Pneumatic extrusion-based bioprinting and flow cytometry: A method for analysing chemotherapy efficacy in 3D bioprinted A375 melanoma cell cultures

Melanoma, a highly aggressive form of skin cancer, continues to be a significant challenge due to its resistance to conventional chemotherapy treatments and the tendency for metastasis. Advancements in cell culture techniques, especially the transition from 2D cell cultures to more physiologically relevant 3D cell cultures, have provided valuable new insights into cancer biology and chemotherapy drug responses. Although various novel 3D cell culture techniques have been used in melanoma research, standardised and scalable 3D cell culture models suitable for high-throughput pre-clinical drug screening applications are still lacking. Therefore, the purpose of this study was to establish a 3D bioprinted melanoma cell culture model that allows the assessment of drug-induced apoptosis through a flow-cytometric analysis method in 96-well plates. To achieve this, the proposed method integrates the BIOX™ pneumatic extrusion-based 3D bioprinter to extrude reproducible cell-laden droplets in a 96-well plate, and an Annexin V/PI flow cytometric analysis technique optimised for 96-well plate format, to enable cell viability and apoptosis quantification in more physiologically relevant 3D bioprinted cell cultures. The proposed method was evaluated on A375 melanoma 2D and 3D bioprinted cell cultures assayed for drug-induced apoptosis through a flow cytometric method. In addition, a resazurin-based analysis method was also used and compared to determine the efficacy of the proposed flow cytometric analysis method. Compared to the 2D cell cultures, the 3D bioprinted cell cultures demonstrated higher levels of resistance to all chemotherapy drugs evaluated. Furthermore, the comparative analysis of the two methods concluded that the flow cytometric evaluation platform is more sensitive in detecting drug dose responses in 3D bioprinted cell culture models. This method is a proposed alternative to quantify drug-induced apoptosis in 3D melanoma research, thereby advancing the pre-clinical application of 3D bioprinting.