Continuous background correction of refractive index signal to improve monoclonal antibody concentration monitoring during UF/DF and SPTFF operations.

Inline refractive index (RI) has the potential for monitoring protein concentration during final bulk concentration. While useful for monitoring and controlling product concentration, RI is sensitive to the respective background buffer being used for processing. This raises concerns around variations in buffer preparations, and during diafiltration where the buffer background is a mixture of different buffers during exchange. This study evaluated whether the use of a RI probe in the permeate line could facilitate continuous background subtraction (dual RI) and improve concentration monitoring during ultrafiltration/diafiltration and single pass TFF concentration for IgG1 and IgG4 antibodies. The proposed dual RI strategy yielded reductions in % error compared to the use of a single refractive index estimate from the retentate line (6.18% vs 8.63% for IgG4 and 2.65% vs 8.85% for IgG1) during traditional ultrafiltration/diafiltration. The improvement in IgG estimates were best during diafiltration where the continuous background subtraction of the permeate RI-enabled continuous monitoring of antibody material without knowledge of what the background buffer was compared to the use of a single RI estimate (6.47% vs 10.79% for IgG4 and 3.29% vs 19.59% for IgG1). In contrast minimal improvement to accuracy was obtained when using SPTFF as a concentration step. The ability to monitor product concentration changes via the proposed dual RI approach removes the need for complex calibrations, minimal worry about changing buffer backgrounds during diafiltration, and could enable better process control during product concentration in the cGMP manufacture of biologics.

Association of Cognitive Function with Amyloid-ß and Tau Proteins in the Vitreous Humor.

BACKGROUND: The eye may serve as source for diagnostic testing for early detection of Alzheimer's disease (AD). Examination of amyloid-ß (Aß) and tau protein content in human vitreous and its correlation to neuro-cognition may improve ocular-based AD detection methods. OBJECTIVE: To evaluate levels of Aß and tau protein in human vitreous humor and investigate the clinical predictive role of these proteins as early diagnostic markers of AD. METHODS: A prospective, single-center, multi-surgeon cohort study. Vitreous humor samples from 80 eyes were measured quantitatively for Aß40-42, pTau, and tTau. Linear regression was used to test associations between AD biomarker levels, Mini-Mental State Exam (MMSE), and serum apolipoprotein E (APOE) allele status, with adjustment for age, sex, and education level of patients. RESULTS: Lower MMSE scores were significantly associated with lower levels of vitreous Aß40 (p = 0.015), Aß42 (p = 0.0066), and tTau (p = 0.0085), and these biomarkers were not associated with any pre-existing eye conditions. Presence of the ɛ4 allele and the ɛ2 allele approached significance with reduced Aß40 level (p = 0.053) and increased p-Tau level (p = 0.056), respectively. CONCLUSION: Patients with poor cognitive function have significantly lower vitreous humor levels of AD-related biomarkers Aß40, Aß42, and tTau. These biomarkers do not correlate with underlying eye conditions, suggesting their specificity in association with cognitive change. This is the first study to our knowledge to correlate cognition with AD-related proteins in the vitreous humor. Results suggest ocular proteins may have a role for early dementia detection in individuals at risk for AD.