title: Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations.
abstract: Compounds wettability is critical for a number of central processes including disintegration, dispersion, solubilisation and dissolution. It is therefore an important optimisation parameter both in drug discovery but also as guidance for formulation selection and optimisation. Wettability for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed, however for six out of seven compounds similar results were obtained by applying a standard pressure (866 MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle. Only for special cases where compounds have poor compressibility would there be a need for a surface-quality-control step before the contact angle determination.
authors.affiliation: Biologics and Pharmaceutical Science, H.Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark. Electronic address: rhol@lundbeck.com.
authors.forename: René
authors.initials: R
authors.lastname: Holm
authors.affiliation: Biologics and Pharmaceutical Science, H.Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark; Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kgs Lyngby, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Borkenfelt
authors.affiliation: Biologics and Pharmaceutical Science, H.Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Allesø
authors.affiliation: Department of Chemistry and Forensic Sciences, College of Science, Botswana International University of Science and Technology (BIUST), Private Bag 16, Palapye, Botswana.
authors.forename: Jens Enevold Thaulov
authors.initials: JE
authors.lastname: Andersen
authors.affiliation: Pharmaceutical Development, Novartis, Basel, Switzerland.
authors.forename: Stefania
authors.initials: S
authors.lastname: Beato
authors.affiliation: Biologics and Pharmaceutical Science, H.Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
authors.forename: Per
authors.initials: P
authors.lastname: Holm
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods*; D019245:Compressive Strength; D057927:Hydrophobic and Hydrophilic Interactions; D016062:Porosity; D013499:Surface Properties
keywords: Sessile drop; Surface porosity; Surface roughness; Wettability