Advancements in 3D-printing strategies towards developing effective implantable drug delivery systems: Recent...

The development of implantable drug delivery systems has played a transformative role in modern medicine through enabling more precise, localized and sustained delivery of therapeutics. This has advantages over systemic delivery routes that often provide suboptimal drug concentrations, frequent redosing requirements and off-target effects. However, one ongoing limitation of current implantable systems has been the inability to navigate the complex and dynamic biological processes. The physical architecture of implantable constructs serves as a powerful method to control the therapeutic release from a biomaterial. Additive manufacturing, or commonly 3D-printing, has emerged as one of the most versatile and widely adopted approaches used in the development of novel biomaterials with macro to nanoscale resolution, offering an efficient and cost-effective method to create highly complex geometries, hierarchical architectures to enable region-specific drug loading. Therefore, in this review, we describe and critically evaluate the implementation of 3D-printing techniques towards designing implantable drug delivery systems. Furthermore, we analyze the effectiveness of existing strategies, discussing their utility, with a particular focus on constructs that are capable of control and sustained release of multiple drugs towards therapeutic treatments and tissue engineering. Lastly, this review discusses the current challenges and the keys opportunities that remain underutilized towards the developing the next generation of implantable drug delivery systems.