Characterization of cell viability during bioprinting processes

Abstract

Bioprinting is an emerging technology in the field of tissue engineering and regenerative medicine. The process consists of simultaneous deposition of cells, biomaterial and/or growth factors under pressure through a micro-scale nozzle. Cell viability can be controlled by varying the parameters like pressure and nozzle diameter. The process itself can be a very useful tool for evaluating an in vitro cell injury model. It is essential to understand the cell responses to process-induced mechanical disturbances because they alter cell morphology and function. We carried out analysis and quantification of the degree of cell injury induced by bioprinting process. A parametric study with different process parameters was conducted to analyze and quantify cell injury as well as to optimize the parameters for printing viable cells. A phenomenological model was developed correlating the percentage of live, apoptotic and necrotic cells to the process parameters. This study incorporates an analytical formulation to predict the cell viability through the system as a function of the maximum shear stress in the system. The study shows that dispensing pressure has a more significant effect on cell viability than the nozzle diameter. The percentage of live cells is reduced significantly (by 38.75%) when constructs are printed at 40 psi compared to those printed at 5 psi.

Advances in bioprinted cell-laden hydrogels for skin tissue engineering

“…Several works showed that stresses transmitted to the cells are a function of the dispensing nozzle characteristics (geometry, diameter and length), applied pressure, deposition speed, and bioink rheological properties. These studies also demonstrated the possibility to determine and to reduce the shear stresses transmitted to the cells through experimental and numerical studies [17,19,30,46,127]. To address the unique requirements of extrusion bioprinting regarding the print fidelity and biological characteristics, research efforts have been focused on the development of bioinks exhibiting appropriate rheological, mechanical and biological properties [28,32,74,82,100,152,169,174].…”

Recent cell printing systems for tissue engineering

“…Viscosity is defined by the concentration of the materials, and the printability and print resolution can be enhanced as the viscosity of the bioink increases. However, it is reported that cell viability can decrease from the severe nozzle wall shear stress generated in a narrow nozzle by high pressure, and this is required to print high-viscosity bioink [63] . In addition, it is known that the ability to crosslink effects the strength and stiffness of the scaffolds and the oxygen and nutrient supply for the cells.…”

Directed assembly of cell-laden hydrogels for engineering functional tissues

“…[53][54][55] The applications of inkjet technology to tissue printing have been rapidly advanced in past few years; however the usage of inkjet tissue printing technique is hampered by some limitations including the size of the jetting needle, the cell concentration, the viscosity of the material and the viability of the printed cells. 56,57 Although inkjet tissue printing has faced some shortcomings, there are some other jet-based techniques which can overcome disadvantages of the inkjet printing.…”

“…Tissue printing is an attractive scaffold free technique with the great potential of constructing delicate 3D tissue-like structures. [51][52][53][54][55][56][57][58][59][60][61] (Fig. 6A-F).…”