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

Abstract

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 E. coli and S. aureus, 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.