Molecular biomarkers correspond to all endogenous or exogenous biomolecules, whose presence or alteration in metabolic pathways indicate the response of a biological system to a disturbance caused by internal or external factors. The search for biomarkers has allowed deepening the knowledge of complex pathophysiological mechanisms of diseases, interactions with potential drugs, and the improvement of diagnostic and therapeutic tests, establishing itself as a central point in personalized medicine. In addition, the development of the omics sciences has fostered an increasing exploration in this field of research. This review presents essential and relevant concepts in biomarker research, explores the various definitions and classifications of biomarkers according to their purpose, the critical aspects to be considered in experimental design, the primary employed study models (in vivo, in vitro, and in silico) and the factors that have hindered their ultimate implementation. Finally, important, and current clinical and pharmacological research areas in which biomarker research play a central role are presented.

Tumores malignos são a causa de milhões de falecimentos no mundo todos os anos, porém a detecção da doença em seu estágio inicial pode salvar vidas. Biomarcadores tumorais permitem diagnósticos mais precoces e menos invasivos, portanto são vitais no tratamento do câncer. Os nucleosídeos têm sido pesquisados como um grupo potencial de biomarcadores tumorais presentes em fluidos biológicos. Neste trabalho, um método para a análise de nucleosídeos por eletroforese capilar com detecção UV (CE-UV) em amostras de soro sanguíneo foi desenvolvido e validado de acordo com a legislação vigente no Brasil. A separação de dez nucleosídeos mais o padrão interno foi atingida em ca. 25 min. O método pode contribuir para o diagnóstico precoce e preciso de casos de câncer.

Malignant tumors are the cause of millions of deaths all over the world every year, but the detection of the disease in the first stages may save lives. Tumor biomarkers allow earlier and less invasive diagnosis, hence they are vital in the cancer treatment. Nucleosides have been investigated as a potential group of tumor biomarkers present in biological fluids. In this work, a method for the analysis of nucleosides in blood serum samples by capillary electrophoresis with UV detection (CE-UV) was developed and validated according to the current legislation in Brazil. Separation of ten nucleosides plus the internal standard was achieved in ca. 25 min. The method may contribute for earlier and more accurate diagnosis of cancer cases.

Os sideróforos provenientes de Xylella fastidiosa de videiras foram investigados. Tais metabólitos seqüestram ferro, um elemento essencial, do hospedeiro, o que os torna um potencial fator de patogenicidade. Em um meio de cultura em placa com limitação de ferro, tais sideróforos foram detectados pela reação com o complexo cromoazurol S (CAS). Diferentes métodos de análise instrumentais foram utilizados para caracterização dos sideróforos, como: cromatografia de afinidade por metal imobilizado (IMAC), cromatografia micelar eletrocinética capilar (MEKC) e espectrometria de massas com ionização por electrospray (ESI-MS). Os resultados obtidos confirmaram a produção de sideróforos. A extração do(s) composto(s) por IMAC com Fe3+ imobilizado foi uma etapa importante. O(s) sideróforo(s) não foi separado por eletroforese capilar de zona, indicando sua neutralidade sob os pHs investigados. As análises por MEKC apresentaram um pico diferente (quando comparadas à análise do controle), com caráter levemente hidrofóbico. A espectrometria de massas mostrou que os compostos alvos podem ter uma massa molecular relativa dentro da esperada para sideróforos, como: 875, 1004 e 1092 Da.

Siderophore molecules from grapevine Xylella fastidiosa were investigated. Such metabolites sequester iron, an essential element, from the host, making them a potential factor of pathogenicty. In an iron-limited medium, siderophores were detected in culture plates of X. fastidiosa containing the complex Chromeazurol S (CAS). A combination of different instrumental analyses was used for siderophore(s) characterization, such as: immobilized metal affinity chromatography (IMAC), micelar electrokinetic capillary chromatography (MEKC) and electrospray-mass spectrometry (ESI-MS). The results show that grapevine X. fastidiosa produced siderophore(s), as confirmed by the CAS plate assay. The extraction of the compound(s) using IMAC with immobilized Fe3+ was important for analyte purification. The chelator was not separated by capillary zone electrophoresis, indicating the possibility of a neutral compound under the investigated pHs. MEKC runs presented a different peak (when compared to the control analysis) which represented a slightly hydrophobic compound. Mass spectrometry showed that the compound(s) may have a relative molecular mass within the expected range for siderophore molecules, such as 875, 1004 and 1092 Da.