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We report the development of a previously undescribed gold nanoparticle bio-barcode assay probe for the detection of prostate specific antigen (PSA) at 330 fg/mL, automation of the assay, and the results of a clinical pilot study designed to assess the ability of the assay to detect PSA in the serum of 18 men who have undergone radical prostatectomy for prostate cancer. Due to a lack of sensitivity, available PSA immunoassays are often not capable of detecting PSA in the serum of men after radical prostatectomy. This new bio-barcode PSA assay is ≈300 times more sensitive than commercial immunoassays. Significantly, with the barcode assay, every patient in this cohort had a measurable serum PSA level after radical prostatectomy. Patients were separated into categories based on PSA levels as a function of time. One group of patients showed low levels of PSA with no significant increase with time and did not recur. Others showed, at some point postprostatectomy, rising PSA levels. The majority recurred. Therefore, this new ultrasensitive assay points to significant possible outcomes: ( i ) The ability to tell patients, who have undetectable PSA levels with conventional assays, but detectable and nonrising levels with the barcode assay, that their cancer will not recur. ( ii ) The ability to assign recurrence earlier because of the ability to measure increasing levels of PSA before conventional tools can make such assignments. ( iii ) The ability to use PSA levels that are not detectable with conventional assays to follow the response of patients to adjuvant or salvage therapies.

The biobarcode assay (BCA) is capable of achieving low detection limits and high specificity for both protein and DNA targets. The realization of a BCA in a microfluidic format presents unique opportunities and challenges. In this work, we describe a modified form of the BCA called the surface immobilized biobarcode assay (SI-BCA). The SI-BCA employs micro channel walls functionalized with antibodies that bind with the intended targets. Compared with the conventional BCA, it reduces the system complexity and results in shortened process time, which is attributed to significantly reduced diffusion times in the micro-scale channels. Raw serum samples, without any pretreatment, were evaluated with this technique. Prostate specific antigen in the samples was detected at concentrations ranging from 40 pM to 40 fM. The detection limit of the assay using buffer samples is 10 fM. The entire assay, from sample injection to final data analysis was completed in eighty minutes.

We have developed a method for the large-scale synthesis of gold nanoparticles (Au NPs) in an aqueous medium stabilized by various water-soluble ligands. Significantly, the narrow size-distribution of the particles is achieved without employing size-selective procedures. The versatility of the procedure is demonstrated for the preparation of three colloidal systems stabilized by different ligands. Transmission electron microscopy (TEM), ζ -potential measurements and UV–vis spectroscopy are used to characterize the three colloidal systems.

A unique polymerization reaction of alkylsilanes to siloxane nanowires, filaments and tubes in presence of gold nanoparticles and water is presented. The gold nanoparticles, which catalyze this reaction also work as templates restricting the shape of the resulting polymers into wires and tubes. High resolution transmission electron microscopy images clearly reveal the presence of gold nanoparticle at the tip of each wire supporting the template hypothesis. Elemental analyses by different methods confirm the stoichiometry to be C 18 H 37 SiO 1.5, when the alkylsilane used was C 18 H 37 SiH 3, thus proving that the alkyl group remains intact during the polymerization reaction.

Herein is reported a metamorphosis taking place in a gold nanosized system. The observed phenomenon of shape and size transformations was found to be completely reversible. Unlike most procedures in the literature where shape and size control occur in the synthetic step by adding growth- and shape-controlling agents such as surfactants or polymers, in this system postsynthetic changes in shape and size can be carried out simply by changing the ratio of reactive, competing reagents, more specifically, alkylthiols versus tetralkylammonium salts. Interestingly, the transfer of gold metal occurs (large prismatic particles to small particles and vice versa) under the influence of reagents that do not cause such interactions with bulk gold. All intermediate steps of the morphology change were observed using HRTEM and electron diffraction. The processes of breaking down and "welding back" solid metal nanoparticles occur under mild conditions and are remarkable examples of the unique chemical properties of nanomaterials. The described process is expected to be relevant to other nanoscale systems where similar structural circumstances could occur.

