Use of microfluidic "chip" devices for assessing the effect of radiation on 3D cell culture models

Microfluidic devices are becoming more prevalent in fundamental and pre-clinical cancer research for their versatility and ease to culture, treat and analyze 3D tumor models of increased complexity and human/in vivo contextualization, paired with their overall user-friendliness and low footprint. Although mainly used for drug development, microfluidic devices and on-chip 3D models are compatible with irradiation, whether with laboratory irradiators or clinical radiotherapy equipment. As such, methodologies for analyzing cellular response to irradiation must be adapted for microfluidic devices (i.e. chips) and associated on-chip 3D tumor models. Here, we present a protocol for the generation of 3D cell culture models on-chip, along with three gold-standard radiobioassays protocols for quantifying their response to irradiation: clonogenic assay, neutral comet assay, and immunofluorescence staining for various markers. Moreover, examples of media-based assays are provided. These methods all offer different insights into response to radiotherapy, from the individual cell to that of the whole sample, and take advantage of the simplified generation of 3D cell culture models on-chip.