LOADING AND RELEASE OF A MODEL DRUG IN MESOPOROUS SILICON OXIDE NANOSTRUCTURE

The sustained delivery of therapeutics with minimal systemic side effects would be a benefit in the treatment of many diseases. Numerous nanostructured materials in various shapes and sizes have been investigated to meet this challenge. This dissertation focuses in particular on the development of nanostructured porous silicon based materials for observable and sustained drug delivery. Porous silicon possesses many fascinating feature making it an attractive candidate as a optical biosensor and drug delivery system, including the controllability of pore size and volume, the ease of chemical modification to load various drugs, a high surface area, biocompatibility and resorbability. Its high surface to volume ration and readily surface chemistry also provide additional control for enhancing selectivity. Combining its optical and physical properties together with tailored surface moieties, porous silicon material can be treated as a multifunctional material allowing detection and accommodation of different biomolecules. The objective of this thesis is to explore porous silicon as a multifunctional material with the ability to detect biomolecules at low concentration in real-time. Interrogation of porous silicon material as a nanostructure involved three major aspects : 1) manipulation of its optical and spectral information for encoding and signal processing applications, 2) examination of the effect of its physical properties on molecular transport within its porous structure 3) investigation of analyte-pore surface iteraction for enhances selectivity or better separation based on analyte surface moieties. In order to improve upon drug release kinetics, loading of drugs into porous silicon particles by physical adsorption were carried out, and the mechanism of drug release was studied. The work was divided in different part. The first one was studied the previous work that have done in the drug delivery community porous silicon. It was studied the mainly properties of porous silicon as a drug delivery system and optical sensors. The second part was focus on the porous silicon oxide nanostructure as vehicle for a specific drug fof the treatment of age related macular degeneration. We found that long-term release of therapeutics (days to mon ths) has not been demonstrated. In the treatment of chronic diseases, it would be advantageous to have a drug delivery system that can provide sustained drug release for prolonged time periods, that is the goal of this thesis. So in the last part of this work we were able to synthesized a nanostructure double layer porous silica shaped as a "bottleneck" structure. The experimental part was divide in : o Determine optimized etching conditions to design a double layer pSilica o Determine optimized loading conditions o Perform Drug Release o Quantify the portein released with a specific assay This protocol was followed working on two different project : we first loaded the nanocarrier with bevacizumanb (avastin), a monoclonal antibody based drugs, by electrostatic adsorption for its potential in the treatment of the retina ; the second project we investigated the functionality of the synthesized nanostructure using Lysozyme as a model of drug, working with its specific enzymatic assay. We had good results about the loading of the Bevacizumab into the single layer, representing the neck and the bottom layer of the bottleneck shape. That results confirm in a previous part that the monoclonal antibody based drug can be loaded in a single nanostructure, using a specific etching and loading condition But the large hydrodymanic diameter about 11nm of the drug, makes it difficult to load it into a porous silica double layer by electrostatic adsorption. For that reason we wanted to investigate and test the functionality of the nanostructure, using a very stable enzyme, with a hydrodymanic diameter about 3.nm. For this part, we chose this enzyme because it is often use as a surrogate for protein based drugs like avastin or lucentis, and also because rather than other functional assay like BCA we can discriminate between active or denaturated protein form after release using his assay (EnzChek Lysozyme Assay E-22013). The double layer porous silica structure was generated by etching crystalline Si wafers in aqueous hydrofluoric acid (HF) solutions contained in a teflon etch cell in a two-electrode configuration under galvanostatic conditions. The porous layer is formed on the surfaces of the Si, which is used as a positive anode. Usually a cathode is made of platinum and the fabrication cell has to be made of HF-resistant material, like Teflon. With the appropriate choice of dopant type, dopant concentrations, and preparation conditions, a wide range of pore sizes are accessible in the porous Si electrochemical system. Table 1 shows the properties of the porous silica film synthesized and used for the experimental setup. chip A Surface modification was carried out by Si-O bond, to passivate the silicon surface film. It has been used the thermal oxidation at 800°C for 1 hour. This method create a thin oxide layer on top that can be readily used to attach biomolucules. The negatively charged surfaces in a solution that is greater than pH 2 also offers a potential route for studying electrostatic interaction between the pore walls and the analytes. Using this etching condition, we was able to verify the loading of the enzyme in a double layer structure. The protein adsorption onto the porous SiO2 result in an increase in the measured EOT optical thickness 2nL. We monitorized the shift of the effective optical thickness, readly obtained from the Fourier transform of the refraction of the porous layer changes. The increase in optical thickness can be attribuited to an increase in the effective index of refraction. The release step was performed in a 1.5 mL of PBS 7.4 PH store at 37° for 12 h, by the degradation of the matrix in physical aqueous solution. The concentration of the amount of protein relased was measured using the micro BCA assay. Silica matrices have been developed as a vehicle to host and transport biomolecule and drugs and we was able to get some good data for controlled drug release profiles using this nanostructure : this mesoporous silica carrier possesses many desiderable features that are ideal for controlled and sustained drug delivery. But an important requirement of many drug delivery applications is that the collection, concentration and immobilization processes not denature or otherwise deactivate the biomolecule of interest. While it has been demonstrated that porous Si matrices can release antibodies, enzymes or other biomolecules in their active form, some composition of porous Si are known to undergo irreversible chemical reactions with drugs or other molecules. In the present case, the enzymatic activity of Lysozyme provides a functional assay of the compatibility of the pSi device with sensitive proteins. We quantify the activity of lysozyme collected in and then released from the nanostructure of porous silica and we compared to the activity of as-received lysozyme and lysozyme expose to the pSi matrix. Activity was quantified using a fluorescence-based lysozyme assay using Micrococcus lysozdeikiticus cells labeled with fluorescein. The activity of lysozyme was compared with a control that had not been ezposed to the pSi film. The concentration of total collected lysozyme was determined using microBCA assay prior to lysozyme activity experimens. Pearson correlation coefficient between the control and the sample released from the device is 98%. The important aspect of the present work is that it demonstrates the example of a porous interferometric biosensors for drug delivery application. The system demonstrated here was able to capture the enzyme and release it in an active form. We test the functionality of the porous silica device comparing two different bottleneck shape nanostructure different by the pores size of the neck layer. We demonstrated the possibility to have a sustained release using this kind of nanostructur

