Diagnostic of Biomphalaria snails and Schistosoma mansoni: DNA obtained from traces of shell organic materials

Freshwater snails belonging to the genus Biomphalaria act as intermediate hosts for the parasite trematode Schistosoma mansoni in Africa and in the neotropical region. Identification of such molluscs is carried out based on morphological characters and the presence of cercariae is verified through squeezing snails between two glass slides or by exposing them to artificial light. However, sometimes, the material collected includes molluscs with decomposed bodies or, yet, only empty shells, which precludes their identification and S. mansoni detection. Due to these difficulties, we have developed a methodology in which DNA may be extracted from traces of organic material from inside shells in order to identify molluscs through polymerase chain reaction and restriction fragment length polymorphism and to detect S. mansoni into these snails, by using low stringency polymerase chain reaction. Species-specific profiles obtained from B. glabrata, B. straminea, and B. tenagophila snails and their shells, maintained in laboratory for ten years, showed the same profiles. S. mansoni profiles showed to be present in shell specimens as far as the eighth week after being removed from aquarium.

Soil fertility, organic carbon and fractions of the organic matter at different distances from eucalyptus stumps

Knowledge on variations in vertical, horizontal and temporal characteristics of the soil chemical properties under eucalyptus stumps left in the soil is of fundamental importance for the management of subsequent crops. The objective of this work was to evaluate the effect of eucalyptus stumps (ES) left after cutting on the spatial variability of chemical characteristics in a dystrophic Yellow Argisol in the eastern coastal plain region of Brazil. For this purpose, ES left for 31 and 54 months were selected in two experimental areas with similar characteristics, to assess the decomposition effects of the stumps on soil chemical attributes. Soil samples were collected directly around these ES, and at distances of 30, 60, 90, 120 and 150 cm away from them, in the layers 0-10, 10-20 and 20-40 cm along the row of ES, which is in-between the rows of eucalyptus trees of a new plantation, grown at a spacing of 3 x 3 m. The soil was sampled in five replications in plots of 900 m² each and the samples analyzed for pH, available P and K (Mehlich-1), exchangeable Al, Ca and Mg, total organic carbon (TOC) and C content in humic substances (HS) and in the free light fraction. The pH values and P, K, Ca2+, Mg2+ and Al3+ contents varied between the soil layers with increasing distance from the 31 and 54-monthold stumps. The highest pH, P, K, Ca2+ and Mg2+ values and the lowest Al3+ content were found in the surface soil layer. The TOC of the various fractions of soil organic matter decreased with increasing distance from the 31 and 54-month-old ES in the 0-10 and 10-20 cm layers, indicating that the root (and stump) cycling and rhizodeposition contribute to maintain soil organic matter. The C contents of the free light fraction, of the HS and TOC fractions were higher in the topsoil layer under the ES left for 31 months due to the higher clay levels of this layer, than in those found under the 54-month-old stumps. However, highest C levels of the different fractions of soil organic matter in the topsoil layer reflect the deposition and maintenance of forest residues on the soil surface, mainly after forest harvest.

