Development and optimization of starch-based biomaterial inks and the effect of infill patterns on the mechanical, physicochemical, and biological properties of 3D printed scaffolds for tissue engineering.

Plant-based hydrogels have wide application as scaffolds in tissue engineering and regenerative medicine due to their low cost and excellent biocompatibility. Scaffolds act as vehicles for cell-based therapeutics and regenerating diseased tissue. While there is a plethora of methods to generate hydrogels with tunable properties to mimic the tissue of interest, 3D bioprinting is a novel emerging technology with the capability to generate versatile patient-specific scaffolds typically embedded with tissue specific cells. Starch-based hydrogels are garnering attention in extrusion-based 3D printing, however owing to their poor mechanical strength and degradation render this material inefficient in its native form. Additionally, the effect of various printing process parameters on mechanical strength and bioactivity is poorly understood. In the present study, we investigate the use of starch and gelatin as composite biomaterial ink and its effect on mechanical, physical and biological properties. We also investigated printability of composite hydrogels with the aim to understand the correlation between two infill patterns and its effect on mechanical, physicochemical, and biological properties. Our results showed that the composite hydrogels had competent mechanical properties and suitable bioactivity when seeded with H9C2 cardiomyocytes. Rheometric analyses provided a broader insight into the required viscosity for printing and has a direct correlation with the composition of the hydrogel. Thus, the composite materials are found to have tissue-specific mechanical properties and may serve as a better, cheaper and personalized alternative to existing scaffolds for the fabrication of engineered cardiac tissue.

Fabrication and Characterization Techniques of In Vitro 3D Tissue Models.

The culturing of cells in the laboratory under controlled conditions has always been crucial for the advancement of scientific research. Cell-based assays have played an important role in providing simple, fast, accurate, and cost-effective methods in drug discovery, disease modeling, and tissue engineering while mitigating reliance on cost-intensive and ethically challenging animal studies. The techniques involved in culturing cells are critical as results are based on cellular response to drugs, cellular cues, external stimuli, and human physiology. In order to establish in vitro cultures, cells are either isolated from normal or diseased tissue and allowed to grow in two or three dimensions. Two-dimensional (2D) cell culture methods involve the proliferation of cells on flat rigid surfaces resulting in a monolayer culture, while in three-dimensional (3D) cell cultures, the additional dimension provides a more accurate representation of the tissue milieu. In this review, we discuss the various methods involved in the development of 3D cell culture systems emphasizing the differences between 2D and 3D systems and methods involved in the recapitulation of the organ-specific 3D microenvironment. In addition, we discuss the latest developments in 3D tissue model fabrication techniques, microfluidics-based organ-on-a-chip, and imaging as a characterization technique for 3D tissue models.

Self-Healing Hydrogels: Preparation, Mechanism and Advancement in Biomedical Applications.

Polymeric hydrogels are widely explored materials for biomedical applications. However, they have inherent limitations like poor resistance to stimuli and low mechanical strength. This drawback of hydrogels gave rise to ''smart self-healing hydrogels'' which autonomously repair themselves when ruptured or traumatized. It is superior in terms of durability and stability due to its capacity to reform its shape, injectability, and stretchability thereby regaining back the original mechanical property. This review focuses on various self-healing mechanisms (covalent and non-covalent interactions) of these hydrogels, methods used to evaluate their self-healing properties, and their applications in wound healing, drug delivery, cell encapsulation, and tissue engineering systems. Furthermore, composite materials are used to enhance the hydrogel's mechanical properties. Hence, findings of research with various composite materials are briefly discussed in order to emphasize the healing capacity of such hydrogels. Additionally, various methods to evaluate the self-healing properties of hydrogels and their recent advancements towards 3D bioprinting are also reviewed. The review is concluded by proposing several pertinent challenges encountered at present as well as some prominent future perspectives.