Silica nanoparticles modified with aminosilanes as carriers for plasmid DNA

Simple coupling chemistry linking carboxyl-containing organic molecules to silicon oxide surfaces under acidic conditions

The coupling chemistry of carboxymethylated amylose with organo-silanized silicon oxide surfaces at pH 7.4 and 2.0 was investigated using atomic force microscopy (AFM) based single-molecule force spectroscopy. At close to neutral pH, carbodiimide activation of a carboxylic acid affords formation of an amide bond with an amino surface linker. At pH 2.0, no activation with carbodiimide was required to anchor carboxymethylated amylose between an AFM tip and a glass substrate. At the same time, the mean bond rupture force f(r) dropped from 1.65 ± 0.37 nN at pH 7.4 to 1.39 ± 0.30 nN at pH 2.0 without carbodiimide, indicating that a different link to the surface can be formed at low pH. The coupling mechanism at pH 2.0 was elucidated by a series of experiments, in which the surface was functionalized with four different organosilanes, each containing characteristic functional groups. The results are rationalized with an acid-catalyzed ester condensation between a carboxyl group and a free, unreacted silanol group in the surface anchor or on the surface.

A nanoencapsulated hypocrellin A prepared by an improved microemulsion method for photodynamic treatment

A new hypocrellin A (HA) encapsulated silica nanoparticles was prepared by an improved microemulsion method based on the unique character of cetyl trimethyl ammonium bromide (CTAB). Stable aqueous dispersions of the HA-loaded nanoparticles, with the diameter about 50 nm, owned superior photo-stability and singlet oxygen generation ability to free HA. In vitro studies demonstrated the active uptake of HA-doped nanoparticles into the cytosol of HeLa (human cervix epithelioid carcinoma) cells. Significant morphology change and phototoxicity to such impregnated tumor cells was observed upon irradiation with light. Thus, the potential of using this method to prepare silica nanoparticles as drug carriers for photodynamic therapy has been demonstrated.

DNA-based applications in nanobiotechnology

Biological molecules such as deoxyribonucleic acid (DNA) have shown great potential in fabrication and construction of nanostructures and devices. The very properties that make DNA so effective as genetic material also make it a very suitable molecule for programmed self-assembly. The use of DNA to assemble metals or semiconducting particles has been extended to construct metallic nanowires and functionalized nanotubes. This paper highlights some important aspects of conjugating the unique physical properties of dots or wires with the remarkable recognition capabilities of DNA which could lead to miniaturizing biological electronics and optical devices, including biosensors and probes. Attempts to use DNA-based nanocarriers for gene delivery are discussed. In addition, the ecological advantages and risks of nanotechnology including DNA-based nanobiotechnology are evaluated.

Protein analysis based on molecular beacon probes and biofunctionalized nanoparticles

With the completion of the human genome-sequencing project, there has been a resulting change in the focus of studies from genomics to proteomics. By utilizing the inherent advantages of molecular beacon probes and biofunctionalized nanoparticles, a series of novel principles, methods and techniques have been exploited for bioanalytical and biomedical studies. This review mainly discusses the applications of molecular beacon probes and biofunctionalized nanoparticles-based technologies for real-time, in-situ, highly sensitive and highly selective protein analysis, including the nonspecific or specific protein detection and separation, protein/DNA interaction studies, cell surface protein recognition, and antigen-antibody binding process-based bacteria assays. The introduction of molecular beacon probes and biofunctionalized nanoparticles into the protein analysis area would necessarily advance the proteomics research.

Lipid-coated nano-calcium-phosphate (LNCP) for gene delivery

While calcium-phosphate has been used to deliver plasmid DNA (pDNA) for decades, the method is typically characterized by low and irreproducible transfection efficiency relative to the other non-viral approaches, such as liposomes and polymers. Here we report a novel gene transfer vector comprising lipid-coated nano-calcium-phosphate (LNCP) that provides consistently efficient and satisfactory pDNA delivery. It is based on core-shell nanoparticles comprising a calcium-phosphate core and a cationic lipid shell. This method, in contrast to the solution precipitation methods used in the past, yields colloidally stable calcium-phosphate nanoparticles inside the cationic liposomes. Our results indicate that the particle size and the size distribution of the LNCP remain virtually unchanged even after 21 days of storage. Atomic force microscopy measurements reveal that the LNCP have a 5-fold higher rigidity than common cationic liposomes. The LNCP transfected pDNA 24 times greater than the naked pDNA and 10-fold greater relative to the standard calcium-phosphate precipitation preparations, suggesting that the LNCP may have potential as a novel transfection agent for gene therapy.

