RAPID ANALYSIS OF BIOSENSOR DATA USING INITIAL RATE DETERMINATION ANDITS APPLICATION TO BIOPROCESS MONITORING

The use is assessed of an optical biosensor to monitor the concentrati on of a protein product in complex environments such as fermentation b roths or cell homogenates. The sensor works on the principle of optica l waveguiding within a Resonant Mirror to follow analyte ligand intera ction. This paper is concerned with ways in which the characterisation can be carried out rapidly utilising the early part of the binding re sponse curve and how similarly rapid correction may be made for non-sp ecific binding, The system chosen for study is the production of antib ody fragments to hen egg lysozyme (HEL) in Escherichia coli. HEL is us ed as the specific ligand on the sensor surface, and in this case turk ey egg lysozyme (TEL) provides a convenient ligand to allow measuremen t of non-specific interactions. The use of a linear regression routine is demonstrated to monitor the initial rate of binding with ancillary routines to allow for changes in the sensor response due to sample co mposition and for the onset of a non-linear response within a short pe riod of the interaction profile. Sensor response is demonstrated over the range 0.2 to 150 mu g ml(-1) of purified antibody fragments using typically just the first 5 s of binding curve. Performance data are gi ven for the monitoring of antibody fragments in fermenter broths. The potential of the sensor is demonstrated to provide a rapid (< 2 min) a ssay of antibody fragments in the production process, compared with EL ISA taking up to 5 h. The lower sensitivity of the sensor compared wit h ELISA is shown not to be of concern for process monitoring purposes.