Facile fabrication and selective detection for cysteine of xylan/Au nanoparticles composite

• Synthesis of AuNPs with xylanas stabilizing and reducing agent was optimized.
• The AuNPs were highly stable and well dispersed with the diameters of 10–30 nm.
• Xylan/AuNPs exhibited highly selective for cysteine detection.
• The limit of detection (LOD) for cysteine by xylan/AuNPs was 0.57 μM.
• Cysteine can be detected in human blood plasma by xylan/AuNPs with good recovery.

This work reported a facile and green method to prepare highly stable and uniformly distributed Au nanoparticles (AuNPs), using biopolymer xylan as stabilizing and reducing agent. Full characterizations were performed and the results revealed that AuNPs were well dispersed with the diameters of 10–30 nm. The optimal condition was as follows: the ratio of xylan to HAuCl4 was 150 mg:15 mg, reaction temperature was 80 °C and reaction time was 40 min. The xylan/AuNPs composite exhibited highly selective and sensitive sensing of cysteine in aqueous solution, it could distinguish cysteine among dozens kinds of amino acids, and the limit of detection (LOD) for cysteine was calculated as 0.57 μM. Besides, the xylan/AuNPs composite was applied for Cys detection in human serum. This study provides a new way for high-value utilization of the rich biomass resource and a cheap, rapid and simple method for Cys detection in real biological samples.