# Development of Analytical Method for the Quantitation of Monoclonal Antibodies Solutions via Raman Spectroscopy: The Case of Bevacizumab

## TL;DR

This paper presents a new Raman spectroscopy method to accurately measure monoclonal antibody concentrations, specifically bevacizumab, in solutions.

## Contribution

A novel Raman spectroscopy-based analytical method for quantifying bevacizumab in solutions is developed and validated.

## Key findings

- The detection limit of bevacizumab using the developed Raman method was found to be 1.06 mg/mL.
- Bevacizumab concentration was found to be highest at the coffee ring formed during droplet drying.
- The lowest detection limit of 0.53 mg/mL was achieved at a specific location on the coffee ring.

## Abstract

Personalized dosages of monoclonal antibodies are being used more regularly to treat various diseases, rendering their quantitation more essential than ever for the right dose administration to the patients. A promising alternative, which overcomes the obstacles of the well-established chromatographic techniques regarding the quantification of biopharmaceuticals, is Raman spectroscopy. This study aimed to develop and validate a novel analytical method for the quantitation of bevacizumab in solutions via Raman spectroscopy. For this purpose, a droplet of the solution was left to dry on a highly reflective carrier and a home-made apparatus was employed for rotation of the sample. Hence, each recorded Raman spectrum was the average of the signal acquired simultaneously from multiple points on a circular circumference. The method was validated, and the detection limit of the antibody was found to be 1.06 mg/mL. Bevacizumab was found to be highly distributed at the formed coffee ring of the dried droplet, though this was a function of solution concentration. Finally, Raman spectra at different distances on the coffee ring were obtained from the four quarters. The lowest bevacizumab detection limit was found at a distance of 75 μm from the external side of the coffee ring and it was determined to be equal to 0.53 mg/mL.