Characterization, biocompatibility, permeation profile and anesthetic efficacy of a formulation of lidocaine-loaded poly(epsilon-caprolactone) nanocapsules

Author(s)

Cleiton Pita dos Santos

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2015-12-11

Examining board members

Maria Cristina Volpato; Viviane Fusco Seixas; Vanessa Rocha Lima Shcaira; José Ranali; Bruno Bueno Silva

• Advisor: Maria Cristina Volpato; Michelle Franz Montan

Abstract

Lidocaine is the gold standard local anesthetic, and presents short onset and moderate anesthesia duration when associated to a vasoconstrictor. However, without vasoconstrictor, promotes short duration pulpal anesthesia and, as topical anesthetic, does not block the injection pain. Drug release systems, such as nanoparticles have shown efficacy in decreasing toxicity, and improving anesthesia duration and drug permeation. Therefore, the objectives of this study were to characterize a formulation of lidocaine encapsulated in poly(epsilon-caprolactone) nanocapsules (LDC-Nano) and to evaluate its cytotoxicity and permeation through mucosa and the anesthetic efficacy in inflamed tissue, comparing to the obtained with lidocaine (LDC) and lidocaine with epinephrine (LDC-Epi). The pH of the suspensions, and nanoparticles size and polidispersivity were evaluated for 120 days (dynamic light scattering). The thermograms of the formulations (LDC-Nano, nanocapsules without anesthetic ¿ Nano), components of the formulations (LDC, poly(epsilon-caprolactone) ¿ PCL) and the physical mixture of them were evaluated by differential scanning calorimetry. Encapsulation efficiency was analyzed by ultrafiltration-centrifugation. The cytotoxicity of the formulations to HaCaT cells were determined by MTT. Permeation profiles were evaluated in vitro across pig esophageal epithelium in Franz-type vertical diffusion cells. The anesthetic efficacy was evaluated in vivo in a model of inflammation (surgical wound in the paw of rats) with von Frey anesthesiometer. Data were analyzed by t test (diameter and polydispersivity), nonlinear fit analysis (MTT assay), unpaired t test with Welch correction (in vitro permeation assay), ANOVA and Holm-Sidak's multiple comparisons test (anesthesia duration) and Log-Rank Mantel-Cox test (anesthesia success), with 5% significance. LDC-Nano and Nano presented, respectively, mean diameter nanocapsules of 557.8 ± 22.7 nm and 530.5 ± 9 nm, polidispersivity of 0.08 ± 0.01 and 0.16 ± 0.02 and pH 8.1 ± 0.21 and 6.3 ± 0.21 and remained stable for 120 days. Encapsulation efficiency was 51.8 ± 1.87%. Differential scanning calorimetry showed interaction between lidocaine and Nano. The LD50 of LDC-Nano and LDC was respectively 0.47% and 0.48% and both differed from LDC-Epi (p <0.0001). LDC-Nano increased steady-state flux (p<0.0001) and permeability (p=0.0002) across esophageal epithelium in relation to LDC. In the in vivo essay LDC-Nano increased anesthesia duration (43 ± 8 min) (p=0.0003) in relation to LDC (24 ± 11min), however LDC-Epi provided a higher duration (118 ± 10 min) (p<0.0001). In conclusion, LDC-Nano presented good physicochemical characteristics and stability, with similar toxicity in relation to lidocaine. It increased anesthesia duration in inflamed tissue, although to a lower degree than that provided by epinephrine. The improvement in permeation opens the perspective of its use as a topical anesthetic (AU)

• FAPESP's process: 12/02590-7 - Biocompatibity and permeation studies of lidocaine-loaded poly(epsilon-caprolactone) nanocapsules formulations
• Grantee: Cleiton Pita dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate