On-deck pH measurement with integrated feedback control on a micro-scale platform for monoclonal antibody low pH...

The increasing demand for efficient monoclonal antibody manufacturing has accelerated the adoption of high throughput process development (HTPD) platforms, which enable rapid, automated screening of downstream operations. However, the integration of non-chromatographic steps such as low pH viral inactivation (VI) within automated workflows remains limited, largely due to the absence of a micro-scale method for accurate, on-deck pH measurement and control. This study presents the development and implementation of an automated pH measurement and feedback control system using optical pH sensors immobilized within 96-well microplates. The approach enables non-invasive, real-time monitoring of pH across the acidic range required for VI and is fully compatible with standard liquid-handling platforms. Integration of a feedback control algorithm allowed autonomous acid and base addition to achieve precise target pH values during both acidification and neutralization phases. The method achieved strong agreement between measured and expected pH values following optimization of measurement conditions, including ionic strength adjustment. The system was further integrated with Sartobind® Q and cation exchange chromatography steps to demonstrate an end-to-end automated workflow. Systematic assessment of cation exchange chromatography performance under controlled loading conditions enabled direct visualization of separation behavior and early identification of sub-optimal operating regions, demonstrating the platform's capability to expand experimental space and accelerate mechanistic process understanding. This work establishes a micro-scale, fully automated downstream platform with pH control, bridging a critical technological gap and advancing the vision of an end-to-end HTPD system for biopharmaceutical purification.