Novel amino-modified silica nanoparticles as efficient vector for hepatocellular carcinoma gene therapy

Due to the ineffective conventional treatment for hepatocellular carcinoma (HCC), the nonviral gene delivery system has been proved to be an attractive alternative to HCC therapy. In this work, we have developed a kind of new self-assembled nanoparticles, which were named as amino-modified silica nanoparticles (AMSNs). Scanning electron microscopy and zeta potential results demonstrated that AMSNs had a diameter of 20-30 nm and positive surface charges of +11.3 mV, respectively. The AMSNs could bind DNA strongly and protect DNA from degradation, which was confirmed by DNA-binding assay and serum protection assay. Furthermore, AMSNs could transfer foreign DNA into targeted cells with high transfection efficiency and little cytotoxicity. Combined with the p53 gene, AMSNs could transfect pp53-EGFP in HepG2 cells and result in a high-level of p53 mRNA and protein expressions. The nude mice treated with AMSNs/pp53-EGFP complexes showed significant tumor growth inhibition. Our results showed the AMSNs, an efficient gene vector, had the potential of gene therapy for HCC.

Nanoparticle-mediated gene delivery

Nonviral gene delivery has been gaining considerable attention recently. Although the efficacy of DNA transfection, which is a major concern, is low in nonviral vector-mediated gene transfer compared with viral ones, nonviral vectors are relatively easy to prepare, less immunogenic and oncogenic, and have no potential of virus recombination and no limitation on the size of a transferred gene. The ability to incorporate genetic materials such as plasmid DNA, RNA, and siRNA into functionalized nanoparticles with little toxicity demonstrates a new era in pharmacotherapy for delivering genes selectively to tissues and cells. In this chapter, we highlight the basic concepts and applications of nonviral gene delivery using super paramagnetic iron oxide nanoparticles and functionalized silica nanoparticles. The experimental protocols related to these topics are described in the chapter.

Layered double hydroxide nanoparticles in gene and drug delivery

Layered double hydroxides (LDHs) have been known for many decades as catalyst and ceramic precursors, traps for anionic pollutants, catalysts and additives for polymers, but their successful synthesis on the nanometer scale a few years ago opened up a whole new field for their application in nanomedicine. The delivery of drugs and other therapeutic/bioactive molecules (e.g., peptides, proteins, nucleic acids) to mammalian cells is an area of research that is of tremendous importance to medicine and provides manifold applications for any new developments in the area of nanotechnology. Among the many different nanoparticles that have been shown to facilitate gene and/or drug delivery, LDH nanoparticles have attracted particular attention owing to their many desirable properties. This review aims to report recent progress in gene and drug delivery using LDH nanoparticles. It summarizes the advantages and disadvantages of using LDH nanoparticles as carriers for nucleic acids and drugs against the general background of bottlenecks that are encountered by cellular delivery systems. It describes further the models that have been proposed for the internalization of LDH nanoparticles into cells so far and discusses the intracellular fate of the particles and their cargo. The authors offer some remarks on how this field of research will progress in the near future and which challenges need to be overcome before LDH nanoparticles can be used in a clinical setting.

