Functionalised particles using dry powder coating in pharmaceutical drug delivery: promises and challenges

INTRODUCTION

Production of functionalised particles using dry powder coating is a one-step, environmentally friendly process that paves the way for the development of particles with targeted properties and diverse functionalities.

AREAS COVERED

Applying the first principles in physical science for powders, fine guest particles can be homogeneously dispersed over the surface of larger host particles to develop functionalised particles. Multiple functionalities can be modified including: flowability, dispersibility, fluidisation, homogeneity, content uniformity and dissolution profile. The current publication seeks to understand the fundamental underpinning principles and science governing dry coating process, evaluate key technologies developed to produce functionalised particles along with outlining their advantages, limitations and applications and discusses in detail the resultant functionalities and their applications.

EXPERT OPINION

Dry particle coating is a promising solvent-free manufacturing technology to produce particles with targeted functionalities. Progress within this area requires the development of continuous processing devices that can overcome challenges encountered with current technologies such as heat generation and particle attrition. Growth within this field requires extensive research to further understand the impact of process design and material properties on resultant functionalities.

Interparticle van der Waals force in powder flowability and compactibility

Particle flowability and compactibility are the two critical process parameters tested when a pharmaceutical material is formulated for a tabletting process. These behavioral descriptions are strongly affected by geometrical, physical, chemical and mechanical particle properties, as well as operational conditions. The property influences are broadly known in a qualitative sense, but have largely escaped fundamental quantitative description. Various measurement methods have been separately developed for each of these properties which provide comparative indices to assist in process and formulation design. This paper seeks to establish the connections between interparticle van der Waals force and both flowability and compactibility, and therefore also the inter-relations between the two apparently distinct properties. Paracetamol and the excipients often associated with it for tabletting are used as test materials to provide an initial validation of the theoretical development. These powders are well-characterized and known to be particularly difficult with respect to flowability and compactibility.

The use of energy indices in estimating powder compaction functionality of mixtures in pharmaceutical tableting

A series of binary powder blends comprising of microcrystalline cellulose (Avicel PH101), alpha-lactose monohydrate or theophylline anhydrous were prepared in order to investigate the densification of binary pharmaceutical powder mixes under compaction pressure. It is postulated that the use of derived energy parameters, as well as various evolved indices, calculated from the work expended during the fabrication and/or rupture of a compact can be employed to quantitatively predict the compaction properties of pharmaceutical powder mixes comprised of the same constituents. The relationship between the net work of compression normalized to powder volume and the resulting compact strength for mix constituents can be used to define a pharmaceutical formulation space in which compact mechanical properties can be estimated for other 'virtual mixes' of the same constituents in different proportions. The approach is successfully applied to the prediction of the mechanical properties of a ternary mix of these constituents.