Synergistic chemo-/photothermal therapy based on supercritical technology-assisted chitosan-indocyanine green/luteolin nanocomposites for wound healing

Abstract

Despite the success, it is highly challenging to battle against pathogenic biofilms-based chronic bacterial infections by conventional antibiotic therapy. Herein, we report a near-infrared (NIR)/acid-induced nanoplatform based on chitosan (CS)-coated indocyanine green (ICG, photosensitizer)/luteolin (LUT, a natural quorum sensing inhibitor) nanocomposites (ICG/LUT-CS) as antibacterial and antibiofilm agents for skin wound healing. Initially, the ICG/LUT nanoplatforms are prepared by the supercritical antisolvent technology and coated with the CS layer. The obtained ICG/LUT-CS with ultra-high encapsulation efficiency exhibited more favorable photothermal conversion effects and improved NIR laser/acid dual-induced drug release behavior than individual modalities, achieving exceptional bacteria-killing and biofilm elimination effects. Moreover, the ICG/LUT-CS realized the synergetic effects of chemotherapy and photothermal therapy outcomes for wound healing. Together, our findings provided an appealing strategy for the rapid preparation and future translational application of ICG/LUT-CS as an ideal agent for fighting against biofilm infections.

Keywords: antibacterial; antibiofilm; photothermal therapy; supercritical carbon dioxide; wound healing.

Graphical abstract

Figure 1.

Schematic illustration of the development process of ICG/LUT-CS and synergistic PTT–chemotherapy for antibiofilm and antibacterial treatments.

Figure 2.

SEM images of ICG/LUT were obtained by the SAS process in different run orders, as shown in Supplementary Table S1. (A) 40 g/min—12 MPa—1 ml/min, (B) 30 g/min—10 MPa—1 ml/min, (C) 30 g/min—12 MPa—0.5 ml/min, (D) 40 g/min—12 MPa—0.5 ml/min, (E) 40 g/min—10 MPa—0.5 ml/min, (F) 30 g/min—12 MPa—1 ml/min, (G) 40 g/min—10 MPa—1 ml/min, (H) 30 g/min—10 MPa—0.5 ml/min and (I) 35 g/min—11 MPa—0.75 ml/min, scale bar = 500 nm.

Figure 3.

Physicochemical properties of ICG/LUT-CS. (A) SEM photograph of ICG/LUT-CS, scale bar = 500 nm, (B) the size distribution of ICG/LUT-CS, (C) zeta potential, (D) FT-IR spectra, (E) UV-vis-NIR spectra, (F) EE of ICG/LUT-CS, (G) photothermal heating curves of ICG/LUT-CS in different concentrations and (H) in vitro cumulative release profiles of LUT in different conditions.

Figure 4.

In vitro antibacterial performance of ICG/LUT-CS, (A) images of S.aureus bacterial colonies and (B) the corresponding bacterial survival rates grown on broth agar plates after different treatments.

Figure 5.

In vitro inhibition effect of S.aureus biofilm formation and S.aureus biofilm ablation performance of ICG/LUT-CS, (A) quantitative analysis of the CV-stained biofilms with different pretreatments for different times, (B) pretreatments with different concentrations of nanoparticles for 24 h, (C) relative S.aureus biofilm biomass after pretreatments with different concentrations of nanoparticles for 24 h, (D) relative the remaining S.aureus biofilm biomass with different incubation time, (E) relative the remaining S.aureus biofilm biomass with different concentrations of nanoparticles for 24 h, (F) membrane permeability of remaining S.aureus biofilms cells, (G) SEM images (scale bar = 5 and 2 μm) and (H) live/dead staining images of remaining S.aureus biofilms with different treatments (scale bar = 50 μm).

Figure 6.

Antibacterial and wound-healing performance of ICG/LUT-CS in vivo. (A) In vivo thermal imaging of S.aureus-infected skin wound treated at different time intervals, and (B) the corresponding temperature variation of wound site after treated with ICG/LUT and ICG/LUT-CS upon 808-nm laser irradiation, (C) representative images of wound, (D) quantitative data of wound area, (E) OD of the different groups after collection form wound site and 4 h incubation on Day 2, (F) photographs of S.aureus colonies isolated from wound site grown on broth agar plates after receiving various treatments on Day 2.

Figure 7.

Histological evaluation of wounds in different groups. (A) H&E staining of infected skin wound tissues, (B) Masson staining of infected skin wound tissue (scale bar = 200 μm), (C) the corresponding quantitative data of granulation tissue thickness and (D) collagen deposition.

Figure 8.

Biosafety assessment of ICG/LUT-CS, (A) hemolysis ratio and corresponding photographs of whole blood after treatment with different concentrations of ICG/LUT-CS, (B) weight change curves in S.aureus-infected mice after different treatments from Day 0 to 8 and (C) H&E staining of major organs after 8 days of treatment (scale bar = 100 μm).