Fig. 6. Identification plots for the PLS-DA model of Raman spectra from (a) THP-1, (b) M0, (c) M1–M2, and (d) M2 cells within soft gelMA hydrogels. Cells located above the red dashed line that represents the classification threshold for each plot were identified as (a) THP-1 cells ( and , n_model = 61, n_test = 60), (b) M0 cells ( and , n_model = 40, n_test = 39), (c) M1–M2 cells ( and , n_model = 21, n_test = 21), and (d) M2 cells ( and , n_model = 21, n_test = 21). VIP score plots for (e) THP-1 cells, (f) M0 cells, (g) M1–M2 cells, and (h) M2 cells. Assignments of labeled peaks: 743 cm⁻¹ (DNA and tryptophan), 788 cm⁻¹ (phosphodiester bonds in DNA), 960 cm⁻¹ (unidentified), 981 cm⁻¹ (proteins), 1013 cm⁻¹ (tryptophan), 1302 cm⁻¹ (collagen and lipids), 1309 cm⁻¹ (collagen and lipids), 1422 cm⁻¹ (DNA/RNA), 1441 cm⁻¹ (lipids), and 1657 cm⁻¹ (lipids, protein, and DNA/RNA).