Monodispersed mesoporous silica nanoparticles with very large pores for enhanced adsorption and release of DNA

Silica nanoparticles with controlled diameter (approximately 70-300 nm) and with uniform pores of 20 nm are prepared by a low temperature (10 degrees C) synthetic method in the presence of a dual surfactant system. While a triblock copolymer (Pluronic F127) acts as supramolecular template and coassembles with hydrolyzed silica species to develop a partially ordered mesophase with face-centered cubic symmetry, a fluorocarbon surfactant with high surface activity (FC-4) surrounds the silica particles through S+X-I+ interactions, thereby limiting their growth. The final textural properties of this material are achieved by means of a subsequent hydrothermal treatment to yield high pore volume mesoporous silica nanoparticles with the largest pore entrance size (17 nm) and cavity diameter (20 nm) reported up to now. After surface modification with aminopropyl groups, the nanoparticles are able to encapsulate inside the pores molecules of the firefly luciferase plasmid DNA (pGL3-Control, 5256 pb), leading to stable conjugates with up to 0.07 microg DNA m(-2), which is the highest content achieved with silica-based materials. Furthermore, plasmid DNA becomes protected from enzymatic degradation when conjugated with the mesostructured nanoparticles.

Nanotechnology, nanotoxicology, and neuroscience

Nanotechnology, which deals with features as small as a 1 billionth of a meter, began to enter into mainstream physical sciences and engineering some 20 years ago. Recent applications of nanoscience include the use of nanoscale materials in electronics, catalysis, and biomedical research. Among these applications, strong interest has been shown to biological processes such as blood coagulation control and multimodal bioimaging, which has brought about a new and exciting research field called nanobiotechnology. Biotechnology, which itself also dates back approximately 30 years, involves the manipulation of macroscopic biological systems such as cells and mice in order to understand why and how molecular level mechanisms affect specific biological functions, e.g., the role of APP (amyloid precursor protein) in Alzheimer's disease (AD). This review aims (1) to introduce key concepts and materials from nanotechnology to a non-physical sciences community; (2) to introduce several state-of-the-art examples of current nanotechnology that were either constructed for use in biological systems or that can, in time, be utilized for biomedical research; (3) to provide recent excerpts in nanotoxicology and multifunctional nanoparticle systems (MFNPSs); and (4) to propose areas in neuroscience that may benefit from research at the interface of neurobiologically important systems and nanostructured materials.

Silica nanoparticles as a delivery system for nucleic acid-based reagents

The transport of nucleic acid-based reagents is predicated upon developing structurally stable delivery systems that can preferentially bind and protect DNA and RNA, and release their cargo upon reaching their designated sites. Recent advancements in tailoring the size, shape, and external surface functionalization of silica materials have led to increased biocompatibility and efficiency of delivery. In this Feature Article, we highlight recent research progress in the use of silica nanoparticles as a delivery vehicle for nucleic acid-based reagents.

Cellular Fate of a Modular DNA Delivery System Mediated by Silica Nanoparticles

Development of efficient molecular medicines, including gene therapeutics, RNA therapeutics, and DNA vaccines, depends on efficient means of transfer of DNA or RNA into the cell. Potential problems, including toxicity and immunogenicity, surrounding viral methods of DNA delivery have necessitated the use of nonviral, synthetic carriers. To better design synthetic carriers, or transfection reagents, the modular design of viruses has inspired a modular approach to DNA and RNA delivery. Each modular component can be designed to circumvent each of the many barriers. The modular approach will allow modification of individual components for a specific application. By utilizing a dense silica nanoparticle to form a ternary complex, transfection efficiency of a DNA-transfection reagent complex was increased by a factor of approximately 10 by concentrating the DNA at the surface of cells. Surface modification of the silica nanoparticles allowed determination of the cellular uptake mechanism with only minor alteration of transfection efficiency. Nanoparticles are internalized by an endosome-lysosomal route followed by perinuclear accumulation. The modification mechanism confirms that surface modification of the modular system can allow specific moieties to be incorporated into the modular system without significant alteration of the transfection efficiency. By showing that the modular system based upon concentration of DNA at the level of the cell can be used to increase transfection efficiency, we have shown that further modification of the system may better target DNA delivery and overcome other barriers of DNA expression.

Synthesis and characterization of ultra-small superparamagnetic iron oxide nanoparticles thinly coated with silica

Ultra-small superparamagnetic iron oxide nanoparticles (SPIOs) were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications as MR contrast agents, biosensors, DNA capturing, bioseparation and enzyme immobilization.

Improved biocompatibility and pharmacokinetics of silica nanoparticles by means of a lipid coating: a multimodality investigation

Silica is a promising carrier material for nanoparticle-facilitated drug delivery, gene therapy, and molecular imaging. Understanding of their pharmacokinetics is important to resolve bioapplicability issues. Here we report an extensive study on bare and lipid-coated silica nanoparticles in mice. Results obtained by use of a wide variety of techniques (fluorescence imaging, inductively coupled plasma mass spectrometry, magnetic resonance imaging, confocal laser scanning microscopy, and transmission electron microscopy) showed that the lipid coating, which enables straightforward functionalization and introduction of multiple properties, increases bioapplicability and improves pharmacokinetics.

Silica-based multimodal/multifunctional nanoparticles for bioimaging and biosensing applications

In the last decade, the field of nanoparticle (NP) technology has attracted immense interest in bioimaging and biosensing research. This technology has demonstrated its capability in obtaining sensitive data in a noninvasive manner, promising a breakthrough in early-stage cancer diagnosis, stem cell tracking, drug delivery, pathogen detection and gene delivery in the near future. However, successful and wide application of this technology relies greatly on robust NP engineering and synthesis methodologies. The NP development steps involve design, synthesis, surface modification and bioconjugation. Each of these steps is critical in determining the overall performance of NPs. It is desirable to obtain NPs that are highly sensitive, stable, imageable, biocompatible and targetable. It is also desirable to obtain multimodal/multifunctional NPs that will enable imaging/sensing of the target using multiple imaging/sensing modalities. In this review, we focus on silica NPs that have been developed for biosensing applications and silica-based multimodal/multifunctional NPs for bioimaging applications.

Europium(III) complexes containing organosilyldipyridine ligands grafted on silica nanoparticles

This work focuses on the grafting of transition metal complexes on silica surface nanoparticles. Nanoscale silica particles in aqueous sols are used as starting silicated materials. We have undertaken the synthesis of europium(III) complexes containing organosilyldipyridine ligands, (EtO)3Si(CH2)3NHCH2-bipy (1) and (EtO)(CH3)2Si(CH2) 3NHCH 2-bipy (2), in view of a direct grafting reaction on silica nanoparticles. Reaction of one molar equivalent of 1 and 2 with Eu(tmhd)3 (tmhd= 2,2,6,6-tetramethyl-3,5-heptanedionato), as precursor, leads to octacoordinated silylated europium(III) complexes [Eu(tmhd)3(1)] (3) and [Eu(tmhd)3(2)] (4) as white solids in 34-54% yields. Europium complexes were characterized by elemental analysis, mass spectrometry, FT-IR, UV, and luminescence spectroscopies. These new complexes are reacting in a 1:10 (v/v) water and ethanol mixture with silica nanoparticles colloidal sol. Elemental analysis and thermogravimetric data indicated grafting ratios of 0.41 and 0.26 mmol of europium(III) complexes per gram of silica. Functionalized silica nanoparticles were characterized by DRIFT spectroscopy and TEM microscopy. The first analysis shows that the chemical integrity of the complexes is retained on the silica surface together with the size and the monodispersity of the nanoscale particles. As expected for europium(III) complexes, luminescence is observed under UV irradiation. Emission and excitation spectra indicate that the metal coordination environment is not modified on the silica surface. Moreover, the sharpness of the luminescence bands and the strong antenna effect are maintained when complexes are covalently bonded to silica. New luminescent europium(III) complexes grafted on silica nanoparticles are therefore obtained from our approach.

Characterization of secondary and tertiary conformational changes of beta-lactoglobulin adsorbed on silica nanoparticle surfaces

Nanoparticles possess unique properties as a result of their large surface area per unit volume and therefore can be functionalized by the immobilization of enzymes for a variety of biosensing applications. Changes in the tertiary conformation of beta-lactoglobulin adsorbed on 90 nm silica nanoparticles with time were inferred using tryptophan fluorescence and Fourier transform infrared spectroscopy (FTIR) for different surface concentrations, temperature, pH, ionic strength, and 2,2,2-trifluoroethanol (TFE) and dithiothreitol (DTT) concentrations. Rapid initial unfolding followed by a much slower rate at longer times was observed, with the extent of unfolding being higher at lower surface concentrations, higher ionic strengths, higher temperature, higher TFE and DTT concentrations, and pI. The effect of temperature on the unfolding of adsorbed protein on the nanoparticle surface was similar to that in the bulk even though the extent of unfolding was higher for adsorbed protein molecules. The results of the extent of change in tertiary conformation using FTIR as indicated by the change in the ratio of amide II'/amide I were consistent with those obtained by tryptophan fluorescence whereas the rates of conformational changes given by FTIR were found to be much faster. Circular dichroism (CD) spectra showed that altering the surface concentration by itself did not change the secondary structure of beta-lactoglobulin on the surface. TFE was found to increase the alpha helix content at the expense of the fraction of the beta sheet, whereas the beta sheet was converted to an unordered conformation in the presence of DTT.

