Oligonucleotide-Modified Gold Nanoparticles for Intracellular Gene Regulation

A label-free biosensor based on gold nanoshell monolayers for monitoring biomolecular interactions in diluted whole blood

Gold nanoshells (GNSs) were self-assembled on the surface of transparent glasses modified with 3-aminopropyltrimethoxysilane (APTES) to form GNS self-assembled monolayers (SAMs). Because the localized surface plasmon resonance (LSPR) of GNSs can be controlled in the near-infrared (NIR) region of the spectrum, where the optical transmission through tissue and whole blood is optimal, GNSs would be used as an effective signal transduction in whole blood. Accordingly, after modified with cystamine and biotin-NHS (N-hydroxy succinimide), GNS SAMs were used as a novel optical biosensor for real-time detection of streptavidin-biotin interactions in diluted human whole blood within short assay time, without any sample purification/separation. An UV-vis-NIR spectrophotometer was used to monitor the absorbance changes at 730 nm as a function of time for different concentrations of streptavidin in 20% whole blood, and the results showed that the biosensor displayed low detection limit of approximately 3 microg/mL and wide dynamic range of approximately 3-50 microg/mL. This approach provides an opportunity to construct LSPR biosensor for protein sensing and cellular analysis in diluted whole blood.

Size-dependent cytotoxicity of gold nanoparticles

Gold nanoparticles are widely used in biomedical imaging and diagnostic tests. Based on their established use in the laboratory and the chemical stability of Au(0), gold nanoparticles were expected to be safe. The recent literature, however, contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background a systematic study of water-soluble gold nanoparticles stabilized by triphenylphosphine derivatives ranging in size from 0.8 to 15 nm is made. The cytotoxicity of these particles in four cell lines representing major functional cell types with barrier and phagocyte function are tested. Connective tissue fibroblasts, epithelial cells, macrophages, and melanoma cells prove most sensitive to gold particles 1.4 nm in size, which results in IC(50) values ranging from 30 to 56 microM depending on the particular 1.4-nm Au compound-cell line combination. In contrast, gold particles 15 nm in size and Tauredon (gold thiomalate) are nontoxic at up to 60-fold and 100-fold higher concentrations, respectively. The cellular response is size dependent, in that 1.4-nm particles cause predominantly rapid cell death by necrosis within 12 h while closely related particles 1.2 nm in diameter effect predominantly programmed cell death by apoptosis.

Novel arylhydrazone-conjugated gold nanoparticles with DNA-cleaving ability: the first DNA-nicking nanomaterial

Arylhydrazones were linked onto gold nanoparticles through the poly(ethylene glycol) spacer to produce a new type of photoinduced DNA-cleaving nanomaterials with great potency.

Water-soluble amphiphilic gold nanoparticles with structured ligand shells

Highly water-soluble mixed monolayer protected "rippled" gold nanoparticles were synthesized through a one step reaction with sodium 11-mercaptoundecanesulfonate and octanethiol ligands at various ratios.

Nonenzymatic detection of bacterial genomic DNA using the bio bar code assay

The detection of bacterial genomic DNA through a nonenzymatic nanomaterials-based amplification method, the bio bar code assay, is reported. The assay utilizes oligonucleotide-functionalized magnetic microparticles to capture the target of interest from the sample. A critical step in the new assay involves the use of blocking oligonucleotides during heat denaturation of the double-stranded DNA. These blockers bind to specific regions of the target DNA upon cooling and prevent the duplex DNA from rehybridizing, which allows the particle probes to bind. Following target isolation using the magnetic particles, oligonucleotide-functionalized gold nanoparticles act as target recognition agents. The oligonucleotides on the nanoparticle (bar codes) act as amplification surrogates. The bar codes are then detected using the Scanometric method. The limit of detection for this assay was determined to be 2.5 fM, and this is the first demonstration of a bar code-type assay for the detection of double-stranded, genomic DNA.

