Food-grade hydroxypropyl methylcellulose-based formulations for electrohydrodynamic processing: part I – role of solution parameters on fibre and particle production

Abstract

Electrohydrodynamic (EHD) processing allows the production of micro and nano structures with high surface-area-to-volume ratio from biopolymers and environmentally friendly solvents. Such structures hold a very significant potential for application in the food area. The aim of this work was to assess the role of solution parameters in the formation of hydroxypropyl methylcellulose (HPMC)-based micro and nanostructures through EHD processing, establishing a relationship between variables such as viscosity and concentration, and processing zones (i.e., combinations of processing conditions that move the system towards electrospinning – fibres are formed – or electrospraying – particles are formed). Micro and nano structures were produced through electrospinning and electrospraying using HPMC with low (HPMC LMW) and high (HPMC HMW) molecular weight. Solutions were characterized regarding surface tension, conductivity, viscosity, zero-shear rate and specific viscosity. Plotting specific viscosity versus concentration allowed determining the electrospraying and electrospinning zones, which were confirmed through scanning electron microscopy analysis. HPMC LMW led to the formation of particles. For concentrations between 1 and 2% (w/v) rod like particles were formed, and round particles were obtained for concentrations ranging from 3 to 6% (w/v). The mean particle diameter varied between 833 and 1188 nm, while the aspect ratio ranged from 1.3 to 3.7. Nanofibres were generated using HPMC HMW, being beaded fibres produced at a concentration of 1% (w/v) and smooth fibres produced for concentrations between 1.5 and 2.25% (w/v). The developed nanofibres displayed a mean diameter ranging between 79 and 161 nm. Electrospraying and electrospinning zones were successfully determined for HPMC LMW and HMW. Nevertheless, near transition zones variability regarding the obtained morphology was observed once other processing parameters (e.g., flow rate) can influence the morphology of fibers and particles.