Design and development of metal-organic framework microcarriers for large scale manufacturing of stem cells

Microcarrier-based culture systems have emerged as an attractive approach for largescale manufacturing of stem cells required for therapeutic applications and tissue engineering due to their large surface-to-volume ratio and the possibility of controlling the culture parameters during cell cultivation. To date, various kinds of microcarriers (MCs) have been developed to enhance cell attachment, proliferation, and harvesting efficiency. Nonetheless, the majority of them do not possess the required physicochemical and surface properties to exploit their full potentials for enhancing cell proliferation and differentiation for clinical applications. In addition, limited studies have been focused on developing efficient methods for harvesting cells from MCs with minimum cell damage. In this research, metal-organic frameworks (MOFs) were used as promising biomaterials in developing MCs to regulate stem cell fate and scale up stem cell manufacturing. MOFs are promising because of their high cytocompatibility, tunable porosity, chemical functionality, and surface topography. Two types of MOFs were utilized in the fabrication of different MCs: Zeolite imidazole framework 8 (ZIF8) and UiO66-NH2 (Zr-based MOFs). The MCs were characterised and used in different applications. The incorporation of MOFs in MCs leads to changing MCs' surface properties, such as roughness, wettability, morphology, and chemical functionality, which enhance the expansion and growth of largescale stem cells. Additionally, MOF-based MCs can potentially improve stem cell differentiation toward the specific lineages. These types of MCs can be highly demanded in tissue engineering applications such as bone regeneration. The results indicated that MOF modification of MCs is a cost-effective and facile method for tuning the culture environment and controlling cell growth, differentiation, and the fate of stem cells on a large scale. Furthermore, this study shows that the surface properties of MOF MCs can be tailored easily by post-modification which would be extremely helpful in designing smart MCs for nonenzymatic cell harvesting. This study showed that the modification of MOF MCs with poly(N-isopropylacrylamide) (PNIPAAm) as a temperature-responsive polymer leads to producing large numbers of cells without irreversible damage to the cells during cell detachment. The fabricated temperature-responsive MCs exhibited high cell attachment and proliferation, and more importantly, almost all the cells could be detached from the surface of MCs by reducing temperature while maintaining the viability, morphology, and differentiation potential of stem cells. Besides, the fabricated MCs are applicable in the VII microfluidic device systems as an automated, large-scale cell harvesting method. Using this method, higher cell harvesting yield can be achieved by taking advantage of the microfluidic device system while maintaining the differentiation potential and therapeutic properties of MSCs.