Laboratory personnel

Listed: name, ext., room, gr., and class.Includes: telephone key, personnel listing, Hazeltine corporation, Bell telephone laboratories, Western Electric company (ADES), RAND corporation, Boeing, summary, and service contacts.List of Division 6 personnel at Lincoln Laboratory in January 1956

An Analysis of Texas’ Bullying Policies & Practices

Bullying is a serious problem affecting youth, families, and communities. Bullying is not an individual problem, but a family and societal one as well. Schools play a vital role in combating this issue. This study evaluates the strengths and weaknesses of the state of Texas’ policy addressing bullying through a comprehensive policy analysis. This study also outlines and provides a guide to future policy makers, school officials, and families on how to reduce and hopefully eliminate bullyin

Personnel list

Listed: name, ext, room, gr, and class.Includes: telephone key, group secretaries, personnel listing, Hazeltine Corporation, Bell Telephone Laboratories, Western Electric Company (ADES), RAND Corporation, Boeing, summary, and service contacts.List of Division 6 personnel at Lincoln Laboratory in 1956

Personnel list

Listed: name, ext, room, gr, and class.Includes: telephone key, group secretaries, personnel listing, Bell Telephone Laboratories, Boeing, Hazeltine Corporation, RAND Corporation, Western Electric Company (ADES), summary, and service contacts.List of Division 6 personnel at Lincoln Laboratory in 1956

Análisis de la degradación de clorofilas en Arabidopsis thaliana: caracterización de Mg-Dequelatasa

Proyecto de Graduación (Bachillerato en Ingeniería en Biotecnología). Instituto Tecnológico de Costa Rica, Escuela de Biología, 2006.El conocimiento actual sobre la dequelatación del magnesio durante la degradación de clorofilas es escaso y los resultados son contradictorios. En el presente trabajo se detectó y caracterizó la actividad Mg-dequelatasa (MDS) en extractos de hojas de Arabidopsis thaliana, utilizando clorofilina como sustrato. Se determinó la Km aparente de la actividad, así como la temperatura y pH óptimos, efecto de activadores e inhibidores y de reguladores del crecimiento. A pesar de presentar algunas similitudes con compuestos MDS de baja masa molecular reportados en la literatura para otros sistemas, en A. thaliana la actividad se debería a un compuesto diferente

Equivalencia y poder de resolución en los modelos unidimensionales de audio-magnetoteluríca

