S'ha desenvolupat una nova estratègia per la síntesi ràpida i eficient de L-[metil-11C]metionina basada en el captive solvent method. La reacció de L-homocisteína (dissolució bàsica en aigua/etanol 1:1) amb [11C]CH3I en un loop de HPLC va permetre la formació del radiotraçador desitjat amb elevat rendiment radioquímic (38.4 ± 4.1%) en un temps curt (< 12 min). Tots el paràmetres analítics compleixen les especificacions requerides per la versió actual de la Farmacopea Espanyola, tot i que els valors d'activitat específica obtinguts van ser relativament baixos. Degut a això, es van estudiar i quantificar les principals fonts que contribueixen a la contaminació de carboni-12 durant les síntesis de [11C]CH3I efectuades segons el "wet" method. Es va observar que la principal font de contaminació de CO2 no radioactiu (contribució>90%) és el propi procés de bombardeig, probablement degut a la combustió (causada per les altes temperatures i pressions assolides durant la irradiació) dels compostos que contenen carboni i que es troben al gas irradiat (o a l'interior del blanc). Es van establir procediments generals per realitzar abans, durant i després de la radiosíntesi per prevenir la contaminació exterior i, d'aquesta manera, augmentar l'activitat específica dels radiotraçadors sintetitzats.En quant al marcatge amb nitrogen-13, s'ha desenvolupat un procés totalment automàtic per a la producció de [13N]NO2- a partir de [13N]NO3- generat en el ciclotró. El precursor radioactiu [13N]NO2- s'ha utilitzat per la radiosíntesi de compostos amb interès biològic com ara S-nitrosotiols (donadors de NO.), N-nitrosamines (molècules amb potencials efectes carcinogènics) i azo compostos (amb possible aplicació com a radiotraçadors per a la detecció in vivo de plaques de &#946;-amiloide). En tots els casos es van obtenir excel·lents conversions radioquímiques (48.7% - 74.5% per S-[13N]nitrosotiols, 45.6% - 53.4% per N-[13N]nitrosamines i 40.0% - 58.3% per 13N-azo compostos) i bons rendiments radioquímics (33.8% - 60.6% per S-[13N]nitrosotiols, 34.0% - 37.8% per N-[13N]nitrosamines i 20.4% - 47.2% per 13N-azo compostos). A més a més, s'ha dissenyat i implementat un mòdul automàtic amb control remot pel marcatge de molècules amb 13N. / Se ha desarrollado una nueva estrategia para la síntesis rápida y eficiente de L-[metil-11C]metionina basada en el captive solvent method. La reacción de L-homocisteína (disolución básica en agua/etanol 1:1) con [11C]CH3I en un loop de HPLC permitió la formación del radiotrazador deseado con elevado rendimiento radioquímico (38.4 ± 4.1%) en un tiempo corto (< 12 min). Todos los parámetros analíticos cumplían las especificaciones requeridas por la versión actual de la Farmacopea Española, aunque los valores de actividad específica obtenidos fueron relativamente bajos. Por ello, se estudiaron y cuantificaron las principales fuentes que contribuyen a la contaminación de carbono-12 durante las síntesis de [11C]CH3I efectuadas según el "wet" method. Se observó que la principal fuente de contaminación de CO2 no radiactivo (contribución>90%) es el propio proceso de bombardeo, probablemente debido a la combustión (causada por las altas temperaturas y presiones alcanzadas durante la irradiación) de los compuestos que contienen carbono y que se encuentran presentes en el gas irradiado (o en el mismo cuerpo del blanco). Se establecieron procedimientos generales para realizar antes, durante y con posterioridad a la radiosíntesis para prevenir la contaminación exterior y, de esta manera, aumentar la actividad específica de los radiotrazadores sintetizados.Respecto al marcaje con nitrógeno-13, se ha desarrollado un proceso totalmente automático para la producción de [13N]NO2- a partir del [13N]NO3- generado en el ciclotrón. El precursor radiactivo [13N]NO2- se ha utilizado para la radiosíntesis de compuestos con interés biológico tales como S-nitrosotioles (donadores de NO.), N-nitrosaminas (moléculas con potenciales efectos carcinogénicos) y azo compuestos (con posible aplicación como radiotrazadores para la detección in vivo de placas de &#946;-amiloide). En todos los casos se obtuvieron excelentes conversiones radioquímicas (48.7% - 74.5% para S-[13N]nitrosotioles, 45.6% - 53.4% para N-[13N]nitrosaminas y 40.0% - 58.3% para 13N-azo compuestos) y buenos rendimientos radioquímicos (33.8% - 60.6% para S-[13N]nitrosotioles, 34.0% - 37.8% para N-[13N]nitrosaminas y 20.4% - 47.2% para 13N-azo compuestos). Además, se ha diseñado e implementado un módulo automático con control remoto para el marcaje de moléculas con 13N. / A new strategy for the fast and efficient synthesis of L-[methyl-11C]methionine based on the captive solvent method has been developed. The in loop reaction of a basic water/ethanol 1:1 solution of L-homocysteine with [11C]CH3I led to the formation of the desired radiotracer with high radiochemical yield (38.4 ± 4.1%) in short production time (< 12 min). All analytical parameters were within the specifications of the current version of the Spanish Pharmacopoeia, although specific radioactivity values were relatively low. Thus, the main sources of carbon-12 during the synthesis of [11C]CH3I by the "wet" method were studied and the contribution attributable to each individual source was quantified. The most relevant contamination of non-radioactive CO2 (contribution>90%) was shown to be generated during the bombardment process, probably due to the combustion (caused by high temperature and pressure during irradiation) of carbon carrier compounds present in the irradiated gas (or target body). General procedures to be performed before, during and after the radiosynthesis were established to prevent external contamination and to improve the specific radioactivity of 11C-labeled radiotracers synthesized from [11C]CH3I produced via the "wet" method. Concerning 13N-labeling, a fully automatic process for the production of [13N]NO2- from cyclotron generated [13N]NO3- has been developed. The radioactive precursor [13N]NO2- has been used for the synthesis of biologically interesting 13N-labeled compounds such as S-nitrosothiols (well-known NO. donors), N-nitrosamines (molecules with potent carcinogenic effects) and azo compounds (with putative application as imaging probes for in vivo detection of &#946;-amyloid plaques). In all cases, excellent radiochemical conversion (48.7% - 74.5% for S-[13N]nitrosothiols, 45.6% - 53.4% for N-[13N]nitrosamines and 40.0% - 58.3% for 13N-labeled azo compounds) and good radiochemical yields (33.8% - 60.6% for S-[13N]nitrosothiols, 34.0% - 37.8% for N-[13N]nitrosamines and 20.4% - 47.2% for 13N-labeled azo compounds) were achieved. An automatic remote controlled synthesis module for the preparation of 13N-labeled structures has been designed and implemented.

