Leveraging femtosecond laser machining for the fabrication of tubular-based Organ-on-Chip systems: modeling cancer metastasis from invasion to intravasation.

Organ-on-Chip (OoC) models often include microchannel-based vessels and ducts with rectangular cross-sections, and therefore these lack the geometry and morphology found in tubular structures in vivo. Channels with round cross-sections can better mimic the physiology and cellular behavior of tubular structures, such as (micro)vessels and breast ducts, by providing a more in vivo-like geometry. Here, we utilize femtosecond laser machining to integrate tubular channels in an Organ-on-Chip device; our "Lumina-Chip" contains two tubular channels, both connected to a central channel along their entire length. This versatile fabrication technique, combined with replica molding, enables us to obtain a medium-throughput version of the device, including nine Lumina-Chips. In this study, we showcase the Lumina-Chip's capability by modeling breast cancer invasion, migration, and intravasation, all within a single device as a representative application. We use the device to observe the progression of breast cancer cells from a breast duct (formed in the first lumen, lined with normal epithelial cells), through an extracellular matrix (comprised of collagen I in the central channel), and ultimately into a vessel (formed in the second lumen, lined with endothelial cells). A permeability analysis confirms that the vessel wall maintains strong barrier functionality in the absence of cancer cells. Two types of breast cancer tumoroids (invasive and non-invasive) introduced into the breast duct exhibit distinctly different invasive behaviors. While we present breast cancer metastasis as a showcase application, the Lumina-Chip also holds potential for other biological applications where epithelial ducts and vessels with tubular structures are critical components.