El objetivo principal de este trabajo es analizar el poder de resolución en la definición de los parámetros, al interpretar con modelos unidimensionales los datos magnetotelúricos en el rango de las audio-frecuencias, 10 a 30.000 Hz.(SAMT). Se estudió en especial un modelo de tres capas, donde la capa intermedia puede ser resistiva o conductora. El poder de resolución en los parámetros de interpretación es obviamente una función de la magnitud del error experimental. Con distintos valores de esta última, se calcularon numéricamente los rangos de indeterminación en el espesor de la capa intermedia al buscar el modelo de mejor ajuste a un conjunto de datos experimentales. En el caso extremo se obtuvieron los valores de los parámetros que marcan el límite de "capa delgada”, situación indicada por la pérdida substancial de variación en los valores calculados del modelo para decrecimientos en el espesor de la capa intermedia. A fin de sopesar las posibilidades entre las técnicas de sondaje eléctrico vertical (SEV) y la SAMT. Se comparó el poder de resolución de ambos métodos para distintos niveles del error experimental.The principal objective of this paper is to discuss the resolving power related with the interpretation by one-dimensional models of magnetotel1uric data in the range of the audio-frecuencies, 10 to 30,000 Hz, (AMTS). The special case of a three layer model, where the intermediate layer could be conductive or resistant, was analyzed. The resolving power associated with the estimation of model parameters obviously depends on the magnitude of the experimental error. Assuming different values for the last one, the indetermination range of the thickness of intermediate layer has been numérically calculated. In the extreme case the ”thin layer limit” is obtained, where a substantial loss of resolution occurs when decreasing the thickness of the intermediate layer. To compare the possibilities between the vertical electric sounding (VES) and the AMTS methods their resolving power are analyzed for different experimental error levels.Asociación Argentina de Geofísicos y Geodesta

Equivalencia y poder de resolución en los modelos unidimensionales de audio-magnetoteluríca

El objetivo principal de este trabajo es analizar el poder de resolución en la definición de los parámetros, al interpretar con modelos unidimensionales los datos magnetotelúricos en el rango de las audio-frecuencias, 10 a 30.000 Hz.(SAMT). Se estudió en especial un modelo de tres capas, donde la capa intermedia puede ser resistiva o conductora. El poder de resolución en los parámetros de interpretación es obviamente una función de la magnitud del error experimental. Con distintos valores de esta última, se calcularon numéricamente los rangos de indeterminación en el espesor de la capa intermedia al buscar el modelo de mejor ajuste a un conjunto de datos experimentales. En el caso extremo se obtuvieron los valores de los parámetros que marcan el límite de "capa delgada”, situación indicada por la pérdida substancial de variación en los valores calculados del modelo para decrecimientos en el espesor de la capa intermedia. A fin de sopesar las posibilidades entre las técnicas de sondaje eléctrico vertical (SEV) y la SAMT. Se comparó el poder de resolución de ambos métodos para distintos niveles del error experimental.The principal objective of this paper is to discuss the resolving power related with the interpretation by one-dimensional models of magnetotel1uric data in the range of the audio-frecuencies, 10 to 30,000 Hz, (AMTS). The special case of a three layer model, where the intermediate layer could be conductive or resistant, was analyzed. The resolving power associated with the estimation of model parameters obviously depends on the magnitude of the experimental error. Assuming different values for the last one, the indetermination range of the thickness of intermediate layer has been numérically calculated. In the extreme case the ”thin layer limit” is obtained, where a substantial loss of resolution occurs when decreasing the thickness of the intermediate layer. To compare the possibilities between the vertical electric sounding (VES) and the AMTS methods their resolving power are analyzed for different experimental error levels.Asociación Argentina de Geofísicos y Geodesta

Modeling of apparent electrical conductivity to improve the assessment of agricultural soil properties

Es de gran interés la utilización de sensores proximales de inducción electromagnética (EMI) en los estudios de las propiedades fisicoquímicas de suelos utilizados en la agricultura. El objetivo de este trabajo fue evaluar la eficiencia de un sensor de EMI en la determinación de la distribución horizontal y vertical de laspropiedades del suelo. Se determinó el modo u operatoria de medición que permite relacionar la conductividad eléctrica aparente (CEa) del suelo con las propiedades edáficas con mayor exactitud y establecer la distribución en profundidad de la conductividad eléctrica (CE) del suelo implementando el método deinversión 1D. Se efectuaron relevamientos de CEa a campo mediante EMI en tres sitios: dos a lo largo de transectas (sitios 1 y 2) y otro en un área de un lote bajo riego (sitio 3). Se analizaron correlaciones entre la CEa y algunas propiedades del suelo, y se confeccionaron mapas de CE con los modelos obtenidos a partir de las inversiones 1D en transectas. Se determinó que el mejor modo de orientación del instrumento es el horizontal. En el sitio 1 la CEa se correlacionó con el contenido de nitrato (r= 0,67) y con la CE del suelo medida en laboratorio (CEs) (r= 0,69). Por otro lado, en el sitio 2, la CEa se correlacionó con la humedad volumétrica (r= 0,91). En el sitio 3, se observó una alta correlación entre la CEa y pH (r= 0,88), CEs (r= 0,87), porcentaje de sodio intercambiable (r= 0,91) y contenido de sodio (r= 0,91). La variabilidad de la CEa explicó el contenido de sales y el grado de sodicidad del suelo. El modelado de la CEa permitió identificar laszonas o ambientes con distintos rangos en las propiedades del suelo relacionadas con la salinización y la sodificación como consecuencia de la aplicación del riego complementario.The use of nearby electromagnetic induction (EMI) sensors is of great interest in the studies of the physicochemical properties of soils used in agriculture. The objective of this work was to evaluate the efficiency of an EMI sensor in determining the horizontal and vertical distribution of soil properties. It was determined the measurement mode or operation that allows relating the apparent electrical conductivity (ECa) of the soil with the edaphic properties with greater accuracy and the depth distribution of the electrical conductivity (EC) of the soil was determined by implementing the 1D inversion method. The ECa surveys were conducted in the field by EMI at three sites: two along transects (sites 1 and 2) and another in an area of a plot under irrigation (site 3). Correlations between ECa and some soil properties were analyzed, and EC maps were made with the models obtained from 1D inversions in transects. The best orientation mode for the instrument was determined to be horizontal. At site 1, ECa was correlated with nitrate content (r= 0.67) and with laboratory-measured soil EC (ECs) (r= 0.69). On the other hand, at site 2, ECa was correlated with volumetric humidity (r= 0.91). At site 3, a high correlation was observed between ECa and pH (r= 0.88), ECs (r= 0.87), percentage of exchangeable sodium (r= 0.91) and sodium content (r= 0.91). The variability of the ECa explained the content of salts and the degree of sodicity of the soil. The ECa modeling allowed the identification of areas or environments with different ranges in soil properties related to salinization and sodification as a consequence of the application of complementary irrigation.Fil: Alonso, Sebastian Javier. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Sainato, Claudia Mabel. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Iseas, Mariano Santiago. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Modeling of apparent electrical conductivity to improve the assessment of agricultural soil properties

