Study On On-line Evaluation Of Three-dimensional Bio-printed Hydrogel Scaffolds By Optical Coherence Tomography

Tissue engineering combines the principles of engineering and life sciences to providesubstitutes that can restore, maintain or augment tissue function. A critical tool in tissue engineeringis the three-dimensional porous scaffolds that can act as the substrates for cell adhesion andproliferation and thus facilitate the formation of new tissue. The combined potential of hydrogelsand rapid prototyping technologies has been an exciting route in developing tissue engineeringscaffolds. The good biocompatibility, biodegradable and hydrophilic of hydrogels make themespecially appealing for repairing and regenerating soft tissue. Rapid prototyping techniques on theother hand, have become an elegant tool for the production of scaffolds with the purpose of cellseeding and/or cell encapsulation, especially the emerging3D bio-printer. Three-dimensionalarchitecture with fully connection, according to the predesigned size and porosity, can be easilyconstructed using3D bio-printer. Hydrogels and3D bio-printing technology has various advavtagesin fabricating scaffolds. However, actually it’s difficult to produced scaffolds are the same aspredesigned structure because of the poor mechanical property of hydrogels. The internal structuralfeatures can directly affect cells behaviors such as migration and proliferation so that eventuallyaffect the function of engineered tissues or organs. Therefore, for3D-printing hydrogel scaffolds,evaluation and quantitative characterization in vivo of internal structure becomes essential.However, hydrogels with high water have highly light scattering, and it’s very difficult to monitorand evaluate the internal structure of3D-printed hydrogel scaffolds.Based on the above, several typical three-dimensional hydrogel scaffolds were fabricated using3D bio-printing technology. And swept-source OCT system, which was made in our laboratory, wasapplied to sterile and quantitative characterization of the gelatin and sodium alginate derivedhydrogel scaffolds in vivo. The three-dimensional high resolution images of hydrogel scaffoldsshowed that the imaging range was5mm×5mm×5mm, imaging resolution was12um×12um×10um (X×Y×Z), and time capturing a3D high resolution image was5.52s. Based on the acquiredhigh resolution3D OCT images, automatic image processing and analysis algorithms, includingVolume rendering,2D en-face information extraction, filtering, Image enhancing, Imagesegmentation, Image morphology operation and3D labeling, were used to quantitatively analyzedpore size (PS), volume porosity (VP) and pore interconnection (PC), and the distribution of poresize and strut size. The results proved that OCT can be utilized as a real time, non-destructive, non-invasive toolto critically monitor tissue-engineered constructs, and the subsequent image processing analysiscould evaluate the produced scaffolds qualitatively and quantitatively. Three-dimensional imageacquisition and analysis may be a key tool for the design optimization and the refinement of3D-printing processes. Q uantitative analysis of morphological parameters would help understandthe3D printing conditions effects on structure parameters and provide a method to feedback controlthe dimensional accuracy of produced3D scaffolds.