Fabrication and Bioconjugation of Micro- and Nanoscale Structures Intended for Cancer-Specific Antigen Detection

Cleanroom processes can be used for fabricating microscale and nanoscale structures, and such structures, when bioconjugated, can be used for detecting low levels of cancer-specific circulating antigens. The concentration of such circulating antigens in human serum continues to increase with cancer progression, and therefore, detection of cancer at very early stages of the disease can be facilitated by monitoring small increases in circulating antigen concentration. Therefore, fabrication and bioconjugation are the first steps in the development of bio-assays for cancer detection. In this work, microscale and nanoscale Au/Cr thin film structures have been fabricated on Si substrate using dc sputtering and electron-beam (e-beam) evaporation in combination with photo and e-beam lithography. Using the fabricated device material stack (Au/Cr/Si), we have assessed the binding affinity of Au, Cr, and Si with Protein G, and antibodies for prostate specific antigen and cancer antigen 125, an ovarian cancer-associated antigen. Based on our experiments, we see that the thin gold layer of the Au/Cr/Si samples provides increased biomaterial binding affinity, and the chromium layer has a similar, if not less, binding affinity compared with the silicon chip alone. Thus, this work demonstrates that the fabricated material stack provides an appropriate platform for antigen detection.