Es de gran interés la utilización de sensores proximales de inducción electromagnética (EMI) en los estudios de las propiedades fisicoquímicas de suelos utilizados en la agricultura. El objetivo de este trabajo fue evaluar la eficiencia de un sensor de EMI en la determinación de la distribución horizontal y vertical de laspropiedades del suelo. Se determinó el modo u operatoria de medición que permite relacionar la conductividad eléctrica aparente (CEa) del suelo con las propiedades edáficas con mayor exactitud y establecer la distribución en profundidad de la conductividad eléctrica (CE) del suelo implementando el método deinversión 1D. Se efectuaron relevamientos de CEa a campo mediante EMI en tres sitios: dos a lo largo de transectas (sitios 1 y 2) y otro en un área de un lote bajo riego (sitio 3). Se analizaron correlaciones entre la CEa y algunas propiedades del suelo, y se confeccionaron mapas de CE con los modelos obtenidos a partir de las inversiones 1D en transectas. Se determinó que el mejor modo de orientación del instrumento es el horizontal. En el sitio 1 la CEa se correlacionó con el contenido de nitrato (r= 0,67) y con la CE del suelo medida en laboratorio (CEs) (r= 0,69). Por otro lado, en el sitio 2, la CEa se correlacionó con la humedad volumétrica (r= 0,91). En el sitio 3, se observó una alta correlación entre la CEa y pH (r= 0,88), CEs (r= 0,87), porcentaje de sodio intercambiable (r= 0,91) y contenido de sodio (r= 0,91). La variabilidad de la CEa explicó el contenido de sales y el grado de sodicidad del suelo. El modelado de la CEa permitió identificar laszonas o ambientes con distintos rangos en las propiedades del suelo relacionadas con la salinización y la sodificación como consecuencia de la aplicación del riego complementario.The use of nearby electromagnetic induction (EMI) sensors is of great interest in the studies of the physicochemical properties of soils used in agriculture. The objective of this work was to evaluate the efficiency of an EMI sensor in determining the horizontal and vertical distribution of soil properties. It was determined the measurement mode or operation that allows relating the apparent electrical conductivity (ECa) of the soil with the edaphic properties with greater accuracy and the depth distribution of the electrical conductivity (EC) of the soil was determined by implementing the 1D inversion method. The ECa surveys were conducted in the field by EMI at three sites: two along transects (sites 1 and 2) and another in an area of a plot under irrigation (site 3). Correlations between ECa and some soil properties were analyzed, and EC maps were made with the models obtained from 1D inversions in transects. The best orientation mode for the instrument was determined to be horizontal. At site 1, ECa was correlated with nitrate content (r= 0.67) and with laboratory-measured soil EC (ECs) (r= 0.69). On the other hand, at site 2, ECa was correlated with volumetric humidity (r= 0.91). At site 3, a high correlation was observed between ECa and pH (r= 0.88), ECs (r= 0.87), percentage of exchangeable sodium (r= 0.91) and sodium content (r= 0.91). The variability of the ECa explained the content of salts and the degree of sodicity of the soil. The ECa modeling allowed the identification of areas or environments with different ranges in soil properties related to salinization and sodification as a consequence of the application of complementary irrigation.Fil: Alonso, Sebastian Javier. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Sainato, Claudia Mabel. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Iseas, Mariano Santiago. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin