Yeast cells are also known as efficient, "green" synthesizers of metallic nanoparticles. As the reduction of metal ions happens partially on the cell surface, we examined the influence of PPEGMA brushes (SI Figure ). In the case of silver nanoparticles (AgNP), the particles released into the supernatant were 13x more abundant using P8 than the naked yeast (SI Figure ) and their ζ-potential values were also more neutral (SI Figure ), a clear sign of the impact of PPEGMA. Nevertheless, AgNP are biocides, and their very efficient production did affect cell viability, which dropped to less than 50% for the cells with PPEGMA (SI Figure ). The yield of palladium nanoparticles (PdNP), on the other hand, was only 2x higher than in the controls (SI Figure ), and viability was not affected (SI Figure ). These *: no initiator/CTA added, used as negative control. †: NHS-BiB conjugated to cells not expressing HRP, mixed with cells expressing HRP but without initiator. ‡: chain extension in P12 of the polymers synthesized in P11.