A Multiplexed diagnostic approach for cardiovascular disease biomarkers

[eng] In the course of this thesis, the optimal epitopes for the subsequent polyclonal rabbit antibody production for cTnI and NT-proBNP have been studied and chosen. cTnI and NT-proBNP are the most relevant cardio-specific biomarkers for the diagnosis of cardiovascular diseases. With these antibodies, a sandwich ELISA for the detection of cTnI has been developed together with a competitive ELISA for the detection of NT-proBNP, both in a microplate format. It has been observed that cTnI has an extraordinary tendency to non-specifically adsorb itself onto surfaces and other biomolecules. This, with the inability to achieve the required detectability for this biomarker, have been the main problems to face with. Regarding the non-specific adsorption, different additives in the analyte or sample buffer have been evaluated. Thus, 0.15% casein in PBST combined with the use of low adsorption microplates (ImmulonTM 2HB) helps considerably to solve this problem. However, the sensitivity obtained for this assay in aqueous buffer is much lower than that required corresponding to the basal levels of cTnI in the blood. For the NT-proBNP ELISA development, the required limit of detection was achieved after studying various parameters related to heterology and other physicochemical parameters. Moreover, a good accuracy with NT-proBNP fortified plasma samples was obtained. It has been possible to develop a multiplexed microarray for the simultaneous detection of 5 biomarkers (cTnI, NT-proBNP, very important in the process of developing cardiovascular diseases, CRP, Cys C and H-FABP). Once the microarray is biofunctionalized using a spatial encoding with the corresponding bioconjugates or capture antibodies, immunoreagents and other biomarkers can be used in a cocktail. Neither cooperativity phenomena (union of immunoreagents that are in solution in sites where there are other biomarkers immobilized) nor cross-reactivity (recognition of different biomarkers from those for which immunoreagents have been developed) have been observed in any case. Only Lp(a) immunoreagents produced such interferences and therefore they were discarded. It has been highlighted the fact that the biomarkers present in different concentration ranges remains one of the main challenges for the multiplexed diagnosis when simultaneous measurements are desired. In this research, it was impossible to quantify the CRP and Cys C in the same microarray than H-FABP, cTnI and NT-proBNP employing direct sampl