Pulmonary Injury Induced via Metal-Organic Frameworks (MOFs): ROS Generation and Inflammatory Responses Mediated by HKUST-1

Abstract

Owing to their tunable structural and functional characteristics, innovative materials known as metal-organic frameworks (MOFs) have become a research focus in scientific communities, demonstrating significant potential across biomedical applications, including targeted drug delivery, tumor detection technologies, and sophisticated medical imaging diagnostics. Despite the growing interest in their therapeutic potential, the systemic and pulmonary toxicity of MOFs remains inadequately explored, particularly about the long-term effects of metal ion release during degradation. This study investigates the pulmonary toxicity of three widely studied MOFs, UiO-66, ZIF-8, and HKUST-1, focusing on the mechanisms of oxidative stress and inflammation. The in vitro and in vivo assays demonstrated that HKUST-1 induced significant cytotoxicity, oxidative stress, and apoptosis in lung cells, primarily due to its copper content. In contrast, UiO-66 and ZIF-8 exhibited minimal toxicity. These results emphasize the essential requirement for understanding the toxicological profiles of MOFs and highlight the necessity of modifying their structure to enhance safety for biomedical applications.

Figure 1

Characterization of UiO-66, ZIF-8, and HKUST-1. (A) TEM of UiO-66, ZIF-8, and HKUST-1. Scale bar: 200 nm. (B) SEM of UiO-66, ZIF-8, and HKUST-1. Scale bar: 300 nm.

Figure 2

(A) XRD of UiO-66, ZIF-8, and HKUST-1. (B) FTIR of UiO-66, ZIF-8, and HKUST-1. (C) N₂ adsorption and desorption isotherms of UiO-66, ZIF-8, and HKUST-1.

Figure 3

(A) Zr, Zn, and Cu content in BEAS-2B after different times (6, 12, and 24 h). (B) Morphological alterations of BEAS-2B cells after overnight treatment with different MOFs. Scale bar: 50 μm. (C–E) Cell viability of UiO-66 at various treatment times (6, 12, and 24 h). (F–H) Cell viability of ZIF-8 following exposure at various treatment (6, 12, and 24 h). (I–K) Cell viability of HKUST-1 after varying treatment durations (6, 12, and 24 h).

Figure 4

(A) The concentration of Ca²⁺ in BEAS-2B cells was assessed following coincubation with UiO-66, ZIF-8, and HKUST-1 using Fluo-4 AM. (B)The mean fluorescence intensity (MFI) corresponding to Ca²⁺ concentrations was measured in BEAS-2B cells after exposure to UiO-66, ZIF-8, and HKUST-1. (C) ROS levels in BEAS-2B cells were quantified after coincubation with UiO-66, ZIF-8, and HKUST-1 using DCFH-DA. (D) ROS MFI in BEAS-2B cells was evaluated following coincubation with UiO-66, ZIF-8, and HKUST-1. (E,F) Apoptosis rates in BEAS-2B cells were determined after coincubation with UiO-66, ZIF-8, and HKUST-1. Scale bar: 50 μm. *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 5

(A) Bcl-2, (B) IL-1β, (C) TGF-β, and (D) TNF-α expression profiles in BEAS-2B cells cocultured with UiO-66, ZIF-8, and HKUST-1. Western blot of (E) P53, (F) Bax, and (G) clv-Caspase-3 expression levels after cocultured with UiO-66, ZIF-8, and HKUST-1.

Figure 6

(A) Histopathological evaluation of lung tissue architecture (H&E staining) following 14-day exposure to UiO-66, ZIF-8, and HKUST-1 nanoparticles, with baseline controls (0-day). Scale: 200 μm. (B) Collagen deposition analysis via Masson’s trichrome staining in corresponding treatment groups. Scale: 200 μm. (C–F) Fibrosis-associated protein mapping: (C) caspase-9 activation, (D) Smad3 nuclear translocation, (E) collagen I, and (F) collagen III distribution patterns by confocal immunofluorescence in HKUST-1-treated pulmonary sections at indicated time points.