DISTRIBUTION OF ORGANIC CARBON IN DIFFERENT SOIL FRACTIONS IN ECOSYSTEMS OF CENTRAL AMAZONIA

Organic matter plays an important role in many soil properties, and for that reason it is necessary to identify management systems which maintain or increase its concentrations. The aim of the present study was to determine the quality and quantity of organic C in different compartments of the soil fraction in different Amazonian ecosystems. The soil organic matter (FSOM) was fractionated and soil C stocks were estimated in primary forest (PF), pasture (P), secondary succession (SS) and an agroforestry system (AFS). Samples were collected at the depths 0-5, 5-10, 10-20, 20-40, 40-60, 60-80, 80-100, 100-160, and 160-200 cm. Densimetric and particle size analysis methods were used for FSOM, obtaining the following fractions: FLF (free light fraction), IALF (intra-aggregate light fraction), F-sand (sand fraction), F-clay (clay fraction) and F-silt (silt fraction). The 0-5 cm layer contains 60 % of soil C, which is associated with the FLF. The F-clay was responsible for 70 % of C retained in the 0-200 cm depth. There was a 12.7 g kg-1 C gain in the FLF from PF to SS, and a 4.4 g kg-1 C gain from PF to AFS, showing that SS and AFS areas recover soil organic C, constituting feasible C-recovery alternatives for degraded and intensively farmed soils in Amazonia. The greatest total stocks of carbon in soil fractions were, in decreasing order: (101.3 Mg ha-1 of C - AFS) > (98.4 Mg ha-1 of C - FP) > (92.9 Mg ha-1 of C - SS) > (64.0 Mg ha-1 of C - P). The forms of land use in the Amazon influence C distribution in soil fractions, resulting in short- or long-term changes.

Organic Matter Fractions and Quality of the Surface Layer of a Constructed and Vegetated Soil After Coal Mining. II - Physical Compartments and Carbon Management Index

Soils constructed after mining often have low carbon (C) stocks and low quality of organic matter (OM). Cover crops are decisive for the recovery process of these stocks, improving the quality of constructed soils. Therefore, the goal of this study was to evaluate the effect of cover crops on total organic C (TOC) stocks, C distribution in physical fractions of OM and the C management index (CMI) of a soil constructed after coal mining. The experiment was initiated in 2003 with six treatments: Hemarthria altissima (T1), Paspalum notatum (T2), Cynodon dactylon (T3), Urochloa brizantha (T4), bare constructed soil (T5), and natural soil (T6). Soil samples were collected in 2009 from the 0.00-0.03 m layer, and the TOC and C stocks in the physical particle size fractions (carbon in the coarse fraction - CCF, and mineral-associated carbon - MAC) and density fractions (free light fraction - FLF; occluded light fraction - OLF, and heavy fraction - HF) of OM were determined. The CMI components: carbon pool index (CPI), lability (L) and lability index (LI) were estimated by both fractionation methods. No differences were observed between TOC, CCF and MAC stocks. The lowest C stocks in FLF and OLF fractions were presented by T2, 0.86 and 0.61 Mg ha-1, respectively. The values of TOC stock, C stock in physical fractions and CMI were intermediate, greater than T5 and lower than T6 in all treatments, indicating the partial recovery of soil quality. As a result of the better adaptation of the species Hemarthria and Brizantha, resulting in greater accumulation of labile organic material, the CPI, L, LI and CMI values were higher in these treatments, suggesting a greater potential of these species for recovery of constructed soils.

ORGANIC MATTER FRACTIONS IN A QUARTZIPSAMMENT UNDER CULTIVATION OF IRRIGATED MANGO IN THE LOWER SÃO FRANCISCO VALLEY REGION, BRAZIL

Improper land use has lead to deterioration and depletion of natural resources, as well as a significant decline in agricultural production, due to decreased soil quality. Removal of native vegetation to make way for agricultural crops, often managed inadequately, results in soil disruption, decreased nutrient availability, and decomposition of soil organic matter, making sustainable agricultural production unviable. Thus, the aim of the present study was to evaluate the impact of growing irrigated mango (over a 20 year period) on the organic carbon (OC) stocks and on the fractions of soil organic matter (SOM) in relation to the native caatinga (xeric shrubland) vegetation in the Lower São Francisco Valley region, Brazil. The study was carried out on the Boa Esperança Farm located in Petrolina, Pernambuco, Brazil. In areas under irrigated mango and native caatinga, soil samples were collected at the 0-10 and 10-20 cm depths. After preparing the soil samples, we determined the OC stocks, carbon of humic substances (fulvic acid fractions, humic acid fractions, and humin fractions), and the light and heavy SOM fractions. Growing irrigated mango resulted in higher OC stocks; higher C stocks in the fulvic acid, humic acid, and humin fractions; and higher C stocks in the heavy and light SOM fraction in comparison to nativecaatinga, especially in the uppermost soil layer.

