Fluorescent Silica Research Articles

Effect of Surface Chemistry on Incorporation of Nanoparticles within Calcite Single Crystals

Inclusion of additives into calcite crystals allows one to embed non-native proprieties into the inorganic matrix and obtain new functional materials. Up to now, few parameters have been taken into account to evaluate the efficiency of inclusion of an additive. Taking inspiration from Nature, we grew calcite crystals in the presence of fluorescent silica nanoparticles carrying different functional groups (PluS-X) to investigate the effect of surface chemistry on the inclusion of the additives. PluS-X allowed us to keep constant all the particle characteristics, including size, while changing exposed functional groups and thus Zeta-potential. The effect on crystal morphology, the loading and distribution of PluS-X within the crystals have been evaluated with different microscopy techniques. Our data indicate that hydroxyl functionalized particles are entrapped more efficiently inside calcite single crystals without distortion of the crystal structure and inhibition of the growth.

Controlled growth of fluorescent silica nanoparticles using two-phase orthogonal solvents for bioimaging

Nanoparticles with excellent physical and chemical properties are very promising for biomedical applications. However, their application in clinical trials may be hindered by their toxicity. Among various biomedical materials, silica nanoparticles (SNPs) are most attractive and widely studied materials owing to their high biocompatibility and functionality. In this study, we have synthesized fluorescent SNPs with controlled shapes and sizes by using SiCl4. To control the reaction rate of SiCl4 with water, two solvents immiscible with each other were employed. Our SNPs exhibit fluorescence near 2.95 eV (420 nm), originated from optically active silanone and dioxasilyrane defects, and are applied to in-vitro bioimaging of lung epithelial carcinoma cells (A549) without cytotoxicity. We believe that our novel synthesis method using orthogonal solvents will broaden the application range of highly reactive but potentially suitable precursors, which successfully realizes SNPs with defect-induced optical properties for various biomedical applications.

Synthesis and Characterization of Fluorescent Mesoporous Silica(Znq-CMS)with a Zinc Complex of 8-Hydroxyquinoline

This experiment is to prepare fluorescent mesoporous silica and explore its characteristics of the zinc complex of 8-hydroxyquinoline, synthesize CMS-SH by base-catalyzed sol-gel method, and then complex the zinc complex of 8-hydroxyquinoline. Go in and successfully synthesize Znq-CMS. In addition, the particle size and potential of CMS-SH and Znq-CMS were characterized by dynamic scattering (DLS), and the fluorescence characteristics of Znq-CMS were characterized by a fluorescence spectrophotometer and an ultraviolet lamp. The results show that Znq-CMS has good dispersibility and fluorescence effect. The purpose of this study is to explore a new model of drug delivery system for stimulus response.

Graphene Oxide-Based Nanostructured DNA Sensor.

Quick detection of DNA sequence is vital for many fields, especially, early-stage diagnosis. Here, we develop a graphene oxide-based fluorescence quenching sensor to quickly and accurately detect small amounts of a single strand of DNA. In this paper, fluorescent magnetic nanoparticles (FMNPs) modified with target DNA sequence (DNA-t) were bound onto the modified graphene oxide acting as the fluorescence quenching element. FMNPs are made of iron oxide (Fe3O4) core and fluorescent silica (SiO2) shell. The average particle size of FMNPs was 74 ± 6 nm and the average thickness of the silica shell, estimated from TEM results, was 30 ± 4 nm. The photoluminescence and magnetic properties of FMNPs have been investigated. Target oligonucleotide (DNA-t) was conjugated onto FMNPs through glutaraldehyde crosslinking. Meanwhile, graphene oxide (GO) nanosheets were produced by a modified Hummers method. A complementary oligonucleotide (DNA-c) was designed to interact with GO. In the presence of GO-modified with DNA-c, the fluorescence intensity of FMNPs modified with DNA-t was quenched through a FRET quenching mechanism. Our study indicates that FMNPs can not only act as a FRET donor, but also enhance the sensor accuracy by magnetically separating the sensing system from free DNA and non-hybridized GO. Results indicate that this sensing system is ideal to detect small amounts of DNA-t with limitation detection at 0.12 µM.

