Composite fibrin sealant reinforced with halloysite nanotubes

We investigated a fibrinogen–thrombin bicomponent formulation in 0.9% NaCl and reinforced with halloysite nanotubes (HNTs) at 0.7% and 1.4% (w/w). Oscillatory rheology (strain and time sweeps) shows progressive stiffening with HNTs: the storage modulus increases from up to 681 Pa whilst tan δ remains ≤ 0.21, indicating solid-like behavior under wet conditions. The linear viscoelastic region (LVER) as well as large-deformation crossover showed HNTs content dependence. Fluorescence microscopy evidences fibrin clustering with HNTs, and uniform gel filling of nanotubes acting as anchoring sites, producing isotropic densification rather than aligned bundling. TGA confirms the presence of halloysite and thermal stabilization. Finally, 0.7% HNTs provides a balanced increase in stiffness and LVER; 1.4% HNTs maximizes stiffness but reduces large-strain tolerance. These findings demonstrate that halloysite nanotubes effectively tailor the rheological and microstructural properties of fibrin-based composites. The present work establishes a proof-of-concept for the use of halloysite nanotubes as nanostructured reinforcing additives in fibrin systems, while future biological, adhesion, and hemostatic studies will be required to assess their biomedical performance.