Photodynamic Inactivation of Bacteria and Biofilms with Benzoselenadiazole-Doped Metal-Organic Frameworks

Abstract

Bacterial biofilms are difficult to treat due to their resistance to traditional antibiotics. Although photodynamic therapy (PDT) has made significant progress in biomedical applications, most photosensitizers have poor water solubility and can thus aggregate in hydrophilic environments, leading to the quenching of photosensitizing activity in PDT. Herein, a benzoselenadiazole-containing ligand was designed and synthesized to construct the zirconium (IV)-based benzoselenadiazole-doped metal-organic framework (Se-MOF). Characterizations revealed that Se-MOF is a type of UiO-68 topological framework with regular crystallinity and high porosity. Compared to the MOF without benzoselenadiazole, Se-MOF exhibited a higher ¹O₂ generation efficacy and could effectively kill Staphylococcus aureus bacteria under visible-light irradiation. Importantly, in vitro biofilm experiments confirmed that Se-MOF could efficiently inhibit the formation of bacteria biofilms upon visible-light exposure. This study provides a promising strategy for developing MOF-based PDT agents, facilitating their transformation into clinical photodynamic antibacterial applications.

Keywords: antimicrobial agents; bacteria; biofilms; irradiation; metal-organic frameworks.

Figure 1

Schematic representation of the preparation for Me-MOF and Se-MOF.

Figure 2

SEM images of (A) Me-MOF and (B) Se-MOF. (C) FT−IR spectra of (a) mTCDP-H2, (b) SeTPDC-H2, (c) Me-MOF, and (d) Se-MOF. (D) XRD patterns of the Me-MOF and Se-MOF.

Figure 3

(A) Nitrogen sorption isotherms and (B) Barrett−Joyner−Halenda pore distribution of the Me-MOF and Se-MOF. (C) Excitation spectra (λ_em = 522 nm) and (D) emission spectra (λ_ex = 390 nm) of the Me-MOF and Se-MOF dispersed in DMF. (E) UV−vis absorption spectra of mTPDC-H2 and SeTPDC-H2 in DMF. (F) ESR spectra of a PBS solution (pH 7.4) containing Me-MOF or Se-MOF before and after light irradiation (450 nm, 3 mW cm⁻²).

Figure 4

(A) Representative photographs of S. aureus colonies in LB agar plates after being incubated with different concentrations of Me-MOF or Se-MOF, followed by irradiation three times with a LED light (450 nm, 3 mW cm⁻²) for 20 min or incubation in the dark. (B,C) Percentage viability of bacteria S. aureus after different treatments, followed by light irradiation (B) or incubation in the dark (C). Data are presented as mean ± standard deviation (n = 3; **p < 0.01).

Figure 5

(A) Representative photographs of CV−stained biofilms after being incubated with Me-MOF or Se-MOF, followed by irradiation three times with LED light (450 nm, 3 mW cm⁻²) for 20 min. (B) Quantification of the OD measurement from the CV−stained biofilms in (A). Data are presented as mean ± standard deviation (n = 3; *p < 0.05 and **p < 0.01).