Biological Application of Polypropylene Microneedles Prepared by Ultrasonic Plasticization Microinjection Molding Technology

Polymer microneedles (MNs) attract considerable attention due to their sound biocompatibility and low manufacturing cost. In this study, we prepared polypropylene (PP) MNs utilizing ultrasonic plasticization microinjection molding (UPMIM) technology, and the compression property, piercing performance, and drug infiltration promotion effect of the products were investigated. In addition, we prepared drug-loaded MNs using UPMIM technology and the dip coating method to reveal their drug loading and release properties. Meanwhile, the photothermal properties of polydopamine (PDA) MNs and their in vivo biological application performance in mice were explored. Results showed that PP MNs have good compressive toughness and piercing performance. They can pierce through mice skin, demonstrating good capability in drug infiltration promotion. The drug loading capacity of MNs rose with the increase of the PVA and sucrose contents and dropped with the rise of the temperature, indicating a fast drug release feature. Moreover, PDA MNs showed relatively strong photosensitivity and good cyclic photothermal properties as well as ideal biological application performance, with the mice skin temperature reaching 21.9 °C in 3 min. This research will provide important theoretical and technical support for the manufacturing of polymer MNs and their biological application.