A High Throughput Protein Formulation Platform: Case Study of Salmon Calcitonin

The feasibility of using high throughput spectroscopy for characterization and selection of physically stable protein formulations was studied. A hundred aqueous formulations of salmon calcitonin (sCT) were prepared using 20 buffer compositions. The solutions had pH values between 2.5 and 10.5. The stability of the sCT formulations was analyzed over 1 week by the following assays: (1) protein concentration, (2) volume control by measuring pathlength, (3) turbidity (absorbance at 350 nm), (4) intrinsic tyrosine fluorescence, (5) 1-anilino-naphthalene-8-sulfonate (ANS) fluorescence, (6) Nile Red fluorescence. Addition of the dyes (Nile Red and ANS) was used to study protein conformational changes. After 1 day, 27 out of the 100 formulations of salmon calcitonin were stable. After 7 days, 12 stable sCT formulations remained. The best salmon calcitonin formulation was in 10 mM sodium acetate buffer with pH values between 3.5 and 5.5. The findings are in accordance with the sCT formulations that were patented and used commercially. This can be considered as a proof of concept for the high throughput protein formulation platform.