Thermostable CNTs@Au NPs nanocomposites for high-temperature assisted SERS molecular fingerprinting of two natural folates.

BACKGROUND

Folate is an essential nutrient, but its bioavailability varies greatly depending on the molecular form present in food. The intake of forms that are not readily absorbed by the human body may lead to insufficient folate levels, particularly during pregnancy, thereby increasing the risk of birth defects. As a result, it is essential to develop a highly sensitive and accurate method capable of distinguishing between the two most common natural folates, 5-methyltetrahydrofolate (5-MTHF) and 5-formyltetrahydrofolate (5-FTHF), to ensure proper folate intake and health outcomes.

RESULTS

In this study, a photochemical method was employed to load gold nanoparticles (Au NPs) onto carbon nanotubes (CNTs), successfully synthesizing CNTs@Au NPs nanocomposites that exhibit excellent thermal stability and robust surface-enhanced Raman scattering (SERS) activity. These nanocomposites, capable of maintaining structural integrity at temperatures as high as 400 °C, serve as highly effective substrates for in situ high-temperature SERS detection. Using this reliable high-temperature-assisted SERS approach, the structural changes of both folates at elevated temperatures were effectively monitored, enabling clear molecular fingerprinting and distinct differentiation between the two natural folates. Moreover, the CNTs@Au NPs demonstrate exceptional sensitivity, achieving a detection limit as low as 10-8 M for both 5-MTHF and 5-FTHF, enabling accurate quantification of mixed folate samples and demonstrating reliable performance in real sample analysis.

SIGNIFICANCE: The CNTs@Au NPs with in situ high-temperature SERS capabilities show great potential for various analytical applications. In particular, they provide an effective method for monitoring the quality of folate in dietary supplements and fortified foods, thus contributing significantly to the safety and quality assurance of folate products in the market.