Detection of Folate Binding Protein with Enhanced Sensitivity Using a Functionalized Quartz Crystal Microbalance Sensor

Abstract

In this report, we describe the development of a quartz crystal microbalance biosensor for detection of folate binding protein (FBP). Using a simple folate-BSA conjugate adsorbed onto a Au-coated quartz sensor, a detection limit of 30 nM was achieved. Binding of FBP to the sensor surface could be blocked at concentrations as high as 1 microM with a 100-fold excess of folic acid, indicating the specificity of the folate-FBP interaction and the absence of nonspecific binding to the functionalized surface. Moreover, capture could be achieved in the presence of blood serum, making the assay amenable to the analysis of bodily fluids. Further signal enhancement based on an anti-FBP antibody and protein-A-coated gold nanosphere sandwich assay extended the detection limit to 50 pM (approximately 3 orders-of-magnitude improvement). Given the overexpression of FBP in certain malignancies and inflammatory disorders, we expect the methodology described here to be useful to detect FBP as a possible biomarker for disease diagnosis.

Using nanoparticles to push the limits of detection

“…In an early report, Zhou and coworkers reported that nanoparticle amplification lowered the limit of detection for a target strand of DNA from 1.7 nM to 0.32 pM, a 100‐fold improvement 54. This approach has also been successful for the detection of proteins, such as the folate‐binding protein 55. Using the same type of sensor setup, Jiang and coworkers reported an even lower limit of detection for DNA of 10 fM 56.…”

Surface Plasmon Resonance and Quartz Crystal Microbalance Methods for Detection of Molecular Interactions

“…An interesting example of developing a protein surface to detect folate-binding protein (FBP) has been reported by Henne et al [43]. A gold surface was modified by immobilization of a folate-bovine serum albumin (BSA) conjugate which enabled the detection of FBP with a detection limit of 30 nM.…”

Development of Individual Plasmonic Nanosensors for Clinical Diagnosis

“…For more accurate and reliable diagnosis in disease state and widespread application, detection methodologies need to be accurate, sensitive, cheap, and easy to use, to facilitate rapid diagnosis, minimize sample decomposition, and decrease patient anxiety. To accomplish the task, many studies have been devoted to development of various signal transduction methods based on optics [1], radioactivity [2,3], fluorescence [4], electrochemistry [5], quartz crystal micro balance [6], piezoelectric cantilever [7], colorimetry [8,9], scanometry [10,11], surface plasmon resonance spectroscopy [12,13], etc. However, each of them still has its shortcomings such as necessitating time-consuming procedures, complicated manipulation and low sensitivity.…”