Quartz-crystal microbalance immunosensor for Schistsoma-japonicum-infected rabbit serum

Lateral field excitation (LFE) of thickness shear mode (TSM) acoustic waves in thin film bulk acoustic resonators (FBAR) as a potential biosensor

Lateral field excitation (LFE) of a thin film bulk acoustic resonator (FBAR) is an ideal platform for biomedical sensors. A thickness shear mode (TSM) acoustic wave in a piezoelectric thin film is desirable for probing liquid samples because of the poor coupling of shear waves into the liquid. The resonator becomes an effective sensor by coating the surface with a bio- or chemi-specific layer. Perturbations of the surface can be detected by monitoring the resonance condition. Furthermore, FBARs can be easily fabricated to operate at higher frequencies, yielding greater sensitivity. An array of sensors offers the possibility of redundancy, allowing for statistical decision making as well as immediate corroboration of results. Array structures also offer the possibility of signature detection, by monitoring multiple targets in a sample simultaneously. This technology has immediate application to cancer and infectious disease diagnostics and also could serve as a tool for general proteomic research.

Aspects of recent development of immunosensors

This chapter focuses on the recent developments in the field of immunosensors. Immunosensors incorporate the specific immunochemical reaction with the modern transducers including electrochemical (potentiometric, conductometric, capacitative, impedance, amperometric), optical (fluorescence, luminescence, refractive index), and microgravimetric transducers. These immunosensor devices with dramatic improvements in the sensitivity and selectivity possess the abilities to investigate the reaction dynamics of antibody–antigen binding and the potential to revolutionize conventional immunoassay techniques. With the rapid development of immunological reagents and detection equipments, immunosensors have allowed an increasing range of analytes to be identified and quantified and in particular, simple-to-use, inexpensive, and reliable immunosensing systems have been developed for areas such as outpatient monitoring, large screening programs, and remote environmental surveillance. Immunosensors with lowered detection limits and increased sensitivities have been developed in various fields, particularly in clinical analysis. A noticeable development trend is also observed in the development of immunosensors combining with other techniques such as flow injection analysis (FIA) or capillary electrophoretic (CE) analysis, which complement and improve the present immunoassay methods. Belov et al. have proposed a novel immunophenotyping method for leukemias which uses a cluster of differentiation antibody microarray, and a microarray of enzyme-linked immunosorbent assay has been developed for autoimmune diagnosis of systematic rheumatic disease. Development of microfluidic immunosensor systems for proteomics and drug discovery have also been reported in recent years where the microfluidic system integrates multiple processes in a single device to improve analytical performance by reducing the reagent consumption and the analysis time, and increasing reliability and sensitivity through automation.

A survey of the 2001 to 2005 quartz crystal microbalance biosensor literature: applications of acoustic physics to the analysis of biomolecular interactions

The widespread exploitation of biosensors in the analysis of molecular recognition has its origins in the mid-1990s following the release of commercial systems based on surface plasmon resonance (SPR). More recently, platforms based on piezoelectric acoustic sensors (principally 'bulk acoustic wave' (BAW), 'thickness shear mode' (TSM) sensors or 'quartz crystal microbalances' (QCM)), have been released that are driving the publication of a large number of papers analysing binding specificities, affinities, kinetics and conformational changes associated with a molecular recognition event. This article highlights salient theoretical and practical aspects of the technologies that underpin acoustic analysis, then reviews exemplary papers in key application areas involving small molecular weight ligands, carbohydrates, proteins, nucleic acids, viruses, bacteria, cells and lipidic and polymeric interfaces. Key differentiators between optical and acoustic sensing modalities are also reviewed.

Real-time detection of mesothelin in pancreatic cancer cell line supernatant using an acoustic wave immunosensor

BACKGROUND

An acoustic wave immunosensor was developed to illustrate the viability of such devices in early detection of molecular cancer biomarkers. The methods described here involve a real-time, less invasive technique for detecting mesothelin, a protein that has been linked to pancreatic and ovarian cancer.

METHODS

Antibodies were immobilized on the gold surface of the device via a self-assembled alkanethiol monolayer. Supernatant from two different pancreatic cancer cell-lines (PL1 and CAPAN2) containing an unknown concentration of mesothelin was tested for the protein by a flow-through analytical technique in three types of experiments. Binding of the mesothelin to the immobilized antibody layer caused a shift in the device's resonant frequency, which was correlated to the concentration of supernatant. A reference sensor was used to correct for frequency shifts caused by pressure or viscosity effects from the injection of the supernatant solution.

RESULTS

Repeated experiments indicate that the sensors are capable of nanogram detection thresholds of mesothelin proteins at room temperature and in complex mixture.

CONCLUSIONS

Acoustic wave device biosensors have the potential to become a valuable tool in screening for pancreatic as well as other types of cancers. The main features include real-time detection, high sensitivity, and ease of use.

Immunosensor for the diagnosis of Chagas’ disease

Trypanosoma cruzi proteins from epimastigote membranes, herein referred as antigens, have been used for the construction of an amperometric immunosensor for serological diagnosis of Chagas' disease. The proteins used had a molecular mass ranging from 30 to 100 kDa. The gold electrode was treated with cysteamine and glutaraldehyde prior to antigen immobilization. Antibodies present in the serum of patients with Chagas' disease were captured by the immobilized antigens and the affinity interaction was monitored by chronoamperometry at a potential of -400 mV (versus Ag pseudo-reference electrode) using peroxidase-labeled IgG conjugate and hydrogen peroxide, iodide substrate. The incubation time to allow maximum antigen-antibody and antibody-peroxidase-labeled IgG interactions was 20 min with a reactivity threshold at -0.104 microA.