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Keywords:

  • dynamic contact angle;
  • hysteresis;
  • medical glass packaging;
  • protein adsorption;
  • reversibility

Abstract

Glass is one of the most important materials in medical packaging. Protein adsorption at the glass walls leads to loss of the active substance in the glass vials and thus to high costs for the pharmaceutical industry, in particular in the case of expensive drugs. Thus more knowledge about the basic mechanisms and the involved parameters in protein interaction with glass surfaces is desirable. In this context, the adsorption of bovine serum albumin (BSA), fibrinogen (FIB), and lysozyme (LYS) on typical glass surfaces (borosilicate glass, quartz glass) was investigated by dynamic contact angle (DCA) measurements as a function of pH value. DCA allows the determination of the relative amount of adsorbed protein and of the reversibility of the adsorption process. It will be shown that the amount of adsorbed protein is governed by electrostatics on quartz glass while on borosilicate glass no influence of the pH value (and hence the electrostatics) can be seen. This can be explained by the different surface composition which has apparently an important influence on the adsorption process. In addition it could be determined that on both glass surfaces, none of the investigated proteins shows a complete reversibility of the adsorption process, i.e., desorption is never complete. In conclusion the interaction with glass surfaces cannot be generalized but electrostatics play a major role and thus the interaction of proteins with glass surfaces may be changed by shifting the pH value of the solutions or the isoelectric point (IEP) of the surfaces.