Changes in Soil Organic Carbon Fractions in Response to Cover Crops in an Orange Orchard

ABSTRACT The cultivation of cover crops intercropped with fruit trees is an alternative to maintain mulch cover between plant rows and increase soil organic carbon (C) stocks. The objective of this study was to evaluate changes in soil total organic C content and labile organic matter fractions in response to cover crop cultivation in an orange orchard. The experiment was performed in the state of Bahia, in a citrus orchard with cultivar ‘Pera’ orange (Citrus sinensis) at a spacing of 6 × 4 m. A randomized complete block design with three replications was used. The following species were used as cover crops: Brachiaria (Brachiaria decumbes) – BRAQ, pearl millet (Pennisetum glaucum) – MIL, jack bean (Canavalia ensiformis) – JB, blend (50 % each) of jack bean + millet (JB/MIL), and spontaneous vegetation (SPV). The cover crops were broadcast-seeded between the rows of orange trees and mechanically mowed after flowering. Soil sampling at depths of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m was performed in small soil trenches. The total soil organic C (SOC) content, light fraction (LF), and the particulate organic C (POC), and oxidizable organic C fractions were estimated. Total soil organic C content was not significantly changed by the cover crops, indicating low sensitivity in reacting to recent changes in soil organic matter due to management practices. Grasses enabled a greater accumulation of SOC stocks in 0.00-0.40 m compared to all other treatments. Jack bean cultivation increased LF and the most labile oxidizable organic C fraction (F1) in the soil surface and the deepest layer tested. Cover crop cultivation increased labile C in the 0.00-0.10 m layer, which can enhance soil microbial activity and nutrient absorption by the citrus trees. The fractions LF and F1 may be suitable indicators for monitoring changes in soil organic matter content due to changes in soil management practices.

Speciation of naturally-accumulated uranium in an organic-rich soil of an alpine region (Switzerland)

Very high concentrations of uranium (up to 4000 ppm) were found in a natural soil in the Dischma valley, an alpine region in the Grisons canton in Switzerland. The goal of this study was to examine the redox state and the nature of uranium binding in the soil matrix in order to understand the accumulation mechanism. Pore water profiles collected from Dischma soil revealed the establishment of anoxic conditions with increasing soil depth. A combination of chemical extraction methods and spectroscopy was applied to characterize the redox state and binding environment of uranium in the soil. Bicarbonate extraction under anoxic conditions released most of the uranium indicating that uranium occurs predominantly in the hexavalent form. Surprisingly, the uranium redox state did not vary greatly as a function of depth. X-ray absorption near edge spectroscopy (XANES), confirmed that uranium was present as a mixture of U(VI) and U(IV) with U(VI) dominating. Sequential extractions of soil samples showed that the dissolution of solid organic matter resulted in the simultaneous release of the majority of the soil uranium content (>95%). Extended X-ray absorption fine structure (EXAFS) spectroscopy also revealed that soil-associated uranium in the soil matrix was mainly octahedrally coordinated, with an average of 1.7 axial (at about 1.76 Å) and 4.6 to 5.3 equatorial oxygen atoms (at about 2.36 Å) indicating the dominance of a uranyl-like (UO22+) structure presumably mixed with some U(IV). An additional EXAFS signal (at about 3.2 Å) identified in some spectra suggested that uranium was also bound (via an oxygen atom) to a light element such as carbon, phosphorus or silicon. Gamma spectrometric measurements of soil profiles failed to identify uranium long-life daughter products in the soil which is an indication that uranium originates elsewhere and was transported to its current location by water. Finally, it was found that the release of uranium from the soil was significantly promoted at very low pH values (pH 2) and increased with increasing pH values (between pH 5 and 9).

