(Nano)materials: sensors and liquid chromatography

La investigación sobre materiales y nuevas estrategias para mejorar el pretratamiento de muestras y / o las técnicas instrumentales ha atraído una gran atención en la Química Analítica actual. Esta Tesis presenta interesantes usos de (nano) materiales que permiten mejorar o desarrollar técnicas de detección, extracción y separación. Dado que unos de los principales objetivos de la Química Analítica es el desarrollo de metodologías ecológicas, se han llevado a cabo estrategias analíticas centradas en: (i) técnicas de pretratamiento de muestra y separación miniaturizadas y (ii) sensores in situ. Los materiales estudiados en esta Tesis se han organizado en función de su composión como materiales basados en silicio (PDMS, C18 y MCF), basados en carbono (MWCNT y SWCNT) y metálicos. (MOF y AgNP). Las versátiles propiedades y el bajo coste del polidimetilsiloxano (PDMS) han promovido su uso como fase de extracción en la microextracción en fase sólida (SPME) Concretamente, se ha estudiado el PDMS como fase de extracción en IT-SPME-Cap-LC para la estimación de compuestos de interés en campos tan diversos como el medioambiental, industrial y forense (DEHP, BAK y DPA). Además, se ha evaluado la potencial aplicación de los nanotubos de carbono como fase extractiva columnas capilares para IT-SPME. Debido a la mejora en la eficiencia de extracción y los perfiles cromatográficos, los CNT han demostrado ser una interesante alternativa a las fases convencionales poliméricas para estimar compuestos de tipo anfetamínico en fluidos orales. La combinación de la microextracción en fase sólida en tubo con cromatografía miniaturizada tipo capilar integra la extracción en línea, preconcentración y separación en un mismo paso, reduciendo así el tiempo de análisis y posible contaminación de la muestra. Otra importante aplicación del PDMS es su uso como soporte encapsulante de reactivos derivatizantes para el desarrollo de dispositivos de análisis in-situ. En este contexto, se han desarrollado en la presente Tesis sensores colorimétricos para la estimación de compuestos con grupos amino como la caseína, biocidas y sustancias tipo anfetamina y ketamina. Además, se ha desarrollado también un sensores plasmónico basado en nanopartículas de plata como kit clínico para la detección in-situ de compuestos volátiles sulfúricos, responsables del mal aliento. Así, se demuestra que las nanopartículas de plata presentan excelente sensibilidad para su aplicación como biosensores. Por otra parte, se ha llevado a cabo una nueva aplicación del material C-18 para dispersión de la matriz en fase sólida. Gracias a su elevada hidrofobicidad, se trata de un material con elevada capacidad de retención de compuestos anfetamínicos. Además, presenta la capacidad conjunta de disrupción, limpieza y derivatización de la muestra. Así, ste material resulta interesante para su aplicación como fase dispersante en el análisis de compuestos anfetamínicos en pelo. También se ha evaluado satisfactoriamente la potencial aplicación de la sílica mesoporosa mesocelular como capa sensible en el desarrollo de microcantilevers piezoeléctricos resonantes. Gracias a su elevada área superficial y estructura mesoporosa, presenta interesantes perspectivas de implantación en este tipo de sensores para la detección de compuestos orgánicos volátiles de interés medioambiental. En cuanto al proceso de fabricación de microcantilevers, también se ha propuesto un proceso de fabricación alternativo donde se sustituye la capa de sacrificio por un material polimérico que se elimina en el proceso de sinterización, simplificando por tanto el proceso de fabricado. En cuanto a los compuestos organometálicos, se ha propuesto un nuevo MOF basado en péptidos que es capaz de llevar a cabo una separación enantioselectiva de drogas polares siendo utilizado como fase quiral en extracción en fase sólida. Así, se ha llevado a cabo por primera vez una enantioseparación de efedrina de más del cincuenta por cien a través de un MOF de Cu basado en tripéptido Gly-L-His-Gly. Las potenciales aplicaciones demostradas para los materiales estudiados han sido demostradas mediante las adecuadas determinaciones de diferentes compuestos en distintas matrices. Estas metodologías han demostrado notables mejoras en términos de coste, rapidez, simplicidad y mejora en figuras de mérito, destacando su respetuosidad con el medio ambiente.The research on materials and new strategies to improve sample pretreatment and/or instrumental techniques has attracted great attention in the current developments of Analytical Chemistry. This Thesis presents interesting uses of (nano)materials to improve or develop sensing, extraction and separation techniques. The recent goal in Analytical Chemistry is the development of ecofriendly methodologies. In order to achieve this aim, analytical strategies focused on green aspects have been carried out: (i) miniaturized sample pretreatment and separation techniques and (ii) in-situ sensors. The materials studied in this Thesis have been organized in silicon-based (PDMS, C18 and MCF), carbon-based (MWCNTs and SWCNTs) and metallic-based (MOF and AgNPs). The versatile properties and low cost of PDMS has promoted its use as extractive phase in SPME and support for sensing devices has grown in importance. PDMS has been studied as extractive phase in IT-SPME-Cap-LC for estimating DEHP, BAK and DPA at trace levels in several matrices of environmental, industrial and forensic interest. The potential use of CNTs as extractive phase has been widely reported. Thus, CNTs have been studied to functionalize capillary columns for IT-SPME. Due to the enhancement on extraction efficiency and chromatographic profiles, CNTs have proved to be a reliable alternative to conventional phases in IT-SPME for estimating amphetamines in oral fluids. The proposed IT-SPME approach coupled to CapLC integrates on-line extraction, preconcentration and separation, reducing the sample treatment steps. Another important application of PDMS is its use as embedding material of dyes for developing optical sensors for in-situ analysis. In this context, colorimetric sensors for on-site estimation of amino compounds such as casein, a biocide, amphetamine-like compounds and ketamine have been developed. Moreover, a sensor based on AgNPs has been also developed as clinical kit for the in-situ and real time detection of volatile sulfur compounds, which are related to oral malodour. AgNPs are highly sensitive materials for their application as plasmonic sensor. A new application of the material C18 has been carried out. Thanks to the retentive capacity for amphetamine compounds, and thus, the capacity of C18 to disrupt as well as to clean-up the sample, this material has been successfully evaluated as dispersant phase for MSPD. This approach integrates matrix disruption, clean-up and derivatization to simplify sample preparation for the determination of amphetamines in hair. A potential applicability of MCF silica as sensing layer for resonant piezoelectric microcantilevers has been tested. In addition, an alternative fabrication procedure by using a polymeric commercial material for the sacrificial layer has been developed. Thus, the fabrication procedure is simplified due to sacrificial layer is removed during the firing step. To our knowledge, the first example of a MOF capable of separating chiral polar drugs by using SPE has been studied in this Thesis. A chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly has been used as extractive phase for the enantioselective separation of ephedrine. The potential applicability of the materials studied has been demonstrated by the determination of several target compounds in different matrices. The proposed methodologies have reported improvements in terms of cost, rapidity, simplicity and sensitivity, besides protecting the operator and the environment

