Fig. 2

Evaluation of SERS metabolic indicators for hUC-MSC expansion. a The mean SERS spectra of all hUC-MSC lysates (cell lysate) and the standard SERS spectra (STD) of pure metabolite solutions (cysteine, guanine, uracil and adenine). The characteristic peaks of the metabolites are exhibited by colored arrows. The coefficients of b cysteine, c uracil, d adenine and e guanine obtained by decomposing the lysate SERS spectra of C1 hUC-MSCs at different generations. The data are displayed by the mean value from three biological replicates (blue, yellow and red) with the error bar indicating the standard deviation (n = 3 technical replicates). f t-SNE visualization of the metabolic coefficients of C1 hUC-MSC lysates. For each cell generation, there are 9 datapoints obtained from three biological replicates, each being measured three times. The changes of SERS peak intensities at g 877 and h 1459 cm⁻¹ along the expansion (from P2 to P10) of three replicates of C1 hUC-MSCs. The SERS bands of 877 and 1459 cm⁻¹ are pointed out by black circles in panel a.