Photonic detection and characterization of DNA using sapphire microspheres.

A microcavity-based deoxyribonucleic acid (DNA) optical biosensor is demonstrated for the first time using synthetic sapphire for the optical cavity. Transmitted and elastic scattering intensity at 1510 nm are analyzed from a sapphire microsphere (radius 500 µm, refractive index 1.77) on an optical fiber half coupler. The 0.43 nm angular mode spacing of the resonances correlates well with the optical size of the sapphire sphere. Probe DNA consisting of a 36-mer fragment was covalently immobilized on a sapphire microsphere and hybridized with a 29-mer target DNA. Whispering gallery modes (WGMs) were monitored before the sapphire was functionalized with DNA and after it was functionalized with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The shift in WGMs from the surface modification with DNA was measured and correlated well with the estimated thickness of the add-on DNA layer. It is shown that ssDNA is more uniformly oriented on the sapphire surface than dsDNA. In addition, it is shown that functionalization of the sapphire spherical surface with DNA does not affect the quality factor (Q . ≈ 04) of the sapphire microspheres. The use of sapphire is especially interesting because this material is chemically resilient, biocompatible, and widely used for medical implants.

Heat-transfer-based detection of SNPs in the PAH gene of PKU patients.

Conventional neonatal diagnosis of phenylketonuria is based on the presence of abnormal levels of phenylalanine in the blood. However, for carrier detection and prenatal diagnosis, direct detection of disease-correlated mutations is needed. To speed up and simplify mutation screening in genes, new technologies are developed. In this study, a heat-transfer method is evaluated as a mutation-detection technology in entire exons of the phenylalanine hydroxylase (PAH) gene. This method is based on the change in heat-transfer resistance (R(th)) upon thermal denaturation of dsDNA (double-stranded DNA) on nanocrystalline diamond. First, ssDNA (single-stranded DNA) fragments that span the size range of the PAH exons were successfully immobilized on nanocrystalline diamond. Next, it was studied whether an R(th) change could be observed during the thermal denaturation of these DNA fragments after hybridization to their complementary counterpart. A clear R(th) shift during the denaturation of exon 5, exon 9, and exon 12 dsDNA was observed, corresponding to lengths of up to 123 bp. Finally, R(th) was shown to detect prevalent single-nucleotide polymorphisms, c.473G>A (R158Q), c.932T>C (p.L311P), and c.1222C>T (R408W), correlated with phenylketonuria, displaying an effect related to the different melting temperatures of homoduplexes and heteroduplexes.

Toward deep blue nano hope diamonds: heavily boron-doped diamond nanoparticles.

The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 10-60 nm with a boron content of approximately 2.3 × 10(21) cm(-3). Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.

An impedimetric immunosensor based on diamond nanowires decorated with nickel nanoparticles.

Nanostructured boron-doped diamond has been investigated as a sensitive impedimetric electrode for the detection of immunoglobulin G (IgG). The immunosensor was constructed in a three-step process: (i) reactive ion etching of flat boron-doped diamond (BDD) interfaces to synthesize BDD nanowires (BDD NWs), (ii) electrochemical deposition of nickel nanoparticles (Ni NPs) on the BDD NWs, and (iii) immobilization of biotin-tagged anti-IgG onto the Ni NPs. Electrochemical impedance spectroscopy (EIS) was used to follow the binding of IgG at different concentrations without the use of any additional label. A detection limit of 0.3 ng mL(-1) (2 nM) with a dynamic range up to 300 ng mL(-1) (2 µM) was obtained with the interface. Moreover, the study demonstrated that this immunosensor exhibits good stability over time and allows regeneration by incubation in ethylenediaminetetraacetic acid (EDTA) aqueous solution.

Detonation nanodiamond: an organic platform for the suzuki coupling of organic molecules.

Detonation nanodiamond possesses facile surface functional groups and can be chemically processed for many engineering applications. In this work, we demonstrate the functionalization of nanoscale diamond particles with aryl organics using Suzuki coupling reactions. In route one, hydrogenated nanodiamond is derivatized with aryl diazonium to form the bromophenyl-nanodiamond complex, this is subsequently reacted with phenyl boronic acid to generate the biphenyl adduct. In route two, the nanodiamond is first derivatized with boronic acid groups to form the boronic acid-nanodiamond complex, this is followed by Suzuki cross coupling with arenediazonium tetrafluroborate salts to generate the biphenyl product. Good chemoselectivity can be obtained in both routes. The efficiencies of the Suzuki coupling reaction can be further improved by performing the chemistry in a microreactor where electro-osmotic flow accelerates the mixing of reactants. Using the Suzuki coupling reactions, we can functionalize nanodiamond with trifluoroaryls and increase the solubilities of nanodiamond in ethanol and hexane. Fluorescent nanodiamond can be generated by the Suzuki coupling of pyrene to nanodiamond.

Using detonation nanodiamond for the specific capture of glycoproteins.

We demonstrate here the functionalization of detonation nanodiamond (ND) with aminophenylboronic acid (APBA) for the purpose of targeting the selective capture of glycoproteins from unfractionated protein mixtures. The reacted ND, after blending with the matrix consisting of alpha-cyano-4-hydroxy-cinnamic acid, could be applied directly for matrix-assisted laser desorption ionization (MALDI) assay. A loading capacity of approximately 350 mg of glycoprotein/g of ND could be attained on ND that has been silanized with an alkyl linker chain prior to linking with the phenylboronic acid. The role of the alkyl spacer chain is to form an exclusion shell which suppresses nonspecific binding with nonglycated proteins and to reduce steric hindrance among the bound glycoproteins. In the absence of the alkyl spacer chain, nonselective binding of proteins was obtained. This work demonstrates the usefulness of functionalized ND as a high-efficiency extraction and analysis platform for proteomics research.