Lactic acid detection based on Pd-coated vesicles and lipid nanotubes

Abstract

Lactic acid is an essential metabolite in the human body. Developing a reliable non-invasive lactic acid sensor faces the challenge of the limited biocompatibility of the sensor-supporting material. Replacing traditional carbon-based materials with biocompatible options such as lipids offers an effective solution. In this study, vesicles are prepared by drying and rehydrating, while lipid nanotubes (LNTs) are synthesized via slow cooling and ultraviolet polymerization to serve as catalyst supports. Both lipid carriers are coated with Pd through seeding and growth. To compare different Pd morphologies and their effectiveness as catalyst supports depending on the lipid carrier, the seeding products on each carrier are examined with transmission electron microscopy. The growth pattern is also monitored at 100 s, 200 s, and 300 s. All Pd-coated lipid carriers detect lactic acid in artificial sweat via cyclic voltammetry. The standard deviation of Pd-coated LNTs is relatively small, and linear fitting results show that Pd-coated LNTs (300 s) are more suitable for lactic acid detection, with an R2 value of 0.984, a low limit of detection of 4.3 mM, and a relatively high sensitivity of 0.176 mA⋅mM⁻¹⋅cm⁻².