Nanoscale Energy Deposition by X-ray Absorbing Nanostructures

Here we wish to demonstrate a unique property of nanomaterials: energy deposition with nanometer precision from low-energy electrons released from these nanostructures interacting with hard X-ray radiation in aqueous solution. Three effects combine to cause this phenomenon: (1) localized absorption of X-rays by nanostructures, (2) effective release of low-energy electrons from small nanostructures, and (3) efficient deposition of energy in water in the form of radicals and electrons. This combination creates localized X-ray absorption and localized energy deposition of nanometer precision. We confirmed the theoretically predicted nanoscale energy deposition distribution by measuring hydroxyl radical-induced DNA strand breaks, and observed enhanced damage to a 5600-bp DNA molecule from approximately 10 chemically conjugated small gold nanoparticles under X-ray radiation. These results provide a general guidance to applications of this new concept in many fields including radiation chemistry, radiology, radiation oncology, biochemistry, biology, and nanotechnology.

A facile synthesis to Zn2SiO4:Mn2+ phosphor with controllable size and morphology at low temperature

Sphere- and rod-shaped Zn(2)SiO(4):Mn(2+) phosphor nanocrystals were synthesized at 230 degrees C. The process consists of tuning the surfactant concentration in the oil/surfactant/ethanol system. Powder X-ray (XRD) and transmission electron microscopy (TEM) were used to characterize the phase purity, size and morphology. Photoluminescent (PL) spectra were collected and analyzed. Fourier transform infrared (FT-IR) spectra of the samples indicate the removal of surfactant in the phosphor nanoparticles. As a result, the sphere-shaped phosphor nanoparticles of 100 nm in size can be redispersed in ethanol ultrasonically. The suspension maintain stable for over 48 h.

Intracellular delivery of quantum dots tagged antisense oligodeoxynucleotides by functionalized multiwalled carbon nanotubes

With the goal of identifying an improved delivery scheme for intracellular tracking and anticancer therapy, we explored a novel double functionalization of a carbon nanotube delivery system containing antisense oligodeoxynucleotides (ASODNs) as a therapeutic gene and CdTe quantum dots as fluorescent labeling probes via electrostatically layer-by-layer assembling. This is the first time that we used mercaptoacetic acid-capped CdTe quantum dots as fluorescent labeling probes for clearly tracking the intracellular transport and evaluating delivery efficiency of ASODNs by functionalized multiwalled carbon nanotubes (MWNTs).

The combination of transition metal ions and hydrogen-bonding interactions

This feature article presents an overview of the types of hydrogen bonding interactions involving metal complexes and their functional effects. It shows with recent examples why hydrogen bonds have become a crucial functional and structural element in modern inorganic chemistry. The relevance of this combination in tackling current chemistry challenges such as energy production and the development of new materials and more effective catalysts, sensors and medicines is illustrated.

Fluorescent magnetic nanocrystals by sequential addition of reagents in a one-pot reaction: a simple preparation for multifunctional nanostructures

Core-shell nanostructures consisting of FePt magnetic nanoparticles as the core and semiconducting chalcogenides as the shell were synthesized by a series of reactions in a one-pot procedure. Adding Cd(acac)2 as the cadmium precursor to a reaction mixture containing FePt nanoparticles afforded FePt@CdO core-shell intermediates. The subsequent addition of chalcogens yielded FePt@CdX core-shell nanocrystals (where X was S or Se). The reverse sequence of addition, i.e., adding X before Cd, resulted in spongelike nanostructures because the chalcogens readily formed nanowires in the solution. Transmission electron microscopy, energy-dispersive X-ray spectrometry, selected area electron diffraction, fluorescence spectroscopy, and SQUID were used to characterize the nanostructures. These core-shell nanostructures displayed superparamagnetism at room temperature and exhibited fluorescence with quantum yields of 2.3-9.7%. The flexibility in the sequence of addition of reagents, combined with the compatibility of the lattices of the different materials, provides a powerful yet convenient strategy for generating sophisticated, multifunctional nanostructures.

Microfluidic Devices for the Analysis of Single Cells: Leaving No Protein Uncounted

Microfluidic devices are revolutionizing bioanalysis, and designs capable of detecting single protein molecules are now available. Two recently described microfluidic devices provide information on the number of beta(2)-adrenergic receptors in individual cultured insect cells and measure the degradation of phycobilisomes in individual cyanobacteria, respectively. This latter experiment, which included the analysis of three single cells in parallel, heralds a bright future for high-throughput single-cell analyzers. These devices could greatly advance research in signal transduction and studies of the effects of environmental stimuli or xenobiotics on cellular responses.

