Label free apta-sensing with fiber optic SPR

The widespread incidence of food allergies presents an important challenge for the food industry. Accurate and reliable product information is essential to inform a rising number of food allergic patients. Tracing allergens, however, is not obvious, since they generally occur in very low quantities, hidden in a food matrix. In this research we present the development of a cost-effective surface plasmon resonance (SPR) probe for label free peanut allergen detection. The home made sensor has a 1-1.5 cm gold sputtered sensor zone and a mirror layer at the end tip. The gold layer is functionalized with an aptamer designed to bind with peanut allergen Ara h2. The interaction of the specific proteins with the DNA aptamers is indirectly monitored by the proportional change of refractive index at the sensor surface which modulates the wavelength of the SPR intensity dip. The aptamers were selected from a fluorescent labeled ssDNA library by the SELEX protocol. The ssDNA-library was mixed with the Ara h2 target molecule and the bound aptamers were isolated using capillary electrophoresis (CE). The selected aptamers were amplified by PCR and purified to obtain an enriched ssDNA pool for further selection rounds. High affinity allergenic binders were found after only 5-7 rounds. The affinity and the specificity of the aptamers were confirmed using fluorescence anisotropy and capillary electrophoresis with laser induced fluorescence. This paper illustrates that the combination of versatile aptamer-technology and sensitive and low cost fiber optic technology is very promising for many biosensor applications.status: publishe