Human serum albumin-derived biosensor for visualizing copper(II) and hydrogen sulfide interactions in cancer cells.

INTRODUCTION

Accurate monitoring of Cu2+ and H2S levels is one of the most reliable methods for diagnosing tumors and assessing treatment efficacy. However, the development of fluorescent probes capable of detecting Cu2+ and H2S in cancer cells against interference from the tumour microenvironment remains a challenge.

OBJECTIVE

This study aimed to develop a novel peptide-based biosensor for monitoring Cu2+ and H2S in cancer cells and visualizing the effects of Cu2+-H2S interactions on redox homeostasis.

METHODS

First, we designed and synthesized the sensor NBD-DAH (NBD-Asp-Ala-His) by mimicking the Cu2+ binding site of human serum albumin (HSA). Second, we evaluated the specificity, sensitivity, and resistance of NBD-DAH to interference from the biological environment in the sequential detection of Cu2+ and H2S. Third, we investigated the binding sites and sensing mechanism between NBD-DAH and Cu2+. Finally, we evaluated the potential and biosafety of NBD-DAH for monitoring Cu2+ and H2S, visualizing their interactions in cancer cells, and exploring the effects and potential mechanisms of these interactions on redox homeostasis.

RESULTS

NBD-DAH can specifically and sensitively detect Cu2+ and H2S in sequence through an "on-off-on" fluorescence response. Because of its high cell membrane permeability, broad pH compatibility, and rapid response, the sensor resists interferences from the complex tumor microenvironment and enables reliable detection of Cu2+ and H2S level changes in cancer cells. Furthermore, live-cell imaging with NBD-DAH revealed a molecular mechanism in which H2S specifically binds to Cu2+ in cancer cells, leading to the depletion of superoxide dismutase 1 (SOD1) activity and subsequent regulation of redox homeostasis.

CONCLUSION

We developed a novel biosensor, NBD-DAH, and successfully used it to monitor Cu2+ and H2S levels and visualize their interactions in cancer cells. The interaction between Cu2+ and H2S influenced intracellular redox homeostasis, potentially through its effect on SOD1 activity.