title: Surface modification on acoustic wave biosensors for enhanced specificity.
abstract: Changes in mass loading on the surface of acoustic biosensors result in output frequency shifts which provide precise measurements of analytes. Therefore, to detect a particular biomarker, the sensor delay path must be judiciously designed to maximize sensitivity and specificity. B-cell lymphoma 2 protein (Bcl-2) found in urine is under investigation as a biomarker for non-invasive early detection of ovarian cancer. In this study, surface chemistry and biofunctionalization approaches were evaluated for their effectiveness in presenting antibodies for Bcl-2 capture while minimizing non-specific protein adsorption. The optimal combination of sequentially adsorbing protein A/G, anti-Bcl-2 IgG and Pluronic F127 onto a hydrophobic surface provided the greatest signal-to-noise ratio and enabled the reliable detection of Bcl-2 concentrations below that previously identified for early stage ovarian cancer as characterized by a modified ELISA method. Finally, the optimal surface modification was applied to a prototype acoustic device and the frequency shift for a range of Bcl-2 concentration was quantified to demonstrate the effectiveness in surface acoustic wave (SAW)-based detection applications. The surface functionalization approaches demonstrated here to specifically and sensitively detect Bcl-2 in a working ultrasonic MEMS biosensor prototype can easily be modified to detect additional biomarkers and enhance other acoustic biosensors.
authors.affiliation: Department of Mechanical Engineering, University of South Florida, 4202 E Fowler Ave, ENB 118, Tampa, FL 33620, USA. onursalonen@mail.usf.edu
authors.forename: Onursal
authors.initials: O
authors.lastname: Onen
authors.forename: Asad A
authors.initials: AA
authors.lastname: Ahmad
authors.forename: Rasim
authors.initials: R
authors.lastname: Guldiken
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Gallant
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000906:Antibodies / Q000737:chemistry; D014408:Biomarkers, Tumor / Q000737:chemistry / Q000652:urine; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D055088:Early Detection of Cancer / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D010051:Ovarian Neoplasms / Q000175:diagnosis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000652:urine; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D013016:Sound; D013499:Surface Properties
chemical_list: D000906:Antibodies; D014408:Biomarkers, Tumor; D019253:Proto-Oncogene Proteins c-bcl-2
keywords: Bcl-2; bioconjugation; early detection; microelectromechanical systems (MEMS); ovarian cancer; point-of-care; polyethylene glycol (PEG); self-assembled monolayer (SAM); sensor; surface acoustic wave (SAW)