Optical coherence tomography for tissue engineering

In tissue engineering, microporous scaffolds are commonly used to promote cell proliferation and differentiation in 3-dimensional structures, where conventional microscopy is inappropriate. A systematic classification of the type and range of parameters affecting tissue growth is hindered by tedious protocols and time-consuming analysis involving sample sacrifices at different time points. To achieve a better understanding and to optimize the engineering of the tissues, we develop non invasive techniques together with computer models to monitor and describe the different stages of tissue engineering: cell seeding, cell growth, cell differentiation, extra-cellular matrix (ECM) deposition, matrix turn-over and tissue organization.

Optical coherence tomography (OCT) is established as a powerful tool in developmental biology to investigate the microstructure of tissue without fluorescent labelling. Within a typical penetration depth in tissue of 2 mm, OCT reconstructs from the backscattered intensity an image comparable to a histology section with a typical resolution of 10 μm for 1300 nm super-luminescent sources. Near-infrared light is used for better penetration in the tissue. OCT image contrast depends on scattering and absorption (low at this wavelength) properties of the sample. Substantial contrast exists between biological components or between scaffold materials and biological components; so no external labelling is needed. As a result, the technique is non-invasive and fast, which allows rapid on-line monitoring of the sample. Continuing development of swept source promises higher resolution and acquisition speed. Typically, video-rate imaging is achieved with xyz resolutions of (12 μm x 12 μm x 9 μm).

Interferometric ‘A’ scan and the envelope used to reconstruct the signal. Phase information is exploited for polarization sensitive OCT and doppler OCT
Interferometric ‘A’ scan and the envelope used to reconstruct the signal. Phase information is exploited for polarization sensitive OCT and doppler OCT