In-situ Quantitative Analysis of Tumor Suppressor Protein (hDMP1) Using a Nanomechanical Cantilever Beam

摘要

This study is focused on testing "immuno-sensors" of micro-cantilever beams for the purpose of future design of high-throughout bioassays. We currently study the aberrant expression, deletion and mutation of hDMP1 (Human DMP1) in human lung cancer. Lung cancer is the leading cause of cancer deaths among men and women in North America. There are four major histological subtypes of human lung cancer: small-cell carcinoma (SCC), adenocarcinoma (AC), squamous cell carcinoma (SCC), and large-cell carcinoma (LCC). The hDMP1 locus is localized on chromosome 7q21, a region frequently deleted as part of the 7q-minus and monosomy 7 abnormalities of acute myeloid leukemia and myelodysplastic syndrome. Recent data demonstrate the critical role of Dmp1 in Ras-Raf-Arf signaling and cellular senescence. In order to study the interactions of hDMP1 gene product and selected tumor markers with BioMEMS devices, protein coating (Antibody) conduct on cantilevers with silicon nitride (SiNx) surfaces. Silicon nitride surface has the potential to provide a good interface for BioMEMS devices, due to enhanced adherence of substances on this surface. The cantilever biosensors coated with hDMP1 antibody were used for the detection of hDMP1 antigen, which is known to be a tumor suppressor protein. Results revealed that the changes in nano-mechanical forces provided sufficient differential torque to bend the cantilever beam upon injection of the antigen. Theoretical models have been developed for the prediction of the vibrational responses of atomic force microscope (AFM) cantilevers before and after antigen/antibody interaction. Exposure of the proteins to micro-cantilever (MC) resulted in un-reversible large stress. Static deflection of micro-cantilever appeared as a result of the surface stresses that are induced by changes upon antibody-antigen interaction. This indicated that the micro-cantilever approach is useful for detecting proteins and tumor markers, and this system is applicable as a model to design miniaturized biosensor systems. We also applied gene micro-array to identify unknown targets for hDMP1 and extend our observation of the complicated process of carcinogenesis.