Effect of Cyclodextrin on Preservative–Surfactant–Protein Interactions

Sammanfattning

Particulate matter formation in parenteral protein formulations poses significant safety risks and quality challenges. In the multi-dose injectable products, therapeutic proteins, surfactants, and antimicrobial preservatives are present together, forming a complex system that is more prone to destabilizing interactions. Cyclodextrin (CD) has been proposed as a potential stabilizer, yet its role in such multiple-component systems remains insufficiently understood. This project systematically investigated the effect of HP-β-CD on the interactions within a protein–surfactant–preservative model system, using bovine serum albumin (BSA) and human growth hormone (hGH) as model proteins, polysorbate 20 (PS20) as the surfactant, and phenol as the preservative. A stepwise experimental approach was adopted, progressing from binary to ternary systems. Instability was characterized by phenol- and salt-induced precipitation thresholds, detected simultaneously through absorbance, fluorescence, and light scattering signals using a Probe Drum titration instrument. Results demonstrated that CD's effect on formulation stability is formulation-dependent, governed by the interplay of CD concentration, protein identity, and surfactant concentration. At high concentration, CD protected PS20 against phenol-induced clouding, whereas low CD concentration (10 mg/mL) showed destabilizing tendencies. Although CD slightly destabilized BSA, the overall performance of the CD-BSA ternary system was similar to that of PS20. CD provided no protective effect against phenol-induced hGH aggregation. In the hGH ternary systems, CD behaved as a destabilizer in the hGH system by disrupting PS20's protective role at intermediate surfactant concentrations. Consequently, in ternary systems, CD expressed its effect on formulation stability primarily through modulation of PS20 behavior. These findings indicate that CD cannot be considered a universally beneficial stabilizer for complex protein formulations containing surfactants and preservatives, and its incorporation requires careful, case-by-case evaluation.