title: A micro-cantilever sensor chip based on contact angle analysis for a label-free troponin I immunoassay.
abstract: Cantilever sensors have been extensively explored as a promising technique for real-time and label-free analyses in biological systems. A major sensing principle utilized by state-of-the-art cantilever sensors is based on analyte-induced surface stress changes, which result in static bending of a cantilever. The sensor performance, however, suffers from the intrinsically small change in surface stress induced by analytes, especially for molecular recognition such as antigen-antibody binding. Through the contact angle change on a tailored solid surface, it is possible to convert a tiny surface stress into a capillary force-a much larger physical quantity needed for a practical sensor application. In this work, a micro-cantilever sensor based on contact angle analysis (CAMCS) was proposed to effectively enhance the sensitivity of a sensor in proportion to the square of the length to thickness ratio of the cantilever structure. CAMCS chips were fabricated using a standard complementary-metal-oxide-semiconductor (CMOS) process to demonstrate a 1250-fold enhancement in the sensitivity of surface stress to bioanalyte adsorption using a piezoresistive sensing method. A real-time and label-free troponin I (cTnI) immunoassay, which is now widely used in clinics and considered a gold standard for the early diagnosis and prognosis of cardiovascular disease, was performed to demonstrate cTnI detection levels as low as 1 pg mL(-1). The short detection time of this assay was within several minutes, which matches the detection time of commercially available instruments that are based on fluorescence-labeling techniques.
authors.affiliation: Department for Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany. tsung-i.yin@imtek.uni-freiburg.de
authors.forename: Tsung-I
authors.initials: TI
authors.lastname: Yin
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Zhao
authors.forename: Josef
authors.initials: J
authors.lastname: Horak
authors.forename: Huseyin
authors.initials: H
authors.lastname: Bakirci
authors.forename: Hsin-Hao
authors.initials: HH
authors.lastname: Liao
authors.forename: Hann-Huei
authors.initials: HH
authors.lastname: Tsai
authors.forename: Ying-Zong
authors.initials: YZ
authors.lastname: Juang
authors.forename: Gerald
authors.initials: G
authors.lastname: Urban
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000936:Antigen-Antibody Complex; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002318:Cardiovascular Diseases / Q000175:diagnosis; D002417:Cattle; D006046:Gold / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D008670:Metals / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D012666:Semiconductors; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism; D019210:Troponin I / Q000032:analysis*
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D008670:Metals; D010087:Oxides; D019210:Troponin I; D012710:Serum Albumin, Bovine; D006046:Gold