Peptide Metal-Organic Frameworks for Enantioselective Separation of Chiral Drugs

We report the ability of a chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid phase extraction (SPE) of a racemic mixture by using Cu(GHG) as extractive phase permits isolating more than 50% of the (+)-ephedrine enantiomer as target compound in only four minutes. To the best of our knowledge, this represents the first example of a MOF capable of separating chiral polar drugs

Estimating Diphenylamine in Gunshot Residues from a New Tool for Identifying both Inorganic and Organic Residues in the Same Sample

A method involving the collection and determination of organic and inorganic gunshot residues on hands using on-line in-tube solid-phase microextraction (IT-SPME) coupled to miniaturized capillary liquid chromatography with diode array detection (CapLC-DAD) and scanning electron microscopy coupled to energy dispersion X-ray (SEM-EDX), respectively, for quantifying both residues was developed. The best extraction efficiency for diphenylamine (DPA) as the main target among organic residues was achieved by using a dry cotton swab followed by vortex-assisted extraction with water, which permits preservation of inorganic residues. Factors such as the nature and length of the IT-SPME extractive phase and volume of the sample processed were investigated and optimized to achieve high sensitivity: 90 cm of TRB-35 (35% diphenyl, 65% polydimethylsiloxane) capillary column and 1.8 mL of the processed sample were selected for the IT-SPME. Satisfactory limit of detection of the method for analysis of DPA deposited on shooters’ hands (0.3 ng) and precision (intra-day relative standard deviation, 9%) were obtained. The utility of the described approach was tested by analyzing several samples of shooters’ hands. Diphenylamine was found in 81% of the samples analyzed. Inorganic gunshot residues analyzed by SEM-EDX were also studied in cotton swab and lift tape kit samplers. Optical microscopy was used to see the inorganic gunshot residues in the cotton swab samplers. The lift tape kits provided lesser sensitivity for DPA than dry cotton swabs—around fourteen times. The possibility of environmental and occupational sources could be eliminated when DPA was found together with inorganic residues. Then, the presence of inorganic and organic residues in a given sample could be used as evidence in judicial proceedings in the forensic field

