Innovative TCSPC-SHG microscopy imaging to monitor matrix collagen neo-synthetized in bioscaffolds.

We propose an innovative invasiveless technique in the field of nonlinear optical imaging to facilitate monitoring of cell/scaffold combinations for tissue repair. By using a near infrared (NIR) femtosecond excitation, we were able to introduce a new index based on decay time response for fluorescence (F) and Second Harmonic Generation (SHG) obtained with Time Correlated Single Photon Counting (TCSPC) microscopy to monitor structural information on the state of the matrix collagen. Some human Mesenchymal Stem Cells (hMSCs) seeded in 3D scaffolds were tested with different culture times (from D7 to D56) to analyze the effect of Tumor Growth Factor beta 1 (TGF-ß1) on type-2 collagen expression in the matrix. After 14 days in the presence of TGF-ß1, our results showed an increase in the expression of type-2 collagen synthesized by hMSCs, and a change in collagen conformation, as an indication of its ability to be detected as a harmonophore by TCSPC-SHG without the need for an exogenous probe.