Repetitive Immunoassay with a Surface Acoustic Wave Device and a Highly Stable Protein Monolayer for On-Site Monitoring of Airborne Dust Mite Allergens

Abstract

This work describes a sensor to be incorporated into the on-site monitoring system of airborne house dust mite (HDM) allergens. A surface acoustic wave (SAW) device was combined with self-assembled monolayers of a highly stable antibody capture protein on the SAW surface that have high resistance to pH change. A sandwich assay was used to measure a HDM allergen, Der f 1 derived from Dermatophagoides farinae. Capture antibodies were cross-linked to a protein G based capture layer (ORLA85) on the sensor surface, thereby only Der f 1 and detection antibodies were regenerated by changing pH, resulting in fast repetition of the measurement. The sensor was characterized through 10 repetitive measurements of Der f 1, which demonstrated high reproducibility of the sensor with the coefficient of variation of 5.6%. The limit of detection (LOD) of the sensor was 6.1 ng·mL(-1), encompassing the standard (20 ng·mL(-1)) set by the World Health Organization. Negligible sensor outputs were observed for five different major allergens including other HDM allergens which tend to have cross-reactivity to Der f 1 and their mixtures with Der f 1. Finally, the sensor lifetime was evaluated by conducting three measurements per day, and the sensor output did not substantially change for 4 days. These characteristics make the SAW immunosensor a promising candidate for incorporation into on-site allergen monitoring systems.

Semicontinuous Measurement of Mite Allergen (Der f 2) Using a Surface Acoustic Wave Immunosensor under Moderate pH for Long Sensor Lifetime

“…1(b)]. (18)(19)(20) The surface modification of the sensing area with the SAM was carried out as per the manufacturer's protocol: the surface was initially rendered hydrophilic in order to prevent nonspecific hydrophobic adsorption of ORLA85 by incubating the sensing area with 1% (v/v) BME in ultrapure water for 5 min. (21) Afterwards, in order to form the Au-S bond between ORLA85 and the gold on the SAW device, disulfide bonds of ORLA85 were reduced by mixing the protein solution with TCEP solution (TCEP 7.5 mg/mL in Tris-HCl) and letting stand for 30 min.…”

“…It suggested that parallel measurement of different HDM allergens, Der f 1 and Der f 2, would be possible by combining it with the previously developed Der f 1 SAW immunosensor, because the Der f 1 sensor also showed high selectivity to Der f 1. (18) …”

“…Recently, we introduced a surface-acoustic-wave (SAW)-based immunosensor for Der f 1, and it allowed rapid and repeated (semicontinuous) measurement with high sensitivity and selectivity. (18) Although ten repetitions of measurement were demonstrated with high reproducibility, the regeneration solution used was pH 1.0 HCl, and there was potential damage of the immobilized capture antibody (cAb) on the sensor surface. Considering that frequent exchange of a sensor chip in the airborne allergen monitoring system is laborious, the lifetime of the sensor must be prolonged.…”

Acoustic biosensors

“…Deoxyribonucleic acid (DNA) detection was demonstrated by Sakong et al [ 39 ] using complementary binding between a probe and a target on a gold-coated SH-SAW device fabricated on a LiTaO 3 substrate. More recently, SH-SAW devices have been used to monitor airborne allergens in a semi-continuous manner over a period of 4 days with a detection limit of 6.1 ng/ml established for a house dust mite allergen Der f 1 [ 40 ].…”

Heat Transfer Characteristics of a Focused Surface Acoustic Wave (F-SAW) Device for Interfacial Droplet Jetting

“…SAW devices are the major components of electronic devices used in various fields as filters, frequency duplexers, and radio frequency identification (RFID) tags [5][6][7][8][9]. In addition, SAW devices are widely used in biochemical detection, drug development, life sciences, and medical research.…”