Interest in developing more accurate and stable sensing has grown in the last decade. Surface plasmon resonance (SPR), enzyme-linked immunoassay (ELISA), quartz crystal micro balance (QCM) are commonly used sensing techniques 1. Each method has distinct advantages. For instance ELISA is a highly sensitive method 2 however the use of labels can require complex sample preparation. SPR and QCM are label free techniques but in the case of SPR, a conducting surface is needed3. Microwave measures the response of a material in the GHz frequency range and has been previously used in biomedical applications such as the detection of glucose.4 The development of new, label free sensing tools is of significant interest. To this end we present the development of a microwave sensor for the detection of protein binding. Changes in the electromagnetic wave signal in the microwave frequency range were used to detect protein adsorption. Inderdigitated gold pattern printed on a woven glass and ceramic reinforced substrate acted as a microwave sensor. When tested, in the microwave frequency range the sensor response showed that the resonant frequency changed when the sensor was in contact with different materials. This method of detection was then used to detect the specific binding of streptavidin to biotinylated protein A. In control experiments minimal non-specific binding was observed. The response of the sensor was also examined on different substrate materials with different topography, with detection of protein binding observed obtained on both smooth (gold) and on rough (hydroxyapatite) surfaces. This label free microwave detection technique can be used to qualitatively detect specific and non-specific protein binding.

(1) Ray, S.; Mehta, G.; Srivastava, S. Proteomics 2010, 10, 731-748.

(2) Lequin, R. M. Clin. Chem. 2005, 51, 2415-2418.

(3) Roh, S.; Chung, T.; Lee, B. Sensors 2011, 11, 1565-1588.

(4) United States, Patent: US2012150000 (A1), WO2010131029 (A1), EP2429397 (A1), 2012.

Marcela Salazar-Alvarez

University of Limerick

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