The 3D-printed bioactive ceramic incorporated Poly(ε-caprolactone) (PCL) scaffolds show great promise as synthetic bone graft substitutes. However, 3D-printed scaffolds still lack adequate surface properties for cells to be attached to them. In this study, we modified the surface characteristics of 3D-printed poly(ε-caprolactone)/hydroxyapatite scaffolds using O2 plasma and sodium hydroxide. The surface property of the alkaline hydrolyzed and O2 plasma-treated PCL/HA scaffolds were evaluated using field-emission scanning microscopy (FE-SEM), Alizarin Red S (ARS) staining, and water contact angle analysis, respectively. The in vitro behavior of the scaffolds was investigated using human dental pulp-derived stem cells (hDPSCs). Cell proliferation of hDPSCs on the scaffolds was evaluated via immunocytochemistry (ICC) and water-soluble tetrazolium salt (WST-1) assay. Osteogenic differentiation of hDPSCs on the scaffolds was further investigated using ARS staining and Western blot analysis. The result of this study shows that alkaline treatment is beneficial for exposing hydroxyapatite particles embedded in the scaffolds compared to O2 plasma treatment, which promotes cell proliferation and differentiation of hDPSCs.

Endoscopic submucosal dissection (ESD) is a surgical procedure to remove early neoplastic lesions in the gastrointestinal tract with the critical issue of perforation. A submucosal fluid cushion, such as normal saline, is used as a cushioning agent to prevent perforation; however, its cushioning maintenance is insufficient for surgery. In this study, we introduce an injectable thermosensitive chitosan solution (CS) with β-glycerophosphate (β-GP) as a submucosal injection agent for ESD. The CS/β-GP system with optimal β-GP concentration showed drastic viscosity change near body temperature while other commercial products did not. Additionally, the injectability of the solution was similar to or greater than other commercial products. The solution with low β-GP concentration showed low cytotoxicity similar to other products. An in vivo preclinical study illustrated maintenance of the high cushioning of the thermosensitive solutions. These results indicate that a CS/β-GP system with optimal β-GP concentration might be used as a submucosal injection agent in ESD, and further studies are needed to validate the effectiveness of the solutions in vivo.

Injectable thermo-sensitive chitosan hydrogels have recently been developed for the use of submucosal fluids in endoscopic submucosal dissections (ESD). This study aimed to investigate the efficacy and safety of chitosan hydrogels during ESD. Submucosal fluids were administered as follows: 0.9% normal saline (NS), 0.4% hyaluronic acid (HA) and chitosan/β-glycerophosphate (CS/GP) hydrogel. Each solution was administered twice into the stomach and colon of a pig, with a total of 72 ESD procedures performed on 12 pigs. The injected volume and procedure-related parameters were recorded and analyzed. ESDs that created ulcers after 7 days were histologically compared. All ESD specimens were resected en bloc. The total injected volumes during ESD of the stomach (NS, 16.09±3.27 vs. HA, 11.17±2.32 vs. CS/GP, 9.44±2.33; p<0.001) and colon (NS, 9.17±1.80 vs. HA, 6.67±1.50 vs. CS/GP, 6.75±1.57; p = 0.001) were significantly different. Hydrogel showed significant differences from normal saline in terms of fluid power (mm²/vol; NS, 35.70±9.00 vs. CS/GP 57.48±20.77; p = 0.001) and consumption rate (vol/min; NS, 2.59±0.86 vs. CS/GP, 1.62±0.65; p = 0.013) in the stomach. Histological examination revealed preserved muscularis propria, although the chitosan hydrogel resulted in a partial inflammatory response, with a hypertrophied submucosal layer. Chitosan hydrogel was found to be superior to normal saline, with an efficacy similar to that of hyaluronic acid. Nonetheless, long-term histological changes should be evaluated before clinical implementation.

The use of bone graft materials is required for the treatment of bone defects damaged beyond the critical defect; therefore, injectable calcium phosphate cement (CPC) is actively used after surgery. The application of various polymers to improve injectability, mechanical strength, and biological function of injection-type CPC is encouraged. We previously developed a chitosan–PEG conjugate (CS/PEG) by a sulfur (VI) fluoride exchange reaction, and the resulting chitosan derivative showed high solubility at a neutral pH. We have demonstrated the CPC incorporated with a poly (ethylene glycol) (PEG)-grafted chitosan (CS/PEG) and developed CS/PEG CPC. The characterization of CS/PEG CPC was conducted using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The initial properties of CS/PEG CPCs, such as the pH, porosity, mechanical strength, zeta potential, and in vitro biocompatibility using the WST-1 assay, were also investigated. Moreover, osteocompatibility of CS/PEG CPCs was carried out via Alizarin Red S staining, immunocytochemistry, and Western blot analysis. CS/PEG CPC has enhanced mechanical strength compared to CPC, and the cohesion test also demonstrated in vivo stability. Furthermore, we determined whether CS/PEG CPC is a suitable candidate for promoting the osteogenic ability of Dental Pulp Stem Cells (DPSC). The elution of CS/PEG CPC entraps more calcium ion than CPC, as confirmed through the zeta potential test. Accordingly, the ion trapping effect of CS/PEG is considered to have played a role in promoting osteogenic differentiation of DPSCs. The results strongly suggested that CS/PEG could be used as suitable additives for improving osteogenic induction of bone substitute materials.