Construction of a 3D Bioprinted Microfluidic Platform to Study Breast Cancer Bone Metastasis and Tumor Microenvironmental Influences

Breast cancer (BrCa) frequently metastasizes to bone, severely compromising patient survival. Preventing metastatic spread is, therefore, a crucial therapeutic goal. Tumor matrix stiffness, growth factor gradients, and the bone microenvironment collectively influence cancer progression; however, existing <i>in vitro</i> models lack the physiological complexity to capture these interactions. To address this, we developed a 3D biomimetic bone metastasis-on-a-chip platform to recapitulate the key microenvironments involved in BrCa dissemination. This study aimed to develop an <i>in vitro</i> metastasis chip that mimics BrCa tumors, the vascular-like region, and the bone microenvironment, enabling investigation of microenvironmental factors during metastasis. Bioinks replicating tumor microenvironments with adjustable stiffness were synthesized, including methacrylated collagen (ColMA) and hyaluronic acid (HAMA). Their chemical, mechanical, and biocompatible properties were optimized. Selected bioinks mimicked BrCa stiffness, allowing tumor spheroid embedding in a two-layered model. The core bioink promoted BrCa proliferation, while the peripheral bioink enhanced stemness and epithelial-mesenchymal transition (EMT), increasing metastatic potential. Furthermore, a 3D bone-like matrix composed of methacrylated gelatin and hydroxyapatite was integrated to simulate the extravasation process, facilitating BrCa cell migration and colonization within the bone-mimicking region. This metastasis-on-a-chip system successfully replicates critical stages of BrCa progression and provides a versatile <i>in vitro</i> platform for studying metastatic mechanisms and evaluating potential antimetastatic therapies.