Melt electrowriting of amorphous solid dispersions: Influence of drug and plasticizer on rheology and printing performance

Drug loaded microfiber scaffolds have potential for sublingual or buccal drug delivery due to their fast dissolution time and tunable porosity. Such microfiber scaffolds can be prepared by melt electrowriting (MEW), wherein a polymer melt is electrostatically drawn out of a syringe onto a computer controlled moving collector. The fabrication of such scaffolds via MEW has previously been shown for a polymer with a glass transition temperature (T_g) just above room temperature, making handling challenging. For this reason, ABA triblock copolymers bearing poly(2-oxazoline) and poly(2-oxazine) with slightly higher T_g were synthesized and their processability into drug loaded microfiber scaffolds was assessed. Additionally, plasticizers commonly used in drug products were added to decrease the fabrication temperature. The aim was to investigate the influence of plasticizers on the melt viscosity and printability to expand the polymer platform for the preparation of drug loaded microfiber scaffolds. Temperature dependent melt rheology measurements of the polymers and their mixtures revealed a drop in viscosity by one order of magnitude by the addition of triethyl citrate and ethylene glycol, respectively. Addition of the model drug indomethacin led to a further decrease in viscosity. Even though the drug loaded samples were printable with and without the addition of triethyl citrate, better fiber stacking and therefore improved printing results were obtained with the plasticizer added. However, the addition of the plasticizer did alter the dissolution profile for some of the polymer samples, leading to longer dissolution times or lower drug release compared to the samples without plasticizer, which makes it difficult to predict the influence of the plasticizer on the dissolution profile.