Diffusion of antibiotics in intervertebral disc.

Area of Science:

• Biomedical Engineering
• Drug Delivery
• Tissue Engineering

Background:

• Delivering charged antibiotics to the intervertebral disc (IVD) is challenging due to its avascular nature and negatively charged extracellular matrix (ECM).
• Understanding antibiotic diffusion is crucial for treating disc infections effectively.

Purpose of the Study:

• To measure the apparent diffusion coefficients of charged antibiotics, vancomycin (positive) and oxacillin (negative), within the IVD.
• To investigate the impact of charge and molecular size on antibiotic transport in the IVD ECM.

Main Methods:

• A one-dimensional steady-state diffusion experiment was conducted using bovine coccygeal annulus fibrosus (AF) tissue.
• The apparent diffusion coefficients of vancomycin and oxacillin were measured under 20% compressive strain.

Main Results:

• Vancomycin's apparent diffusion coefficient was significantly lower (7.94 × 10⁻¹² m²/s) than oxacillin's (2.26 × 10⁻¹⁰ m²/s).
• Slower vancomycin diffusion is attributed to its larger molecular size and potential reversible binding with the negatively charged ECM.

Conclusions:

• Antibiotic charge significantly influences diffusion rates within the IVD ECM.
• Further research is needed to elucidate the precise relationship between antibiotic charge and diffusion coefficients for optimizing treatment strategies.
• This quantitative data is vital for computational modeling to enhance antibiotic delivery for disc infections.