(443b) Assessing the Impact of Dry Coating on the Surface Properties of Pharmaceutical Formulations | AIChE

(443b) Assessing the Impact of Dry Coating on the Surface Properties of Pharmaceutical Formulations


Hadjittofis, E. - Presenter, Imperial College London
Zhang, G. G. Z., AbbVie Inc.
Heng, J., Imperial College London
Dry coating of materials of pharmaceutical interest with nanopowders is recently gaining momentum as a promising formulation approach as it enables significant improvement of flowability under high relative humidity (RH) conditions, preventing, also, the caking upon storage under high RH.1-3 Nevertheless, it remains a challenging and sophisticated process, where coating is, occasionally, accompanied by some undesirable phenomena.

This work proposes the use of vibrations for the efficient dry coating of materials of pharmaceutical interest with silica nanopowder.4 The API or excipient of interest are placed in a jar, attached on a shaker, along with different loadings of silica nanopowder. The vibrations created by the shaker lead to the efficient coating. The coating efficiency is examined using SEM. The influence of particle habit and surface anisotropy on the efficiency of the coating was, also, investigated.

Inverse gas chromatography (IGC) was employed to provide an in depth understanding on the influence of coating on the surface properties of the particles. The surface energy of the coated particles, measured with IGC, decreases abruptly in the presence of relative humidity. For measurements conducted at RH>30 %, the surface energy measured was effectively the same. This suggests that the interactions were mainly driven by the presence of a water layer on the particles. Furthermore, IGC experiments were used to assess the roughness of the coated particles.5 The measurements suggest that higher shaking times lead to a more rough area, associated with better flowability.

This study proposes an efficient, compact and moving parts-free dry coating process. It examines the influence of particle properties on dry coating and furthermore it employs vapour sorption tools to examine the roots of the improved behaviour of particles coated with nanopowders.


1. Yang J, Sliva A, Banerjee A, Dave RN, Pfeffer R. Dry particle coating for improving the flowability of cohesive powders. Powder Technol. 2005, 158, 21-33.

2. Luo Y, Zhu J, Ma Y, Zhang H. Dry coating, a novel coating technology for solid pharmaceutical dosage forms. Int J Pharm. 2008, 358, 16-22.

3. Zhang GZG, Ping T. Dry powder coating of silica nanoparticles on hygroscopic materials: Improving flow and reducing sensitivity to moisture. Proceedings of 2013 AAPS Annual Meeting. 2013.

4. Polizzi M, Langdon BA, Beach LE, Mullarney MP. Applying dry powder coatings. Pharmaceutical Technology. 2011, 35, 94-102.

5. Burnett DJ, Heng JYY, Thielmann F, Garcia RA, Naderi M, Acharya M. Measuring surface roughness of pharmaceutical powders using vapor sorption methods. AAPS Pharmaceutical Science Technology. 2011, 12, 56-61.