An evaluation of the inorganic and organic geochemistry of the San Vicente Mississippi Valley-type zinc-lead district, central Peru: Implications for ore fluid composition, mixing processes, and sulfate reduction

Mississippi Tialley-type zinc-lead deposits and ore occurrences in the San Vicente belt are hosted in dolostones of the eastern Upper Triassic to Lower Jurassic Pucara basin, central Peru. Combined inorganic and organic geochemical data from 22 sites, including the main San Vicente deposit, minor ore occurrences, and barren localities, provide better understanding of fluid pathways and composition, ore precipitation mechanisms, Eh-pH changes during mineralization, and relationships between organic matter and ore formation. Ore-stage dark replacement dolomite and white sparry dolomite are Fe and rare earth element (REE) depleted, and Mn enriched, compared to the host dolomite. In the main deposit, they display significant negative Ce and probably Eu anomalies. Mixing of an incoming hot, slightly oxidizing, acidic brine (H2CO3 being the dominant dissolved carbon species), probably poor in REE and Fe, with local intraformational, alkaline, reducing waters explains the overall carbon and oxygen isotope variation and the distributions of REE and other trace elements in the different hydrothermal carbonate generations. The incoming ore fluid flowed through major aquifers, probably basal basin detrital units, with limited interaction with the carbonate host rocks. The hydrothermal carbonates show a strong regional chemical homogeneity, indicating access of the ore fluids by interconnected channelways near the ore occurrences. Negative Ce anomalies in the main deposit, that are absent at the district scale, indicate local ore-fluid chemical differences. Oxidation of both migrated and indigenous hydrocarbons by the incoming fluid provided the local reducing conditions necessary for sulfate reduction to H2S, pyrobitumen precipitation, and reduction of Eu3+ to Eu2+. Fe-Mn covariations, combined with the REE contents of the hydrothermal carbonates, are consistent with the mineralizing system shifting from reducing/rock-dominated to oxidizing/fluid-dominated conditions following ore deposition. Sulfate and sulfide sulfur isotopes support sulfide origin from evaporite-derived sulfate by thermochemical organic reduction; further evidence includes the presence of C-13-depleted calcite cements (similar to-12 parts per thousand delta(13)C) as sulfate pseudomorphs, elemental sulfur, altered organic matter in the host dolomite, and isotopically heavier, late, solid bitumen. Significant alteration of the indigenous and extrinsic hydrocarbons, with absent bacterial membrane biomarkers (hopanes) is observed. The light delta(34)S of sulfides from small mines and occurrences compared to the main deposit reflect a local contribution of isotopically light sulfur, evidence of local differences in the ore-fluid chemistry.

Soil organic matter in fire-affected pastures and in an Araucaria forest in South-Brazilian Leptosols

The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

OLED-teknologia silmänäytössä ja linssiokulaarin korvaaminen muoviprismalla

Tämä diplomityö esittelee monikäyttöisen kamerajärjestelmän, mikä on pääsääntöisesti tarkoitettu valovahvistimen perään integroitavaksi. Tarkoituksena on parantaa sotilaan pimeätoimintakykyä ja urbaanissa ympäristössä operointia. Järjestelmän yhtenä moduulina on silmänäyttö, joka perustuu itse-emittoivaan orgaaniseen LED-näyttöelementtiin ja perinteiseen okulaarioptiikkaan. Työssä tutustutaan näyttöelementin teknologiaan, sen mahdollisiin rajoituksiin sekä selvitetään optisilla mittauksilla, voitaisiinko konventionaalinen linssiokulaari korvata muovisella prismaokulaarilla. Tämä mahdollistaisi pienemmän ja kevyemmän silmänäytön kehittämisen, mikä parantaisi kamerajärjestelmän käytettävyyttä ja kilpailukykyä.