In Situ Synthesis of Fluorescent Mesoporous Silica\u2013Carbon Dot Nanohybrids Featuring Folate Receptor-Overexpressing Cancer Cell Targeting and Drug Delivery

HighlightsA one-pot method was developed for the preparation of fluorescent mesoporous silica nanoparticles–carbon dots (MSNs–CDs) nanohybrid.The MSNs–CDs nanohybrid showed stable and bright yellow emission, excellent biocompatibility, and specific targeting capability toward folate receptor-overexpressing cancer cells and can be applied as fluorescence imaging-guided drug carriers for effectively delivering anticancer drugs to tumor sites.

A new alternative method for quantitative analysis by thin layer chromatography using a lab-made multi-track device and image-based chromatograms

This work describes a simple, low-cost, and innovative approach to perform quantitative analyses by thin layer chromatography (TLC) combined with image-based detection with UV revelation, which enables the acquisition of chromatograms. Lab-made aluminium TLC devices containing eight individual tracks with thin fluorescent silica layers were developed, evaluated, and used to perform the separation and quantification of acetaminophen (ACM), caffeine (CAF), and acetylsalicylic acid (ASA) in medicine tablets by using image-based detection performed with a webcam and software written in VisualStudio. The proposed device enables vertical development of the separation with proper reproducibility of retention factors (<2%) and of the peak heights (<8%), without occurrence of silica damage, demonstrating the applicability of the new approach. By using a mixture of ethyl acetate/acetic acid (80:2 v/v) as eluent, analytical curves were obtained for the analytes based on the chromatographic peak heights, providing linear relationships (R > 0.996) for the studied concentration ranges ACM (0.18–0.54 mg mL−1), CAF (0.50–3.00 mg mL−1) and ASA (0.70–4.50 mg mL−1) with estimated limits of detection (LOD) of 0.14 mg mL−1, 0.40 mg mL−1 and 0.56 mg mL−1, for ACM, CAF and ASA, respectively. In addition, no significant differences (95% confidence level) were observed by comparing the average concentration of the analytes determined by the proposed method and those obtained by a reference HPLC based method, indicating an adequate accuracy of the procedures.

Polycarboxylated Dextran as a Multivalent Linker: Synthesis and Target Recognition of the Antibody-Nanoparticle Bioconjugates in PBS and Serum.

Nanoparticles (NPs) functionalized with antibodies on their surface are used in a wide range of research applications. However, the bioconjugation chemistry between the antibodies and the surface of nanoparticles can be very challenging, often accompanied by several undesired effects such as nanoparticle aggregation, antibody denaturation, or poor target recognition of the surface-bound antibodies. Here, we report on a synthesis of fluorescent silica nanoparticle-antibody (NP-Ab) conjugates, in which polycarboxylated dextran is used as the multivalent linker. First, we present a synthetic methodology to prepare polycarboxylated dextrans with molecular weights of 6, 40, and 70 kDa. Second, we used water-soluble, polycarboxylated dextrans as a multivalent spacers/linkers to immobilize antibodies onto fluorescent silica nanoparticles. The prepared NP-Ab conjugates were tested in a direct binding assay format in both phosphate-buffered saline buffer and whole serum to investigate the role of the spacer/linker in the capacity of the NP-Ab to specifically recognize their target in "clean" and also in complex media. We have compared the dextran conjugates with two standards: (a) NP-Ab with antibodies attached on the surface of nanoparticles through the classical physical adsorption method and (b) NP-Ab where an established poly(amidoamine) (PAMAM) dendrimer was used as the linker. Our results showed that the polycarboxylated 6 kDa dextran facilitates antibody immobilization efficiency of nearly 92%. This was directly translated into the improved molecular recognition of the NP-Ab, which was measured by a direct binding assay. The signal-to-noise ratio in buffered solution for the 6 kDa dextran NP-Ab conjugates was 81, nearly 3 times higher than that of PAMAM G4.5 conjugates and 9 times higher than the physically adsorbed NP-Ab sample. In whole serum, the effect of 6 kDa dextran was more hindered due to the formation of protein corona but the signal-to-noise ratio was at least double that of the physically adsorbed NP-Ab conjugates.

Silica-Based Organic-Inorganic Hybrid Fluorescent Ink for Security Applications.

