Xueyun Fu,1 Lina Zhang,1 Jing Lin,1 Qian Wang,1 Ziyi Wang,1 Menghui Chi,1 Daohao Li,2 Guiqiu Zhao,1 Cui Li1 

1Department of Ophthalmology, The Affiliated Hospital of Qingdao University, Qingdao, People’s Republic of China; 2State Key Laboratory of Bio-fibers and Eco-Textiles, Institute of Marine Biobased Materials, College of Materials Science and Engineering, Qingdao University, Qingdao, People’s Republic of China

Correspondence: Guiqiu Zhao, Department of Ophthalmology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, Shandong, 266003, People’s Republic of China, Email zhaoguiqiu_good@126.com Cui Li, Department of Ophthalmology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, Shandong, 266003, People’s Republic of China, Email yankelicui@126.com

Background: Fungal keratitis is a severe vision-threatening corneal infection with a prognosis influenced by fungal virulence and the host’s immune defense mechanisms. However, there is still a lack of effective drugs that attenuate fungal virulence while relieving the inflammatory response caused by fungal keratitis.
Purpose: Finding an effective treatment to solve these problems is particularly important.
Methods: We synthesized Zeolitic imidazolate framework-90 (ZIF-90) by water-based synthesis method and characterized it. In vitro experiments included mycelium electron microscopy, Cell Counting Kit-8 (CCK-8), and Enzyme-linked immunosorbent assay (ELISA). These trials verified the disruptive effects of ZIF-90 on morphology, cell membrane, cell wall, and biofilm formation of Aspergillus fumigatus (A. fumigatus). These experiments also demonstrated the impact of ZIF-90 on the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Moreover, the effect of ZIF-90 on mitochondrial reactive oxygen species (mtROS) of cells and fungi was verified by MitoSOX Red Mitochondrial Superoxide Indicator (MitoSOX). In vivo, corneal toxicity test, establishment and treatment of mycotic keratitis mouse model, and immunofluorescence staining were used to evaluate the efficacy of ZIF-90 in the procedure of fungal keratitis. In addition, to investigate whether the metal-ligand zinc and the organic ligand imidazole acted as essential factors in ZIF-90, we investigated the in vitro antimicrobial and anti-inflammatory effects of ZIF-8, ZIF-67 and Metal-Organic Frameworks-74 (Zn) (MOF-74 (Zn)) by Minimum Inhibitory Concentration (MIC) and ELISA experiments.
Results: ZIF-90 has therapeutic effects on fungal keratitis, which could break the protective organelles of A. fumigatus, such as the cell wall. In addition, ZIF-90 can also be targeted to increase the amount of mtROS in fungi and promote apoptosis of macrophages. The results demonstrated that both zinc ions and imidazole possessed antimicrobial and anti-inflammatory effects. In addition, ZIF-90 exhibited better antifungal properties than ZIF-8, ZIF-67, and MOF-74 (Zn).

Keywords: zeolite imidazolate framework, nanomedicine, fungal infection, keratitis