Bare silver and gold nanospheres: potential role as nanosensors for selective detection of L-carnosine and monothioglycerol

L-carnosine and monothioglycerol are the most commonly found antioxidants in meat products and the pharmaceutical industry, respectively. Current high-throughput monitoring methods are laborious, costly, and require technical expertise. This study aimed to develop a cost-effective, rapid, and selective detection method for these antioxidants using bare metal (gold/silver) nanospheres. This study screened a wide range of antioxidants (n = 17) for selective detection of L-carnosine/monothioglycerol using bare metal (gold/silver) nanospheres. A colorimetric and spectrophotometric probe was developed, utilizing sub-15 nm bare silver and gold nanospheres. Results showed that bare gold nanospheres selectively detected monothioglycerol, while bare silver nanospheres detected both monothioglycerol and L-carnosine. The silver nanospheres exhibited good linearity for both antioxidants within the 0-20 µM range, with detection limits of 3.97 µM for monothioglycerol and 1.87 µM for L-carnosine. Gold nanospheres showed good linearity for monothioglycerol in the 5-40 µM range with a detection limit of 4.24 µM. Interference studies revealed that other antioxidants from different sources could inhibit detection, which was exploited to quantify these interferents using the nanospheres. In addition, bare silver nanospheres successfully quantified the concentration of L-carnosine in chicken breast samples. The concentration was 7.05 μM and 6.94 μM after extraction of L-carnosine in methanol and double distilled water, respectively. These findings suggest the potential for developing user-friendly, reliable, and cost-effective nanosensors for food quality control, environmental monitoring, and biomedical research applications.