AXISYMMETRICAL DROP SHAPE-ANALYSIS (ADSA) APPLIED TO PROTEIN SOLUTIONS

Axisymmetric drop shape analysis (ADSA) is applied to study time evolution of profiles of pendant and sessile insulin and protein solution drops. Human, bovine and porcine insulin preparations are studied with respect to surface tension kinetics (pendant drop) and contact angle kinetics on hydrophobic FC-721 (fluorocarbon) surfaces. ADSA permits high resolution between the different insulin preparations, which can be distinguished by slight but reproducible differences in surface tensions and contact angles. Application of Young's equation, however, results in nearly identical solid-protein solution interfacial tensions. The time dependence of contact angles of albumin and fibrinogen solution drops on Acetal and FC-721 is presented. Scatter of data is more pronounced on the hydrophilic Acetal surface than on the hydrophobic FC-721 one. Further, an irregular motion of the three-phase contact line is observed. The applicability of Young's equation to albumin and fibrinogen solutions is discussed in terms of the solid-protein solution interfacial tensions.