A facile formulation of fast-drying fluorescent ink made from nanostructured fluorescent silica nanocrystals is presented. The rheostable viscous ink suitable for screen printing was developed by careful selection of organic vehicle components, which was later printed onto various rigid and flexible substrates. Photoluminescence studies of the printed film confirmed that the formulated ink composition did not show noticeable influence on the excitation property of the fluorescent silica. The developed cost-effective and fast-curing fluorescent silica ink with desirable luminescent property makes it a suitable candidate for information encryption, optical devices, and energy conversion applications.

High-Performance Chromatographic Characterization of Surface Chemical Heterogeneities of Fluorescent Organic-Inorganic Hybrid Core-Shell Silica Nanoparticles.

In contrast to small-molar-mass compounds, detailed structural investigations of inorganic core-organic ligand shell hybrid nanoparticles remain challenging. The assessment of batch-reaction-induced heterogeneities of surface chemical properties and their correlation with particle size has been a particularly long-standing issue. Applying a combination of high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC) to ultra-small (<10 nm diameter) poly(ethylene glycol)-coated (PEGylated) fluorescent core-shell silica nanoparticles, we elucidate here previously unknown surface heterogeneities resulting from varying dye conjugation to nanoparticle silica cores and surfaces. Heterogeneities are predominantly governed by dye charge, as corroborated by molecular dynamics simulations. We demonstrate that this insight enables the development of synthesis protocols to achieve PEGylated and targeting ligand-functionalized PEGylated silica nanoparticles with dramatically improved surface chemical homogeneity, as evidenced by single-peak HPLC chromatograms. Because surface chemical properties are key to all nanoparticle interactions, we expect these methods and fundamental insights to become relevant to a number of systems for applications, including bioimaging and nanomedicine.

Quantitative Measure of the Size Dispersity in Ultrasmall Fluorescent Organic-Inorganic Hybrid Core-Shell Silica Nanoparticles by Small-angle X-ray Scattering.

Small-angle X-ray scattering (SAXS) was performed on dispersions of ultrasmall (d < 10 nm) fluorescent organic-inorganic hybrid core-shell silica nanoparticles synthesized in aqueous solutions (C' dots) by using an oscillating flow cell to overcome beam induced particle degradation. Form factor analysis and fitting was used to determine the size and size dispersity of the internal silica core containing covalently encapsulated fluorophores. The structure of the organic poly(ethylene glycol) (PEG) shell was modelled as a monodisperse corona containing concentrated and semi-dilute regimes of decaying density and as a simple polydisperse shell to determine the bounds of dispersity in the overall hybrid particle. C' dots containing single growth step silica cores have dispersities of 0.19-0.21; growth of additional silica shells onto the core produces a thin, dense silica layer, and increases the dispersity to 0.22-0.23. Comparison to FCS and DLS measures of size shows good agreement with SAXS measured and modelled sizes and size dispersities. Finally, comparison of a set of same sized and purified particles demonstrates that SAXS is sensitive to the skewness of the gel permeation chromatography elugrams of the original as-made materials. These and other insights provided by quantitative SAXS assessments may become useful for generation of robust nanoparticle design criteria necessary for their successful and safe use, for example in nanomedicine and oncology applications.

Highly ordered AIEgen directed silica hybrid mesostructures and their light-emitting behaviours

Mesostructured fluorescent silica hybrids (MFSHs) were synthesized by using tetraphenylethylene (TPE)-based quaternary ammonium salts as surfactants with typical aggregation-induced emission (AIE) behaviours.

Controllable fabrication of stimuli-responsive fluorescent silica nanoparticles using a tetraphenylethene-functionalized carboxylate gemini surfactant

A fluorophore-free green synthetic strategy was presented for the preparation of stimuli-responsive FSNs, which could be further tuned using N16-TPE-N16.

Achieving long-lived thermally activated delayed fluorescence in the atmospheric aqueous environment by nano-encapsulation.

Fluorescent silica nanoparticles, which encapsulated dye DCF-BYT with thermally activated delayed fluorescence (TADF) were fabricated by a simple synthetic method. Even in the atmospheric aqueous environment, the obtained DCF-BYT nanoparticles exhibited extremely long TADF lifetime up to 9.33 ms, which imparts these nanoparticles with great potential in biological applications, like time-resolved fluorescence imaging.

Ultrabright fluorescent silica nanoparticles for in vivo targeting of xenografted human tumors and cancer cells in zebrafish.