Plasma Concentrations of BDNF and IGF-1 in Abstinent Cocaine Users with High Prevalence of Substance Use Disorders: Relationship to Psychiatric Comorbidity

Recent studies have identified biomarkers related to the severity and pathogenesis of cocaine addiction and common comorbid psychiatric disorders. Monitoring these plasma mediators may improve the stratification of cocaine users seeking treatment. Because the neurotrophic factors are involved in neural plasticity, neurogenesis and neuronal survival, we have determined plasma concentrations of brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1) and IGF-1 binding protein 3 (IGFBP-3) in a cross-sectional study with abstinent cocaine users who sought outpatient treatment for cocaine (n = 100) and age/body mass matched controls (n = 85). Participants were assessed with the diagnostic interview 'Psychiatric Research Interview for Substance and Mental Disorders'. Plasma concentrations of these peptides were not different in cocaine users and controls. They were not associated with length of abstinence, duration of cocaine use or cocaine symptom severity. The pathological use of cocaine did not influence the association of IGF-1 with age observed in healthy subjects, but the correlation between IGF-1 and IGFBP-3 was not significantly detected. Correlation analyses were performed between these peptides and other molecules sensitive to addiction: BDNF concentrations were not associated with inflammatory mediators, lipid derivatives or IGF-1 in cocaine users, but correlated with chemokines (fractalkine/CX3CL1 and SDF-1/CXCL12) and N-acyl-ethanolamines (N-palmitoyl-, N-oleoyl-, N-arachidonoyl-, N-linoleoyl- and N-dihomo-γ-linolenoyl-ethanolamine) in controls; IGF-1 concentrations only showed association with IGFBP-3 concentrations in controls; and IGFBP-3 was only correlated with N-stearoyl-ethanolamine concentrations in cocaine users. Multiple substance use disorders and life-time comorbid psychopathologies were common in abstinent cocaine users. Interestingly, plasma BDNF concentrations were exclusively found to be decreased in users diagnosed with both primary and cocaine-induced disorders for mood and anxiety disorders. In summary, BDNF, IGF-1 and IGFBP-3 were not affected by a history of pathological use of cocaine supported by the absence of associations with other molecules sensitive to cocaine addiction. However, BDNF was affected by comorbid mood disorders. Further research is necessary to elucidate the role of BDNF and IGF-1 in the transition to cocaine addiction and associated psychiatric comorbidity.The present study has been supported byInstituto de Salud Carlos III (ISC-III), Red deTrastornos Adictivos UE-FEDER 2012 (RD12/0028);Ministerio de Economía y Competitividad (PI13/02261); Plan Nacional sobre Drogas 049/2009 and049/2013; Consejería de Economía, Innovación yCiencia, Junta de Andalucía UE-FEDER (CTS-433);Consejería de Salud y Bienestar Social, Junta Andalucía (PI0228-2013 and PI0823-2012);Departament d’Innovació, Universitats i Empresa,Generalitat de Catalunya (2014-SGR-680). JS, ASand FJP hold a“Miguel Servet”research contractfrom ISC-III (CP12/03109, CP14/00173 and CP14/00212, respectively). PR-S holds a“Río Hortega”research contract from ISC-III (CM13/0115). EC-Oholds a“Sara Borrell”research contract from ISC-III(CD12/00455). The funders had no role in studydesign, data collection and analysis, decision topublish, or preparation of the manuscript

Plasma Concentrations of BDNF and IGF-1 in Abstinent Cocaine Users with High Prevalence of Substance Use Disorders: Relationship to Psychiatric Comorbidity

