Multi-antibody array chip for immunoassay of different-grade bladder cancer cell lysates based on DEP manipulations of nanoprobes

Abstract

This paper develops a multi-antibody array biochip for detection of different-grade bladder cancer cell lysates based on protein expression level. Two nanoprobes modified with antibodies, Galectin-1 (Gal-1) and Lactate Dehydrogenase B (LDH-B), were immobilized in an array manner by sequent DEP manipulation steps including focusing, guiding and trapping, therefore, two different protein levels can be achieved in single chip without complex microchannel design. The structure of DEP chip consists of three electrode layers, top electrode made of Indium Tin Oxide (ITO), middle Au electrode on SU-8 surface for focusing and guiding of nanoprobes, and bottom ITO dot electrodes under SU-8 cavity for trapping of nanoprobes. In our experiments, two different grade bladder cancer cell lysates (grade I:RT4 and grade III:T24) were introduced into immunosensor, the expression levels of Gal-1 and LDH-B displayed different fluorescent responses for RT4 and T24 cell lysates. Accordingly, the fluorescence intensity of Gal-1 is higher than the value of LDH-B for T24 cell lysate; however, the response for RT4 is opposite, i.e. LDH-B > Gal-1. Consequently, determining of different-grade bladder cancer cell can be achieved by using present multi-antibody immunosensor. In addition, the DEP manipulations of nanoprobes also demonstrate the feasibility for multi-biomarker array in single chip for point-of-care diagnostics.