Flow cytometry-based high-throughput screening of synthetic peptides for palladium adsorption

Conventionally, the measurement of metal ion adsorption capacity in biosorbent relies on expensive and time-consuming ICP-OES technique. Herein, a semi-quantitative method to measure Pd(II) adsorption capacity of single cells has been presented by analyzing side scatter (SSC) intensity in flow cytometry. Within the sensitive range and applicable conditions, excellent linearity correlation (R² ranges from 0.89 to 0.96) between the amount of Pd(II) absorbed on yeast and the fold increase in SSC intensity has been observed. Using this method, six strains with high Pd adsorption capacities have sorted from a yeast library with metal-binding peptides displayed (up to 10⁷ strains) based on SSC signal intensity. The optimal peptide (EF1) displayed on yeast and E. coli surface demonstrated Pd adsorption improvements of ∼32% and ∼200%, respectively. In summary, our study proposes an alternative high-throughput method for analyzing the Pd(II) adsorption capacity of individual yeast cells, enabling the screening of specific peptides/proteins with high Pd(II) affinity from extensive libraries.