Measuring urinary tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronide conjugate may provide the best biomarker of tobacco smoke lung carcinogen metabolism. Existence of differences in the extent of NNAL metabolism rates may be potentially related to an individuals’ lung cancer susceptibility. Low concentrations of NNAL in smokers urine (<1 ng/mL) require sensitive and selective methods for analysis. Traditionally, this involves extensive, time-consuming sample preparation that limits throughput and adds to measurement variability. Molecularly imprinted polymers (MIPs) have been developed for the analysis of urinary NNAL by offline cartridge extraction combined with LC-MS/MS. This method when reproduced demonstrated problems with matrix effects. In the first part of this work, investigation of matrix effects and related problems with sensitivity for the published offline extraction method has been conducted. In order to address the need to improve throughput and other analytical figures of merit for the original method, the second part of this work deals with development of a high-throughput online microfluidic method using capillary-columns packed with MIP beads for the analysis of urinary NNAL. The method was validated as per the FDA guidance, and enabled low volume, rapid analysis of urinary NNAL by direct injection on a microfluidic column packed with NNAL specific MIP beads. The method was used for analysis of urinary NNAL and NNAL-Gluc in smokers. Chemometric methods were used with this data to develop a potential cancer-risk-assessment tool based on pattern recognition in the concentrations of these compounds in urine. In the last part, method comparison approaches for the online and the offline sample extraction techniques were investigated. A ‘fixed’ range acceptance criterion based on combined considerations of method precision and accuracy, and the FDA bioanalytical guidance limits on precision and accuracy was proposed. Data simulations studies to evaluate the probabilities of successful transfers using the proposed criteria were performed. Various experimental designs were evaluated and a design comprised of 3 runs with 3 replicates each with an acceptance range of ±20% was found appropriate. The off-line and the on-line sample extraction methods for NNAL analysis were found comparable using the proposed fixed range acceptance criteria.

La evidencia sobre el efecto de las nitrosaminas (NA) sobre el cáncer gástrico (CG) es insuficiente. El objetivo fue evaluar el efecto de las NA (exógenas y endógenas ) y sus alimentos fuente sobre el riesgo de CG. El estudio incluyó 521.457 individuos del estudio EPIC (European prospective Investigation into Cancer and Nutrition) y 314 casos incidentes de C. Estimamos la exposición exógena aplicando una tabla de composición que desarrollamos para tal fin. Para estimar las NA endógenas creamos un índice de formación endógena (ENOC) basado en datos previamente publicados. Observamos un efecto de carnes rojas, procesadas y ENOC restringida a la región distal y en individuos positivos el Helicobacter Pylori. No se observó ningún efecto de las NA exógenas sobre el CG. Se observo una interacción entre ENOC y vitamina C. En resumen, el riesgo de CG se ve afectado por la interrelación entre ENOC, Hp y vitamina C. / Evidence relating nitrosamines (NA) and gastric cancer (GC) risk is not conclusive. The risk of GC associated with meat and NA intake and endogenous formation of NA (ENOC) was investigated in the European Prospective Investigation into Cancer and Nutrition with a population of 521.457 subjects and 314 incident cases of GC. To estimate NA intake we developed a food composition database. An index of ENOC was created using information from previous published studies. The risk of CG increases with intake of red and processed meat and ENOC restricted to non-cardia site and mainly in Helicobacter pylori (Hp) infected subjects. There were no association between NA intake and GC. We observed an interaction between ENOC and vitamin C. In summary, Hp infection, vitamin C and ENOC play an important role on GC risk.

The aim of diploma thesis has been development and optimization of method determination of N- nitrososarcosine and N-nitrosoproline in malt by gas chromatography with chemiluminiscence detector. Optimization of extraction method has been performed by response surface method. Quantification has been performed by internal standard method (N-nitrosopipecolic acid, in which matrix effects has been studied. These has been verified in münchen and pilsen malt, therefore matrix-matched calibration has been constructed. The developed method has been aplicated on wheat, münchen and pilsen malt. N- nitrosoproline was detected only in münchen malt and in other cases has been under limit of detection (LOD=4,0 µg/kg). N-nitrososarcosine was in all cases under limit of detection (LOD=3,7 µg/kg). The matrix-matched calibration has been constructed for experimental münchen malt with N-nitrosoproline concentration at 13,2 ± 2,9 µg/kg. Powered by TCPDF (www.tcpdf.org)