Polymer-based microneedle composites for enhanced non-transdermal drug delivery

The applications of microneedles (MNs) are becoming popular with the promise of efficient and advanced drug delivery. MNs were developed to overcome the limitations of conventional drug delivery systems and bypass biological barriers. While most MN applications in the past decades focused on transdermal biomedical applications, recent advancements in engineering and technology have enabled MNs to be used in a wide range of non-transdermal applications. Compared with the other types of MNs, polymer-based MN composites have attracted more attention for non-transdermal drug delivery because they exhibit excellent biological properties, including being nontoxic, biocompatible, and biodegradable, making them ideal biomaterials for drug delivery applications that overcome the metabolic constraints of drug delivery for macromolecular payloads across a variety of tissues and organs other than the skin. This review provides an overview of recent advancements in polymer-based MN composite carriers that aim to overcome the delivery challenges for non-transdermal drug delivery, specifically in the vascular, ocular, gastrointestinal tract, buccal transmucosal, periodontal, cardiovascular, and vaginal tissue. Furthermore, this review will discuss future perspectives and challenges for polymeric MN composites in non-transdermal drug delivery that must be resolved.