Carbon based materials for electronic bio-sensing

n/

The detection of drugs of abuse in biological matrices using enzyme-linked immunosorbent assay and liquid chromatography-tandem mass spectrometry

The aim of this study was to investigate the potential use of ELISA and LC-MS-MS in combination and as individual techniques, for the detection of drugs of abuse in biological matrices. Overall the LC-MS-MS method showed good correlation results for opiates compared to the GC-MS method. 6-MAM was however detected in more root segments and segments excluding roots by LC-MS-MS. Morphine was detected in a greater number of root segments by LC-MS-MS compared to GC-MS. However, morphine was detected in a greater number of segments excluding roots by GC-MS. Codeine and dihydrocodeine were also detected in a greater number of root segments and segments excluding roots by GC-MS. The cocaine results showed excellent qualitative correlation between the LC-MS-MS and GC-MS methods for cocaine and benzoylecgonine. The GC-MS method did not however extract greater concentrations of cocaine and its metabolites compared to LC-MS-MS due to the higher recovery of the drug group specific GC-MS method. Cocaethylene and EME were detected in some samples by LC-MS-MS method for opiates and cocaine and its metabolites compared to the GC-MS method; there may be some cases where the GC-MS method would detect the analytes where the LC-MS-MS method would not. This has been demonstrated in 3 samples for morphine and in 6 samples for codeine. The LC-MS-MS method analysed for and detected amphetamines in samples that were not tested for amphetamines by GC-MS. In one sample that was tested by both methods, amphetamine was detected in the root sample by LC-MS-MS where GC-MS failed to detect it. Also a greater concentration of amphetamine was extracted using the LC-MS-MS method in the segment without roots. The LC-MS-MS method was useful for the analysis of 17 drugs of abuse in post-mortem hair samples in forensic toxicology cases. Using this method, it is possible to obtain maximum information from one hair sample which is extremely useful when the sample weight is limited. The ability of the LC-MS-MS method to extract and analyse a greater number of drug groups from one hair sample highlights the advantages of using this method over GC-MS which targets individual drug groups and requires splitting of the sample. This method is particularly applicable for implementation in the forensic toxicology laboratory at the University of Glasgow where currently GC-MS methods that target individual drug groups are used for routine hair screening and confirmation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Gold Nanomaterials as a new tool for bio-analytical applications of Laser Desorption Ionization Mass Spectrometry

Nanomaterials have emerging importance in laser desorption ionization mass spectrometry (LDI–MS) with the ultimate objective being to overcome some of the most important limitations intrinsically related to the use of conventional organic matrices in matrix-assisted (MA) LDI–MS. This review provides a critical overview of the most recent literature on the use of gold nanomaterials as non-conventional desorption ionization promoters in LDI– MS, with particular emphasis on bioanalytical applications. Old seminal papers will also be discussed to provide a timeline of the most significant achievements in the field. Future prospects and research needs are also briefly discussed

Non-destructive depth profile reconstruction of bio-engineered surfaces by parallel angle resolved x-ray photoelectron spectroscopy

Label-free biosensors are of considerable interest for various clinical and biological applications. In these systems, achieving an optimized receptor immobilization strategy critically influence the sensing performance in terms of specificity, sensitivity, response kinetics and detection limits. However, monitoring the receptor spatial organization and the interfaces composition on a nanometer or sub-nanometer scale is a very hard challenge. In the present contribution Parallel Angle Resolved X-ray Photoelectron Spectroscopy (PAR-XPS) was proposed as useful tool to address the challenge of probing the near-surface region of bio-active sensors surface (1). A model receptor was chosen and a well-established functionalization procedure (2) was systematically characterized by PAR-XPS. Commercially available Thermo Avantage-ARProcess software was used to generate non-destructive concentration depth profiles of protein functionalized silicon oxide substrates. At each step of the functionalization procedure, the surface composition, the over layer thickness, the in-depth organization and the in-plane homogeneity were evaluated. Compared to multi-techniques characterization approaches previously proposed in the literature, the present analytical approach boasted the peculiar advantage of providing, simultaneously, morphological and compositional information from the same data set. The critical discussion of the generated profiles highlighted the relevance of the information provided by PAR-XPS technique

Virus-PEDOT Composite Films for Impedance-Based Biosensing

Composite films composed of poly(3,4-ethylenedioxythiophene), PEDOT, and the filamentous virus M13K07 were prepared by electrooxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous solutions containing 8 nM of the virus at planar gold electrodes. These films were characterized using atomic force microscopy and scanning electron microscopy. The electrochemical impedance of virus-PEDOT films increases upon exposure to an antibody (p-Ab) that selectively binds to the M13 coat peptide. Exposure to p-Ab causes a shift in both real (Z(RE)) and imaginary (Z(IM)) impedance components across a broad range of frequencies from 50 Hz to 10 kHz. Within a narrower frequency range from 250 Hz to 5 kHz, the increase of the total impedance (Z(total)) with p-Ab concentration conforms to a Langmuir adsorption isotherm over the concentration range from from 6 to 66 nM, yielding a value for K(d) = 16.9 nM at 1000 Hz

Designing functionalized gold surfaces and nanostructures for Laser Desorption Ionisation Mass Spectrometry

The present work is aimed at developing gold nanostructures functionalized with antenna systems to exploit the synergistic nanostructure/antenna desorption-ionization efficiency. A potential Matrix- Assisted Laser Desorption Ionisation (MALDI) organic matrix has been modified introducing specific functional groups or molecular linker and used as a capping agent for gold nanostructures. In particular, conjugated naphthyl-thio-derivative, i.e. 4-mercaptonaphthalene-1,8-dicarboxylic acid, was synthesized and characterized by means of nuclear magnetic resonance, UVevisible and X-ray photoelectron spectroscopies. Afterwards, the thio-derivative was used as covalent surface modifier for flat gold surfaces and nanostructured gold films. These surfaces were thoroughly characterized by means of parallel angle-resolved X-ray photoelectron spectroscopy to obtain quantitative information about elemental composition, chemical speciation, and in-depth distribution of the target chemical functional groups. Finally the compound was preliminarily tested as a non-conventional matrix in Laser Desorption Ionisation Mass Spectrometry (LDI-MS) analysis of low molecular weight biomolecules in order to assess its capability of acting as the antenna system and proton donor after covalent bonding to gold nanomaterials

Scouting for Naturally Low-Toxicity Wheat Genotypes by a Multidisciplinary Approach

Over the last years, great efforts have been devoted to develop effective gluten detoxification strategies with a consequent detrimental alteration of the technological properties as well. Obtaining low-gluten products without affecting the rheological properties of wheat could still be considered a new challenge to face. In this investigation, we presented a comprehensive characterization of durum wheat genotypes aimed at identifying low gluten ones, which combine the potential lower toxicity/immunogenicity with conserved yield and rheological properties to encompass the perspective usability for bread or pasta making. A preliminary profiling of gluten proteins was accomplished by immunoassay-based quantification and liquid chromatography coupled to UV detection, focusing on the gliadin fraction as main responsible for immunoreactivity in celiac disease patients. In addition, data on grain protein content, grain yield per spike, dry gluten and gluten index were collected in order to provide complementary information about productivity-related traits and quali-quantitative characteristics related to wheat nutritional value and its technological properties. The whole pool of data was statistically evaluated driving to the selection of a preferred list of candidate low-toxicity genotypes that were subjected to in-vitro simulated gastroduodenal digestion and untargeted HR-MS/MS peptide identification. Finally, an in-silico risk assessment of potential toxicity for celiac disease patients was performed according to the most recent guidance provided by EFSA