Chronopotentiometry and Faradaic impedance spectroscopy as signal transduction methods for the biocatalytic precipitation of an insoluble product on electrode supports: routes for enzyme sensors, immunosensors and DNA sensors.

The biocatalyzed precipitation of an insoluble product produced on electrode supports is used as an amplification path for biosensing. Enzyme-based electrodes, immunosensors and DNA sensors are developed using this biocatalytic precipitation route. Faradaic impedance spectroscopy and chronopotentiometry are used as transduction methods to follow the precipitation processes.

Imprinting of chiral molecular recognition sites in thin TiO2 films associated with field-effect transistors: novel functionalized devices for chiroselective and chirospecific analyses.

(R)- or (S)-2-Methylferrocene carboxylic acids, (R)-1 or (S)-1, (R)- or (S)-2-phenylbutanoic acid, (R)-2 or (S)-2, and (R)- or (S)-2-propanoic acid, (R)-3 or (S)-3, can be imprinted in thin TiO2 films on the gate surface of ion-sensitive field-effect transistor (ISFET) devices. The imprinting is performed by hydrolyzing the respective carboxylate TiIV butoxide complex on the gate surface, followed by washing off the acid from the resulting TiO2 film. The imprinted sites reveal chiroselectivity only towards the sensing of the imprinted enantiomer.

Amplified detection of DNA and analysis of single-base mismatches by the catalyzed deposition of gold on Au-nanoparticles.

A novel amplification route for DNA detection based on the deposition of gold on a 10 nm Au-colloid/avidin conjugate label acting as a 'seeding' catalyst, is described. Microgravimetric quartz-crystal-microbalance measurements are employed to transduce the catalyzed deposition of gold on the piezoelectric crystals. Three different DNA detection schemes are described: (i) analysis of a 27-base nucleic acid fragment; (ii) analysis of the entire M13phi DNA (7229 bases); and (iii) detection of a single-base mismatch in a DNA.

Endoscopic treatment of post-liver transplantation biliary leaks with stent placement across the leak site.

Background: Biliary tract leaks occur in over 10% of patients undergoing liver transplantation and are the most common cause of biliary tract-related death in these patients. A number of treatment options are available, but a standard approach has not been established.

Methods: Twenty-six patients were retrospectively studied who had post-transplantation leaks develop with special reference to those who underwent endoscopic placement of a "leak-bridging" stent.

Lithium reduction of the bowl-shaped C60 fragment diindeno[1,2,3,4-defg;1',2',3',4'-mnop]chrysene: an interplay between experiment and calculation.

Diindeno[1,2,3,4-defg;1',2',3',4'-mnop]chrysene (DIC) (one of the smallest symmetrical bowl-shaped fragments of C60) and its tetra-tert-butyl derivative are reduced with lithium metal to yield dianions and tetraanions. Due to the high degree of symmetry (C2v) of DIC and its derivative, their NMR spectra cannot be assigned using the standard two-dimensional NMR techniques. A novel carbon-edited NOESY method was used to complete the assignments of the neutral and dianion species, whereas the tetraanions are aided by DFT calculations for their assignment.

The decision-making value of magnetic resonance cholangiopancreatography in patients seen in a referral center for suspected biliary and pancreatic disease.

Objective: To assess the ability of MRCP to alter the differential diagnosis and to prevent diagnostic and/or therapeutic ERCP. The diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) for biliary and pancreatic disease is well documented. Some believe MRCP may prevent diagnostic ERCP or add useful information, however there are no reports of its impact on clinical management.

Electronic transduction of DNA sensing processes on surfaces: amplification of DNA detection and analysis of single-base mismatches by tagged liposomes.

Tagged, negatively charged, liposomes are used to amplify DNA sensing processes. The analyses of the target DNA are transduced electrochemically by using Faradaic impedance spectroscopy, or by microgravimetric measurements with Au-quartz crystals. By one method, a probe oligonucleotide (1) is assembled on Au-electrodes or Au-quartz crystals.