Silicalite nanoparticles that promote transgene expression

Here, we report on a new zeolite-based silicalite nanoparticle that can enhance the transfection efficiencies generated by poly ethylene imine-plasmid DNA (PEI-pDNA) complexes via a sedimentation mechanism and can enhance the transfection efficiencies of pDNA alone when surface functionalized with amine groups. The silicalite nanoparticles have a mean size of 55 nm. Functionalizing the silicalite nanoparticles with amine groups results in a clear transition in zeta potential from -25.9 ± 2.3 mV (pH 7.4) for unfunctionalized silicalite nanoparticles to 4.9 ± 0.7 mV (pH 7.4) for amine functionalized silicalite nanoparticles. We identify that silicalite nanoparticles used to promote non-viral vector acceleration to the cell surface are found in acidic vesicles or the cytoplasm but not the nucleus. An MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay showed that the silicalite nanoparticles were non-toxic at the concentrations tested for transfection. We show that surface functionalization of silicalite nanoparticles with amine groups results in a significant (230%) increase in transfection efficiency of pDNA when compared to unfunctionalized silicalite nanoparticles. Silicalite nanoparticles enhanced pDNA-PEI induced transfection of human embryonic kidney (HEK-293) cells by over 150%.

Potential applications of nanotechnologies to Parkinson's disease therapy

Nanotechnology will play a key role in developing new diagnostic and therapeutic tools. Nanotechnologies use engineered materials with the smallest functional organization on the nanometre scale in at least one dimension. Some aspects of the material can be manipulated resulting in new functional properties. Nanotechnology could provide devices to limit and reverse neuropathological disease states, to support and promote functional regeneration of damaged neurons, to provide neuroprotection and to facilitate the delivery of drugs and small molecules across the blood-brain barrier. All of them are relevant to improve current therapy of Parkinson's disease (PD).

Application of a new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid purification

A new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid (DNA) extraction was prepared in situ by polymerization of N-(beta-aminoethyl)-gamma-aminopropyltriethoxysilane (AEAPTES) and tetraethoxysilane (TEOS). The main extraction mechanism was based on the Coulombic force between DNA and the amino silica hybrid monolithic column. DNA extraction conditions, such as pH, ion concentration and type, and loading capacity, were optimized online by capillary electrophoresis with laser-induced fluorescence detection. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 48 ng DNA with an extraction efficiency of 74+/-6.3% (X+/-RSD). The DNA extraction process on this monolithic column was carried out in a totally aqueous system for the successful purification of DNA and removal of proteins. The PBE2 plasmid could be extracted from Bacillus subtilis (B. subtilis) crude lysate within 25 min, and the purified DNA was suitable for the amplification of a target fragment by polymerase chain reaction. This study demonstrates a new attractive solid-phase support for DNA extraction to meet the increasingly miniaturized and automated trends of genetic analyses.

Inorganic/Organic Hybrid Silica Nanoparticles as a Nitric Oxide Delivery Scaffold

