Determination of oxygen gradients in engineered tissue using a fluorescent sensor

Area of Science:

• Biomedical Engineering
• Tissue Engineering
• Cell Biology

Background:

• Adequate nutrient and oxygen supply is critical for successful tissue engineering.
• Previous oxygen measurement techniques were limited in resolution and invasiveness.
• Understanding oxygen gradients is essential for optimizing engineered tissue development.

Purpose of the Study:

• To develop and apply a noninvasive, high-resolution method for measuring oxygen partial pressure (pO(2)) in cultivated tissues.
• To analyze oxygen gradients and their impact on tissue development over a 3-week culture period.
• To correlate oxygen levels with histological findings in cartilage explants and engineered cartilage.

Main Methods:

• Utilized time-resolved pO(2) sensing with optical sensor foils containing luminescent O(2)-sensitive indicator dyes.
• Immobilized cylindrical tissue samples (cartilage explants and engineered cartilage) on sensor foils.
• Measured luminescence decay time to determine two-dimensional pO(2) distributions across tissue cross-sections.

Main Results:

• Demonstrated continuous, noninvasive, high-resolution pO(2) monitoring over 3 weeks.
• Observed monotonously decreasing pO(2) gradients from tissue surface to center, with nearly anoxic conditions (~0 Torr) in engineered constructs after 1 day.
• Identified a critical pO(2) threshold of approximately 11 Torr below which proper cartilage development was impaired, correlating with a maximum development depth of ~1.3 mm.

Conclusions:

• The developed method precisely assesses oxygen demand in cartilage cultures.
• Oxygen supply is significantly influenced by cell density and function.
• Maintaining adequate oxygen levels is crucial for achieving functional engineered tissues, particularly cartilage.