Production of biosensors with exchangeable enzyme-containing threads.

We introduce a simple method for the construction of biosensors, based on coiling an enzyme-containing, thread-shaped material around a cylindrical signal transducer in the form of winding stairs with a variable length of step and so forming a variable biocatalytic membrane on the sensor surface, which can be easily modified for particular purposes. In the model system, we immobilized glucose oxidase (GO) on a nylon thread, formatted from a sheaf of numerous minor filaments and used as a biorecognition element integrated with a Clark-type oxygen sensor. The immobilized enzyme was evenly distributed throughout the thread, and the activity of the enzyme could be measured in units of length. Appropriate pieces of the enzyme-containing thread with a certain amount of GO could be cut for a definite biosensor or bioreactor. The enzyme amount and substrate diffusion parameters, which together control the sensor's working range and sensitivity, could be changed simultaneously with the change of the length of the thread. Besides glucose oxidase, experiments with other enzymes have confirmed the applicability of the proposed technological solution. Thus, the thread-type matrixes enable one to construct sensors with a required range of work, sensitivity, and selectivity, which can be easily customized within seconds.