Recent studies have identified biomarkers related to the severity and pathogenesis of cocaine addiction and common comorbid psychiatric disorders. Monitoring these plasma mediators may improve the stratification of cocaine users seeking treatment. Because the neurotrophic factors are involved in neural plasticity, neurogenesis and neuronal survival, we have determined plasma concentrations of brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1) and IGF-1 binding protein 3 (IGFBP-3) in a cross-sectional study with abstinent cocaine users who sought outpatient treatment for cocaine (n = 100) and age/body mass matched controls (n = 85). Participants were assessed with the diagnostic interview 'Psychiatric Research Interview for Substance and Mental Disorders'. Plasma concentrations of these peptides were not different in cocaine users and controls. They were not associated with length of abstinence, duration of cocaine use or cocaine symptom severity. The pathological use of cocaine did not influence the association of IGF-1 with age observed in healthy subjects, but the correlation between IGF-1 and IGFBP-3 was not significantly detected. Correlation analyses were performed between these peptides and other molecules sensitive to addiction: BDNF concentrations were not associated with inflammatory mediators, lipid derivatives or IGF-1 in cocaine users, but correlated with chemokines (fractalkine/CX3CL1 and SDF-1/CXCL12) and N-acyl-ethanolamines (N-palmitoyl-, N-oleoyl-, N-arachidonoyl-, N-linoleoyl- and N-dihomo-γ-linolenoyl-ethanolamine) in controls; IGF-1 concentrations only showed association with IGFBP-3 concentrations in controls; and IGFBP-3 was only correlated with N-stearoyl-ethanolamine concentrations in cocaine users. Multiple substance use disorders and life-time comorbid psychopathologies were common in abstinent cocaine users. Interestingly, plasma BDNF concentrations were exclusively found to be decreased in users diagnosed with both primary and cocaine-induced disorders for mood and anxiety disorders. In summary, BDNF, IGF-1 and IGFBP-3 were not affected by a history of pathological use of cocaine supported by the absence of associations with other molecules sensitive to cocaine addiction. However, BDNF was affected by comorbid mood disorders. Further research is necessary to elucidate the role of BDNF and IGF-1 in the transition to cocaine addiction and associated psychiatric comorbidity.The present study has been supported byInstituto de Salud Carlos III (ISC-III), Red deTrastornos Adictivos UE-FEDER 2012 (RD12/0028);Ministerio de Economía y Competitividad (PI13/02261); Plan Nacional sobre Drogas 049/2009 and049/2013; Consejería de Economía, Innovación yCiencia, Junta de Andalucía UE-FEDER (CTS-433);Consejería de Salud y Bienestar Social, Junta Andalucía (PI0228-2013 and PI0823-2012);Departament d’Innovació, Universitats i Empresa,Generalitat de Catalunya (2014-SGR-680). JS, ASand FJP hold a“Miguel Servet”research contractfrom ISC-III (CP12/03109, CP14/00173 and CP14/00212, respectively). PR-S holds a“Río Hortega”research contract from ISC-III (CM13/0115). EC-Oholds a“Sara Borrell”research contract from ISC-III(CD12/00455). The funders had no role in studydesign, data collection and analysis, decision topublish, or preparation of the manuscript

Correlation analyses between plasma concentrations of BDNF, IGF-1 and IGFBP-3 and age in abstinent cocaine users (black circles) and control subjects (white circles).

<p><b>A)</b> BDNF (pg/mL); <b>B)</b> IGF-1 (ng/mL); and <b>C)</b> IGFBP-3 (μg/mL). Dots are individual values. (r) Pearson´s correlation coefficient; (rho) Spearman´s correlation coefficient; (p) p-value for statistical significance.</p

Plasma concentrations of BDNF, IGF-1 and IGFBP-3 according to sex in abstinent cocaine users and control subjects.

<p><b>A)</b> BDNF (pg/mL); <b>B)</b> IGF-1 (ng/mL); and <b>C)</b> IGFBP-3 (μg/mL). Bars are the means and SD. Data were analyzed by two-way analyses (cocaine use [cocaine group and control group] and sex [women and men]).</p

Plasma concentrations of BDNF, IGF-1 and IGFBP-3 in abstinent cocaine users grouped by diagnosis of common psychiatric disorders in substance users.

<p>Plasma concentrations of BDNF, IGF-1 and IGFBP-3 in abstinent cocaine users grouped by diagnosis of common psychiatric disorders in substance users.</p