Ensuring the quality of 3D printed medicines: Integrating a balance into a pharmaceutical printer for in-line uniformity of mass testing

Abstract

Semi-solid extrusion (SSE) 3D printing has great potential to be integrated in a clinical setting, with the use of pre-filled and disposable pharma-ink syringes meeting regulatory good manufacturing practice (GMP) requirements. Uniformity of mass testing is a critical quality attribute and is carried out by weighing a specific amount of dosage units in a single batch and finding the average mass to evaluate any deviations. However, this test for small batches of 3D printed medicines may require weighing the entire manufactured batch. To overcome this limitation, an in-line analytical balance was implemented inside a GMP pharmaceutical 3D printer, with a specialised software-controlled weighing system for the automated mass uniformity testing of the entire printed batch. Three different dose batches (n = 28) of hydrocortisone pharma-ink were 3D printed and subjected to in-line mass uniformity testing. The developed software was capable of registering the weights of all individual printlets and accurately detecting any deviations within the accepted limits. Only one printlet was outside the accepted weight range, a result of the first print often being imperfect due to the semi-solid nature of the pharma-ink. The weight results were compared against an external analytical balance, and no significant differences were found. This study is the first to integrate an analytical balance inside a pharmaceutical printer, automating the dosage form mass uniformity testing which can save time, labour, and resources, whilst improving the quality control testing of 3D printed pharmaceuticals.