Surface Energy and Interparticle Force Correlation in Model pMDI Formulations

Abstract

It is suggested that the polar contributions of the surface free energy measurements of particles may play a crucial role in particle interaction within propellant-based systems. Together with the application of a SCA model, this approach may be capable of predicting suspension stability of pMDI formulations.

Applications of the Atomic Force Microscope in the Development of Propellant-based Inhalation Formulations

“…This contrasts with traditional approaches that measure dispersion stability and particle interactions from a bulk perspective as in sedimentation rate experiments 17) , centrifugal technique 18) , laser scattering 19) , and inverse gas chromatography (IGC) 20) . In this work we focus on the application of AFM and its related techniques to systems of relevance to Hydrofluoroalkane (HFA)-based pMDIs.…”

Characterisation of dry powder inhaler formulations using atomic force microscopy

“…A comparison of the actual and the theoretical ratio of adhesive and cohesive forces, although not matching exactly, also indicated a positive relationship. The results strongly recommend the consideration of polar and non-polar interactions in theoretical models (Traini et al, 2005). Additionally, a linear relationship was identified between the theoretical work of adhesion calculated using CA measurements and results from colloidal probe AFM (Traini et al, 2006) for the interaction of salbutamol sulphate, budesonide, formoterol fumarate dihydrate and different container materials.…”

“…The SCA model included the impact of polar components and was based on results from CA and inverse gas chromatography experiments (Traini et al, 2005). Colloidal probe AFM was used to obtain the separation force of two API particles.…”

“…AFM measurements are also valuable for understanding the prevailing forces in pressurised MDIs. Colloidal probe force measurements can be performed within liquid cells, allowing the impact of propellants such as 2H, 3H decafluoropentane or 2H, 3H perfluoropentane (Ashayer et al, 2004;Bouhroum et al, 2010;Rogueda et al, 2011;Traini et al, 2005Traini et al, , 2007 to be assessed.…”

“…While the CAB approach is useful in many cases (Begat et al, 2005;Hooton et al, 2008Hooton et al, , 2006bJones et al, 2008a) and is widely used as it overcomes the limitations of instrumental validation and environmental conditions and removes the necessity to normalise the measured force values (Begat et al, 2004a;Nanopharm Ltd., 2009;Traini et al, 2005), it must be remembered that CAB gives a measure of the balance of forces relatively to each other rather than absolute values.…”