Measuring bacterial growth by refractive index tapered fiber optic biosensor

A single-mode tapered fiber optic biosensor was utilized for real-time monitoring of the Escherichia colt (E coli K-12) growth in an aqueous medium The applied fiber tapers were fabricated using heat-pulling method with waist diameter and length of 6-7 mu m and 3 mm respectively The bacteria were immobilized on the tapered surface using Poly-c-Lysine By providing the proper condition bacterial population growth on the tapered surface increases the average surface density of the cells and consequently the refractive index (RI) of the tapered region would increase The adsorption of the cells on the tapered fiber leads to changes in the optical characteristics of the taper This affects the evanescent field leading to changes in optical throughput The bacterial growth rate was monitored at room temperature by transmission of a 1558 17 nm distributed feedback (DFB) laser through the tapered fiber At the same condition after determining the growth rate of E coli by means of colony counting method we compared the results with that obtained from the fiber sensor measurements This novel sensing method promises new application such as rapid analysis of the presence of bacteria (C) 2010 Elsevier B V All rights reserved