Dodecanethiol-stabilized gold nanoparticles with similar average size organize into different superlattice structures depending upon the method of preparation of the nanocrystals. Particles synthesized by the inverse micelle technique preferentially assemble into face-centered cubic (fcc) structures with long-range translational and orientational ordering. Gold nanoparticles obtained by the solvated metal atom dispersion (SMAD) method behave like “hard” spheres and predominantly organize into hexagonal close-packed (hcp) nanocrystal superlattices with long-range translational ordering. Different packing behavior results from differences in nanoparticle core morphologies induced by the synthetic method; fcc ordering is preferred by single crystalline nanoparticles, while hcp is preferred by polycrystalline nanoparticles. A combination of optical microscopy, transmission electron microscopy (TEM and HRTEM), selected area electron diffraction (SAED), atomic force microscopy (AFM), and X-ray diffraction (XRD)...

Several ligands, such as alkylthiols, -amines, -silanes, -phosphines, -halides, and simple alkanes, were employed for digestive ripening, a process in which a colloidal suspension in a solvent is refluxed at the solvent boiling temperature in the presence of a surface-active ligand to convert a highly polydisperse colloid into a nearly monodisperse one. Apart from thiols, which are the only established digestive-ripening ligands, amines, silanes, and phosphines were found to be similarly efficient for this purpose. The important steps involved in the digestive ripening were identified to be (1) breaking the polydisperse colloid into smaller size particles upon addition of the ligand, (2) isolating this colloid from the reaction side products, and finally (3) heating this isolated colloid in the presence of the ligand to form a nearly monodisperse colloid. The successful ligands could be differentiated from the others based on their effectiveness to perform the different tasks in each step. Namely, they br...

Digestive ripening, heating a colloidal suspension at or near the solvent boiling point in the presence of a surface-active ligand, was applied to polydisperse colloidal gold in toluene using a series of alkylthiols, viz., octyl-, decyl-, dodecyl-, and hexadecylthiols. In all the instances, digestive ripening significantly reduced the average particle size and polydispersity. All the colloids remain suspended in solution above 80 °C, but at room temperature the tendency to form 3D superlattices and precipitate increased with declining alkyl chain length. For example, using octanethiol as the ligand makes the colloids aggregate into big 3D superlattices and precipitate; decane- and dodecanethiol also produce precipitated 3D superlattices along with separate particles, while hexadecanethiol-coated particles remain well separated from each other. The optical spectra at room temperature reveal, apart from the gold plasmon band at 530 nm, a large tail above 700 nm for Au−octanethiol and Au−decanethiol cases an...

Synthesis of metallic nanoparticles has captured the attention of scientists for decades, especially for their application in the area of catalysis, but more recently due to their unusual properties, different from those of the atomic or bulk metal. In addition, ordered structures of metallic nanoparticles display properties that lie between those of the isolated particles and the bulk material. Nanoparticles can act as building blocks to form well-organized structures, known as nanocrystal superlattices (NCSL). A narrow particle size distribution is required to obtain long-range superlattice ordering. The collective properties of metallic NCSL can be engineered by controlling the particle size and the type of ligand used to stabilize the colloidal system. The most widely studied metallic systems have been the ones prepared using gold nanoparticles [1,2,3], but there are other studies where silver [4,5,6,7], and cobalt [8] have been used to prepare NCSL. In this paper, we present for the first time the synthesis of NCSL by selfassembly of thiol stabilized copper nanoparticles, which have been prepared using the solvated metal atom dispersion (SMAD) method. The main advantage of the SMAD technique is that it allows us to prepare large quantities of the metal colloid, free of impurities. This is in great contrast to other techniques such as chemical reduction. A novel method discovered in our laboratories [9,10,11], called “digestive ripening” (i.e. allowing sufficient time and temperature (usually at the solvent’s boiling point) to attain a structural equilibrium.), has been used to attain a narrow particle size distribution. The same procedure as described here has previously been used to prepare NCSL from gold and silver colloids. Herein, it is shown to be applicable for copper as well.