New ultrabright fluorescent silica nanoparticles capable of the fast targeting of epithelial tumors in vivo are presented. The as-synthesized folate-functionalized ultrabright particles of 30-40 nm are 230 times brighter than quantum dots (QD450) and 50% brighter than the polymer dots with similar spectra (excitation 365 nm and emission 486 nm). To decrease non-specific targeting, particles are coated with polyethylene glycol (PEG). We demonstrate the in vivo targeting of xenographic human cervical epithelial tumors (HeLa cells) using zebrafish as a model system. The particles target tumors (and probably even individual HeLa cells) as small as 10-20 microns within 20-30 minutes after blood injection. To demonstrate the advantages of ultrabrightness, we repeated the experiments with similar but 200× less bright particles. Compared to those, ultrabright particles showed ∼3× faster tumor detection and ∼2× higher relative fluorescent contrast of tumors/cancer cells.

Identifying a Membrane-Type 2 Matrix Metalloproteinase-Targeting Peptide for Human Lung Cancer Detection and Targeting Chemotherapy with Functionalized Mesoporous Silica.

Membrane-type 2 matrix metalloproteinase (MT2-MMP) is critical for the aggressive lung tumor growth, progression, and metastasis. Here, to obtain the peptides in binding specifically to MT2-MMP, a phage-displayed 12 peptide library was used and the affinity of peptides toward MT2-MMP was identified by multitest methods. The results showed that a specific MT2-MMP-targeting peptide with the sequence of HHRLHSAPPPQA (MT2-AF5p) exhibited a high specificity and strong affinity against lung tumors. To further achieve specific targeting and precise therapeutic effects, MT2-AF5p was conjugated onto fluorescent mesoporous silica nanoparticles (FMSN-NH2) and loaded with doxorubicin (DOX) to construct a chemotherapeutic drug-targeting delivery system (DOX-loaded FMSN@MT2-AF5p). The DOX-loaded FMSN@MT2-AF5p achieved a boost in DOX release in an acidic environment. Most importantly, FMSN@MT2-AF5p efficiently targeted the tumor area, as seen in the fluorescent imaging ex vivo. The novel peptide-functionalized nanoparticles with a good biocompatibility are promising for clinical use as a precise targeting nanodrug for lung cancer diagnosis and therapy.

An improved class of fluorescent silica nanoparticles for indirect immunofluorescence detection of MCF-7 cells

In this work, we have developed an efficient method based on silica fluorescent dye-doped nanoparticles and second antibody for cancer cell labeling. The dye-doped silica nanoparticles were synthesized by the reverse microemulsion method with the conjugate of 3-aminopropyltriethoxysilane and rhodamine B isothiocynate. A PEG with flexible long chain as the bridge was introduced onto the surface of the nanoparticle via cyanogens bromide method. The second antibody, goat anti-rabbit IgG, was conjugated on the surface of the PEG-terminal modified silica fluorescent nanoparticles by covalent binding to the PEG linkers via the EDC/sulfo-NHS method. The concentrations of goat anti-rabbit IgG covering the nanoparticles were quantified via the Bradford method. The silica fluorescent nanoparticles functionalized with rabbit anti-MUC1 antibody were employed as bioprobes for the recognition of MUC1 protein in human breast carcinoma molecules MCF-7 cells. Compared with fluorescent dye labeled IgG, the fluorescent nanoprobes display dramatically increased photostability.

Turn-On Fluorescence Detection of Glutathione Based on o-Phthaldialdehyde-Assisted SiO2 Particles

We report about the fluorometric method for the determination of glutathione (GSH) in dietary supplements. The fluorometric assay is based on the use of functionalized silica particles (SiO2-SH) in combination with o-phthaldialdehyde (OPA). The fluorescence excitation and emission wavelengths were located at 340 nm and 430 nm. The relative fluorescence intensity was linear in the concentration range between 1.0 × 10−7 mol/L and 1.0 × 10−5 mol/L (M) with the detection limit of 3.4 × 10−7 M. The fluorescent silica particle-based sensor was successfully employed for the determination of GSH in dietary supplements with excellent recoveries. The proposed sensor may pave a new way for fluorescence sensing of other substances in food samples.

