PhD Thesis Colloquium: Ms. Sruthi C S (16/07/24)
Thesis title:
Mucin-Based Photocrosslinkable Bioinks for 3D Bioprinting and Tissue Engineering
Faculty advisor(s):
Prof. Ashok M Raichur
When?
16th July, 2024 (Tuesday), 03:00 PM (India Standard Time)
Where
KPA Auditorium, Department of Materials Engineering
Abstract:
The growing demand for treatment strategies to address organ damage caused by chronic illness, trauma, and aging, along with the demand for disease models and drug testing, has spurred significant advancements in tissue engineering research. Developing scaffolds that can accurately mimic the complex physiology of human tissues is crucial. Among the various fabrication methods, 3D bioprinting has emerged as a revolutionary technique capable of creating intricate structures by precisely depositing cells within a matrix of biomaterials. Various biomaterials such as gelatin, alginate, collagen, hyaluronic acid, and agarose have been utilized to fabricate bioinks owing to their properties that support tissue growth and organization. However, these materials often fail to meet the diverse mechanical and biophysical requirements of different tissues, and there is a growing need for polymers that offer additional biomedically beneficial properties, such as inherent anti-biofouling capabilities. Thus highlighting the necessity for further exploration of suitable biomaterials. In addressing these challenges, our study explores mucin as a bioink material. Mucin, a glycoprotein found abundantly in mucus that lines mucosal surfaces, possesses unique hydrogel properties. Beyond its role in hydration, lubrication, and forming protective barriers, mucin exhibits complex biochemical structures that facilitate chemical modifications. Despite these advantages, mucins are relatively underexplored in the field of 3D bioprinting.
In our research, we synthesized a mucin-based bioink and evaluated its rheological behavior, printability, and compatibility with cells. By modifying mucin with methacrylic anhydride (MA), we synthesized a photocrosslinkable derivative methecrylated mucin (MuMA). Using lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as a visible light (405 nm) photoinitiator, we ensured cell safety compared to UV-induced crosslinking methods used in other bioinks. This approach highlights mucin’s versatility and potential as a bioink material, offering a pathway to develop advanced tissue engineering constructs that meet the diverse needs of biomedical applications.
In our initial work, to create a bioink with optimum viscosity, we combined MuMA with bare mucin. The inherent inter- and intra-molecular interactions facilitated the physical crosslinking between the MuMA and mucin. The bioink demonstrates favorable rheological, gelation, and structural properties when crosslinked. It exhibits shear thinning behavior, ensuring cell safety during printing, while its EGF-like domains, rich in cysteine, facilitate the growth, migration, and differentiation of fibroblast NIH3T3 cells. The printed scaffolds feature optimal swelling and degradation properties, with a pore size of <100 µm, promoting the migration and proliferation of NIH3T3 cells. Varying the crosslinking time provides insights into the properties of the 3D-printed scaffolds. An increase in cell numbers after 21 days indicates the matrix’s cell-supportive nature. Our findings demonstrate that mucin-based bioink promises a significant advancement toward expanding the repertoire of bioinks available for 3D bioprinting and tissue engineering.
To improve the properties of the bioink further, we have combined hyaluronic acid (HA) and MuMA to be used for lung tissue engineering. HA, a crucial extracellular matrix component, is mucoadhesive and enhances ink viscosity and printability. Rheological tests reveal shear-thinning behavior, aiding cell protection during printing and improved MuMA bioink viscosity by adding HA. The printed structures exhibited porous behavior conducive to nutrient transport and cell migration. After four weeks in phosphate-buffered saline (PBS), the scaffolds retain 70% of their mass, highlighting stability. Biocompatibility tests with lung epithelial cells (L-132) confirm cell attachment and growth, suggesting suitability for lung tissue engineering. In the following study, for cartilage tissue engineering, ionically crosslinkable alginate was incorporated into the MuMA bioink, forming a double crosslinked interpenetrating network (IPN) hydrogel bioink. Furthermore, HA, naturally occurring in cartilage and synovial fluid, was introduced to enhance scaffold characteristics. HA has been shown to improve cartilage lubrication, regulate inflammation, promote cell proliferation, and enhance extracellular matrix (ECM) deposition and regeneration, proving beneficial in cartilage tissue engineering. The study demonstrated that double crosslinked scaffolds made of MuMA, alginate, and HA exhibited compressive moduli similar to native cartilage, contrasting with single crosslinked counterparts. Degradation profile, water uptake, and porosity were also influenced by double crosslinking, ensuring scaffold durability and stability to support chondrocytes. Biocompatibility tests with C28/I2 cells and collagen type II profiling suggest the chondrogenesis and cell-supportive nature of the bioink. This study proves mucin to be a versatile material for tailored cartilage tissue engineering applications.
Our study concludes that mucin demonstrates promising potential as a bioink material that can be customized to suit specific applications, thus broadening the spectrum of available bioinks.