We present a novel method for size-selectively separating mixtures of nanoparticles in aqueous media utilizing the inherent chemical recognition properties of DNA and the cooperative binding properties of DNA-functionalized gold nanoparticles. We have determined that the melting temperatures (T(m)s) of aggregates formed from nanoparticles interconnected by duplex DNA are dependent upon particle size. This effect is proposed to derive from larger contact areas between the larger particles and therefore increased cooperativity, leading to higher T(m)s. The separation protocol involves taking two aliquots of a mixture of particles that vary in size and functionalizing them with complementary DNA. These aliquots are mixed at a temperature above the T(m) for aggregates formed from the smaller particles but below the T(m) for aggregates formed from the larger particles. Therefore, the aggregates that form consist almost exclusively of the larger particles and can be easily separated by sedimentation and centrifugation from the smaller dispersed particles. This unusual size-dependent behavior and separation protocol are demonstrated for three binary mixtures of particles and one ternary mixture.

We have developed the chemistry for preparing a universal probe and the appropriate nano- and microparticle labels that can be used to do highly selective multiplexed detection of three protein cancer markers at low-femtomolar concentration in buffer and serum media. The approach relies on a new multiplexed version of the biobarcode amplification method and offers new opportunities for studying multiple protein markers in a single sample. This could lead to new forms of disease diagnosis and monitoring disease recurrence in a variety of settings.

The recently developed bio-bar-code assay for the PCR-less detection of protein and nucleic acid targets has been shown to be extraordinarily sensitive, exhibiting low attomolar sensitivity for protein targets and high zeptomolar sensitivity for nucleic acid targets. In the case of DNA detection, the original assay relies on three distinct oligonucleotide strands on a single nanoparticle for target identification and signal amplification. Herein, we report the development of a new nanoparticle probe that can be used in the bio-bar-code assay, which requires only one thiolated oligonucleotide strand. This new assay relies on the ability to liberate the adsorbed thiolated oligonucleotides from the gold nanoparticle surface with dithiothreitol (DTT), which simplifies the assay and increases its quantitative capabilities. The utility of this new DTT-based system is demonstrated by detecting a mock mRNA target using both fluorescent and scanometric assay readouts. When the scanometric readout is used, the sensitivity of the assay is 7 aM and quantification can be accomplished over the low-attomolar to the mid-femtomolar concentration range.

A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell.

Applicability of Atomic Force Microscopy (AFM) for structural characterization of nanocrystal superlattices is demonstrated on high-resolution imaging of superlattices formed by thiol stabilized gold nanoparticles on carbon coated and hydrophobic supports. Thin (

Novel two-component oligonucleotide-modified nanoparticle probes have been designed and used in a bio-bar-code assay with a 500 zeptomolar target DNA sensitivity limit.

Nanoparticles of gold prepared by condensation of gold vapor in cold pentanone serve as active catalysts for the polymerization of an alkylsilane C18H35SiH3 with water, to form nanowires and filaments. This reaction takes place under relatively mild conditions (refluxing pentanone).

We describe a synthetic procedure for preparation of large quantities of monodisperse thiol-stabilized gold colloids in toluene solution. The method is based on the solvated metal atom dispersion technique (SMAD), which is very suitable for preparation of large amounts of metal colloidal solutions, as well as of metal sulfide, metal oxide, and other types of dispersed compounds in different solvents. A combination of two different solvents like acetone and toluene is used for the preparation of the gold colloids. The necessity of initially carrying out the SMAD reaction in acetone comes from its high degree of solvation of gold particles. Acetone acts as a preliminary stabilizing agent. After its removal from the system, the particles are stabilized by dodecanethiol molecules, which enable their very good dispersion in toluene solution. A digestive ripening procedure is carried out with the gold-toluene colloid, and for this purpose pure toluene as solvent is necessary. This has a dramatic effect on the narrowing of particle size distribution and almost monodisperse colloids are obtained (some discussion of the probable mechanism of this remarkable digestive ripening step is given). These colloidal solutions have a great tendency to organize in two- and three-dimensional structures (nanocrystal superlattices, NCSs). We believe that this procedure provides a real opportunity to synthesize large amounts of gold nanocrystals as well as NCSs.

Novel two-component oligonucleotide-modified nanoparticle probes have been designed and used in a bio-bar-code assay with a 500 zeptomolar target DNA sensitivity limit.