 8(3), 932–940. https://doi.org/10.1039/C4EE01100G)

6 Xiao D., Jia H.Z., Ma N., et al. (2015). A redox-responsive mesoporous silica nanoparticle capped with amphiphilic peptides by self-assembly for cancer targeting drug delivery. Nanoscale. 7(22), 10071–10077. https://doi.org/10.1039/C5NR02247A

7 Appiah-Ntiamoah R., Jadhav A.H., Puguan J.M.C., et al. (2015). A silica nanoparticle supported fluorescence ‘turn-on’ fluoride ion sensing system with tunable structure and sensitivity. RSC Adv. 5(39), 30526–30536. https://doi.org/10.1039/C5RA02158H

8 Liang, X., Lian, L., Liu, Y., et al. (2016). Controlled synthesis of monodisperse silica particles. Micro & Nano Letters. 11(9), 532–534. https://doi.org/10.1049/mnl.2016.0189

9 Elias, L., Fenouillot, F., Majesté, J.C., et al. (2008). Immiscible polymer blends stabilized with nano-silica particles: Rheology and effective interfacial tension. Polymer. 49(20), 4378–4385. https://doi.org/10.1016/j.polymer.2008.07.018

10 Latterini, L., Amelia, M. (2009). Sensing Proteins with Luminescent Silica Nanoparticles. Langmuir. 25, 4767?4773. https://doi.org/10.1021/la803934f

11 Kumar, R., Roy, I., Ohulchanskyy, T., et al. (2008). Covalently DyeLinked, Surface-Controlled, and Bioconjugated Organically Modified Silica Nanoparticles as Targeted Probes for Optical Imaging. ACS Nano. 2(3), 449?456. https://doi.org/10.1021/nn700370b

12 Rosenholm, J., Sahlgren, C., Linden, M. (2010). Towards Multifunctional, Targeted Drug Delivery Systems Using Mesoporous Silica Nanoparticles?Opportunities & Challenges. Nanoscale. 2, 1870?1883. https://doi.org/10.1039/c0nr00156b

13 Xia, T., Kovochich, M., Liong, M., et al. (2009). Polyethyleneimine Coating Enhances the Cellular Uptake of Mesoporous Silica Nanoparticles and Allows Safe Delivery of siRNA and DNA Constructs. ACS Nano. 3, 3273?3286. https://doi.org/10.1021/nn900918w

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