Gradually-frozen aligned bacterial nanocellulose membranes loaded with gallic acid exhibit enhanced mechanical and dual antithrombotic-antimicrobial properties

Bacterial nanocellulose (BNC) is a versatile natural polymer with unique morphological properties. However, its susceptibility to biofouling limits its utility in healthcare. To address this challenge, this study explores the incorporation of gallic acid, a phenolic acid with potent antimicrobial and antithrombotic properties, into BNC membranes. Additionally, a novel drying method termed gradual freezing is introduced, resulting in a directionally-aligned BNC membrane with enhanced mechanical integrity and high porosity. Using glycerol as a solvent and plasticizer, gallic acid was loaded into air-dried BNC (AD-BNC), freeze-dried BNC (FD-BNC), and gradually-frozen BNC (GF-BNC) membranes. Successful drug-loading into FD-BNC and GF-BNC significantly increased the elasticity of the films, however mechanical testing indicated that GF-BNC and its gallic acid/glycerol loaded counterpart (GF-GG-BNC) achieved overall optimal mechanical strength and elasticity. These samples were selected for further antifouling testing. Antibacterial assays demonstrated the practical efficacy of GF-GG-BNC in inhibiting the proliferation and biofilm formation of <i>E. coli</i> and <i>S. aureus</i>, while favorable antithrombotic behaviour prevented clot formation and red blood cell adhesion on the material's surface when compared to GF-BNC membranes. These findings highlight the potential of GF-GG-BNC as a multifunctional biomaterial for the prevention of biofouling in biomedical applications.