Metal-Organic Framework Shell Encapsulation for pH-Responsive Protection of Yeast Cells

Encapsulating living cells within porous crystalline materials has emerged as a powerful strategy for improving cellular stability in chemically or physically harsh conditions.In this study, individual yeast cells were encapsulated with a zeolitic imidazolate framework-8 (ZIF-8) crystals via a biomimetic self-assembly process.Morphological analysis using electron microscopy confirmed the successful formation of a uniform and continuous protective shell around each cell.To evaluate the cytoprotective effect of the ZIF-8 coating, the encapsulated yeast cells were exposed to a range of pH conditions (pH 2~12).Fluorescence microscopy using fluorescein diacetate (FDA) staining revealed that over 50 % of the ZIF-8 encapsulated cells remained viable in alkaline environments (pH 8, 10, and 12), whereas non-encapsulated yeast cells showed 0 % viability across all tested conditions.The enhanced survival in alkaline media was attributed to the stability of the crystalline ZIF-8 shell, which remained partially intact and provided structural protection.In contrast, acidic conditions degraded the ZIF-8 shell, leading to cell membrane rupture and loss of viability.These findings demonstrate that ZIF-8 encapsulation can significantly improve the chemical resilience and survival of living yeast cells.This strategy holds great promise for applications in long-term cell preservation, transport, and pH-responsive biotechnological systems.