Determination of protein concentration in downstream biomanufacturing processes by in-line index of refraction.

Protein concentration determination is a necessary in-process control for the downstream operations within biomanufacturing. As production transitions from batch mode to an integrated continuous bioprocess paradigm, there is a growing need to move protein concentration quantitation from off-line to in-line analysis. One solution to fulfill this process analytical technology need is an in-line index of refraction (IoR) sensor to measure protein concentration in real time. Here the performance of an IoR sensor is evaluated through a series of experiments to assess linear response, buffer matrix effects, dynamic range, sensor-to-sensor variability, and the limits of detection and quantitation. The performance of the sensor was also tested in two bioprocessing scenarios, ultrafiltration and capture chromatography. The implementation of this in-line IoR sensor for real-time protein concentration analysis and monitoring has the potential to improve continuous bioprocess manufacturing.

Estimating probabilistic confidence for mixture components identified using a spectral search algorithm.

Providing a confidence measure associated with the substance(s) identified in an unknown mixture by a spectral search technique is critical for non-expert users of devices and techniques based on spectroscopy. In this work, a technique for estimating probabilities associated with substances identified by spectral searching is described. In the proposed approach, a mixture analysis algorithm processes the spectrum of an unknown sample using a spectral library to generate a list of substances that may be present in the sample. The partial correlation of each of the substances in the list is then computed. The estimation of the probability is accomplished through a generalized linear model that converts the partial correlation values to a probability measure for each of the mixture components. The statistical properties of partial correlation allow probability estimation irrespective of whether a substance is present in a pure form or within a mixture. The technique was evaluated using both simulated and real Raman spectra of multi-component mixtures, and adequate performance was demonstrated.