Figure is a Scanning Electron Microscopic (SEM) view of the composite (PCL + dECM) fibers, and Figure shows the fiber diameter distribution. As shown in Figure in the Supplementary Information, fibers were deposited onto a polystyrene (PS) sheet with precut holes. After electrospinning, the sheet with fibers was laser-cut again around the outside of each hole to generate circular inserts. What remained was a PS ring with a layer of nanofibers on top, fused by the heat generated from the laser cutting. A total of 38 dECM inserts could be prepared in one electrospinning session, which enhanced efficiency and enabled experiments to be conducted on inserts from the same batch, reducing possible variations. Figure compares two inserts: PCL-only fibers (left) and PCL + dECM fibers (right). The inserts were incubated with Picrosirius red, a common dye in histology to stain collagen . After thorough rinsing, the dECM insert remained red, compared to the PCL-only fibers which were white. Because Picrosirius red is moderately fluorescent , we scanned the inserts with a plate reader and observed fluorescent signal heatmaps on the fibers with dECM (bottom panel of Figure ). Further, Figure shows fluorescent microscopic views of the composite (PCL + dECM) fibers stained with Picrosirius red, and Figure shows staining by collagen I antibodies conjugated with CoraLite 488 of the composite fibers. Moreover, Fourier Transform Infrared (FTIR) spectroscopy was conducted over the fiber layers. As shown in Figure , plain PCL fibers showed clusters of peaks between 1000-1200 cm -1 and 1400-1500 cm -1 , mainly corresponding to -C-O stretching and -C-H bending in PCL. However, with the inclusion of the dECM in the electrospinning solution, the resulting fibers showed a broad FTIR peak above 3000 cm -1 (arrow), a typical signal of -OH groups. New peaks at 1540 cm -1 and 1640 cm -1 strongly indicate secondary amide (peptide bonds; inset of Figure ).