**5. Conclusions**

Our study has shown the detailed methodology for the development of immediate-release 3D printed tablets with liquid crystal-forming itraconazole. The development stage included both the optimization of the formulation composition and the correlation between the geometry of the printed object, namely the degree of infill, with shape reproducibility and drug dissolution.

The use of well-printable PVA polymer alongside the functionalized excipients, i.e., polyvinylpyrrolidone derivatives, during the hot-melt extrusion process covered not only the optimization of the mechanical properties of the filament and its printability but also the function of the polymer matrix in terms of intended drug release profiles. The results of the dissolution study and physicochemical analysis indicated that improved disintegration obtained due to the use of Kollidon ®CL-M was more beneficial than the molecular rearrangemen<sup>t</sup> and liquid crystal phase transitions. The lower infill density favored faster dissolution of the drug from printed tablets.

Micro-computed tomography was utilized to confirm that the design of printed objects was properly reconstructed. The comprehensive analysis revealed that the infill density, which is often considered as a way to control or improve drug dissolution, should be utilized with a deep understanding of its e ffect on the 3D printed objects' reproducibility. In the case of low infill densities, reproducibility issues, i.e., path disorder, increased layer dimension, and the path cohesion between cross-points, may occur. On the contrary, dense infill limits the surface area available for dissolution media and slows down the dissolution of the API.

In the case of the presented results, the most appropriate properties, i.e., good reproducibility during the object printing combined with superior drug dissolution, were achieved for the filament composed of 20% of itraconazole, 76% of PVA, and 4% of crospovidone acting as a disintegrant.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1996-1944/13/21/4961/s1, Figure S1: 3D printed itraconazole-loaded tablet with 20% infill density; Figure S2: 3D printed itraconazole-loaded tablet with 35% infill density; Figure S3: 3D printed itraconazole-loaded tablet with 60% infill density.

**Author Contributions:** Conceptualization, W.J., M.P. and R.J.; validation, J.S.-S.; investigation, W.J., J.P., M.K., J.K.-K., K.J., B.L. and A.W.; writing—original draft preparation, W.J.; writing—review and editing, J.P., M.K., J.S.-S., J.K.-K., M.P. and R.J.; visualization, W.J. and M.K.; supervision, R.J.; project administration, R.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Science Centre (Poland), gran<sup>t</sup> number: OPUS 16 No. 2018/31/B/ST8/01327. K.J. is grateful for the financial support from the Foundation for Polish Science within the START program.

**Conflicts of Interest:** The authors declare no conflict of interest.
