Label-free test kit for d-amino acid analysis by 1,4-benzenediboronic-acid-induced aggregation of gold nanoparticles†
The level of D-amino acids (DAAs) is significantly related to bacterial contamination in health and disease, food science and nutrition, and industrial applications. Most sensing methods for the detection of DAAs need expensive equipment, and skilled operation experience, making the test kit for DAA analysis much more complex and challenging. Toward this end, we exploited a label-free DAA test kit based on 1,4-benzenediboronic acid (BDBA)-induced gold nanoparticles (AuNPs) aggregations. DAAs were first catalyzed by their specific catalase (DAAO, D-amino acid oxidase) and oxidized to produce H2O2. Then, the produced H2O2 inhibited the citrate-capped AuNPs aggregation under BDBA, while the unreacted BDBA could lead to AuNPs aggregation. As a result, the UV/vis absorption spectra and optical photographs of the AuNPs solution are changed in the presence of different DAA target amounts. This method not only can be used for qualitative and semi-quantitative analysis with a naked-eye readout, but also it can quantify DAAs in aqueous solutions with high sensitivity and specificity. Furthermore, the DAAs test kit provided an effective and selective quantification of DAAs with excellent precision and accuracy in bacterial samples. We believe this DAA test kit provides the potential to be further developed for DAA detection for satisfying both lab and practical needs in different fields.