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Tissue engineers rely on expensive, time-consuming, and destructive techniques to monitor the composition and function of engineered tissue equivalents. A non-destructive solution to monitor tissue quality and maturation would greatly reduce costs and accelerate the development of tissue-engineered products. A label-free multimodal system combining fluorescence lifetime imaging (FLIm) and optical coherence tomography (OCT) via a single fiber-optic interface was used for evaluation of biochemical and structural properties of tissue-engineered articular cartilage in a murine model of cartilage maturation. Nude mice (n=5) received 2 dorsal subcutaneous tissue-engineered cartilage implants each consisting of: 1) latent transforming growth factor-beta1 (LAP) treated; and 2) untreated control (CTL) constructs. At 6 weeks post-implantation, mice were sacrificed and multimodal imaging was performed in situ. FLIm showed clear delineation of the implant in all spectral bands (SB). Quantification of the cartilage construct fluorescence lifetime (LT) showed a lower LT in SB-1 (375-410 nm) and higher SB-3 LT (515-565 nm) as compared to the surrounding muscle tissue. Comparison between treatment groups showed a significant increase in FLIm SB-3 LT in LAP-treated constructs over CTL (p < 0.01). Quantification of OCT images allowed implant morphology and 3D volume comparisons between treatment groups. These results suggest that FLIm-OCT based tools are a potential non-destructive method for quantitatively monitoring the growth and quality of tissue engineered articular cartilage. The use of optical techniques to monitor maturation could represent a significant element in reducing costs in research, meeting the FDA regulatory requirements for manufacturing, and providing novel diagnostic tools in the clinic.
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