Sustainable Antibacterial Electrospun Fibers and Textures Using Hydrophobic Polymers

Filters play a vital role in purification systems by removing harmful impurities and moisture from air within closed environments. Currently, non-woven fabrics made from various polymers are the standard for air filtration, designed to block pollutants, absorb odors and gases and prevent bacteria and allergens. Sustainable solutions are focusing on materials with intrinsic bactericidal properties (chemical action) and antifouling surface designs (physical action) that prevent bacterial adhesion and fouling. These approaches often involve low-energy surfaces, steric repulsion mechanisms, or superhydrophobic structures to repel contaminants.
Antimicrobial and antifouling technologies are particularly appealing as they reduce reliance on chemicals, lowering health risks and resistance concerns. Developing eco-friendly, non-toxic materials with these properties is crucial for modern filtration.
Our recent research focused on the evaluation of poly(alkylene furanoates) (PAFs). These polymer family is the bio-based and best performing alternative to petroleum-based poly(ethylene terephthalate) (PET).
We synthesized 4 different PAFs aimed to enhance the material hydrophobicity: Poly(butylene 2,5-furanoate) (PBF; M_w: 87600), Poly(2 ethyl-2 butyl-1,3-propylene furanoate) (PBEF; M_w: 60000) homopolyesters, and two copolymers. The first was a random copolymers of poly(hexamethylene 2,5-furanoate) containing Pripol moiety (P(HF₈₀-r-HPripol₂₀) (PHF-HPrip; M_w: 124000)). The latter was a copolyesterammide of poly(butylene 2,5-furanoate) containing Priamine [P(BF70-r-PriamineF30) (PHF-Priam; M_w: 9900)]. The polymers were processed via electrospinning using Hexafluoro Isopropanol (HFIP) as a solvent. The obtained fibrous meshes were characterized by Scanning Electron Microscopy (SEM), and water contact angle was measured to evaluate surface wettability; subsequently, they were incubated with E. coli ATCC25922 and evaluation of adhesion/growth after 24 h was performed by SEM imaging. Electrospun fibers were obtained from all the PAF polymers, except from PHF-Priam. PBEF gave rise to beaded fibers. PBF was a good substrate for bacterial growth; differently, the other PAF-based copolymers revealed the presence of highly damaged bacteria. The best results, in terms of fiber morphology and bacterial damage were so far obtained using PHF-HPrip.
As a strategy to obtain superhydrophobic surfaces, we developed and validated layer-by-layer electrospun fiber deposition of a commercial hydrophobic polymer [poly(vinylidene fluoride-co-trifluoro ethylene) P(VDF-TrFE)], used as a model. We obtained fibers with controlled orientations leading to antifouling surfaces due to enhanced hydrophobicity. The 10-layer surface morphology at 90°-layer orientation was able to efficiently prevent adhesion of E. coli and P. aeruginosa by establishing a superhydrophobic-like behavior compatible with the Cassie-Baxter regimen. Moreover, the results highlighted that surface wettability and bacteria adhesion could be controlled using fibers with diameter comparable to bacteria size and by tuning the intra-fiber spacing, with relevant implications in the future design of surface coatings.
Having bio-based hydrophobic polymers, such as PAFs, and developing specific textures could be effective in promoting antibacterial air filters.

Funded by HORIZON JU Research and Innovation Actions, FURIOUS project, G.A. 101112541.