Biopierces: drug-eluting ear tags for infection prevention in animal tagging

Ear tagging is a routine practice in livestock management, but it can be associated with bacterial colonization and infection at puncture sites. This study evaluated drug-eluting ear tags (Biopierce), incorporating chlorhexidine (CHX) in a poly(lactic-co-glycolic acid) (PLGA) matrix, due to their ability to reduce microbial burden and support wound healing. Biopierce eartags were fabricated by coating commercial ear tags with CHX–PLGA and compared to untreated controls. In vitro, Biopierces demonstrated a rapid burst release of CHX (~75% within 2 h), plateauing by 8 h, with eluates showing strong antimicrobial activity against Staphylococcus aureus in disk and tag diffusion assays. In vivo, five adult commercial boars each received one Biopierce and one control tag, with bacterial colonization assessed at 3, 7, 14, and 28 days using MALDI-TOF identification and semi-quantitative scoring. The Biopierce tags significantly reduced bacterial load, halving the prevalence of heavy contamination (27% vs. 12.6%, p = 0.0015) and doubling the prevalence of scant growth (9% vs. 21%, p = 0.017). Mean bacterial load scores were significantly lower with Biopierces (2.25 vs. 2.73, p < 0.05), and regression modeling confirmed a 20.1% reduction (p < 0.001). Histopathology on Day 28 showed trends toward reduced swelling (+45.2% vs. +57.6%) and increased full epithelialization (66% vs. 37%), though these did not reach statistical significance due to the small sample size. Taken together, these results demonstrate that Biopierce eartags provide localized CHX delivery that reduces bacterial colonization at tagging sites and may promote improved healing, supporting their potential as a practical infection and inflammation prevention strategy in livestock management.