A novel fluorescent sensor based on CdTe quantum dots and DTAB-modified Au nanoparticles through aggregation-induced fluorescence recovery for the detection of l-lysine.

BACKGROUND: l-Lysine (l-Lys), an essential amino acid, serves as a core indicator for evaluating food nutritional quality. Although naturally abundant in ingredients such as soybeans, its content must be precisely regulated during processing to meet nutritional standards. Moreover, improper processing and storage can induce l-Lys degradation or conversion, compromising both nutritional value and food safety. Given its pivotal role in nutritional balance and quality assurance, there is an urgent need for simple, rapid, and highly sensitive analytical methods for l-Lys detection.

RESULTS: An innovative 'off-on' fluorescent sensor tailored for food-related applications was developed, utilizing CdTe quantum dots as the fluorophore and dodecyl trimethyl ammonium bromide self-assembled citrate-capped gold nanoparticles (DTAB-AuNPs) as the quencher for the rapid detection of l-lys. During the detection process, l-lys served as a binding bridge, facilitating the aggregation of DTAB-AuNPs. This reduction inhibited fluorescence resonance energy transfer between the fluorophore and the quencher, leading to fluorescence recovery. The degree of aggregation-induced fluorescence recovery exhibited a linear correlation with the concentration of l-lys within the range of 0.5-10 μm (R = 0.999). This newly developed sensing method demonstrated an impressive limit of detection of 3.22 nm. It was successfully applied to detect l-lys in various food-relevant samples, including milk, soybean, plasma and compound amino acid oral solution used in food-related nutritional supplements.

CONCLUSION: The results highlight its great potential for practical applications in multiple fields such as quality control of dairy and agricultural products, as well as clinical diagnosis related to nutritional status assessment. © 2026 Society of Chemical Industry.