Cutting and Bonding Parafilm^® to Fast Prototyping Flexible Hanging Drop Chips for 3D Spheroid Cultures

A fast and low-cost fabrication process of flexible hanging drop chips for 3D spheroid cultures was proposed by cutting and bonding Parafilm^®, a cohesive thermoplastic. The Parafilm^® Hanging Drop Chip (PHDC) was assembled by two-layer of Parafilm^® sheet with different sizes of holes. The hole on the upper layer of the Parafilm^® is smaller than the hole on the bottom layer. The impact of hole size and sample volume on hanging drop formation and 3D spheroid formations in the hanging drop were investigated. The results showed that 20 µL solution on PHDC with a 3 mm hole could form stabile drop and facilitate spheroid formation. The initial cell number determinates the size of the formed spheroids. Exchanging liquid from the upper hole of the PHDC enables the co-culture of two types of cells in one spheroid and drug efficacy testing in hanging drops. The relative expression of cell adhesion and hypoxia-related genes from spheroids in hanging drop and conventional culture plate suggested the relevance of 3D spheroids and in vivo tumor tissue. The economical hanging drop chip can be fabricated without wet chemistry or expensive fabrication equipment, strengthening its application potential in conventional biological laboratories.