Oligonucleotides forming an i-motif: the pH-dependent assembly of individual strands and branched structures containing 2'-deoxy-5-propynylcytidine

Non-branched and branched oligonucleotides incorporating consecutive runs of 2'-deoxy-5-propynylcytidine residues () instead of 2'-deoxycytidine () were synthesized. For this, phosphoramidite building blocks of 2'-deoxy-5-propynylcytidine () were prepared using acetyl, benzoyl or N,N-di-n-butylaminomethylidene protecting groups. The formation of the i-motif assemblies incorporating 2'-deoxy-5-propynylcytidine residues was confirmed by temperature-dependent CD- and UV-spectra as well as by ion-exchange chromatography. The low pK(a)-value of nucleoside (pK(a) = 3.3) compared to dC (pK(a) = 4.5) required strong acidic conditions for i-motif formation. Branched oligonucleotide residues with strands in a parallel orientation lead to a strong stabilization of the i-motif allowing aggregation even at non-optimal pH conditions (pH = 5). The immobilization of oligonucleotides incorporating multiple residues of on 15 nm gold nanoparticles generated DNA-gold nanoparticle conjugates which are able to aggregate into i-motif structures at pH 5.

Silver nanoparticles: partial oxidation and antibacterial activities

The physical and chemical properties of silver nanoparticles that are responsible for their antimicrobial activities have been studied with spherical silver nanoparticles (average diameter approximately 9 nm) synthesized by the borohydride reduction of Ag+ ions, in relation to their sensitivity to oxidation, activities towards silver-resistant bacteria, size-dependent activities, and dispersal in electrolytic solutions. Partially (surface) oxidized silver nanoparticles have antibacterial activities, but zero-valent nanoparticles do not. The levels of chemisorbed Ag+ that form on the particle's surface, as revealed by changes in the surface plasmon resonance absorption during oxidation and reduction, correlate well with the observed antibacterial activities. Silver nanoparticles, like Ag+ in the form of AgNO3 solution, are tolerated by the bacteria strains resistant to Ag+. The antibacterial activities of silver nanoparticles are related to their size, with the smaller particles having higher activities on the basis of equivalent silver mass content. The silver nanoparticles aggregate in media with a high electrolyte content, resulting in a loss of antibacterial activities. However, complexation with albumin can stabilize the silver nanoparticles against aggregation, leading to a retention of the antibacterial activities. Taken together, the results show that the antibacterial activities of silver nanoparticles are dependent on chemisorbed Ag+, which is readily formed owing to extreme sensitivity to oxygen. The antibacterial activities of silver nanoparticles are dependent on optimally displayed oxidized surfaces, which are present in well-dispersed suspensions.

Silver nanoparticles: partial oxidation and antibacterial activities

The physical and chemical properties of silver nanoparticles that are responsible for their antimicrobial activities have been studied with spherical silver nanoparticles (average diameter approximately 9 nm) synthesized by the borohydride reduction of Ag+ ions, in relation to their sensitivity to oxidation, activities towards silver-resistant bacteria, size-dependent activities, and dispersal in electrolytic solutions. Partially (surface) oxidized silver nanoparticles have antibacterial activities, but zero-valent nanoparticles do not. The levels of chemisorbed Ag+ that form on the particle's surface, as revealed by changes in the surface plasmon resonance absorption during oxidation and reduction, correlate well with the observed antibacterial activities. Silver nanoparticles, like Ag+ in the form of AgNO3 solution, are tolerated by the bacteria strains resistant to Ag+. The antibacterial activities of silver nanoparticles are related to their size, with the smaller particles having higher activities on the basis of equivalent silver mass content. The silver nanoparticles aggregate in media with a high electrolyte content, resulting in a loss of antibacterial activities. However, complexation with albumin can stabilize the silver nanoparticles against aggregation, leading to a retention of the antibacterial activities. Taken together, the results show that the antibacterial activities of silver nanoparticles are dependent on chemisorbed Ag+, which is readily formed owing to extreme sensitivity to oxygen. The antibacterial activities of silver nanoparticles are dependent on optimally displayed oxidized surfaces, which are present in well-dispersed suspensions.

