Rheological characterization of polymeric solutions used in spray drying process

Probucol-Ursodeoxycholic Acid Otic Formulations: Stability and In Vitro Assessments for Hearing Loss Treatment

Targeted drug delivery is an ongoing aspect of scientific research that is expanding through the design of micro- and nanoparticles. In this paper, we focus on spray dried microparticles as carriers for a repurposed lipophilic antioxidant (probucol). We characterise the microparticles and quantify probucol prior to assessing cytotoxicity on both control and cisplatin treated hair cells (known as House Ear Institute-Organ of Corti 1; HEI-OC1). The addition of water-soluble polymers to 2% β-cyclodextrin resulted in a stable probucol formulation. Ursodeoxycholic acid (UDCA) used as formulation excipient increases probucol miscibility and microparticle drug content. Formulation characterisations reveals spray drying results in spherical UDCA-drug microparticles with a mean size distribution of ∼5-12 μm. Probucol microparticles show stable short-term storage conditions accounting for only ∼10% loss over seven days. By mimicking cell culture conditions, both UDCA-probucol (67%) and probucol only (82%) microparticles show drug release in the initial two hours. Furthermore, probucol formulations with or without UDCA preserve cell viability and reduce cisplatin-induced oxidative stress. Mitochondrial bioenergetics results in lower basal respiration and non-mitochondrial respiration, with higher maximal respiration, spare capacity, ATP production and proton leak within cisplatin challenged UDCA-probucol groups. Overall, we present a facile method for incorporating lipophilic antioxidant carriers in polymer-based particles that are tolerated by HEI-OC1 cells and show stable drug release, sufficient in reducing cisplatin-induced reactive oxygen species accumulation.

Use of low-field NMR and rheology to evaluate the microstructure and stability of a poly(d,l-lactide-co-glycolide)-based W/O emulsion to be processed by spray drying

Drug-loaded emulsions for spray drying should be optimised for their rheological behaviour and stability under operating conditions, as this is essential for achieving the desired physicochemical properties of the final dry product. Our aim was therefore to investigate the structure and stability of a water-in-oil (W/O) emulsion containing vancomycin hydrochloride as the active ingredient in the aqueous phase, poly(d,l-lactide-co-glycolide) as the structural polymer in the dichloromethane-based organic phase, and various stabilisers using low-field nuclear magnetic resonance (LF NMR) and rheological characterisation. Four emulsions were tested, namely-one without stabiliser, one with Poloxamer® 407, one with chitosan and Span™ 80 and one with chitosan only. The theoretical interpretation of the rheological data allowed the determination of the velocity and the shear rate/stress profiles inside the feed path of the W/O emulsion, aspects that are critical for the industrial scale-up of the emulsion drying process. In addition, LF NMR demonstrated that shaking was sufficient to restore the original emulsion structure and that the droplet size of all emulsions was in the range of 1-10 μm, although the emulsion with chitosan had the narrowest droplet size distribution and the higher zero shear viscosity, which accounts for the increased long-term stability due to impeded droplets movement.

Wood Hemicelluloses as Innovative Wall Materials for Spray-Dried Microencapsulation of Berry Juice: Part 1—Effect of Homogenization Techniques on their Feed Solution Properties

The use of wood hemicelluloses, including galactoglucomannans (GGM) and glucuronoxylans (GX), in spray-dried microencapsulation of bioactive compounds has not been reported. Our study aims to investigate the benefits of spray-dried GGM and GX powders (sGGM and sGX) along with the effects of homogenization techniques (magnetic stirring, ultrasonication, and a combination of UltraTurrax homogenization and microfluidization) on the physicochemical properties of feed solutions (10–20%, w/w). Feed solutions of bilberry juice with sGGM, sGX, and mixtures of either sGGM or sGX with methylcellulose (MC) or carboxymethylcellulose (CMC) were examined to produce highly stable feed solutions for spray-dried microencapsulation. The effects of ultrasonication amplitudes (30–80%) on the viscosity and particle size distribution of sGGM feed solutions were more profound than observed in their sGX counterparts. Unlike sGX feed solutions, sGGM feed solutions homogenized by ultrasonication and microfluidization formed a gel-like structure. Microfluidization also caused a loss of total anthocyanin content (TAC) of the feed solutions. Magnetic stirring resulted in no gel formation and in the lowest viscosity of the feed solutions; hence, it is an effective method for preparing hemicellulose feed solutions. sGGM and sGX powders have high heat stability with melting temperatures of 170–180 °C. The sGGM + CMC combination was more stable over 1 week of storage than the sGGM and sGX feed solutions. Storing the feed solutions reduced TAC and increased sGGM viscosity. Our results indicated that GGM and GX have high potential for use as wall materials in the spray-dried microencapsulation of bioactive compounds.