Influence of low molecular weight salts on the viscosity of aqueous-buffer bovine serum albumin solutions

Zdovc, Blaž (author), Jaklin, Matej (author), Hribar-Lee, Barbara (author), Lukšič, Miha (author)

Pharmaceutical design of protein formulations aims at maximum efficiency (protein concentration) and minimum viscosity. Therefore, it is important to know the nature of protein-protein interactions and their influence on viscosity. In this work, we investigated the dependence of the viscosity of BSA in an aqueous 20 mM acetate buffer at pH = 4.3 on protein concentration and on temperature (5–45 °C). The viscosity of the solution increased with protein concentration and was 230% higher than the viscosity of the protein-free formulation at 160 mg/mL. The viscosity decreased by almost 60% in the temperature range from 5 to 45 °C. The agreement of the modified Arrhenius theory with experiment was quantitative, whereas a hard-sphere model provided only a qualitative description of the experimental results. We also investigated the viscosity of a 100 mg/mL BSA solution as a function of the concentration of added low molecular weight salts (LiCl, NaCl, KCl, RbCl, CsCl, NaBr, NaI) in the range of salt concentrations up to 1.75 mol/L. In addition, the particle size and zeta potential of BSA-salt mixtures were determined for solutions containing 0.5 mol/L salt. The trends with respect to the different anions followed a direct Hofmeister series (Cl$^–$ > Br$^–$ > I$^–$), whereas for cations in the case of viscosity the indirect Hofmeister series was observed (Li$^+$ > Na$^+$ > K$^+$ > Rb$^+$ > Cs$^+$), but the values of particle sizes and zeta potential did not show cation-specific effects. Since the protein is positively charged at pH = 4.3, anions are more attracted to the protein surface and shield its charge, while the interaction with cations is less pronounced. We hypothesize that salt surface charge shielding reduces protein colloidal stability and promotes protein aggregate formation.

• Language: English
• Keywords: bovine serum albumin, viscosity, zeta-potential, ion-specific effects, protein aggregation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: 16 str.
• Numbering: Vol. 27, iss. 3, art. 999
• PID: 20.500.12556/RUL-136984
• UDC: 577.322
• ISSN on article: 1420-3049
• DOI: 10.3390/molecules27030999
• COBISS.SI-ID: 96153859
• Publication date in RUL: 27.05.2022

Record is a part of a journal

• Title: Molecules
• Shortened title: Molecules
• Publisher: MDPI
• ISSN: 1420-3049
• COBISS.SI-ID: 18462981

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 01.02.2022

Secondary language

• Language: Slovenian
• Keywords: proteini, goveji serumski albumin, soli, viskoznost, zeta potencial