Functionalized gold nanoparticles for drug delivery

Functionalized gold nanoparticles represent highly attractive and promising candidates in the applications of drug delivery owing to their unique dimensions, tunable functionalities on the surface and controllable drug release. This review illustrates the recent advances in the field of drug delivery using gold nanoparticles as carriers for therapeutic agents.

Gum arabic as a phytochemical construct for the stabilization of gold nanoparticles: in vivo pharmacokinetics and X-ray-contrast-imaging studies

Gold nanoparticles (AuNPs) have exceptional stability against oxidation and therefore will play a significant role in the advancement of clinically useful diagnostic and therapeutic nanomedicines. Despite the huge potential for a new generation of AuNP-based nanomedicinal products, nontoxic AuNP constructs and formulations that can be readily administered site-specifically through the intravenous mode, for diagnostic imaging by computed tomography (CT) or for therapy via various modalities, are still rare. Herein, we report results encompassing: 1) the synthesis and stabilization of AuNPs within the nontoxic phytochemical gum-arabic matrix (GA-AuNPs); 2) detailed in vitro analysis and in vivo pharmacokinetics studies of GA-AuNPs in pigs to gain insight into the organ-specific localization of this new generation of AuNP vector, and 3) X-ray CT contrast measurements of GA-AuNP vectors for potential utility in molecular imaging. Our results demonstrate that naturally occurring GA can be used as a nontoxic phytochemical construct in the production of readily administrable biocompatible AuNPs for diagnostic and therapeutic applications in nanomedicine.

Applications of microfluidics for neuronal studies

Microfabrication processes have changed the technology used in consumer goods, and have now advanced into applications in biology. Microfluidic platforms are microfabricated tools that are gaining popularity for studies of molecular and cellular biology. These platforms can allow precise control of the environment surrounding individual cells and they have been used to study physiologic and pharmacologic responses at the single-cell level. This article reviews microfluidic technology with emphasis on advances that could apply to the study of the nervous system, including architecture for isolation of axons, integrated electrophysiology, patterned physical and chemical substrate cues, and devices for the precisely controlled delivery of possible therapeutic agents such as trophic factors and drugs. The potential of these chips for the study of neurological diseases is also discussed.

Multi-functional gold nanoparticles for drug delivery

Multi-functional gold nanoparticles have been demonstrated to be highly stable and versatile scaffolds for drug delivery due to their unique size, coupled with their chemical and physical properties. The ability to tune the surface of the particle provides access to cell-specific targeting and controlled drug release. This chapter describes current developments in the area of drug delivery using gold nanoparticles as delivery vehicles for multiple therapeutic purposes.

Maximizing DNA loading on a range of gold nanoparticle sizes

We have investigated the variables that influence DNA coverage on gold nanoparticles. The effects of salt concentration, spacer composition, nanoparticle size, and degree of sonication have been evaluated. Maximum loading was obtained by salt aging the nanoparticles to approximately 0.7 M NaCl in the presence of DNA containing a poly(ethylene glycol) spacer. In addition, DNA loading was substantially increased by sonicating the nanoparticles during the surface loading process. Last, nanoparticles up to 250 nm in diameter were found have approximately 2 orders of magnitude higher DNA loading than smaller (13-30 nm) nanoparticles, a consequence of their larger surface area. Stable large particles are attractive for a variety of biodiagnostic assays.

Tracking the pathway of calcium phosphate/DNA nanoparticles during cell transfection by incorporation of red-fluorescing tetramethylrhodamine isothiocyanate–bovine serum albumin into these nanoparticles

Calcium phosphate nanoparticles were prepared by precipitation from water and were then functionalized by DNA. These particles are taken up by living cells and function as gene transfer agents, i.e., the DNA is brought into a cell's nucleus and is incorporated there into the cell's genome (transfection). DNA which encodes for enhanced green fluorescent protein leads to green fluorescence of successfully transfected cells. By adding the red-fluorescing marker tetramethylrhodamine isothiocyanate-bovine serum albumin (TRITC-BSA) to the nanoparticles, their pathway into the cell and within the cell could be followed by fluorescence microscopy. A clear correlation between the uptake of nanoparticles and the efficiency of transfection was found. Aggregates of DNA/TRITC-BSA alone were not able to enter the cells, i.e., the inorganic nanoparticles are necessary as a carrier through the cell membrane.