Synthesis of gold–cellobiose nanocomposites for colorimetric measurement of cellobiase activity

• Gold–cellobiose nanocomposites were prepared for cellobiase activity assay.
• The probe displayed advantages of rapid response, high selectivity and sensitivity.
• Cellobiase activity could be detected with a wide linear from 3.0 to 100.0 U L−1.

Gold–cellobiose nanocomposites (GCNCs) were synthesized by reducing gold salt with a polysaccharide, cellobiose. Here, cellobiose acted as a controller of nucleation or stabilizer in the formation of gold nanoparticles. The obtained GCNCs were characterized with UV–visible spectroscopy; Zetasizer and Fourier transform infrared (FT-IR) spectrophotometer. Moreover, 6-Mercapto-1-hexanol (MCH) was modified on GCNCs, and the MCH–GCNCs were used to determine the cellobiase activity in compost extracts based on the surface plasmon resonance (SPR) property of MCH–GCNCs. The degradation of cellobiose on MCH–GCNCs by cellobiase could induce the aggregation, and the SPR absorption wavelength of MCH–GCNCs correspondingly red shifted. Thus, the absorbance ratio of treated MCH–GCNCs (A650/A520) could be used to estimate the cellobiase activity, and the probe exhibited highly sensitive and selective detection of the cellobiase activity with a wide linear from 3.0 to 100.0 U L−1 within 20 min. Meanwhile, a good linear relationship with correlation coefficient of R2 = 0.9976 was obtained. This approach successfully showed the suitability of gold nanocomposites as a colorimetric sensor for the sensitive and specific enzyme activity detection.

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