Identification of adducts of 2-hydroxyethyl methacrylate with N-acetylcysteine or glutathione through capillary electrophoresis analysis

In recent years the capillary electrophoresis (CE) analytical technique have had a large impact in chemical, biotechnological, environmental and pharmaceutical field because of its high efficiency and resolution power exhibited towards extremely small amounts of a wide variety of compounds, including peptides, proteins, nucleotides, DNA, enantiomers, carbohydrates, vitamins, inorganic ions and drugs. Methacrylic compounds such as 2-hydroxyethyl methacrylate (HEMA) are largely present in auto- or photo-polymerizable composite resins utilized in dentistry and in other biomedical applications. After performing dental restorations with composite resins, small amounts of monomers are released from the incompletely polymerized material into either the oral cavity and – through dentinal diffusion – into the pulpal tissues. Subsequently, methacrylic monomers may cause, or at least contribute to, adverse biological effects, like damages to the oral soft tissues, already observed in vivo, a remarkable in vitro cytotoxicity and a depletion of glutathione (GSH). The latter is produced in all organs and cells, where it accomplishes several physiological tasks including relevant protection against oxidative stress by its oxidation to GSSG and the concurrent reduction of hydrogen peroxide and lipid peroxides; moreover GSH binds to xenobiotics facilitating their removal. Several reports have also demonstrated a protective effect of N-acetyl cysteine (NAC) against the cytotoxicity of dental resins or materials containing HEMA also via the formation of a molecular adduct. The present work summarizes the recent results obtained by capillary electrophoresis-mass spectrometry (CE-MS) and micellar electrokinetic capillary chromatography (MEKC) techniques in the detection of the adducts between NAC or GSH and the above mentioned methacrylic compound both in complex systems represented by primary gingival fibroblasts and 3T3-Swiss albino-mouse fibroblasts cell line, evidencing the key role of CE technique in the analytical separation. Cell-free systems were also investigated. Both CE-MS and MECK analytical techniques were able to successfully separate and characterize the adducts present inside and outside fibroblasts. The discovery of the formation of the above described molecular adducts is of relevant interest to explain the direct detoxifying mechanism exerted by NAC towards HEMA (and presumably towards other methacrylates) and to provide important information regarding the metabolic destiny of this monomer after bonding to GSH.