Engineering Multicellular Spheroids for Tissue Engineering and Cell Therapy Applications

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Background and motivation: In the past decades, cell-based bioassays have transitioned from 2-D monolayers to 3-D models, as the 3-D models better mimic the in-vivo physiological conditions. Multicellular spheroids are promising approaches as 3-D constructs for emerging applications in tissue engineering, drug discovery and cell therapy. Multicellular spheroids are spherical self-organizing cell aggregates ranging from 150-500µm in diameter, generated from a monolayer suspension of one or multiple cells, using methods such as hanging droplets among others. These methods are generally labor-intensive, low-yielded, time-consuming, and generate heterogeneous spheroids in shape and size which limits their scaled-up application. Microfluidics has shown the promise of overcoming some of the technical hurdles in spheroid formation by offering precise manipulation of cells and controlled physical conditions, homogenous size distribution, and maintaining continuous perfusion which regulates the nutrients and oxygen supply to cells. U-traps microfluidics and microwell are explored to form spheroids. However, their throughput is not applicable to clinical scales and they also need complex mechanisms for spheroids retrieval, and the lack of fluid flow limits the mass transport of nutrients or chemical stimuli. Objectives and methodology: Our long-term objective is to implement surface acoustic wave (SAW)-based microfluidic platforms for the development of multicellular spheroids for tissue engineering, cell therapy and to model diseases by 1) implementing SAW devices for multicellular spheroid fabrication; 2) Investigating and customizing working parameters of SAW; 3) Feasibility study for spheroid fabrication and coating; and 4) Developing multicellular spheroids for tissue engineering and cell therapy applications and disease modelling. Two multipurpose modules of SAW device will be developed for `biofabrication' and `applications' of mono and multi-cellular spheroids using soft lithography and replica mold techniques using PDMS. Effect of various parameters on size, formation of stable spheroids, cell viability and proliferation will be investigated. The SAW device will be used to promote vascularization in multicellular spheroid constructs. Conformal coating using layer-by-layer approach will be used to induce immunomodulatory properties in the construct. The SAW will be adopted for co-culturing multiple cell lines to promote vascularization or to produce 3D bioprintable spheroids as building block for bone tissue engineering. Impact: This proposal provides a new research stream to the PI's research program on lab/tissue-on-a chip platforms where 9 trainees will be involved in a multidisciplinary research. It delivers acoustic microfluidics platforms as cost-effective solution for the fabrication of multicellular spheroid considered as pseudo tissue to generate relevant data prior to designing costly and ethically challenging animal studies.