TiO2 photocatalytic inactivation under simulated solar light of bacterial consortia in domestic wastewaters previously treated by UASB, duckweed and facultative ponds

In this work, TiO2 photocatalysis was used to disinfect domestic wastewaters previously treated by different biological treatment systems: Upward-flow Anaerobic Sludge Blanket (UASB), facultative pond, and duckweed pond. The microorganisms monitored were E. coli, total coliforms, Shigella species, and Salmonella species. Photocatalytic experiments were carried out using two light sources: a solar simulator (UV intensity: 68-70 W m-2) and black-light lamps (BLL UV intensity: 17-20 W m-2). Samples were taken after each treatment stage. Results indicate that bacterial photocatalytic inactivation is affected by characteristics of the effluent, including turbidity, concentration of organic matter, and bacterial concentration, which depend of the type of biological pretreatment previously used.

Metabolite and light regulation of metabolism in plants: lessons from the study of a single biochemical pathway

We are using molecular, biochemical, and genetic approaches to study the structural and regulatory genes controlling the assimilation of inorganic nitrogen into the amino acids glutamine, glutamate, aspartate and asparagine. These amino acids serve as the principal nitrogen-transport amino acids in most crop and higher plants including Arabidopsis thaliana. We have begun to investigate the regulatory mechanisms controlling nitrogen assimilation into these amino acids in plants using molecular and genetic approaches in Arabidopsis. The synthesis of the amide amino acids glutamine and asparagine is subject to tight regulation in response to environmental factors such as light and to metabolic factors such as sucrose and amino acids. For instance, light induces the expression of glutamine synthetase (GLN2) and represses expression of asparagine synthetase (ASN1) genes. This reciprocal regulation of GLN2 and ASN1 genes by light is reflected at the level of transcription and at the level of glutamine and asparagine biosynthesis. Moreover, we have shown that the regulation of these genes is also reciprocally controlled by both organic nitrogen and carbon metabolites. We have recently used a reverse genetic approach to study putative components of such metabolic sensing mechanisms in plants that may be conserved in evolution. These components include an Arabidopsis homolog for a glutamate receptor gene originally found in animal systems and a plant PII gene, which is a homolog of a component of the bacterial Ntr system. Based on our observations on the biology of both structural and regulatory genes of the nitrogen assimilatory pathway, we have developed a model for metabolic control of the genes involved in the nitrogen assimilatory pathway in plants.

Blue and Uv-Emitting Upconversion Nanoparticles: Synthesis and (Bio) Analytical Applications.

Rare-earth based upconverting nanoparticles (UCNPs) have attracted much attention due to their unique luminescent properties. The ability to convert multiple photons of lower energy to ones with higher energy through an upconversion (UC) process offers a wide range of applications for UCNPs. The emission intensities and wavelengths of UCNPs are important performance characteristics, which determine the appropriate applications. However, insufficient intensities still limit the use of UCNPs; especially the efficient emission of blue and ultraviolet (UV) light via upconversion remains challenging, as these events require three or more near-infrared (NIR) photons. The aim of the study was to enhance the blue and UV upconversion emission intensities of Tm3+ doped NaYF4 nanoparticles and to demonstrate their utility in in vitro diagnostics. As the distance between the sensitizer and the activator significantly affect the energy transfer efficiency, different strategies were explored to change the local symmetry around the doped lanthanides. One important strategy is the intentional co-doping of active (participate in energy transfer) or passive (do not participate in energy transfer) impurities into the host matrix. The roles of doped passive impurities (K+ and Sc3+) in enhancing the blue and UV upconversions, as well as in influencing the intense UV upconversion emission through excess sensitization (active impurity) were studied. Additionally, the effects of both active and passive impurity doping on the morphological and optical performance of UCNPs were investigated. The applicability of UV emitting UCNPs as an internal light source for glucose sensing in a dry chemistry test strip was demonstrated. The measurements were in agreement with the traditional method based on reflectance measurements using an external UV light source. The use of UCNPs in the glucose test strip offers an alternative detection method with advantages such as control signals for minimizing errors and high penetration of the NIR excitation through the blood sample, which gives more freedom for designing the optical setup. In bioimaging, the excitation of the UCNPs in the transparent IR region of the tissue permits measurements, which are free of background fluorescence and have a high signal-to-background ratio. In addition, the narrow emission bandwidth of the UCNPs enables multiplexed detections. An array-in-well immunoassay was developed using two different UC emission colours. The differentiation between different viral infections and the classification of antibody responses were achieved based on both the position and colour of the signal. The study demonstrates the potential of spectral and spatial multiplexing in the imaging based array-in-well assays.

Kinetic and mechanistic studies for the molybdenum- catalyzed oxidation of organic sulfides and olefins by t- DuO2H

This research was focussed on the effects of light, solvent and substituents in the molybdenum-catalyzed oxidation of phenylmethyl sulfides with t-Bu02H and on the effect of light in the molybdenum-catalyzed epoxidation of l-octene with t-Bu02H. It was shown that the Mo(CO)6-catalyzed oxidation of phenylmethyl sulfide with t-Bu02H~ at 35°C, proceeds 278 times faster underUV light than under laboratory lighting, whereas the Mo02(acac)2-catalyzed oxidation proceeds only 1.7 times faster under UV light than under normal laboratory lighting. The difference between the activities of both catalysts was explained by the formation of the catalytically active species, Mo(VI). The formation of the Mo(VI) species, from Mo(CO)6 was observed from the IR spectrum of Mo(CO)6 in the carbonyl region. The Mo(CO)6-catalyzed epoxidation of l-octene with t-Bu02H showed that the reaction proceeded 4.6 times faster under UV light than in the dark or under normal laboratory lighting; the rates of epoxidations were found to be the same in the dark and under normal laboratory lighting. The kinetics of the epoxidations of l-octene with t-Bu02H, catalyzed by Mo02(acac)2 were found to be complicated; after fast initial rates, the epoxidation rates decreased with time. The effect of phenylmethyl sulfide on the Mo(CO)6-catalyzed epoxidation of l-octene waS studied. It was shown that instead of phenylmethyl sulfide, phenylmethyl sulfone, which formed rapidly at 85°C, lowered the reaction rate. The epoxidation of l-octene was found to be 2.5 times faster in benzene than in ethanol. The substituent effect on the Mo02(acac)2-catalyzed oxidations of p-OH, p-CHgO, P-CH3' p-H, p-Cl, p-Br, p-CHgCO, p-HCO and P-N02 substituted phenylmethyl sulfides were studied. The oxidations followed second order kinetics for each case; first order dependency on catalyst concentration was also observed in the oxidation of p-CHgOPhSMeand PhSMe. It was found that electron-donating groups on the para position of phenylmethyl sulfide increased the rate of reaction, while electronwithdrawing groups caused the reaction rate to decrease. The reaction constants 0 were determined by using 0, 0- and 0* constants. The rate effects were paralleled by the activation energies for oxidation. The decomposition of t-Bu02H in the presence of M.o (CO)6, Mo02 (acac)2 and VO(acac)2 was studied. The rates of decomposition were found to be very small compared to the oxidation rates at high concentration of catalysis. The relative rates of the Mo02(acac)2-catalyzed oxidation of p-N02PhSMe by t-Bu02H in the presence of either p-CH30PhSMe or PhSMe clearly show that PhSMe and p-CHgOPhSMe act as co-catalysts in the oxidation of p-N02PhSMe. Benzene, mesity1ene and cyclohexane were used to determine the effect of solvent in the Mo02 (acac)2 and Mo(CO)6-catalyzed oxidation of phenylmethyl sulfide. The results showed that in the absence of hydroxylic solvent, a second molecule of t-Bu02H was involved in the transition state. The complexation of the solvent with the catalyst could not be explained.The oxidations of diphenyl sulfoxide catalyzed by VO(acac)2, Mo(CO)6 and Mo02(acac)2 showed that VO(acac)2 catalyzed the oxidation faster than Mo(CO)6 and Mo02 (acac)2_ Moreover, the Mo(CO)6-catalyzed oxidation of diphenyl sulfoxide proceeded under UV light at 35°C.

