Articaine: toxicometabolomics and development of lipid nanoparticles to improve anesthesia at inflamed tissues

Articaine (ATC) is one of the new local anesthetics (LA) released in the market, although it is already the second most used LA in the dental clinic. While it is considered an anesthetic of the amino-amide type, it has some chemical peculiarities such as a thiophene ring and an ester group, which bring some advantages, namely its use in a higher clinical concentration. Although all LAs present neurotoxicity, there are reports of a higher rate of paresthesia associated with the use of ATC. However, the reason for this is not clear and there is no concise literature about the greater neurotoxicity of ATC compared to other LAs. In addition, another problem related to dental anesthesia is the anesthetic failure, or a lower degree of analgesia, that can occur in places with an inflammatory process. In this case, the clinical treatment becomes extremely painful, stressful and without alternatives for effective pain control. Given these two perspectives about LAs, the focus of this work was the use of toxicometabolomics to deepen the knowledge about the neurotoxicity of ATC in relation to lidocaine (LDC) (Part 1) and the development of formulations of nanostructured lipid carriers (NLC) for sustained release of ATC to increase its anesthetic potency in inflamed tissue (Part 2). Part 1: In this part, we used Proton Nuclear Magnetic Resonance (1H-NMR) metabolomics to study the biological effects of ATC in relation to LDC (LDC, "gold standard") through the detection of metabolic changes caused in neuronal cells. Despite the literature indicating that there are no differences between ATC and other LAs in relation to in vitro toxicity, metabolomics analysis in Schwann cells (SC) showed that ATC produces different metabolic changes in relation to LDC. Specifically, ATC was found to stimulate glycolysis and to induce increases in intracellular levels of several amino acids (leucine, isoleucine, valine, phenylalanine, methionine, histidine, tyrosine, and glycine), while the concentration of these amino acids decreased in lidocaine-treated SC. In addition, ATC produces greater changes in the rate of cellular oxygen consumption compared to LDC. Besides, the expression of proteins indicates the presence of reticulum stress and apoptosis in ATC-treated cells. Thus, the in vitro metabolomics study of ATC identified differential metabolic responses which allow us to question whether its toxicity is the same in relation to other LAs. Part 2: In this part, Design of Experiments (DoE) and zebrafish model were used to select the best functional excipient, copaiba oil (CO), and to obtain an optimized formulation of NLC-ATC. Afterwards, optimized NLC-ATC were characterized by DSC, XRD and MET. In vivo, in the carrageenan-induced inflammatory pain model, NLC-ATC showed an increase (50%) in the anesthetic activity and a prolonged action time compared to free (non-encapsulated) ATC, with synergistic activity between ATC and CO being observed on inflammatory pain control. In addition, using local tissue microdialysis, the pharmacokinetic results revealed the greatest anesthetic effect to be associated with the ability of prolonged delivery of ATC by NLC-ATC in the inflamed tissue, preventing its accelerated systemic removal due to the inflammatory process. Thus, the functionalized NLC-ATC formulation developed showed promising results in relation to anesthetic failure in inflamed tissue, with an innovative perspective for the dental market (AU)