Materials Science and Engineering, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Bayview Ave, Clayton 3168, Australia.
Anal Chim Acta. 2010 Feb 5;659(1-2):109-14. doi: 10.1016/j.aca.2009.11.025. Epub 2009 Nov 26.
Small electroactive chemicals (e.g. ferrocene and metals) have been used as labels in electrochemical biosensors, including immunosensors. However, the fact that each of these molecules generates only one electron during oxidation suggests they may not be the most sensitive electroactive labels. An electroactive polymer, which can generate a large number of electrons during electrochemical oxidation, could serve to amplify the electrochemical signal and therefore enhance the detection sensitivity. In this study, polytyrosine was chosen to test this hypothesis. We first characterized the oxidation of polytyrosine by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) on bare and multiwalled carbon nanotubes (MWCNTs)-modified glassy carbon electrodes at different pH and varying amount of MWCNTs. The use of MWCNTs on the electrodes enhanced the electrochemical signal by 84 times both in CV and DPV when compared with bare electrodes. This enabled the detection of as low as 10 ng (or 0.4 pmol) of polytyrosine. Polytyrosine was then conjugated to a prostate-specific antigen (PSA) peptide and used as an electroactive label in competitive electrochemical immunoassays in which a PSA antibody was immobilized on MWCNTs. Addition of the free peptide to the assays decreased the current in a concentration dependent manner. The sensitivity of the detection was calculated to be 12.8% inhibition/nM peptide and the limit of detection was approx. 1 nM. These results therefore demonstrated that polytyrosine could potentially serve as a label for signal amplification in electrochemical biosensors.
小分子电活性化学物质（例如二茂铁和金属）已被用作电化学生物传感器（包括免疫传感器）中的标记物。然而，这些分子在氧化过程中每个分子仅产生一个电子的事实表明，它们可能不是最敏感的电活性标记物。电活性聚合物在电化学氧化过程中可以产生大量电子，这可以放大电化学信号，从而提高检测灵敏度。在本研究中，选择聚酪氨酸来验证这一假设。我们首先通过循环伏安法（CV）和差分脉冲伏安法（DPV）在不同 pH 值和不同量的多壁碳纳米管（MWCNT）修饰的玻碳电极上对聚酪氨酸的氧化进行了表征。与裸电极相比，MWCNT 在电极上的使用使 CV 和 DPV 的电化学信号增强了 84 倍。这使得能够检测低至 10ng（或 0.4pmol）的聚酪氨酸。然后，将聚酪氨酸与前列腺特异性抗原（PSA）肽缀合，并用作竞争性电化学免疫测定中的电活性标记物，其中 PSA 抗体固定在 MWCNT 上。将游离肽添加到测定中会使电流呈浓度依赖性降低。检测的灵敏度计算为 12.8％抑制/nM 肽，检测限约为 1nM。因此，这些结果表明聚酪氨酸有可能作为电化学生物传感器中信号放大的标记物。