The preparation and characterization of nitric oxide (NO)-releasing silica particles formed following the synthesis of N-diazeniumdiolate-modified aminoalkoxysilanes are reported. Briefly, an aminoalkoxysilane solution was prepared by dissolving an appropriate amount of aminoalkoxysilane in a mixture of ethanol, methanol, and sodium methoxide (NaOMe) base. The silane solution was reacted with NO (5 atm) to form N-diazeniumdiolate NO donor moieties on the amino-alkoxysilanes. Tetraethoxy- or tetramethoxysilane (TEOS or TMOS) was then mixed with different ratios of N-diazeniumdiolate-modified aminoalkoxysilane (10 - 75 mol%, balance TEOS or TMOS). Finally, the silane mixture was added into ethanol in the presence of an ammonia catalyst to form NO donor silica nanoparticles via a sol-gel process. This synthetic approach allows for the preparation of NO delivery silica scaffolds with remarkably improved NO storage and release properties, surpassing all macromolecular NO donor systems reported to date with respect to NO payload (11.26μmol·mg-1), maximum NO release amount (357000 ppb·mg-1), NO release half-life (253 min), and NO release duration (101 h). The N-diazeniumdiolate-modified silane monomers and the resulting silica nanoparticles were characterized by 29Si nuclear magnetic resonance (NMR) spectroscopy, UV-visible spectroscopy, chemiluminescence, atomic force microscopy (AFM), gas adsorption-desorption isotherms, and elemental analysis.

Intracellular delivery of core-shell fluorescent silica nanoparticles

Highly fluorescent core-shell silica nanoparticles made by the modified Stöber process (C dots) are promising as tools for sensing and imaging subcellular agents and structures but will only be useful if they can be easily delivered to the cytoplasm of the subject cells. This work shows that C dots can be electrostatically coated with cationic polymers, changing their surface charge and enabling them to escape from endosomes and enter the cytoplasm and nucleus. As an example of cellular delivery, we demonstrate that these particles can also be complexed with DNA and mediate and trace DNA delivery and gene expression.

Importance of divalent cations in nanolipoplex gene delivery

Gene therapy is a promising therapeutic strategy to combat genetic or acquired diseases at their root cause rather than just treating symptoms. It is well recognised that there is an urgent need for non-toxic and efficient gene delivery vectors to fully exploit the current potential of gene therapy in molecular medicine. Cell-specific targeting of bioactive nucleotides is a prerequisite to attain the concentration of nucleic acids required for therapeutic efficacy in the target tissue. Many metal ions such as Mg2+, Mn2+, Ba2+ and, most importantly, Ca2+ have been demonstrated to have significant roles in gene delivery. These inorganic cations show low toxicity, good biocompatibility and promise for controlled delivery properties, thus presenting a new alternative to toxic and immunogenic carriers. Recently, inorganic nanoparticles alone, or in combination with a colloidal particulate system such as nanoliposome, an advanced approach to gene delivery, were found to exert a positive effect on gene transfer. In this report, the role of the divalent cations in nucleic acid delivery, particularly with respect to the potential improvement of transfection efficiency of nanolipoplexes, is reviewed.

Poly (amino ester) Composed of Poly (ethylene glycol) and Aminosilane Prepared by Combinatorial Chemistry as a Gene Carrier

PURPOSE

Application of combinatorial chemistry and high throughput screening for the synthesis and evaluation of mini-library of novel biodegradable poly (beta-amino ester)s (PAE)s composed of gamma-aminopropyl-triethoxysilane (APES) and poly (ethylene glycol) diacrylate (PEGDA) for gene delivery efficiency and safety in 293T and HeLa cells in the presence of and absence of serum.

MATERIALS AND METHODS

PAEs were synthesized at different mole ratios of APES and PEGDA by Michael addition reaction and synthesis was confirmed by 1H nuclear magnetic resonance (1H-NMR). Ninety six ratios of polyplexes were evaluated for luciferase and MTS assay in 293T and HeLa cells in the presence of and absence of serum. Relationship between transfection efficiency and DNA binding ability of PAEs was studied by gel electrophoresis. Particle sizes and molecular weight of selected PAEs were measured by dynamic light scattering and gel permeation chromatography multi-angle light scattering, respectively.

RESULTS

1H-NMR confirmed the synthesis of PAEs. In both cell lines, transfection efficiency and cell viability were increased for PAEs obtained from R106 (0.7:1, APES:PEGDA) to R121 (6:1, APES:PEGDA) with a marginal increase in APES concentration. Transfection pattern was uniform in the absence of and presence of serum. In both cell lines, PAE obtained from R121 demonstrated high transfection efficiency and low cytotoxicity as compared to polyethylenimine (25 KDa) and Lipofectamine. PAE obtained from R121 showed good DNA binding and condensation with average particle sizes of 133 nm.

