Engineered Cyanobacteria-Based Living Materials for Bioremediation of Heavy Metals Both In Vitro and In Vivo.

The pollution caused by heavy metals (HMs) represents a global concern due to their serious environmental threat. Photosynthetic cyanobacteria have a natural niche and the ability to remediate HMs such as cadmium. However, their practical application is hindered by a low tolerance to HMs and issues related to recycling. In response to these challenges, this study focuses on the development and evaluation of engineered cyanobacteria-based living materials for HMs bioremediation. Genes encoding phytochelatins (CSs) and metallothioneins (Ts) were introduced into the model cyanobacterium sp. PCC , creating PM/6803. The strain exhibited improved tolerance to multiple HMs and effectively removed a combination of Cd, Zn, and Cu. Using Cd as a representative, PM/6803 achieved a bioremediation rate of approximately 21 μg of Cd/OD under the given test conditions. To facilitate its controllable application, PM/6803 was encapsulated using sodium alginate-based hydrogels (PM/6803@SA) to create "living materials" with different shapes. This system was feasible, biocompatible, and effective for removing Cd under simulated conditions of zebrafish and mice models. Briefly, in vitro application of PM/6803@SA efficiently rescued zebrafish from polluted water containing Cd, while in vivo use of PM/6803@SA significantly decreased the Cd content in mice bodies and restored their active behavior. The study offers feasible strategies for HMs bioremediation using the interesting biomaterials of engineered cyanobacteria both in vitro and in vivo.