Monitoring of Zika-VLP production by 2D fluorescence spectroscopy and multi-way partial least squares

This work aimed to develop chemometrics models based on multi-way partial least squares (MPLS) in combination with 2D fluorescence spectral data to monitor biochemically the Zika-virus-like particles upstream stage using baculovirus/insect cell expression platform. Four bioreactor experiments using different operation conditions were performed, and 96 samples were collected to obtain spectral and biochemical data. The biochemical parameters under study were glutamate (Glu), lactate (Lac), glutamine (Gln), ammonium (NH₄⁺), and total protein (Tp) concentrations, as well as viable cell density (Xv), cell viability (Cv), and virus titer. Absolute and relative prediction errors were calculated together with their standard deviations. Besides, VLP formation was confirmed by transmission electron microscopy with immunostaining. The relative errors of 3.7 %, 1.5 %, 0.1 %, 2.4 %, 0.007 %, 1.4 %, and 3.2 % were confirmed for Glu, Lac, Gln, Xv, Cv, NH₄⁺, log₁₀ (Vt), and Tp, respectively. These relative errors were lower than those obtained for the same expression system using other spectroscopical techniques like Raman, Near infrared, and Mid-infrared. These results underscore the effectiveness of 2D-fluorescence spectroscopy as a valuable technique for monitoring and optimizing VLP production processes.