From liquid nanocapsules to 3D-printed medicines: effect of freeze-drying on dexamethasone release and intestinal...

Liquid nanocapsule (NC) suspensions are recognised as effective carriers for drug delivery. Freeze-drying offers a valuable strategy to enhance their storage stability and enable their incorporation into solid dosage forms, thereby facilitating clinical translation. However, limited information is available regarding the effects of freeze-drying on the drug release behaviour and intestinal permeation of drug-loaded NCs. In this study, dexamethasone-loaded ethylcellulose NCs (NC-EC-DEX) were produced and subjected to freeze-drying to assess the influence of this process on their physicochemical and in vitro performance using Caco-2 cell models. The freshly prepared NC-EC-DEX showed a nanometric size (136 ± 3 nm), narrow size distribution (polydispersity index, 0.10 ± 0.02), negative zeta potential (-16.4 ± 1.3 mV), and drug content of 0.47 mg mL^-1. Mannitol was tested as a cryoprotectant at concentrations of 3 %, 5 %, and 10 % (w/v), with only the highest concentration ensuring full recovery of nanometric size after drying (232 ± 19 nm; polydispersity index, 0.33 ± 0.02). The freeze-dried formulation (FD_NC-EC-DEX) exhibited a more sustained drug release and slower permeation across Caco-2 cells compared with the liquid suspension, while maintaining high cell viability (>80 %). This preservation of nanoscale behaviour after reconstitution was essential to demonstrate that the freeze-dried powder could function as an intermediate suitable for further processing. The freeze-dried powder was subsequently used as feedstock for the fabrication of solid dosage forms via semi-solid extrusion 3D printing, thereby establishing a rational technological sequence in which the liquid nanosuspension is first stabilised through lyophilisation and then transformed into a printable matrix. Overall, this study provides a proof of concept for a continuous workflow, from liquid nanosuspension to a more stable intermediate powder, and ultimately to 3D-printed solid dosage forms-highlighting its potential for processing powders with limited flowability, such as those obtained through freeze-drying. This integrated approach strengthens the technological justification for employing 3D printing as a downstream manufacturing solution for nanomedicines, establishing a versatile technological platform for the development of innovative 3D-printed nanomedicines.