## 2 Materials and Methods
### Cell Adhesion, Morphology and Intracellular Structures in Real-Time  
hDPSCs adhesion, morphology and subcellular structure were observed in real-time through live-cell imaging with holotomographic microscopy (HTM) as previously reported [17]. For cellular morphology, hDPSCs at passage 4 were seeded onto NTAPP-treated dish (FluoroDish, World Precision Instrument, Sarasota, FL, USA) and incubated for 24 h. For cellular adhesion, hDPSCs at passage 4 were seeded (5.0 \(\times\) 10\({}^{2}\) cells/slice) on dentin that had either been treated with NaOCl and EDTA alone (controls), or with NaOCl and EDTA followed by NTAPP (plasma-treated). HTM was performed with 3D Cell Explorer-fluo (Nanolive, Ecublens, Switzerland) using 60\(\times\) air objective (NA = 0.8), wavelength (\(\lambda\)) of 520 nm (class 1 low power laser, sample exposure 0.2 mW/mm\({}^{2}\)), and USB 3.0 CMOS Sony IMX174 sensor, with quantum efficiency (typical) 70% (at 545 nm), dark noise (typical) 6.6 e', dynamic range (typical) 73.7 dB, field of view 90 \(\times\) 90 \(\times\) 30 \(\upmu\)m, axial resolution 400 nm, and maximum temporal resolution 0.5 3D RI volume per second. Physiological conditions for live cell imaging were attained with a top-stage incubator (Ok  
Figure 1: Schematic diagram of experimental setup with air plasma jet system (**left**) and the optical emission spectrum. (**right**). The spectrum is dominated by emissions from the second positive system (SPS) of molecular nitrogen (N\({}_{2}\) at 315–400 nm), the first negative system (FNS) of N\({}_{2}\)\({}^{+}\) (391–427 nm), and atomic oxygen (777 and 844 nm).  
lab, Pozzuoli, Italy), and temperature (37 \({}^{\circ}\)C), humidity and CO\({}_{2}\) (5%) were maintained throughout image acquisitions.  
An export was performed within the STEVE software, which controls the HTM microscope, to transform RI volumes into.tiff format. By doing so, RI volumes can be read by the FIJI program. The exported 3D.tiff files must be in float format to keep the explicit RI for each voxel value. The 3D RI volumes in.tiff format were then processed in batch within FIJI for performance purposes. Then 3D RI volumes were transformed into 2D RI maps using maximum intensity projections and were also saved as.tiff files. The resulting series of 2D frames could then be processed using CP3, which does not support full 3D data analysis yet. The CP3 pipeline was designed to load each 2D RI map, segment the contained objects using the primary objects detection module, and extract area, shape, and intensity features using the measurements modules. A critical point for proper object detection was to use a manual threshold value. The object size limits that we entered were designed to encompass the full spectrum of potential lipid droplet diameters from 1 to 5 pixels. The segmented objects were finally used to extract the area and the mean RI value of each lipid droplet in each frame of the time-lapse experiment. The data were exported as a.csv file, in which we used the extracted count, spherical volume, and surface area of lipid droplets [18].  
Real-time changes of hDPSCs behaviors around NTAPP-treated dentin were observed. Dentin slice was trimmed to thickness of 0.05 mm for visualization under Nanolive. Pre-treated dentin slices with 1.5% NaOCl and 17% EDTA as aforementioned served as control. Cellular attraction and attachment images were acquired at 2 h interval until 8 h after thawing.