Development of highly fluorescent silica nanoparticles chemically doped with organic dye for sensitive DNA microarray detection

High-sensitivity detection of two H7 subtypes of avian influenza viruses (AIVs) by immunochromatographic assay with highly chromatic red silica nanoparticles

In this work, a sensitive and quantitative immunochromatographic assay (ICA) detection method for avian influenza viruses (AIVs) of the H7 hemagglutinin (HA) antigen was established based on highly chromatic red silica nanoparticles (SiNPs). It can detect two H7 subtypes of influenza viruses, H7N2 and H7N9. The highly chromatic red SiNPs were prepared by adsorbing C.I. Direct Red 224 on the surface of the SiNPs for multiple times using the layer by layer (LbL) self-assembly method under the electrostatic action of ethylene imine polymer (PEI) and poly(sodium-p-styrenesulfonate) (PSS). The highly chromatic red silica nanoparticles modified with anti-H7 HA mAb1 were used as immunodetection probes. The accumulated highly chromatic red SiNPs on the T-line can be observed by the naked eye to qualitatively detect the H7 HA antigen. The quantitative analysis is carried out by using a camera and Image J software. Within the range of 0.1-10 ng mL-1, the linear equation between the H7 HA antigen concentration and the peak area of the T-line gray value was y = 868.9722 + 435.4836X (R2 = 0.9716), and the limit of detection (LOD) of this method was 0.08 pg mL-1 (S/N = 3). The highly chromatic red SiNP based ICA for the detection of H7 HA has no cross activity with other subtypes of influenza viruses. This method of combining highly chromatic colored markers with ICA has great potential in practical applications for the rapid and quantitative detection of other types of AIVs.

Chemical and photonic interactions in vitro and in vivo between fluorescent tracer and nanoparticle-based scavenger for enhanced molecular imaging

We hereby present a concept of scavenging excess imaging agent prior to a diagnostic imaging session, consequently allowing for enhanced contrast of signals originating from the tissue area of interest to the signals originating from systemic imaging agent residues. In our study, a prospective silica core-shell nanoparticle-based scavenger was designed and explored for its feasibility to scavenge a specific imaging agent (tracer) in the bloodstream. The developed tracer-scavenger system was first investigated under in vitro conditions to ensure proper binding between tracer and scavenger is taking place, as confirmed by Förster/fluorescence resonance energy transfer studies. In vivo, two-photon imaging was utilized to directly study the interaction of the scavenger particles and the tracer molecules in the vasculature of mice. To our knowledge, a methodological solution for in vivo differentiation between signals, originating from tissue and blood, has not been presented elsewhere.

NIR-Fluorescent Multidye Silica Nanoparticles with Large Stokes Shifts for Versatile Biosensing Applications

We have synthesized and characterized of a series of single and multidye copolymerized nanoparticles with large to very large Stokes shifts (100 to 255 nm) for versatile applications as standalone or multiplexed probes in biological matrices. Nanoparticles were prepared via the Stöber method and covalently copolymerized with various combinations of three dyes, including one novel aminocyanine dye. Covalently encapsulated dyes exhibited no significant leakage from the nanoparticle matrix after more than 200 days of storage in ethanol. Across multiple batches of nanoparticles with varying dye content, the average yields and average radii were found to be highly reproducible. Furthermore, the batch to batch variability in the relative amounts of dye incorporated was small (relative standard deviations <2.3%). Quantum yields of dye copolymerized nanoparticles were increased 50% to 1000% relative to those of their respective dye-silane conjugates, and fluorescence intensities were enhanced by approximately three orders of magnitude. Prepared nanoparticles were surface modified with polyethylene glycol and biotin and bound to streptavidin microspheres as a proof of concept. Under single wavelength excitation, microsphere-bound nanoparticles displayed readily distinguishable fluorescence signals at three different emission wavelengths, indicating their potential applications to multicolor sensing. Furthermore, nanoparticles modified with polyethylene glycol and biotin demonstrated hematoprotective qualities and reduced nonspecific binding of serum proteins, indicating their potential suitability to in vivo imaging applications.

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.

Aptamer Combined with Fluorescent Silica Nanoparticles for Detection of Hepatoma Cells

PURPOSE

The purpose of this study is to develop a simple, effective method to label hepatoma cells with aptamers and then detect them using fluorescent silica nanoparticles (FSNPs).