CONCLUSION

Addition of PEGDA over APES resulted in a novel PAE which has high safety and transfection efficiency. Transfection and cytotoxicity are very sensitive to monomer ratios and mainly governed by concentration of amine monomer.

From Nutraceuticals to Pharmaceuticals to Nanopharmaceuticals: A Case Study in Angiogenesis Modulation During Oxidative Stress

This report reviews the potential applications of nanotechnology in various therapeutics and diagnostics areas with special emphasis on key frontiers in angiogenesis modulation using naturally driven drug targets including compounds that modulate oxidative stress and inflammatory pathways for the potential treatment of vascular, cancer, inflammatory, and ocular disorders. Recent advances of the nanotechnology mediated gene delivery are also described in this paper.

Transsynaptic delivery of nanoparticles to the central auditory nervous system

CONCLUSION

Silica nanoparticles may serve as a nonviral delivery system to the sensory hair cells, spiral ganglion cells within the cochlea, and the vestibular organ, as well as the cochlear nucleus.

OBJECTIVES

At present there are no targeted therapeutics for inner ear disease. A variety of viral vector systems have been tested in the inner ear with variable efficacy but they are still not regarded as safe systems for inner ear delivery. Nanoparticles are a nonviral method of delivering a variety of macromolecules that potentially can be used for delivery within the auditory system. In this study, we evaluated the distribution and safety of nanoparticles in the inner ear.

MATERIALS AND METHODS

Cy3-labeled silica nanoparticles were placed on the round window membrane of adult mice. Hearing thresholds were determined after nanoparticle delivery by auditory brainstem responses (ABRs). Distribution of particles was determined by histological evaluation of the cochlea, vestibular organs, and brain stem.

RESULTS

Fluorescent microscopy demonstrated Cy3-labeled nanoparticles signals in the sensory hair cells and the spiral ganglion neurons of both the treated and contralateral inner ears. Additionally, the distal part of the central auditory pathway (dorsal cochlear nucleus, superior olivary complex) was found to be labeled with the Cy3-linked silica nanoparticles, indicating a retrograde axonal transport. No hearing loss or inflammation was noted in the treated cochlea.

Mesoporous silica spheres from colloids

A novel method has been developed to synthesize mesoporous silica spheres using commercial silica colloids (SNOWTEX) as precursors and electrolytes (ammonium nitrate and sodium chloride) as destabilizers. Crosslinked polyacrylamide hydrogel was used as a temporary barrier to obtain dispersible spherical mesoporous silica particles. The influences of synthesis conditions including solution composition and calcination temperature on the formation of the mesoporous silica particles were systematically investigated. The structure and morphology of the mesoporous silica particles were characterized via scanning electron microscopy (SEM) and N2 sorption technique. Mesoporous silica particles with particle diameters ranging from 0.5 to 1.6 microm were produced whilst the BET surface area was in the range of 31-123 m2 g-1. Their pore size could be adjusted from 14.1 to 28.8 nm by increasing the starting particle diameter from 20-30 nm up to 70-100 nm. A simple and cost effective method is reported that should open up new opportunities for the synthesis of scalable host materials with controllable structures.

An antisense oligonucleotide carrier based on amino silica nanoparticles for antisense inhibition of cancer cells

