SERS-based biosensor for detection of f-PSA%: Implications for the diagnosis of prostate cancer

In diagnosing prostate cancer and distinguishing it from other prostate diseases, the ratio of the concentration of free prostate-specific antigen (f-PSA) to total prostate-specific antigen (t-PSA), i.e., (f-PSA%) is more accurate than the concentration of t-PSA alone. Immunoassay based on surface-enhanced Raman scattering (SERS) frequency shift has been proven to be particularly suitable for detecting large biomolecules with high reproducibility. Along similar lines, the present study developed a SERS-based biosensor that simultaneously detects t-PSA and f-PSA. The 4-mercaptobenzoic acid (MBA) on the immunocapture substrate is coupled to the t-PSA antibody through the carboxyl group, and the combination of t-PSA induces the Raman frequency shifts of MBA. The immunocolloidal gold attached with f-PSA antibodies selectively capture the f-PSA that immobilized on the MBA-modified SERS substrates, allowing for f-PSA quantification according to the SERS intensities of the 5, 5'-Dithiobis (succinimidyl-2-nitrobenzoate) (DSNB) probe. The results show that f-PSA and t-PSA have good linear response in the concentration scale of 0.1-20 ng/mL, and 1-200 ng/mL, respectively. The biosensor combines Raman frequency shifts and intensities, which greatly simplifies traditional procedures for f-PSA% detection. All the results demonstrated the great potential of the proposed biosensor in highly reproducible and accurate diagnosis of prostate cancers.

在诊断前列腺癌并将其与其他前列腺疾病区分开时，游离前列腺特异性抗原（f-PSA）与总前列腺特异性抗原（t-PSA）的浓度之比，即（f-PSA％）比单独的t-PSA浓度更准确。基于表面增强拉曼散射 (SERS) 频移的免疫测定已被证明特别适合于高重现性检测大生物分子。沿着类似的思路，本研究开发了一种基于 SERS 的生物传感器，可以同时检测 t-PSA 和 f-PSA。免疫捕获基质上的4-巯基苯甲酸（MBA）通过羧基与t-PSA抗体偶联，t-PSA的结合引起MBA的拉曼频移。附着有 f-PSA 抗体的免疫胶体金选择性捕获固定在 MBA 修饰的 SERS 基底上的 f-PSA，从而根据 5, 5'-二硫双（琥珀酰亚胺基-2-硝基苯甲酸酯）(DSNB) 探针的 SERS 强度进行 f-PSA 定量。结果表明，f-PSA和t-PSA分别在0.1-20 ng/mL和1-200 ng/mL的浓度范围内具有良好的线性响应。该生物传感器结合了拉曼频移和强度，极大地简化了 f-PSA% 检测的传统程序。所有结果都证明了所提出的生物传感器在前列腺癌的高度可重复和准确的诊断方面的巨大潜力。