For the development of the HFF piezoelectric immunosensor, 100 MHz quartz crystals were used as transducer elements. The gold electrode surface was functionalized by covalent immobilization of the target biomarker through mixed self-assembled monolayers (mSAM) of carboxylic alkane thiols. A competitive immunoassay based on Myc-31 MAb was integrated with the transducer as sensing bio-recognition event. Reliable assay signals were obtained using low concentrations of antigen for functionalization and MAb for the competitive immunoassay. Under optimized conditions, the HFF immunosensor calibration curve for 38 kDa determination showed a limit of detection as low as 11 ng mL-1 of the biomarker. The high detectability attained by this immunosensor, in the picomolar range, makes it a promising tool for the easy, direct and sensitive detection of the tuberculosis biomarker in biological fluids such as sputum.

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Biochar-derived C-Dots from Picea, Molinia caerulea and Elaeis guineensis were synthesized through a hydrothermal process, and their physicochemical and optical characteristics and environmental effects were compared. These C-Dots were characterized by techniques such as Attenuated Total Reflection–Fourier Transform Infrared (ATR-FTIR), UV-Vis spectrophotometry, fluorescence spectroscopy, dynamic light scattering (DLS), Z potential, and High-Resolution Transmission Electronical Microscopy (HR-TEM). The ecotoxicity tests were performed using the Microtox™ test, making this study one of the few that use this method. The C-Dots from Molinia caerulea showed the best quantum yield (QY) of 8.39% and moderate ecotoxicity, while Elaeis guineensis has the lowest QY (2.31%) but with zero toxicity. Furthermore, the C-Dots from Picea presents good optical properties but showed high toxicity and limits its use. Finally, all C-Dots showed functional groups that could be biofunctionalized with biomolecules, especially C-Dots from Molinia caerulea and Elaeis guineensis show potential for use in the development of optical biosensors.

Monoclonal antibodies have been applied in biomedical research for diagnosis of various diseases and for the treatment of increasing prevalence diseases such as tuberculosis. There is a need to develop systems capable of detecting tuberculosis-related biomarkers that can provide a quick diagnosis to begin treatment immediately. Thanks to the advances in research for detection, biosensors technologies are emerging as a good alternative for clinical applications. The aim of this work was to develop a piezoelectric immunosensor for rapid and efficient tuberculosis detection. To this purpose, 12 hybridomas and their secreted monoclonal antibodies specific for a biomarker of Mycobacterium tuberculosis were obtained as potential bio-receptors. The monoclonal antibody affinity to the antigenic protein of interest was tested by ELISA. Surface functionalization of the gold electrode -the transducer -of a Quartz Crystal Microbalance (QCM) was simulated by the formation of Self-Assembled Monolayers (SAM) of BSA as a model protein. The functionalized surface was image-characterized by Atomic Force Microscopy (AFM). The appropriate electronic instrumentation system for QCM characterization, with temperature control, was also developed. The obtained immunoreagents will be used as specific recognition bioactive molecules, in combination with functionalized quartz crystals, to build a piezoelectric immunosensor for the detection of Mycobacterium tuberculosis biomarkers, which can be related to the disease.

High frequency (100, 150 MHz) quartz crystal microbalance (QCM) piezoelectric genosensor for the determination of the Escherichia coli O157 rfbE geneEscherichia coli O157 (E. coli O157) is responsible for outbreaks of high morbidity in food-borne infections. The development of sensitive, reliable, and selective detection systems is of great importance in food safety. In this work, it was designed and validated two high fundamental frequency (HFF) piezoelectric genosensor (100 and 150 MHz) for the rfbE gene detection, which encodes Oantigen in E. coli O157. HFF resonators offer improved sensitivity, small sample volumes, and the possibility of integration into lab-on-a-chip devices, but their sensing capabilities have not yet been fully explored. This HFF-QCM genosensor uses the method of physisorption based on the union between the streptavidin protein and the biotin molecule to immobilize the genetic bioreceptor on the surface and detect its hybridization with the target sequence. Parameters such as molecular coating, specificity, and variability have been tested to enhance its performance. Although, the genosensors evaluated can determine the target, the 100 MHz device has a higher response to the analyte than the 150 MHz platform. This is the first step in the development of an HFF-QCM genosensor that could be used as a trial test of E. coli O157 in large batch samples.