Points quantiques : caractérisation et applications en sciences pharmaceutiques

L’imagerie médicale a longtemps été limitée à cause des performances médiocres des fluorophores organiques. Récemment la recherche sur les nanocristaux semi-conducteurs a grandement contribué à l’élargissement de la gamme d’applications de la luminescence dans les domaines de l’imagerie et du diagnostic. Les points quantiques (QDs) sont des nanocristaux de taille similaire aux protéines (2-10 nm) dont la longueur d’onde d’émission dépend de leur taille et de leur composition. Le fait que leur surface peut être fonctionnalisée facilement avec des biomolécules rend leur application particulièrement attrayante dans le milieu biologique. Des QDs de structure « coeur-coquille » ont été synthétisés selon nos besoins en longueur d’onde d’émission. Dans un premier article nous avons modifié la surface des QDs avec des petites molécules bi-fonctionnelles portant des groupes amines, carboxyles ou zwitterions. L’effet de la charge a été analysé sur le mode d’entrée des QDs dans deux types cellulaires. À l’aide d’inhibiteurs pharmacologiques spécifiques à certains modes d’internalisation, nous avons déterminé le mode d’internalisation prédominant. L’endocytose par les radeaux lipidiques représente le mode d’entrée le plus employé pour ces QDs de tailles similaires. D’autres modes participent également, mais à des degrés moindres. Des disparités dans les modes d’entrée ont été observées selon le ligand de surface. Nous avons ensuite analysé l’effet de l’agglomération de différents QDs sur leur internalisation dans des cellules microgliales. La caractérisation des agglomérats dans le milieu de culture cellulaire a été faite par la technique de fractionnement par couplage flux-force (AF4) associé à un détecteur de diffusion de la lumière. En fonction du ligand de surface et de la présence ou non de protéines du sérum, chacun des types de QDs se sont agglomérés de façon différente. À l'aide d’inhibiteur des modes d’internalisation, nous avons corrélé les données de tailles d’agglomérats avec leur mode d’entrée cellulaire. Les cellules microgliales sont les cellules immunitaires du système nerveux central (CNS). Elles répondent aux blessures ou à la présence d’inflammagènes en relâchant des cytokines pro-inflammatoires. Une inflammation non contrôlée du CNS peut conduire à la neurodégénérescence neuronale et est souvent observée dans les cas de maladies chroniques. Nous nous sommes intéressés au développement d’un nanosenseur pour mesurer des biomarqueurs du début de l’inflammation. Les méthodes classiques pour étudier l’inflammation consistent à mesurer le niveau de protéines ou molécules relâchées par les cellules stressées (par exemple monoxyde d’azote, IL-1β). Bien que précises, ces méthodes ne mesurent qu’indirectement l’activité de la caspase-1, responsable de la libération du l’IL-1β. De plus ces méthode ne peuvent pas être utilisées avec des cellules vivantes. Nous avons construit un nanosenseur basé sur le FRET entre un QD et un fluorophore organique reliés entre eux par un peptide qui est spécifiquement clivé par la caspase-1. Pour induire l’inflammation, nous avons utilisé des molécules de lipopolysaccharides (LPS). La molécule de LPS est amphiphile. Dans l’eau le LPS forme des nanoparticules, avec des régions hydrophobes à l’intérieure. Nous avons incorporé des QDs dans ces régions ce qui nous a permis de suivre le cheminement du LPS dans les cellules microgliales. Les LPS-QDs sont internalisés spécifiquement par les récepteurs TLR-4 à la surface des microglies. Le nanosenseur s’est montré fonctionnel dans la détermination de l’activité de la caspase-1 dans cellules microgliales activées par le LPS. Éventuellement, le senseur permettrait d’observer en temps réel l’effet de thérapies ciblant l’inflammation, sur l’activité de la caspase-1.