[pt] As doenças trasmitidas pelo sangue, assim como a necessidade de bancos de sangue para um pronto auxílio em casos de acidentes tem estimulado esforços para desenvolver substitutos do sangue. A albumina serica humana (HSA do ingles Human Serum Albumin) é a proteína mais abundante no plasma sanguíneo. A molécula heme é a transportadora de oxigênio no sangue. Portanto, um estudo detalhado da interação HSA/heme seria útil em pesquisas que visam tornar o complexo HSA-heme em um substituto do sangue. Nesta tese, foram usadas técnicas de dinâmica molecular e ferramentas estatísticas para estudar o sistema HSA-heme em solvente explícito. Tanto o ligante quanto a proteína foram também estudados separadamente em meio aquoso. Dentre outros resultados, nosso estudo revelou a organização da água circundante, os efeitos da ligação do heme na HSA, os mecanismos moleculares da ligação do heme, os movimentos coletivos da proteína livre e ligada, assim como também os aminoácidos que atuam como dobradiças moleculares na mudança conformacional que sofre a proteína ao ligar o heme. / [en] Diseases transmitted through the blood, as well as the need for blood banks to help in case of accidents, stimulated efforts to develop blood substitutes. The human serum albumin (HSA) is the most abundant protein in blood plasma. The heme molecule is the carrier of oxygen in the blood. Therefore, a detailed study of the interaction HSA/heme could give useful insights in the research aimed to convert the HSA-heme complex into a blood substitute. In this thesis, molecular dynamics techniques and statistical tools were applied to study the HSA-heme system in explicit solvent. Both ligand and protein were also studied separately in aqueous medium. Among other results, our study reveals the organization of the surrounding water, the effects of the heme upon its binding to HSA, the molecular mechanisms for heme binding, the collective motions of the protein with and without the heme, as well as the amino acids that act as molecular hinges in the conformational change between the free and bound forms of the protein.

To address the challenge of accurate, low cost and robust biosensors for diabetes management and early detection of diabetes complications, we have developed novel, robust sensing chemistry (or receptors) for electrochemical POC biosensors. The biosensors have been developed for the bio-markers associated with diabetes management such as glycated haemoglobin (HbA1c), glycated albumin, glucose, biomarkers associated with diabetes complications such as microalbuminuria, urine creatinine and albumin-to-creatinine ratio (ACR) and biomarkers associated with anaemia and malnutrition conditions such as haemoglobin and serum albumin. For haemoglobin detection, a new POC bio sensing technique has been developed based on Aza-heterocyclic chemicals. The repeatability and accuracy of the biosensor have been tested on real pathology samples. The glycated form of haemoglobin, called glycated haemoglobin or HbA1c, is the gold standard test in diabetes management as it gives the 90-days average blood glucose value. We demonstrate a simple method for electrochemical detection of HbA1c by combining bosonic affinity principle along with aza-heterocyclic receptors. The technique has been verified on the real clinical patient samples. Albumin is the most abundant protein in the human blood. Human serum albumin (HSA) is either alone or an associative biomarker in several chronic diseases like necrosis, nephrosis, hepatitis, malnutrition, arthritis, immune disorders, cancer, diabetes and in some severe infections. In pathology laboratories, the serum albumin is usually tested on serum samples and not in whole blood samples. Since albumin is not a metalloproteinase, it is very difficult to develop electrochemical POC biosensor. We have developed a novel technique for the electrochemical detection of serum albumin in whole blood samples, by exploiting its binding property with redox active copper salts. The accuracy of technique has been verified on both real human blood plasma as well as whole blood samples. Glycated albumin, which is the glycated form of serum albumin, is emerging as a novel biomarker for diabetes management, as it gives the average blood glucose value of 15-20 days. It is also extremely useful in chronic kidney disease patients and patients with hemoglobinopathies where HbA1c can give the erroneous results. By combining the copper chemistry along with bosonic affinity principle, we present the first ever demonstration of glycated albumin sensing. Instant blood glucose monitoring is an integral part of diabetes management. Most of the glucometers available in the market are based on glucose oxidase enzyme. We have demonstrated a low cost non-enzymatic electrochemical technique for blood glucose detection using alkaline methylene blue chemistry. The accuracy of the technique has been verified on real human blood plasma samples. Glucometer is one of the most easily available POC biosensor and a useful tool for diabetes population. India has second largest diabetes population in the world. To analyse the accuracy of the POC glucometers which are available in Indian market, a comprehensive study was conducted. The results were compared with clinical accuracy guidelines using exhaustive statistical analysis techniques. The shortcomings of the commercial glucometers are elucidated, regarding different international standards. Diabetic nephropathy is one of the major diabetes complications and is the primary cause of chronic kidney disease (CKD). The presence of albumin in urine is a well-established biomarker for the early detection of diabetic nephropathy. We have developed a technique for electrochemical detection of microalbuminuria for point of care applications by exploring the binding property of human albumin with electrochemically active molecules like copper and hemin. Methylene blue mediated sensing technique has also been proposed. Urine Albumin-to creatinine ratio (ACR) is another variant of the microalbumuria test that can be done any time and does not suffer from the dilution factor of urine. Iron binding property of creatinine is exploited to develop creatinine biosensor, thus enabling POC ACR tests.