Electronically transduced molecular mechanical and information functions on surfaces.

Supramolecular chemistry and nanotechnology, along with their use in the construction of functional assemblies and devices, have merged into a challenging field of study. The development of methodologies for the integration and interfacing of molecular building blocks with solid supports and electronic transducers is essential for this research. We address recent applications of molecular, macromolecular, and biomolecular substances in the organization of signal-activated, electronically transduced molecular architectures on electrode surfaces.

Electronic Transduction of Polymerase or Reverse Transcriptase Induced Replication Processes on Surfaces: Highly Sensitive and Specific Detection of Viral Genomes.

Replication, precipitation, and amplification: Polymerase or reverse transcriptase induced replication of DNA/RNA on a transducer (electrode or piezoelectric crystal) leads to the ultrasensitive specific electronic transduction of viral genomes. Biotin tags (B) on the double-stranded assembly provide docking sites for a conjugate between avidin (A) and an alkaline phosphatase (AP). Enzyme biocatalysis of substrate (S) to the insoluble product (P), which precipitates onto the transducer (yellow surface), provides amplification in the analysis of the target DNA.

An integrated relay/nitrate reductase field-effect transistor for the sensing of nitrate (NO3-).

An integrated enzyme-functionalized field-effect transistor (ENFET) device for the sensing of nitrate ions is described. An aminosiloxane-functionalized gate interface is modified with N-methyl-N'-(carboxyalkyl)-4,4'-bipyridinium relay units. The complex formed between nitrate reductase and the bipyridinium units on the gate surface is crosslinked with glutaric dialdehyde to yield a stable relay-enzyme layer on the gate interface.

Biomaterials integrated with electronic elements: en route to bioelectronics.

Bioelectronics is a progressing interdisciplinary research field that involves the integration of biomaterials with electronic transducers, such as electrodes, field-effect-transistors or piezoelectric crystals. Surface engineering of biomaterials, such as enzymes, antigen-antibodies or DNA on the electronic supports, controls the electrical properties of the biomaterial-transducer interface and enables the electronic transduction of biorecognition events, or biocatalyzed transformation, on the transducers. Bioelectronic sensing devices, biosensors of tailored sensitivities and specificities, are being developed.

Lanthanide oxide-doped titanium dioxide photocatalysts: novel photocatalysts for the enhanced degradation of p-chlorophenoxyacetic acid.

The photocatalytic degradation of p-chlorophenoxyacetic acid has been investigated in oxygenated aqueous suspensions of lanthanide oxide-doped TiO2 photocatalysts. Complete mineralization was achieved. The enhanced degradation is attributed to the formation of Lewis acid-base complex between the lanthanide ion and the substrate.

Detection of single-base DNA mutations by enzyme-amplified electronic transduction.

Here we describe a method for the sensitive detection of a single-base mutation in DNA. We assembled a primer thiolated oligonucleotide, complementary to the target DNA as far as one base before the mutation site, on an electrode or a gold-quartz piezoelectric crystal. After hybridizing the target DNA, normal or mutant, with the sensing oligonucleotide, the resulting assembly is reacted with the biotinylated nucleotide, complementary to the mutation site, in the presence of polymerase.

Tailored chemosensors for chloroaromatic acids using molecular imprinted TiO2 thin films on ion-sensitive field-effect transistors.

The SiO2 gate of an ion-sensitive field-effect transistor, (ISFET), is functionalized with a TiO2 film that includes imprinted molecular sites for 4-chlorophenoxy acetic acid, (1), or 2,4-dichlorophenoxy acetic acid, (2). The functionalized devices that include the imprinted interfaces reveal an impressive selectivity in the sensing of the imprinted substrates Na+ -1 or Na+ -2. The detection limit for Na+ -1 is (5+/-2) x 10(-4) M, which corresponds to 38 mV x dec(-1) in the concentration range of 0.

An integrated NAD+-dependent enzyme-functionalized field-effect transistor (ENFET) system: development of a lactate biosensor.

