A novel tetrahedral framework nucleic acid-based antibiotic delivery system: overcoming biofilm barriers to combat chronic infections.

Background: Overcoming bacterial biofilm barriers to enhance the efficacy of antibiotics remains a major therapeutic challenge, necessitating the development of efficient and biocompatible drug delivery systems. While framework nucleic acids (FNAs) have emerged as promising candidates for overcoming biological barriers, their biofilm penetration efficiency and mechanistic interactions require systematic exploration. This study evaluates the biofilm-penetrating capacity of FNAs with distinct topological configurations (linear, triangular, and tetrahedral), investigates their antibiotic delivery performance in biofilm-infected models, and elucidates the structure-dependent interactions between FNAs and bacteria.

Results: DNA tetrahedron (Td) demonstrated superior biofilm penetration, exhibiting 44-fold and 11-fold stronger fluorescence intensity at a biofilm depth of 20 μm compared to linear and triangular counterparts, respectively, while maintaining structural stability. The optimized polymyxin B-loaded Td (PMB@Td, with a PMB: Td ratio of 10:1) enhanced biofilm permeability by 6-fold relative to free PMB. PMB@Td outperformed conventional liposome-encapsulated PMB (PMB@Lipo), achieving half-maximal biofilm eradication concentrations (MBEC₅₀) of 12.8 µM versus 16.3 µM for PMB@Lipo. In murine models of biofilm- associated skin and pulmonary infections, PMB@Td effectively controlled bacterial burden and mitigated inflammatory responses without observable toxicity. Mechanistic studies revealed that the tetrahedral topology facilitated efficient diffusion within the biofilm matrix and enhanced Td adhesion to bacterial membranes.

Conclusions: This work establishes Td as a robust nanoplatform for overcoming biofilm-mediated antibiotic resistance. The topology-dependent interactions provide critical design principles for engineering next-generation nanocarriers against biofilm-associated chronic infections, with significant translational potential in antibiofilm therapy.