The particle formation process for microparticles of cellulose acetate butyrate dried from an acetone solution was investigated experimentally and theoretically. A monodisperse droplet chain was used to produce solution microdroplets in a size range of 55-70 μm with solution concentrations of 0.37 and 10 mg/mL. As the droplets dried in a laminar air flow with a temperature of 30, 40, or 55 °C, the particle formation process was recorded by two independent optical methods. Dried particles in a size range of 10-30 μm were collected for morphology analysis, showing hollow, elongated particles whose structure was dependent on the drying gas temperature and initial solution concentration. The setup allowed comprehensive measurements of the particle formation process to be made, including the period after initial shell formation. The early particle formation process for this system was controlled by the diffusion of cellulose acetate butyrate in the liquid phase, whereas later stages of the process were dominated by shell buckling and folding.

A droplet chain technique was used to study the influence of the crystallization process on the morphology of spray dried microparticles. A piezoceramic dispenser produced a chain of monodisperse solution droplets with an initial diameter in the range of 60-80 mm. Aqueous solutions of sodium nitrate were prepared in concentrations ranging from 5 mg/ml to 5Á10 ¡5 mg/ml. The solution droplets were injected into a laminar flow with gas temperatures varying from 25 to 150 C, affecting the droplet temperature and the evaporation rate, accordingly. Dried particles with diameters between 0.3 and 18 mm were collected. The properties of the collected microparticles were studied and correlated with a particle formation model which predicted the onset of saturation and crystallization. The model accounted for the dependence of the diffusion coefficient of sodium nitrate in water on droplet viscosity. The viscosity trend for sodium nitrate solutions was determined by studying the relaxation time observed during coalescence of two aqueous sodium nitrate droplets levitated in optical tweezers. The combination of theoretical derivations and experimental results showed that longer time available for crystallization correlates with larger crystal size and higher degrees of crystallinity in the final microparticles.

Insulin nanoparticles (NPs) with high loading content have found diverse applications in different dosage forms. This work aimed to evaluate the impact of freeze-drying and spray drying process on the structures of insulin-loaded chitosan nanoparticles, with or without mannitol as cryoprotectants. We also assessed the quality of these nanoparticles by redissolving them. Before dehydration, the chitosan/sodium tripolyphosphate/insulin crosslinked nanoparticles were optimized to 318 nm of particle size, 0.18 of PDI, 99.4% of entrapment efficiency, and 25.01% of loading content. After reconstitution, all nanoparticles, except the one produced by the freeze-drying method without using mannitol, maintained their spherical particle structure. The nanoparticles dehydrated by spray drying without mannitol also showed the smallest mean particle size (376 nm) and highest loading content (25.02%) with similar entrapment efficiency (98.7%) and PDI (0.20) compared to mannitol-containing nanoparticles dehydrated by either spray drying or freeze-drying techniques. The nanoparticles dried by spray drying without mannitol also resulted in the fastest release and highest cellular uptake efficacy of insulin. This work shows that spray drying can dehydrate insulin nanoparticles without the need for cryoprotectants, creating a significant advantage in terms of greater loading capacity with lower additive requirements and operating costs as compared to conventional freeze drying approaches.

A simple to make, multifunctional, heatable, and sprayable superhydrophobic and electrically conductive coating is developed by dispersing carbon nanofibers (CNFs) into a water repelling polymer matrix. The developed coating exhibits an average static and hysteresis contact angles of 160° and 5°, respectively. An electrical conductivity of 1100 S m−1 and a thermal conductivity of 0.001 W m−1 K−1 are obtained with a sample of dimensions: 3 cm × 1 cm × 20 µm. A 12 µm thick coating under an average electric current of 75 mA reaches to a surface temperature of more than 140 °C for a dry coating. The coating when in contact with ice or water (water at 25 °C for 300 h, and at 85 °C for less than an hour) does not show a deterioration of wetting performance. Furthermore, it is shown how this coating can be used to mitigate the ice formation on cold surfaces. The ability of application of the developed coating to various substrates is also shown.