Characterisation and surface-profiling techniques for composite particles produced by dry powder coating in pharmaceutical drug delivery

•Dry powder coating is a promising one-step process to produce composite particles with improved functionalities.•Blend characterisation is based on the use of proper sampling techniques.•The selection of the right surface characterisation technique is essential to determine resultant functionality and optimisation of process parameters. The production of composite particles using dry powder coating is a one-step, environmentally friendly, process for the fabrication of particles with targeted properties and favourable functionalities. Diverse functionalities, such flowability enhancement, content uniformity, and dissolution, can be developed from dry particle coating. In this review, we discuss the particle functionalities that can be tailored and the selection of characterisation techniques relevant to understanding their molecular basis. We address key features in the powder blend sampling process and explore the relevant characterisation techniques, focussing on the functionality delivered by dry coating and on surface profiling that explores the dynamics and surface characteristics of the composite blends. Dry particle coating is a solvent- and heat-free process that can be used to develop functionalised particles. However, assessment of the resultant functionality requires careful selection of sensitive analytical techniques that can distinguish particle surface changes within nano and/or micrometre ranges.