Safety concerns arising from cytotoxic behavior of nanoparticles (NPs) in complex biological environment remain the main problem limiting NPs application in biomedicine. In this study, we have investigated cytotoxicity of NPs with different composition, shape and size, namely SiO2 NPs (SiNPs, 7-14 nm), superparamagnetic iron oxide NPs (SPIONs, 8 nm) and carboxylated multiwalled carbon nanotubes (CNTCOOHs, diameter: 60-100 nm, length: 1-2 μm). Cytotoxicity was evaluated with newly designed screening assay capable to simultaneously assess activity of cell dehydrogenases, activity of lactate dehydrogenase (LDH) released from cells into environment and number of intact cell nuclei and apoptotic bodies in human umbilical vein endothelial cell (HUVEC) culture growing in the very same well of the 96-well plate. Aforementioned attributes were subsequently utilized to obtain information about cell viability and necrotic and apoptotic aspects of cell death. Results from this "three-in-one" cell death screening (CDS) assay showed that SiNPs and CNTCOOHs evoked pronounced cytotoxic effect demonstrated as decrease of cell viability and development of apoptotic bodies formation. In contrast to this, SPIONs induced only mild cytotoxicity. Moreover, SiNPs impaired cell membrane leading to increased LDH release...

Alzheimer's disease (AD) was first described more than 100 years ago and is today the most common cause of dementia. It is one of the progressive neurodegenerative diseases that affect 47 million people around the world between the ages of 60 and 90. One of the contributing factors to AD is extracellular amyloid – β (Aβ) plaques that form as a result of protein aggregation. These Aβ proteins are neurotoxic, leading to degeneration of brain neurons and loss of cognitive abilities. Because AD largely affects society, researchers are constantly working to find a cure, which currently does not exist. The purpose of this study was to use Drosophila melanogaster as a living organism model for the expression of two types of Aβ proteins related to AD, Arctic (Glu22Gly) and TandemAβ, and to study the survival of these AD flies when Bovine serum albumin (BSA) was added to the fly food. The hypothesis was that BSA would be effective in slowing down and/or preventing formation of toxic Aβ-aggregates. The focus was therefore to investigate whether the AD flies would live longer if they were allowed to eat Bovine serum albumin and whether the soluble/insoluble Aβ levels in these flies would decrease in comparison to the control AD flies that were not allowed to eat BSA. The effect of BSA on toxicity was evaluated using survival assay on male flies and the levels of soluble/insoluble Aβ were evaluated using Meso Scale Discovery (MSD) on female flies. In both experiments, the following six groups of flies were examined: myow1118 ± BSA; myoArctic ± BSA; myoTandemAβ ± BSA. Conclusions from the studies are that the survival of AD flies could not be extended by adding 0.61 mM BSA to the food, rather the data showed a weak but significant toxic effect in the presence of BSA in the AD flies. However, MSD data showed a reduction of insoluble Aβ aggregates and an equilibrium shift from insoluble Aβ aggregates to soluble Aβ aggregates in the presence of BSA in the AD flies. Equilibrium shifts were particularly detectable in Myo-TandemAβ flies fed with BSA. In Myo-Arctic flies fed with BSA only reduction of insoluble Aβ could be detected. This shows that it is not the amount of Aβ aggregates that is decisive for toxicity, but rather the presence of specific aggregates that have toxic properties. If BSA shows good results in further studies, it could be used in the future to improve AD symptoms in patients.