Spectrofluorometric method for detection glycogen using chemically gold nanoparticles: Cyanobacteria as biological model

The bio-conversion of Au3+ ions into AuNPs via the glycogen molecule in cyanobacteria. [Display omitted] •A simple spectrofluorometric method is used a luminscent AuNPs to determine the concentration of glycogen.•The detection limit of the method was 0.89 × 10−6 M.•The glycogen portion in cyanobacteria plays an important role in the bioconversion of Au3+ to Au0.•Density functional theory was used to provide the association of gold nanoparticles and glycogen. There is a need for simple spectrofluorimetric method for detection of glycogen molecule based on binding to nanogold. Here we propose such a quantification method for glycogen using cyanobacteria as a biological model. Biologically, two strains of cyanobacteria were selected based on their previously tested nanogold biosynthetic abilities. Chemically, spherical gold nanoparticles were prepared and tested for binding to the glycogen molecule. Experimental analyses were conducted to determine the morphological and optical properties of the Au–glycogen hydrocolloids. Results: The plasmon band of biosynthesized AuNPs-glycogen was centered at 520–540 nm with size diameter was 41.7 ± 0.2 nm. The vibrational bands of glycogen were observed at 1,000 to 1,200 cm−1. The Au3+/Au0 redox coupling cycle was observed. The luminescence of AuNPs showed more stability by the addition of gradual concentrations of glycogen molecules. The detection (LOD) and quantitation limits (LOQ) were observed to be 0.89 and 2.95 µmol L−1 respectively (R2 = 0.99). The good chemical stability of this colloidal system and the glycogen molecule studied via density functional theory (DFT). The HOMO level of glycogen unit was closed near to LUMO level of Au3+. Conclusion: The associations formed between the gold nanoparticles and glycogen resulted in good chemical stability. This indicates that the quantification method proposed can be stably applied.