Encapsulation of bacterial cells in cytoprotective ZIF-90 crystals as living composites

Abstract

Exploiting metal-organic frameworks (MOFs) as selectively permeable shelters for encapsulating engineered cells to form hybrid living materials has attracted increasing attention in recent years. Optimizing the synthesis process to improve encapsulation efficiency (EE) is critical for further technological development and applications. Here, using ZIF-90 and genetically engineered Escherichia coli (E. coli) as a demo, we fabricated E. coli @ZIF-90 living composites in which E. coli cells were encapsulated in ZIF-90 crystals. We illustrated that ZIF-90 could serve as a protective porous cage for cells to shield against toxic bactericides including benzaldehyde, cinnamaldehyde, and kanamycin. Notably, the E. coli cells remained alive and could self-reproduce after removing the ZIF-90 crystal cages in ethylenediaminetetraacetic acid, suggesting a feasible route for protecting and prolonging the lifespan of bacterial cells. Moreover, an aqueous multiple-step deposition approach was developed to improve EE of the E. coli @ZIF-90 composites: the EE increased to 61.9 ± 5.2%, in contrast with the efficiency of the traditional method (21.3 ± 4.4%) prepared with PBS buffer. In short, we develop a simple yet viable strategy to manufacture MOF-based living hybrid materials that promise new applications across diverse fields.

Tailoring Heterogeneous Catalysts at the Atomic Level: In Memoriam, Prof. Chia-Kuang (Frank) Tsung

“…However, not all living cells can be encapsulated in MOFs while retaining their optimized self-sustaining processes, so refinement of the synthetic process to improve the encapsulation efficiency is needed. In light of this requirement, Prof. Tsung and Prof. Chao Zhong of ShanghaiTech University demonstrated an aqueous multiple-step deposition approach to encapsulate Escherichia coli ( E. coli ) in ZIF-90 microcrystals . This method promotes the encapsulation efficiency to 61.9 ± 5.2%, well above the 21.3 ± 4.4% efficiency achieved through conventional methods.…”

“…In light of this requirement, Prof. Tsung and Prof. Chao Zhong of ShanghaiTech University demonstrated an aqueous multiple-step deposition approach to encapsulate Escherichia coli (E. coli) in ZIF-90 microcrystals. 128 This method promotes the encapsulation efficiency to 61.9 ± 5.2%, well above the 21.3 ± 4.4% efficiency achieved through conventional methods. The resulting encapsulated E. coli remained active and could self-reproduce after the removal of the ZIF-90 coatings.…”

Engineered Living Materials For Sustainability

“…Due to MOFs' selective permeability, microorganisms encapsulated in the MOF structure can survive toxic bactericides such as benzaldehyde, cinnamaldehyde, and kanamycin antibiotics. 412 In another example, Ji et al applied MOFs to protect the physiological activity of strictly anaerobic bacteria in the presence of oxygen (Figure 26d−g). 413 The molecular structure of the interface between MOFs and bacteria suggests that multivalent coordination bonds are formed between inorganic MOF molecules and phosphate moieties of teichoic acid in the cell wall, thus enabling MOFs to spontaneously and rapidly encapsulate microorganisms (Figure 26e,f).…”

In situ Synthesis of a Mesoporous MIL-100(Fe) Bacteria Exoskeleton

“…However, this field is still in its infancy and, to date, only a few works concern MOF association with bacteria-whose relevance in the living materials domain is paramount. [15][16][17][18][19][20] The mismatch between bacteria size (in the micrometer range) and MOF pores (below 5 nm) excludes direct bacterial colonization within the MOFs internal porosity. Two alternative encapsulation strategies have thus been employed, either by assembly of preformed 2D-MOF sheets 20 or by the in-situ synthesis of MOF in presence of bacteria.…”

“…Two alternative encapsulation strategies have thus been employed, either by assembly of preformed 2D-MOF sheets 20 or by the in-situ synthesis of MOF in presence of bacteria. [15][16][17][18][19] The main challenges lie in obtaining an intimately-assembled bio-hybrid while preserving bacteria integrity. The former strategy involves strong host-guest interactions between the MOF layer and the cell surface, which should be fine-tuned for each cell/MOF couple.…”