Examples of such surfaces are coatings of end-products, such as pharmaceutical tablets, whose properties significantly influence both the delivery and the release of the drug compound. Other surfaces of great importance are all those that the drug comes in contact with during the formulation, storage and administration stages, and where each surface interaction may affect the stability of the drug.
Coatings on pharmaceutical tablets serve several purposes. Coatings are used to mask taste or odor, to protect the drug from the acid environment of the stomach or to protect the stomach lining from aggressive drugs. Coatings can also be designed to control the release profile of the drug. For whatever reason, the coating is applied to a tablet core, and one of the requirements for success is a good adhesion of the coating to the tablet.To ensure good adhesion, the coating formulation should spread completely over the surface of the tablet. Adhesion will be enhanced if there is some penetration into the pores of the tablet. Spreading of the coating formulation on the tablet surface can be evaluated through contact angle and surface free energy measurements. As surface porosity also plays a role, conjugated surface roughness measurements and determining the roughness corrected contact angles can give more insight to the issue.
In some cases, compressing a pharmaceutical substance into tablet form is not possible as it is shown to change its wetting properties. The Washburn method has thus been often used to determine the contact angle of drug compounds. The Washburn method has also been used to study wettability in processes such as dry polymer coating, where the contact angle of polymer powder against different additives is of interest.
Understanding the wetting behavior of powders is important to the pharmaceutical industry, where the use of different powders as drug compounds is typical.
The wettability of powders can be measured by using the Washburn method with Sigma 700/701. In the Washburn method, the contact angle is calculated from the weight increase over time when the powder is in contact with the liquid.
Due to better toxicity and side effect profiles, protein drugs are becoming more common than small molecules, which on the other hand are both easier to make and purify, and are much more stable. Antibodies in particular, are quite specific, binding only to their target molecule and causing less toxicity compared to small molecules which can have side effects and issues with non-specific interactions and toxicity.
A downside with proteins is that they are inherently less stable, more “sticky” and bind to whatever surfaces they interact with, which makes production, purification, and storage more difficult. During the manufacturing and formulation stages, the protein will meet a variety of materials, such as filters, tubing, vials, syringes and bag polymers, where each material presents a risk of protein adsorption, aggregation and loss of dose.
To minimize the loss of expensive therapeutic proteins during manufacturing and to ensure the development of a fully functional drug component at end-use, there is hence a need to analyze the protein stability in the formulation, storage and delivery stages, and to understand the propensity for proteins to aggregate in the presence of specific materials, at certain temperatures and protein concentrations, and in the presence of an excipient.
QSense® QCM-D is a label-free method that enables high precision characterization of protein-surface interactions and the effect of both surface, the surfactants, the protein concentration and storage factors, such as temperature.