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AFM colloidal probe measurements implicate capillary condensation in punch-particle surface interactions during tableting

Badal Tejedor, Maria, Nordgren, Niklas, Schuleit, Michael, Millqvist-Fureby, Anna and Rutland, Mark (2017) AFM colloidal probe measurements implicate capillary condensation in punch-particle surface interactions during tableting. Langmuir the ACS journal of surfaces and colloids., 33. pp. 13180-13188. ISSN 1520-5827; 0743-7463


Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface-surface adhesive interactions. AFM colloid probe is a surface characterization technique that allows measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on Ibuprofen, MCC, α-lactose monohydrate and spray dried lactose particles as an approach to modeling the punch-particle surface interactions during tableting. The excipients showed constant, small, attractive and adhesive forces towards the steel surface after repeated number of contacts. In comparison, Ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and jump-in/jump-out separation distance. The type of interaction acting in the excipients-steel interface can be related to a Lifshitz force, relatively weak and short ranged. In contrast, the Ibuprofen-steel interaction is described by a capillary force profile. Even though Ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow “contact flooding” upon contact with the steel probe. Capillary forces increase due to “harvesting” of moisture - due to fast condensation kinetics- leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent flooding of the contact zone and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and non-sticky propensity of the materials and allows a mechanistic description.

Item Type: Article
Keywords: surface characterization, excipients, atomic force microscopy, colloid probe, tableting, ibuprofen
Date Deposited: 18 Jan 2018 00:45
Last Modified: 18 Jan 2018 00:45


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