A novel gold nanoparticle-based approach for the rapid diagnosis of meningococcal infection

The bacterial meningitis caused by Neisseria meningitidis is responsible for considerable morbidity and mortality throughout the world. Given the limitations of existing diagnostic tests and the severity of the illness associated with the disease, there is a clear requirement for a rapid and specific diagnostic assay. This thesis describes the development of nanoparticle based tests for the detection of Neisseria meningitidis specific cell surface markers. As an initial target antigen, a recombinant form of highly conserved outer membrane protein, OMP85 was used. Within the OMP85 protein sequence, a predicted antigenic sequence between residues 720 and 745 was identified and found to be unique to this organism. This amino acid sequence was synthesised as peptide (SR1) with a gly-gly-cysteine spacer sequence at the N-terminus using t-boc chemistry. Also, the major virulence factor, capsular polysaccharide of N. meningitidis serogroup B bacteria was purified. Polyclonal antibodies were raised against purified OMP85 antigen in rabbits and against SR1 peptide and also against formalin inactivated N. meningitidis serogroup B whole cell bacteria in sheep. This panel of different antibodies including the commercial anti-capsular monoclonal antibodies were examined for cross reactivity against a range of closely related Gram negative bacteria. Based on these cross-reactivity studies, a highly specific anti-NM antibody was developed following purification of the anti-SR1 antiserum by immuno-affinity chromatography. Purified OMP85 antigen and anti-OMP85 antibody were successfully conjugated on 13, 30, 40, 50 and 60 nm gold nanoparticles by an electrostatic adsorption method. Coupling of the gold nanoparticles results in a shift of the respective surface plasmon peak toward longer wavelengths (in the range of 600-800 nm) resulting in a change of the colour of the colloidal suspension from red to purple to blue. An attempt was made to develop a rapid diagnostic assay based on gold nanoparticle induced colour shift assay for N. meningitidis by utilising the specific interaction of OMP85 and anti-OMP85 antibody conjugated to gold nanoparticles as a model system. However, this system was not reproducible and is likely to be due to problems with stability of gold nanoparticles during the conjugation process. As an alternative approach, a highly selective quartz crystal microbalance (QCM)-based immunosensor was designed using the same OMP85/anti-OMP85 antibody system. A method was developed using polyvinylidene fluoride (PVDF) coated QCM crystals with protein A for the directional orientation of the antibodies. To further enhance the sensitivity of the test, OMP85-conjugated gold nanoparticles were used as signal amplification probes for the reproducible detection of the target down to 300 ng/mL, corresponding to a five fold increase in sensitivity compared to detection of OMP85 antigen alone. Also, this sensor has successfully been employed to detect whole cell bacteria at a concentration as low as 100 cfu/mL. Thus, in this study using the real-time QCM measurements, a novel strategy has been developed for the sensitive detection of both N. meningitidis bacteria and the protein antigen at very low concentrations, using gold nanoparticles as signal amplification probes

CsF–Al<SUB>2</SUB>O<SUB>3</SUB> mediated rapid condensation of phenols with aryl halides: comparative study of conventional heating vs. microwave irradiation

Biaryl ethers and thio ethers are formed in high yields by the condensation of phenols and thiophenols with electron-deficient aryl halides using CsF supported on Al2O3 under microwave irradiation in solvent-free conditions

Metal triflates catalyzed efficient synthesis of 3,4-dihydro-2H-1-benzopyrans

Ytterbium triflate efficiently catalyzes an unusual cyclization of o-hydroxybenzaldehydes with 2,3-dihydrofuran and 3,4-dihydro-2H-pyran in the presence of trimethyl orthoformate at ambient temperature to afford a new class of compounds, furo- and pyrano[2,3-b]benzopyrans in excellent yields with high diastereoselectivity. Also, o-hydroxybenzaldehydes reacted smoothly with acetophenones in the presence of a catalytic amount of scandium triflate under similar reaction conditions to give the corresponding 2,4-dialkoxy-2-aryl-3,4-dihydro-2H-1-benzopyrans in high yields

Indium-mediated efficient conversion of azides to carbamates

A novel and efficient method for the high yield preparation of carbamates by the reaction of azides with several chloroformates using indium metal in DMF at ambient temperature is described for the first time

Dy(OTf)<SUB>3</SUB>-immobilized in ionic liquids: a novel and recyclable reaction media for the synthesis of 2,3-unsaturated glycopyranosides

D-Glycals react smoothly with a variety of alcohols, phenols and hydroxy α-amino acids in the presence of 5 mol% dysprosium triflate immobilized in 1-butyl-3-methylimidazolium hexafluorophosphate under mild reaction conditions to afford the corresponding 2,3-unsaturated glycopyranosides in excellent yields with high α-selectivity. The catalyst immobilized in ionic liquids was recycled in subsequent reactions without any apparent loss of activity

Lithium perchlorate catalyzed regioselective ring opening of aziridines with sodium azide and sodium cyanide

Aziridines react smoothly with sodium azide and sodium cyanide in the presence of catalytic amount of lithium perchlorate under essentially mild and neutral reaction conditions to afford the corresponding β-azido and β-cyanoamines in high yields with high regioselectivity

Highly stereoselective synthesis of 2,3- unsaturated thioglycopyranosides employing molecular iodine

Molecular iodine has been utilized for the first time for the thioglycosidation of D-glycals with various thiols to afford the corresponding 2,3-unsaturated thioglycosides in high yields. In the case of tri-O-acetyl-D-glucal, the α-anomer was obtained exclusively. The use of readily available iodine makes this method quite simple, more convenient, and practical

LiBF<SUB>4</SUB>-mediated C-glycosylation of glycals with allyltrimethylsilane: a facile synthesis of allyl C-glycosylic compounds

The treatment of glycals with allyltrimethylsilane in the presence of lithium tetrafluoroborate in acetonitrile gave the corresponding allyl 2,3-unsaturated C-glycosylic compounds in excellent yields with high anomeric selectivity

Iodine-catalyzed three-component reaction: A rapid synthesis of α-alkoxy azides and homoallyl ethers

Iodine is found to be an efficient catalyst for the three-component coupling of aldehydes, alcohols, and TMSN3 under mild and neutral conditions to provide α-alkoxy azides in good yields and with high selectivity. Allyltrimethylsilane also reacts rapidly with aldehydes in the presence of alcohols to produce homoallyl ethers under similar conditions. The use of iodine makes this procedure simple, convenient and cost-effective