An integrated NAD+-dependent enzyme field-effect transistor (ENFET) device for the biosensing of lactate is described. The aminosiloxane-functionalized gate interface is modified with pyrroloquinoline quinone (PQQ) that acts as a catalyst for the oxidation of NADH. Synthetic amino-derivative of NAD+ is covalently linked to the PQQ monolayer.

Biomaterial engineered electrodes for bioelectronics.

A series of single-cysteine-containing cytochrome c, Cyt c, heme proteins including the wild-type Cyt c (from Saccharomyces cerevisiae) and the mutants (V33C, Q21C, R18C, G1C, K9C and K4C) exhibit direct electrical contact with Au-electrodes upon covalent attachment to a maleimide monolayer associated with the electrode. With the G1C-Cyt c mutant, which includes the cysteine residue in the polypeptide chain at position 1, the potential-induced switchable control of the interfacial electron transfer was observed. This heme protein includes a positively charged protein periphery that surrounds the attachment site and faces the electrode surface.

Liposomes labeled with biotin and horseradish peroxidase: a probe for the enhanced amplification of antigen--antibody or oligonucleotide--DNA sensing processes by the precipitation of an insoluble product on electrodes.

Liposomes labeled with biotin and the enzyme horseradish peroxidase (HRP) are used as a probe to amplify the sensing of antigen-antibody interactions or oligonucleotide-DNA binding. The HRP-biocatalyzed oxidation of 4-chloro-1-naphthol (1) in the presence of H2O2, and the precipitation of the insoluble product 2 on electrode supports, are used as an amplification route for the sensing processes. The anti-dinitrophenyl antibody (DNP-Ab) is sensed by a dinitrophenyl-L-cysteine antigen monolayer associated with an Au electrode.

Nanoparticle arrays on surfaces for electronic, optical, and sensor applications.

Particles in the nanometer size range are attracting increasing attention with the growth of interest in nanotechnological disciplines. Nanoparticles display fascinating electronic and optical properties as a consequence of their dimensions and they may be easily synthesized from a wide range of materials. The dimensions of these particles makes them ideal candidates for the nanoengineering of surfaces and the fabrication of functional nanostructures.

From homoleptic to heteroleptic double stranded Copper(I) helicates: the role of self-recognition in self-assembly processes.

The ligands 2,9-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-1,10-phenanthroline (6), 6' ',6' "-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl)]-2' ',2' "-bipyridine (2), 5,5'-bis[(6-methyl-2,2'-bipyridin-6'yl)methyleneoxymethylenyl]-2, 2'-bithiophene (7), and 6,6'-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-2,2'-biphenyl (8) and their respective homo- and heteroleptic double-stranded copper(I) complexes were prepared and characterized in order to estimate the importance of self-recognition in the self-assembly processes of double-stranded copper complexes. The homoleptic double-stranded copper complexes of 2, 6, 7, and 8 were characterized by NMR, FAB-MS, and electrochemistry. It was found that 6 and 2 each form a single double-stranded helicate having the structure of [(L)(2)Cu(3)](3+) (L = 2 or 6), 7 forms two double-stranded [(7)(2)Cu(3)](3+) complexes, and 8 results in a mixture of at least two [(8)(2)Cu(2)](2+) complexes.

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications.

Integration of redox enzymes with an electrode support and formation of an electrical contact between the biocatalysts and the electrode is the fundamental subject of bioelectronics and optobioelectronics. This review addresses the recent advances and the scientific progress in electrically contacted, layered enzyme electrodes, and discusses the future applications of the systems in various bioelectronic devices, for example, amperometric biosensors, sensoric arrays, logic gates, and optical memories. This review presents the methods for the immobilization of redox enzymes on electrodes and discusses the covalent linkage of proteins, the use of supramolecular affinity complexes, and the reconstitution of apo-redox enzymes for the nanoengineering of electrodes with protein monolayers of electrodes with protein monolayers and multilayers.