Sensitive Detection of Goat αs1-Casein Using Tapered Optical Fiber Sensor

We present a new approach for the detection of α
_s1
-casein, a milk allergen, using tapered optical fiber sensor. The single-mode optical fiber of 125 μm diameter was tapered to produce waist diameter and length of 12 μm and 15 mm, respectively. The fiber sensor was functionalized using sodium hydroxide, (3-aminopropyl) triethoxysilane, and glutaraldehyde to the tapered region. Anti-peptide polyclonal antibody from N-terminal sequence of α
_s1
-casein was immobilized onto the tapered region, which subsequently bound to the introduced targeted α
_s1
-casein. Measurement of transmission spectrum was performed within the wavelength range of 1500-1600 nm. Results showed that the shift of the wavelength in the fabricated sensor was linearly proportional to the increment of α
_s1
-casein from 0.1 to 1.0 nM. The sensitivity of the sensor towards α
_s1
-casein was measured at 1.139 nm/nM. Specificity was validated using bovine α-casein as a negative control with no significant wavelength shift. The sensor was tested using goat milk sample in three different dilutions to illustrate the applicability of the sensor in food matrices.