design and fabrication of a silver nanocluster-based aptasensor for lysozyme detection

Lysozyme is a universal part of the innate immune system and is present in various bodily fluids. it is also vastly studied as a biomarker for a variety of diseases and is used in the food industry as a preservative. however, due to lack of a universal and precise detection method, new techniques are highly sought after for this purpose. here, we introduce a silver nanocluster-based aptasensor to detect lysozyme with high sensitivity. the sensor consists of an rna aptamer and a complementary dna sequence with a silver nanocluster template. silver nanoclusters were synthesized by reduction of silver nitrate in the presence of complementary dna sequence and characterized by transmission electron microscopy, uv-visible, fluorescence, and circular dichroism spectroscopy. emission of the silver nanoclusters switched between low and high intensity based on the quenching ability of the aptamer for dna-silver nanoclusters and the binding affinity of the aptamer for lysozyme. in the presence of the aptamer, dna-silver nanoclusters show low fluorescence due to the hybridization of the aptamer, and hence disruption in the formation of dna-silver nanoclusters. upon addition of lysozyme, aptamer binding to the dna-templated silver nanoclusters will be inhibited due to the stronger interaction between the aptamer and lysozyme. presence of the free dna template leads to a restored fluorescence signal of dna-silver nanoclusters which is dependent upon the lysozyme concentration. by utilizing this strategy, the complementary dna-templated silver nanoclusters sensor can detect concentrations of lysozyme lower than 10 nm via a signal in the visible spectral region. the proposed sensor presents valuable features such as low-cost, high sensitivity, easy fabrication, and convenient operation for detection of lysozyme.