Fluorescent amphiphilic silica nanopowder for developing latent fingerprints

ABSTRACTDeveloping latent fingerprints with silica nanopowder is strategically beneficial due to its synthetic simplicity, low production cost, high surface area and easy tailoring of surface phenomena. However, it is necessary to optimize the surface amphiphilicity of silica nanoparticles for their use in a powder dusting method. In this work, we demonstrate the tuning of amphiphilicity of silica nanopowders (average size 135 ± 10 nm) by modifying hydrophilic silica surfaces with different alkyl chains (e.g. –C5H11, –C11H23 and –C17H35). This structural amendment maximizes the efficacy of silica nanopowder for developing latent fingerprints. It was also observed that –C11H23 and –C17H35 containing amphiphilic silica nanopowders perform very efficiently for latent fingerprint development under visible light. To produce a luminescent silica nanopowder with a similar surface character, a Pt(II)C^N^N–C12H25 luminophore with long hydrophobic aliphatic chain (–C12H25) was introduced to the silica surface. This fluorescent and amphiphilic silica nanopowder performs very efficiently for developing latent fingerprints on various surfaces under illumination with 365 nm wavelength UV light.

A Tetraphenylethene Luminogen-Functionalized Gemini Surfactant for Simple and Controllable Fabrication of Hollow Mesoporous Silica Nanorods with Enhanced Fluorescence.

Nanoparticles that possess unique structures and properties are highly desired in the production of multifunctional materials because of their combinational performance. In this study, a facile and effective fabricating strategy is developed to controllably prepare fluorescent hollow mesoporous silica nanorods via the cetyltrimethylammonium bromide (CTAB) and tetraphenylethene (TPE) luminogen-functionalized gemini surfactant (CTPE-C6-CTPE) guided dual-templating approach. Because of its unique chemical structure, water solubility, surface activity, and fluorescent properties, the designed CTPE-C6-CTPE will not only provide an anchored fluorophore for silica nanoparticles but also serve as an intimate partner of CTAB to regulate their construction in the structure-directing process. By properly tuning the molar ratio of CTAB/CTPE-C6-CTPE, the shape-controlled aggregation-induced emission hollow mesoporous silica nanoparticles (AIE-MSNs) can be prepared directly, producing two kinds of silica nanorods (AIE-MSNs-15 and AIE-MSNs-7). In particular, the incorporated bulky TPE luminogens will not only endow AIE-MSNs-7 with enhanced fluorescence intensity (2.3-fold) after the removal of CTAB but also bring about high accessible surface area (606.6 m2/g) and larger pore size (3.2 nm) and pore volume (0.634 cm3/g) for effective loading and sustained release of the hydrophobic anticancer drug camptothecin. CTPE-C6-CTPE enriches the family of gemini surfactants and provides important insights into the convenient fabrication of advanced fluorescent mesoporous materials.

Fabrication and characterization of the composite nanofibers of polyacrylonitrile/fluorescent core-shell silica particles with their potential use for anticounterfeiting purposes in the textile industry

Composite nanofibers of polyacrylonitrile/fluorescent core–shell silica particles were fabricated. Two different sizes of fluorescent core–shell silica particles were synthesized. The first one consisted of particles with the diameter of about 310 nm (Bigger size fluorescent core-shell silica particles [BFSPs]) and the other one had the diameter of about 166 nm (smaller size fluorescent core-shell silica particles [SFSPs]). The images obtained by scanning and transmission electron microscopy confirmed the synthesis of spherical and nearly uniform particles. However, some clusters of smaller unformed silica particles were observed, especially in SFSPs. The results of Fourier transform infrared spectra spectroscopy confirmed the linkage between silica and fluorescein isothiocyanate. Scanning electron microscopy images of the composite nanofibers showed that the shell had a uniform morphology; however, there were some points having a higher diameter, where the core–shell particles were located. The fluorescence microscopy images of the composite nanofibers also showed the fluorescence property of the composite nanofibers with bright spots on them, where the particles were located. The fluorescence intensity of the composite nanofibers was significantly increased with the enhancement of the pH value in the range of 4.00–8.00. The observed pattern of composite nanofibers under ultraviolet radiation suggested that these composite nanofibers could be applied as anticounterfeiting markers for special clothes as well as pH-sensitive parts in smart clothing.