Electrospinning Machine| Covalent binding of Vitamin K3 photosensitizers to nanofibrous membranes for daylight-driven antimicrobial applications

The continuous spread of the COVID-19 pandemic fully demonstrates the severe threat of infectious diseases caused by pathogenic microorganisms to global public health security. In pandemic control, medical personnel rely on personal protective equipment (PPE) such as medical masks and protective clothing as primary means of protection. However, these traditional PPE only reduce infection risk through physical barriers, while long-term survival of pathogens on PPE surfaces increases cross-infection risk. Therefore, endowing PPE with efficient antibacterial functions has become an ideal solution to reduce pathogen infection. Existing technologies mainly achieve this by adding antimicrobial agents, but these agents gradually deactivate due to irreversible chemical reactions. Although studies show that photosensitizers can continuously produce reactive oxygen species (ROS) under specific light for antibacterial purposes, their weak interaction with matrix materials may lead to leaching during long-term use, reducing photobactericidal efficiency. Based on this, developing a novel PPE material with stable daylight-driven antibacterial function by chemically bonding photosensitizers is of significant clinical value and application prospects.

Recently, Associate Professor Ma Yue's team from the University of Shanghai for Science and Technology published their latest research titled "Covalent binding of Vitamin K3 photosensitizers to nanofibrous membranes for daylight-driven antimicrobial applications" in the journal Chemical Engineering Journal. The researchers designed and synthesized a daylight-driven antibacterial nanofibrous membrane by covalently grafting photosensitizer VK3 onto an EVOH nanofibrous membrane. The resulting VK3-EVOH membrane rapidly generates ROS (OH· = 17.6 μmol g⁻¹ h⁻¹; H₂O₂ = 17.8 μmol g⁻¹ h⁻¹; ¹O₂ = 13.6 μmol g⁻¹ h⁻¹), demonstrating broad-spectrum antibacterial activity and high antibacterial efficiency. Furthermore, the developed VK3-EVOH nanofibrous membrane exhibits effective contact-killing properties against both aerosol and liquid-transmitted pathogens, showing potential for application in masks and protective clothing.

Fig. 1: Preparation and characterization of VK3-EVOH nanofibrous membrane.

By epoxidizing VK3 to VK3O and covalently grafting it onto an electrospun EVOH nanofibrous membrane (Fig. 1a). SEM images showed that the average fiber diameter increased from 440 nm to approximately 500 nm after grafting, but the porous structure of the membrane was preserved, ensuring the breathability and ROS generation capacity of VK3-EVOH. Overall, the preparation process of this nanofibrous membrane is simple, the modification procedure is straightforward, and it uses readily available electrospinning substrates, demonstrating potential for scalable production (Fig. 1b). FT-IR and XPS spectra confirmed the formation of C-O-C ether bonds and C=O from naphthoquinone rings, verifying the successful grafting of photosensitizer VK3 onto the EVOH nanofibrous membrane (Fig. 1c, 1d, 1e, 1f).

Fig. 2: Mechanism of ROS generation by VK3-EVOH nanofibrous membrane.

Fig. 3: Type I and Type II photoreactions and ROS generation of VK3-EVOH nanofibrous membrane.

 As shown in Fig. 2, ROS generation by the VK3-EVOH nanofibrous membrane follows the mechanism described by the Jablonski diagram (Fig. 2b). The photoreaction excitation process mainly involves excitation to S₈ and S₆ states (singlet) followed by intersystem crossing to T₁ (triplet) to generate ROS (Fig. 2c), primarily through n HOMO to π* LUMO energy level transitions (Fig. 2d). Electron density analysis via electrostatic potential (ESP) mapping confirmed that the triplet state VK3-EVOH has stronger oxidative ability than the singlet state (Fig. 2e). After transitioning to the triplet state, the ESP charge (σ) of the carbonyl oxygen near the EVOH skeleton increased from -0.477 to -0.401, while that near the hydroxyl end decreased from -0.484 to -0.519. The overall enhancement in oxidative capacity makes triplet-state VK3-EVOH more likely to participate in oxidation reactions such as hydrogen abstraction or electron transfer, thereby promoting ROS generation. Fig. 3 shows that Type I and Type II photoreactions for ROS generation occur spontaneously, with continuous ROS production (OH· = 17.6 μmol g⁻¹ h⁻¹; H₂O₂ = 17.8 μmol g⁻¹ h⁻¹; ¹O₂ = 13.6 μmol g⁻¹ h⁻¹). 

Fig. 4: Antibacterial performance and mechanism of VK3-EVOH nanofibrous membrane.

Fig. 5: Medical protection applications of VK3-EVOH nanofibrous membrane.

Additionally, the prepared VK3-EVOH nanofibrous membrane exhibited sustained antibacterial efficiency with or without COD. The excellent continuous antibacterial performance makes the VK3-EVOH nanofibrous membrane a potential novel PPE material. Thus, VK3-EVOH can serve as an efficient antibacterial surface protection layer integrated into conventional PPE, providing strong biological protection against various aerosol and liquid-transmitted pathogens.

Paper link: https://doi.org/10.1016/j.cej.2025.166068