Antisense oligonucleotides (anti-ODNs), which are able to interfere with gene expression at the mRNA level, have potential activity in the treatment of viral infections or cancer. However, the application of therapies based on anti-ODNs is hampered by their instability to cellular nuclease and their weak intracellular penetration. Among the many efforts to increase their stability and cellular penetration have been modifications of ODNs and introduction of particulate carriers. Here we report an anti-ODNs carrier based on amino silica nanoparticles (NH(2)SiNPs) and its preliminary applications in cancer cells. The positively charged NH(2)SiNPs were synthesized by a water-in-oil microemulsion method. The NH(2)SiNP-ODN complexes were formed by electrostatic interaction, and their cellular uptake was visualized by using fluorescein isothiocyanate (FITC)-labeled ODNs and NH(2)SiNPs doped with rhodamine 6G isothiocyanate (RITC) as fluorescent signal indicators. The antisense inhibition efficiency of anti-ODNs delivered by NH(2)SiNPs was evaluated using MTT (3,4,5-dimethylthiazol-2,5-diphenyl tetrazolium bromide) assay and western blot analysis. Uniform NH(2)SiNPs with an average diameter of 25 nm were obtained and could combine with anti-ODNs to form a bioconjugate favorable for cellular uptake. The NH(2)SiNPs were able to protect anti-ODNs from degradation by DNase I. In vitro experiments showed that the NH(2)SiNPs could greatly improve the inhibition efficiency of anti-ODNs for the proliferation and survivin expression in Hela cells and A549 cells. Compared with liposomes, the NH(2)SiNPs presented a better biocompatibility and had almost no cytotoxicity at the concentrations required for efficient transfection. Our results suggest that the NH(2)SiNPs may be a promising carrier for delivery of anti-ODNs.

Synthesis of nitric oxide-releasing silica nanoparticles

The synthesis and characterization of a new nitric oxide (NO)-releasing scaffold prepared from amine-functionalized silica nanoparticles are reported. Inorganic-organic hybrid silica was prepared via cocondensation of tetraethoxy- or tetramethoxysilane (TEOS or TMOS) and aminoalkoxysilane with appropriate amounts of ethanol (or methanol), water, and ammonia. The amine functional groups in the silica were converted to N-diazeniumdiolate NO donors via exposure to high pressures of NO (5 atm) under basic conditions. Control over both the structure and concentration of the silane precursors (i.e., tetraalkoxy- and aminoalkoxysilanes) and specific synthetic conditions allowed for the preparation of NO donor silica particles of widely varying sizes (d = 20-500 nm), NO payloads (50-1780 nmol.mg-1), maximum amounts of NO released (10-5500 ppb.mg-1), half-lives (0.1-12 h), and NO release durations (up to 30 h). The silica nanoparticles were characterized by solid-state 29Si nuclear magnetic resonance (NMR), atomic force microscopy (AFM), elemental analysis, and gas adsorption-desorption isotherms. The advantages of silica-derived NO storage/delivery systems over previously reported macromolecular NO donors include the ability to (1) store large quantities of NO, (2) modulate NO release kinetics, and (3) readily tune particle size based on the composition of the particle. In addition, a one-pot strategy for preparing the NO donor silica allows for straightforward, high-throughput synthesis and purification.

Optimization of the methods for introduction of amine groups onto the silica nanoparticle surface

The luminescent silica nanoparticle has attracted the researchers' concentration in bioanalysis recently. Its extensive application is based on the immobilization of various biomolecules such as deoxyribonucleic acid, antibody, and so forth onto the surface. By comparing different introduction methods of amine groups, it was confirmed that the "two-step" route is more preferable by adding tetraethyl orthosilicate and 3-aminopropyl-(triethoxyl)silane in sequence, to attain ideal amine-modified silica nanoparticles. On this basis, carboxyl groups were derived from amine groups on the nanoparticle surface and then were activated by 1-ethyl-3-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. Finally, mouse monoclonal antihuman CD71 antibody (McAb CD71) and transferrin were effectively linked with the carboxyl groups and successfully labeled the receptors in the membrane of fibroblast cells, respectively.

Surface Charge Modification of Nano-Sized Silica Colloid

The surface of commercial 30-nm colloidal silica particles were modified by reaction with functional silanes. The high specific surface area and reactivity of the particles, due to their small size, makes the process susceptible to irreversible aggregation not found previously with larger particles. The present study compares surface charge results from amino silanes with one or three alkoxy groups. Measurements of the zeta potential as a function of pH, and gelation kinetics shed light on the mechanism of surface charge changes from the modification. Instability in suspensions before and after the surface modification is also studied using a new data analysis technique from simple light-scattering equipment. Experimental results show very stable particles are obtained by amino silane surface modification. Factors affecting susceptibility of small particles to irreversible aggregation caused by a non-aqueous solvent or high concentration of a trialkoxy silane, including the large number of reactive silanol groups in the surface gel layer of the particles, are discussed.