
<ArticleTitle>Bioassay of <prot>prostate-specific antigen</prot> (<prot>PSA</prot>) using microcantilevers.</ArticleTitle>
<AbstractText>Diagnosis and monitoring of complex diseases such as cancer require quantitative detection of multiple proteins. Recent work has shown that when specific biomolecular binding occurs on one surface of a microcantilever beam, intermolecular nanomechanics bend the cantilever, which can be optically detected. Although this label-free technique readily lends itself to formation of microcantilever arrays, what has remained unclear is the technologically critical issue of whether it is sufficiently specific and sensitive to detect disease-related proteins at clinically relevant conditions and concentrations. As an example, we report here that microcantilevers of different geometries have been used to detect two forms of <prot>prostate-specific antigen</prot> (<prot>PSA</prot>) over a wide range of concentrations from 0.2 ng/ml to 60 microg/ml in a background of <prot>human serum albumin</prot> (<prot>HSA</prot>) and <prot>human plasminogen</prot> (<prot>HP</prot>) at 1 mg/ml, making this a clinically relevant diagnostic technique for prostate cancer. Because cantilever motion originates from the free-energy change induced by specific biomolecular binding, this technique may offer a common platform for high-throughput label-free analysis of protein-protein binding, DNA hybridization, and DNA-protein interactions, as well as drug discovery.</AbstractText>
