Real-time Monitoring of Critical Quality Attributes of Bioprinted Constructs in Manufacturing of Engineered Tissues

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Bioprinting is the process of automated deposition of biological molecules, such as living cells and associated biomaterials, to form a 3D heterogeneous construct. Several bioprinting techniques have been developed to fabricate functional cellular and tissue constructs for applications in engineered tissues and organs. Bioprinting process parameters can affect biological quality attributes of encapsulated cells within fabricated constructs. Currently, assessment of these critical biological quality attributes must be performed offline by subjecting the constructs to destructive assays that require staining and sectioning. This drawback affects the translation of bioprinting processes to industrial practice. This award supports fundamental research to enable predicting the quality attributes of the bioprinted constructs using a real-time and in-process characterization technique. Research results will contribute to US biomanufacturing strengths, particularly towards advancing personalized medicine.In a bioprinting process, the electrical impedance of encapsulated cells in response to an alternating current at different frequencies can be measured, and any perturbations in the impedance signals are affected by the biological attributes of the constructs. The first research objective is to determine interactions between process parameters (nozzle diameter, extrusion pressure, and hydrogel concentration) and critical biological quality attributes (cell viability, density, and metabolic state) of benchmark bioprinted cellular constructs. To achieve this objective, the permittivity of printed constructs under the influence of an alternating electric field (100 KHz to 20 MHz) will be measured by using a dielectric probe. The obtained permittivity curves will be analyzed to extract beta-dispersion attributes (critical frequency, capacitance drop, and rate of capacitance change) which will be correlated to the bioprinting process parameters. The second objective is to understand the mechanism responsible for alterations in cellular membrane polarization of encapsulated cells in a bioprinting process under an applied electric field. To achieve this objective, a multi-physics model of the bioprinting process will be developed, combining the dielectric properties of encapsulated cells, biomaterial properties, and cellular kinetics. The model will be experimentally calibrated through state-of-the-art offline characterization methods. It then will be used to predict the cellular polarization states under the influence of an electric field. Simulations results will be verified by measuring the biological quality attributes of the printed constructs. The third objective is to determine the effects of bioprinting process parameters on the dielectric properties of mammalian and bacterial cells. The extracted permittivity attributes will be used to predict the biological quality state of the constructs in real-time. These predictions will be confirmed by offline construct characterization methods.