Microcantilever biosensors have been proposed in the last years as very sensitive mass detectors, but few works focused on the precision and specificity of such tools. We measured the repeatability and reproducibility of our cantilever-based system, proponing the combination of results coming from both the first and second mode of vibration. Then, we optimized two biodesigns (a receptor-based and an antibody-based) to the detection of Angiopoietin-1, a possible marker in tumor progression. The reported results show that our microcantilever-based system can detect Angiopoietin-1 masses of the order of few hundreds of picograms with less than 0.5% of relative uncertainty. We showed that the evaluation of the protein surface density (number of molecules per cm(2)) could reveal interesting features concerning the multimerization state of the targeted protein. We also performed negative controls (dipping the sample in PBS without proteins) and specificity tests (dipping the sample in PBS with a "false" antigen). The related frequency shifts coming from non-specific interactions were found to be at least one order of magnitude lower than typical variations due to specific protein binding. Thanks to its fine precision and optimal specificity, our microcantilever-based system can be successfully applied as a quantitative tool for systems biology studies such as the comprehension of angiogenic machinery and cancer progression.
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