Spray-dried simvastatin-loaded dry emulsions as preformulations for 2D printing inks: effects of carrier and ink medium composition on redispersion and stability

This study evaluated spray-dried simvastatin-loaded dry emulsions as preformulations for the extemporaneous preparation of two-dimensional (2D) printing inks. The concept was based on stable solid intermediates intended for redispersion immediately before use, rather than storage as pre-mixed drug-loaded liquid inks. Oil-in-water emulsions containing simvastatin were prepared using lactose, maltodextrin, nanocrystalline cellulose (NCC)/lactose and NCC/maltodextrin as carrier systems, with and without antioxidants, and converted into dry emulsions by spray drying. The resulting powders were characterized for particle size, morphology, drug solid state, encapsulation efficiency and redispersibility, and were subjected to one-month stability testing. After redispersion in different propylene glycol/water media, the reconstituted systems were evaluated for particle size, surface tension and viscosity, together with physical and chemical stability. Carrier composition strongly affected powder properties and simvastatin retention. Lactose formulations showed higher encapsulation efficiency than maltodextrin formulations, while NCC affected simvastatin retention in a carrier- and condition-dependent manner, with NCC/lactose showing the most favorable chemical stability profile. Simvastatin was partly crystalline in lactose and NCC/lactose particles, whereas it was amorphous in maltodextrin and NCC/maltodextrin systems. NCC/lactose provided the most favorable simvastatin retention across both dry and redispersed formulations, while maltodextrin-based systems produced smaller dry and redispersed particles that showed higher physical stability over the storage period. The blank ink medium also influenced redispersion performance: water-rich media promoted smaller particles, whereas propylene glycol-rich media resulted in higher simvastatin retention regardless of the carrier used. This demonstrates the potential of spray-dried dry emulsions as solid preformulations for 2D printing inks, while highlighting the need to tailor both carrier and blank ink medium composition to the physicochemical properties of the incorporated drug.