## 4 Conclusions  
This paper presents the development of a fibrous scaffold material coated with type I collagen, designated as PET-COL, utilizing PET polyester fiber as its fundamental scaffolding component. The manufacturing process encompasses the carboxylation of the PET surface, activation and crosslinking facilitated by EDC/NHS, and the subsequent coupling of collagen. Furthermore, this article delves into the characterization of the material's physicochemical properties and biological effects, with the ultimate goal of verifying its potential utility in artificial liver support systems. The obtained results indicate the following:  
* FTIR analysis revealed that PET-COL displays characteristic absorption peaks of type I collagen, specifically Amid II at 1550 cm\({}^{-1}\), Amid I at 1665 cm\({}^{-1}\), and Amid A at 3330 cm\({}^{-1}\). Concurrently, the nitrogen content on the material surface amounted to 17.36%. The application of a collagen coating significantly enhanced the hydrophilicity of the material, resulting in a decrease in the water contact angle of the PET-COL scaffold from 132.97\({}^{\circ}\) to 74.74\({}^{\circ}\) (\(p<\) 0.001). Utilizing second harmonic generation microscopy, we visually observed the presence of a green fluorescent signal emanating from the collagen on the PET-COL surface. Furthermore, HPLC-MS analysis confirmed a collagen coating content of 33.30 \(\mathrm{\SIUnitSymbolMicro g}\)/piece;
* The biological efficacy of the material was assessed through in vitro cell culture experiments. The outcomes indicated a substantial proliferation of HepaRG cells on the PET-COL substrate. Notably, cell viability, albumin secretion, urea synthesis, and CYP3A4 and CPS1 expression were markedly elevated compared to the untreated group (\(p<\) 0.001), highlighting robust biological activity. These observations implicate that the application of a collagen coating has the potential to augment the biocompatibility of PET materials, thereby facilitating cell adhesion and proliferation.  
The present study integrated the stability inherent in synthetic polymer materials with the excellent biocompatibility of natural polymers, aiming to create a composite hepatocyte culture scaffold featuring a fiber structure. This scaffold promotes cell adhesion, proliferation, and differentiation, thus serving as an ideal substrate for hepatocytes cultured in bioreactors and being a promising candidate for application in bioartificial livers.  
Figure 10: Cell function of HepaRG cells growing on PET and PET-COL fibers on day 1, day 3, day 5, and day 8. (**A**) Albumin secretion; (**B**) BUN synthesis; (**C**) CYP3A4 expression; (**D**) CPS1 expression. Data are mean \(\pm\) SD, n = 3; *: \(p<\) 0.05; ***: \(p<\) 0.001.  
**Author Contributions:** Conceptualization, Y.L.; Methodology, G.Z.; Validation, S.L.; Investigation, Y.Z. and J.G.; Writing--original draft, Y.L.; Writing--review and editing, G.Z.; Supervision, Y.Z. and S.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the National Key R&D Program of China (2022 YFA1104900), the National Natural Science Foundation of China (31972926).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
**Acknowledgments:** The authors would like to thank the institute of Process Engineering, Chinese Academy of Sciences, for creating the research infrastructure.  
**Conflicts of Interest:** The authors declare no conflicts of interest.