An investigation into the effects of ink formulations of semi-solid extrusion 3D printing on the performance of printed solid dosage forms

Semi-solid extrusion (SSE) 3D printing has recently attracted increased attention for its pharmaceutical application as a potential method for small-batch manufacturing of personalised solid dosage forms. It has the advantage of allowing ambient temperature printing, which is especially beneficial for the 3D printing of thermosensitive drugs. In this study, the effects of polymeric compositions (single hydroxypropyl methylcellulose (HPMC) system and binary HPMC + polyvinylpyrrolidone (PVP) system), disintegrant (silicon oxide (SiO2)), and active pharmaceutical ingredients (tranexamic acid (TXA) and paracetamol (PAC)) on the printability of semisolid inks and the qualities of SSE printed drug-loaded tablets were investigated. Printability is defined by the suitability of the material for the process in terms of its physical properties during extrusions and post-extrusion, including rheology, solidification time, avoiding slumping, etc. The rheological properties of the inks were investigated as a function of polymeric compositions and drug concentrations and further correlated with the printability of the inks. The SSE 3D printed tablets were subjected to a series of physicochemical properties characterisations and in vitro drug release performance evaluations. The results indicated that an addition of SiO2 would improve 3D printing shape fidelity (e.g., pore area and porosity) by altering the ink rheology. The pores of HPMC + PVP + 5PAC prints completely disappeared after 12 hours of drying (pore area = 0 mm2). An addition of SiO2 significantly improved the pore area of the prints which are 3.5 ± 0.1 mm2. It was noted that the drug release profile of PAC significantly increased (p < 0.05) when additive SiO2 was incorporated in the formulation. This could be due to a significantly higher porosity of HPMC + PVP + SiO2 + PAC (70.3 ± 0.2%) compared to HPMC + PVP + PAC (47.6 ± 2.1%). It was also likely that SiO2 acted as a disintegrant speeding up the drug release process. Besides, the incorporation of APIs with different aqueous solubilities, as well as levels of interaction with the polymeric system showed significant impacts on the structural fidelity and subsequently the drug release performance of 3D printed tablets.