2024 AIChE Annual Meeting

Affinity Engineered Living Materials for Protein Immobilization

Engineered living materials (ELMs) are a class of composite materials where a living organism is combined with a synthetic polymer to generate emergent features. One challenge in biosynthetic ELMs, where a protein product is produced from an organism, is containing the protein component within the material. This work aimed to modify the hydrogels’ structures to increase the affinity for secreted proteins, therefore containing the proteins of interest.

Sodium alginate was utilized as a scaffold with nickel (II) chloride hexahydrate and nickel sulfate hexahydrate introduced as new cross-linkers that bind to histidine-tagged proteins, preventing them from escaping into the media. This was inspired by immobilized metal affinity chromatography (IMAC), which takes advantage of an amino acid tag’s affinity for metal ions to separate the tagged proteins from a solution. Using this idea, the proteins are anticipated to be contained within the hydrogel.

We investigated the effect of polymer and crosslinker concentrations on the structural properties of these hybrid materials. Additionally, this biocomposite was characterized to determine mechanical properties, morphology, and nickel toxicity to cells. As mentioned, only proteins with a His-tag can bind to the gel. Moreover, genetically modified cyanobacteria that secrete a protein of interest with a His-tag were compared to wild-type cyanobacteria. The His-tagged protein is blue, so the gels are expected to have higher absorbance readings at longer wavelengths.

This project aims to better understand how organisms can behave in ELMs, ultimately offering more control over the living material’s outputs. In addition, this gel could offer another means for protein purification.