Zeolite Encapsulation of Indole as an Antibacterial with Controllable Release Property

Effective regulation of the release behavior of bactericidestoavoid both too fast release and too slow release to maximize theirantibacterial ability is still the face of a grand challenge. In thisstudy, indole as a bactericide was encapsulated into three types ofzeolites (denoted as indole@zeolite), including the ZSM-22 zeolite,ZSM-12 zeolite, and beta zeolite with different topologies, respectively,to obtain indole@ZSM-22, indole@ZSM-12, and indole@Beta complexesfinally. Benefiting from the confinement effect of zeolites, the releaserate of indole from these three zeolite encapsulation systems showeda much slower release rate than that of indole impregnated onto acounterpart zeolite (denoted as indole/zeolite), thus avoiding thetoo-fast and too-slow release very well. As determined by moleculardynamics simulation combined with experimental results, attributedto the unequal diffusion coefficient in these three encapsulationsystems caused by different zeolite topologies, the release rate ofindole within these three complexes was different from each other,hence providing an effective way to avoid a too-slow release ratethrough choosing different zeolite topologies. The simulation resultsshowed that the timescale of hopping of indoles in zeolites playsan important role in the dynamics in zeolites. Taking killing Escherichia coli as an instance, compared with indole/zeolite,the corresponding indole@zeolite sample exhibited more efficient andsustainable antibacterial activity for its controlled-release behavior.

Automated summary

Effectively regulating the release behavior of bactericides to avoid both too fast and too slow release is a major challenge. In this study, indole was encapsulated into three types of zeolites with different topologies. The zeolite encapsulation systems showed a much slower release rate of indole compared to indole impregnated onto a counterpart zeolite, thus avoiding undesirable release behavior.