Silicon-Based Technology for Ligand-Receptor Molecular Identification

One of the most important goals in the fields of biology and medicine is the possibility to dispose of efficient tools for the characterization of the extraordinary complexity of ligand-receptor interactions. To approach this theme, we explored the use of crystalline silicon (cSi) technology for the realization of a biotechnological device in which the ligand-receptor interactions are revealed by means of optical measurements. Here, we describe a chemical procedure for the functionalization of microwell etched on silicon wafers, and the subsequent anchoring of biological molecules like an antibody anti-A20 murine lymphoma cell line. The optical analysis of the interaction on the biochips between the bound biomolecule and their corresponding ligand indicated that the functionalized cSi is suitable for this application. 1. Introduction Circulating tumor cells (CTCs) are emerging as a powerful prognostic and predictive biomarker in several types of cancer, including breast, colon, and prostate. However, studies of CTCs in metastasis and further development of CTCs as a biomarker in cancer have been hampered by the low concentration of CTCs in peripheral blood and by the inherent difficulties to recover CTCs from blood of patients. For this reason, it is compelling to implement novel devices and procedures to improve isolation rate and in vitro expansion of CTCs. Moreover, the extraordinary complexity of ligand-receptor interaction limits our knowledge of the molecular mechanisms of tumorigenesis and is a major obstacle in developing cancer-specific therapeutic agents. Pioneer studies of protein complexes have revealed that a given protein can physically associate to tens (>200) of different proteins [1]. In the case of eukaryotic cells, 20,000 proteins or more may establish an extraordinary large number of functional interactions with cell receptors, making unrealistic a systematic approach where each ligand-receptor interaction is studied as a single network. To overcome these hurdles, we recently dedicated to a comprehensive analysis of ligand-receptor interactions in mammalian cells [2, 3] developing a novel biochip based on the chemical and optical properties of porous silicon [4] where the ligand-receptor interaction is transduced, at high levels of specificity and sensitivity, in an optical signal generated by change of pSI refractive index [5–7]. Here, we propose to develop a device based on crystalline silicon that combines analytic and preparative properties to improve speed and efficiency of isolation of CTCs from blood of patients affected by