# Monitoring Changes in Salivary Amino Acids in Smokers Using Nanofiber-Based Solid-Phase Extraction Combined With High-Performance Liquid Chromatography

## TL;DR

This study developed a method to detect amino acid changes in saliva after smoking, finding that glycine and alanine levels significantly increase.

## Contribution

A novel method using PEDOT nanofibers and HPLC for sensitive amino acid detection in saliva is introduced.

## Key findings

- The method achieved a recovery rate of 61.8% to 130.2% for 13 amino acids in saliva.
- Smoking significantly increased the concentration of glycine and alanine in saliva within 15 minutes.
- The method improved detection sensitivity and reduced interference in complex biological samples.

## Abstract

Introduction: Smoking causes a variety of diseases and is the primary cause of preventable death. Smoking can cause metabolic disorders of amino acids (AAs) in body fluids. However, the trace concentration of AAs and complex background interference in biological samples pose a challenge for the determination of AAs. Conventional solid-phase extraction for the concentration and purification of AAs is often ineffective because AAs are highly polar.

Materials and methods: We selected poly-3,4-ethylenedioxythiophene (PEDOT) nanofibers as adsorbents for the extraction of AAs from saliva after derivatization with dansyl chloride. Thirteen AAs in saliva were determined by high-performance liquid chromatography (HPLC) with an ultraviolet detector. The proposed method was used to determine the dynamic changes of AA concentrations in the saliva of six subjects before and after smoking.

Results: Under the optimized conditions, adjusting the acidity of the sample solution to pH 2 and the loading amount of PEDOT nanofibers to 18 mg, the established method provided a quantitative limit of 0.15 to 0.45 micrograms per milliliter for the 13 AAs, with a recovery rate of 61.8% to 130.2% and a precision of 3.6-12.0%. Compared with the no-smoking blank, the areas under the concentration-time curves for glycine and alanine in saliva were significantly increased (p< 0.05). The concentrations of these two AAs in saliva reached their peak 15 minutes after smoking, suggesting that these two AAs may potentially play a role in the mechanism of the smoking effect.

Conclusions: The method, developed using PEDOT nanofibers for solid-phase extraction of AAs coupled with HPLC, thereby improving detection sensitivity and reducing interference, was suitable for the quantitative determination of AAs in saliva. It was found that smoking caused significant dynamic changes in salivary glycine and alanine.