HME-FDM 3D-Printed Implantable Drug Delivery Systems-From Design to Characterization

Implantable devices have undergone enormous development in the past several decades and more results are expected as there are still unanswered questions. In manufacturing, a relatively new technology called three-dimensional (3D) printing has become increasingly involved, from which hot-melt extrusion (HME) coupled with fused deposition modeling (FDM) is one of the most researched methods in producing implantable drug delivery systems (IDDS). The HME process is used to produce polymer filaments that are the carriers of the applied drugs, while FDM creates the implant itself from the filaments, based on the computer-aided designs. The availability of several polymers like polycaprolactone, polylactic acid, or thermoplastic polyurethane, etc., allows the incorporation of many active pharmaceutical ingredients while digital designs offer numerous variabilities in designs, formulations, and applications of 3D-printed IDDS. This allows more specific and detailed modifications in the end product which can forecast the possibility of personalized treatments and therapies. In this review, our research group gathered together different HME-FDM-printed IDDS to provide examples about the diverse applicability of 3D printing. These products, just like any other device and medicine in the medical field, must be characterized and evaluated properly. The methods and technology that are needed already exist and can be repeatedly used in the characterization of IDDSs; we also discuss these methods based on the available publications. In conclusion, every condition is given to make research and manufacture personalized 3D-printed IDDSs possible, however more research work and proof of safe usage are crucial to make these devices applicable in everyday medical treatments.