Enhanced Antitumor Activity of Lidocaine Nanoparticles Encapsulated by a Self-Assembling Peptide

Abstract

Although local anesthetics (LAs) such as lidocaine have been traditionally used for pain relief, their antitumor activity has attracted more and more attentions in recent years. However, since nearly all LAs used in clinic are in their hydrochloride forms with small molecular weight and high water-solubility, their fast absorption and clearance greatly limit their antitumor activity in vivo. To better exploit the antitumor activity of LAs, lidocaine nanoparticles (LNPs) are prepared by using a self-assembling peptide to encapsulate the hydrophobic base form of lidocaine. In cultured A375 human melanoma cells, the LNPs show much higher cellular uptake level than the clinic formulation of lidocaine hydrochloride, which leads to enhanced efficacy in inhibiting the proliferation, migration and invasion of the cells, as well as in inducing cell apoptosis. Compared with lidocaine hydrochloride, LNPs can also significantly slow down the release rate of lidocaine. In nude mice, LNPs can effectively inhibit the development of solid tumors from seeded A375 cells and prevent the recurrence of tumors after surgical excision. These results indicate that by using self-assembling peptide to fabricate nanoparticle formulations of local anesthetics, their antitumor activity can be significantly enhanced, suggesting a potential postoperative treatment to prevent tumor recurrence after surgical excision.

Keywords: antitumor activity; lidocaine; local anesthetics; nanoparticles; self-assembling peptide; tumor recurrence.

FIGURE 1

Characterization of LNPs. (A) photo pictures of LB dispersed in water (left) or in GQY (right). (B) TEM (left) and AFM (right) images of empty GQY nanoparticles and LNPs. (C) size distribution of LNPs and empty GQY nanoparticles. (D) zeta potential of LNPs and empty GQY nanoparticles. (E) ThT-binding fluorescence of GQY, LNPs, and LH. (F) FTIR spectra of GQY, LH, LB, LNP, and LB + GQY.

FIGURE 2

Enhanced cellular uptake and cytotoxicity of LNPs. (A) cytotoxicity of LH incubated with A375 cells for 4 or 24 h. (B) co-localization of GQY (stained green by ThT) and encapsulated DOX (red) in A375 cells. (C) cellular uptake of LH and LNPs. (D) cytotoxicity of LH and LNPs with 4-h of incubation. *p < 0.05, ***p < 0.001,****p < 0.0001 by one-way ANOVA with Tamhane’s T2.

FIGURE 3

LNPs inhibit migration and invasion of A375 cells. (A) representative images of wound healing, with the “wound” area marked by red lines. (B) comparison of normalized migration distance between different groups. (C) representative images of cells invaded through the membrane of transwell. (D) comparison of normalized invasion rate between different groups. *p < 0.05, ****p < 0.0001 by one-way ANOVA with Tamhane’s T2.

FIGURE 4

Apoptosis of A375 cells induced by LNPs or LH. Representative flow images were shown for the control group (A), LH group (B), and LNP group (C). Comparison of analyzed apoptosis rate between different groups was shown in (D). *p < 0.05, **p < 0.01 by one-way ANOVA with Tamhane’s T2 post-hoc test.

FIGURE 5

In vitro release profile of LH and LNPs. ****p < 0.0001 by one-way ANOVA with Tamhane’s T2.

FIGURE 6

LNPs inhibited tumor development in vivo. (A) different formulations were injected subcutaneously on day 3 after cell injection and the development of solid tumor was monitored. (B) change of body weight of animals during tumor development. (C) change of tumor volume measured during tumor development. (D) weight comparison and representative pictures (right) of harvested tumors from different groups. **p < 0.01 by one-way ANOVA with Tamhane’s T2 post-hoc test.

FIGURE 7

(A) preformed tumors were partially excised and different formulations were injected on day 0, and the recurrence of tumors was monitored from day 12. (B) survival curve and (C) survival time were compared between different groups, determined based on a tumor volume of 1,500 mm³. **p < 0.01 by one-way ANOVA with Tamhane’s T2 post-hoc test.

FIGURE 8

Schematic illustration of LNPs preparation. (A) chemical structure of LH and LB. (B) chemical structure of GQY peptide with hydrophobic motifs in side-chain shown in blue. (C) proposed model for the formation of LNPs.