Rheological Characterization and 3D Fabrication of Artificial Bacterial Biofilms

Area of Science:

• Biomaterials Science
• Microbiology
• Bioengineering

Background:

• Biofilms contribute to diseases like cancer and respiratory infections, adhering to soft tissues.
• Understanding biofilm development in 3D matrices is crucial for new therapeutics, as 3D biofilms are more treatment-resistant than 2D.
• Current models lack the complexity of natural bacterial communities in soft tissues.

Purpose of the Study:

• To investigate the viscoelastic effects on biofilms within 3D alginate hydrogel environments.
• To explore how varying concentrations of *Salmonella* Typhimurium affect hydrogel rheology and bacterial viability.
• To establish bioprinted 3D biofilm models for studying bacterial interactions and therapeutic screening.

Main Methods:

• Formulation of two alginate-based hydrogels to encapsulate *Salmonella* Typhimurium.
• Rheological analysis to assess hydrogel properties at different bacterial concentrations.
• Extrusion-based bioprinting to create 3D biofilm models and evaluate bacterial viability over time.

Main Results:

• Hydrogels exhibited shear-thinning behavior.
• High bacterial concentrations (1 × 10¹⁰ CFU mL^-1) significantly reduced hydrogel viscosity and modulus.
• Optimal bioprinting parameters maintained high bacterial viability (>80%) over 4 days.
• Lower bacterial concentrations formed larger aggregates compared to higher concentrations.

Conclusions:

• 3D biofilm formation is influenced by initial bacterial density and matrix rigidity.
• Bioprinted 3D models provide insights into bacterial interactions within complex environments.
• Physicochemically tuned bioprinted communities can advance *in vitro* therapeutic screening for biofilm-related diseases.