METHOD

Streptavidin was conjugated to carboxyl-modified fluorescein isothiocyanate (FITC)-doped silica nanoparticles which were prepared by the reverse microemulsion method. The resulting streptavidin-conjugated fluorescent silica nanoparticles (SA-FSNPs) were mixed with hepatoma cells that had been labeled with biotin-conjugated aptamer TLS11a (Bio-TLS11a). The specificity and sensitivity of the nanoprobes were assessed using flow cytometry and fluorescence microscopy. Their toxicity was assessed in normal human liver cell cultures using the MTT assay, as well as in nude mice using immunohistochemistry.

RESULTS

SA-FSNPs showed uniform size and shape, and fluorescence properties of them was similar to the free FITC dye. SA-FSNPs were able to detect aptamer-labeled hepatoma cells with excellent specificity and good sensitivity, and they emitted strong, photobleach-resistant fluorescent signal. SA-FSNPs showed no significant toxic effects in vitro or in vivo.

CONCLUSION

The combination of biotin-conjugated aptamers and SA-FSNPs shows promise for sensitive detection of hepatoma cells, and potentially of other tumor cell types as well.

Bioprobes Based on Aptamer and Silica Fluorescent Nanoparticles for Bacteria Salmonella typhimurium Detection

In this study, we have developed an efficient method based on single-stranded DNA (ssDNA) aptamers along with silica fluorescence nanoparticles for bacteria Salmonella typhimurium detection. Carboxyl-modified Tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (RuBPY)-doped silica nanoparticles (COOH-FSiNPs) were prepared using reverse microemulsion method, and the streptavidin was conjugated to the surface of the prepared COOH-FSiNPs. The bacteria S. typhimurium was incubated with a specific ssDNA biotin-labeled aptamer, and then the aptamer-bacteria conjugates were treated with the synthetic streptavidin-conjugated silica fluorescence nanoprobes (SA-FSiNPs). The results under fluorescence microscopy show that SA-FSiNPs can be applied effectively for the labeling of bacteria S. typhimurium with great photostable property. To further verify the specificity of SA-FSiNPs out of multiple bacterial conditions, variant concentrations of bacteria mixtures composed of bacteria S. typhimurium, Escherichia coli, and Bacillus subtilis were treated with SA-FSiNPs.In addition, the feasibility of SA-FSiNPs for bacteria S. typhimurium detection in chicken samples was assessed. All the results display that the established aptamer-based nanoprobes exhibit the superiority for bacteria S. typhimurium detection, which is referentially significant for wider application prospects in pathogen detection.

Aptamer-Functionalized Fluorescent Silica Nanoparticles for Highly Sensitive Detection of Leukemia Cells

A simple, highly sensitive method to detect leukemia cells has been developed based on aptamer-modified fluorescent silica nanoparticles (FSNPs). In this strategy, the amine-labeled Sgc8 aptamer was conjugated to carboxyl-modified FSNPs via amide coupling between amino and carboxyl groups. Sensitivity and specificity of Sgc8-FSNPs were assessed using flow cytometry and fluorescence microscopy. These results showed that Sgc8-FSNPs detected leukemia cells with high sensitivity and specificity. Aptamer-modified FSNPs hold promise for sensitive and specific detection of leukemia cells. Changing the aptamer may allow the FSNPs to detect other types of cancer cells.

New naphthalimide modified polyethylenimine nanoparticles as fluorescent probe for DNA detection

A new naphthalimide modified polyethylenimine (PEI) nanoparticles (called NPEI-NPs) was synthesized and applied as fluorescent probe for rapid, selective and sensitive fluorometric detection of trace DNA. The synthesis involved the covalent modification of PEI with 4-butylamino-N-carboxymethyl-1,8-naphthalimide(BACMN) for getting amphiphilic polymer. Then the amphiphilic polymer was self-assembled in water to give the NPEI-NPs. NPEI-NPs was soluble in water and emitted fluorescence at 545 nm with exciting at 460 nm. The fluorescence spectra resulting from the interaction between NPEI-NPs and DNA indicated that the fluorescence of NPEI-NPs increased in the present of DNA. Therefore, a fluorescence enhancement method was developed for the determination of trace fish sperm DNA (fsDNA) and calf thymus DNA (ctDNA). Under the optimal conditions, the calibration curves were linear over the concentration ranges of 0.05-2.8 μg/mL for fsDNA and 0.08-3.0μg/mL for ctDNA. The detection limits for fsDNA and ctDNA were 1.6 and 2.0 ng/mL, respectively. The proposed method has been employed to quantify DNA in synthetic samples with the satisfactory results.