Chitosan/zinc nitrate microneedles for bacterial biofilm eradication

Chronic wounds are greatly health threatening owing to the increasing morbidity, and bacterial biofilm is a major cause of chronic wounds. The critical for bacterial biofilm eradication is overcome the barrier of extracellular polymeric substances (EPS) produced by the bacteria, and promote the diffusion of drugs within the biofilm. In this article, composite microneedles (MNs) of chitosan and zinc nitrate (CS-Zn[II] MNs) were investigated to eradicate bacterial biofilm. The CS-Zn(II) MNs combined the structure characteristic of MNs with the antibacterial properties of CS and Zn²⁺ . The MNs can pierce the EPS due to the needle-like structure, and can transport directly the CS and Zn²⁺ into the bacterial biofilm. The needle-like structure of MNs also increased the contact area between drug carrier and bacterial biofilm nearly 14-23% comparing with membrane without needle-like structure, and facilitated the diffusion of drugs. What is more, the synergistic effect of CS and Zn²⁺ make the CS-Zn(II) MNs obtain excellent antibiofilm properties. Counting the colony forming units and bacterial live/dead staining tests confirmed the fascinating antibacterial abilities (up to 100% inhibition) and biofilm eradication properties, respectively, of the CS-Zn(II) MNs. The inhibition zone test shown that the antibiofilm effect of MNs was superior to membrane and the antibiofilm effect of MNs was become increasingly obvious along with the increase of the treatment time. Besides, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays proved that the CS-Zn(II) MNs possess brilliant cytocompatibility. These results indicate that the CS-Zn(II) MNs are promising method for bacterial biofilm eradication.