Daylight-driven rechargeable antibacterial and antiviral nanofibrous membranes for bioprotective applications

Abstract

Emerging infectious diseases (EIDs) are a significant burden on global economies and public health. Most present personal protective equipment used to prevent EID transmission and infections is typically devoid of antimicrobial activity. We report on green bioprotective nanofibrous membranes (RNMs) with rechargeable antibacterial and antiviral activities that can effectively produce biocidal reactive oxygen species (ROS) solely driven by the daylight. The premise of the design is that the photoactive RNMs can store the biocidal activity under light irradiation and readily release ROS under dim light or dark conditions, making the biocidal function "always online." The resulting RNMs exhibit integrated properties of fast ROS production, ease of activity storing, long-term durability, robust breathability, interception of fine particles (>99%), and high bactericidal (>99.9999%) and virucidal (>99.999%) efficacy, which enabled to serve as a scalable biocidal layer for protective equipment by providing contact killing against pathogens either in aerosol or in liquid forms. The successful synthesis of these fascinating materials may provide new insights into the development of protection materials in a sustainable, self-recharging, and structurally adaptive form.

Fig. 1. Design, structure, and biocidal function of RNMs.

(A) Chemical structure of BA-RNM, BD-RNM, CA-RNM, and BDCA-RNM. (B) Microscopic architecture of various RNM samples. (C) Optical photograph of the BDCA-RNM sample. (D) Schematic demonstration of the biocidal functions of RNMs by releasing ROS. (E) Jablonski diagrams representing the singlet excitation and following ISC to triplet. (F) Proposed mechanism for the photoactive and photo-storable biocidal cycles.

Fig. 2. Photoactivity and excitation features of the RNMs.

(A to D) Diffuse reflection UV-vis spectra of BA-RNM (A), BD-RNM (B), CA-RNM (C), and BDCA-RNM (D) along with theoretically assigned percentage contributions (>10%) of T₁ orbitals; the acronyms of HOMO and LUMO stand for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively. λ_max is the predicted maximum absorption wavelength. a.u., arbitrary units. (E) Normalized UV-vis spectra of various RNMs samples along with the spectrum of the D65 standard light source. (F and G) Quantification of OH• (F) and H₂O₂ (G) generated by various RNMs samples versus time (irradiation in white and dark periods in gray). (H) Calculated ΔG of RNMH•/³RNM* and RNM/RNMH• transition. The i, ii, iii, iX, and X represent BA-RNM, BD-RNM, CA-RNM, inter–BDCA-RNM, and intra–BDCA-RNM, respectively. (I) ESP-mapped electron density of the ground state and T₁ state of various RNMs samples. The values of δ were the ESP charge on oxygen atoms in the carbonyl group.

Fig. 3. Photo-induced rechargeable biocidal functions of RNMs.

(A to D) UV-vis spectra of BA-RNM (A), BD-RNM (B), CA-RNM (C), and BDCA-RNM (D) under increasing daylight irradiation time. (E) Schematic description of the formation of the DPM and LAT structures. (F) Representative absorbance at 262 (DPM) and 420 nm (LAT) as a function of irradiation time. (G and H) Quantification of OH• (G) and H₂O₂ (H) released by various RNMs under dark conditions after 1 hour of daylight irradiation. (I) Rechargeable capability of BDCA-RNM when repeatedly charging and quenching over seven cycles. (J) FE-SEM images of BDCA-RNM after seven cyclic recharging tests. (K) Change of LAT structure of BDCA-RNM versus storage time.

Fig. 4. Antibacterial and antiviral properties of BDCA-RNM.

(A and B) Bactericidal activity against E. coli and L. innocua of BDCA-RNM under daylight irradiation (A) and charged BDCA-RNM under dark conditions (B). (C and D) Five cycle antibacterial test of BDCA-RNMs under daylight irradiation (C) and charged BDCA-RNMs under dark conditions (D). (E to L) Morphology (E to H) and live/dead bacterial viability assay (I to L) of E. coli and L. innocua cells in contact with control membranes and BDCA-RNM with 1-hour daylight irradiation. (M and N) Measurement of the leakage of nucleic acid (M) and proteins (N) from E. coli and L. innocua cells. (O and P) Biocidal assay against T7 phage for BDCA-RNM under daylight irradiation (O) and charged BDCA-RNM under dark conditions (P).

Fig. 5. Bioprotection performance of BDCA-RNMs.

(A) Filtration efficiency and pressure drop of BDCA-RNM as a function of airflow. (B) SEM images of the top and bottom surface of BDCA-RNM after filtration (airflow of 90 liter min⁻¹, testing for 5 min). (C) QF values of selected fibrous filter materials with various basis weights. (D) Bacterial aerosol generation apparatus and the interception test by N100 mask. (E and F) Three selected test areas on the mask (E) and the relevant CFU count of E. coli (F). (G) Photograph showing the protective suit was loaded with T7 phage. (H and I) Three selected test areas on the protective suit (H) and the relevant PFU count of T7 phages (I).