Surface charge adaptive nitric oxide nanogenerator for enhanced photothermal eradication of drug-resistant biofilm infections

Abstract

Due to protection of extracellular polymeric substances, the therapeutic efficiency of conventional antimicrobial agents is often impeded by their poor infiltration and accumulation in biofilm. Herein, one type of surface charge adaptable nitric oxide (NO) nanogenerator was developed for biofilm permeation, retention and eradication. This nanogenerator (PDG@Au-NO/PBAM) is composed of a core-shell structure: thermo-sensitive NO donor conjugated AuNPs on cationic poly(dopamine-co-glucosamine) nanoparticle (PDG@Au-NO) served as core, and anionic phenylboronic acid-acryloylmorpholine (PBAM) copolymer was employed as a shell. The NO nanogenerator featured long circulation and good biocompatibility. Once the nanogenerator reached acidic biofilm, its surface charge would be switched to positive after shell dissociation and cationic core exposure, which was conducive for the nanogenerator to infiltrate and accumulate in the depth of biofilm. In addition, the nanogenerator could sustainably generate NO to disturb the integrity of biofilm at physiological temperature, then generate hyperthermia and explosive NO release upon NIR irradiation to efficiently eradicate drug-resistant bacteria biofilm. Such rational design offers a promising approach for developing nanosystems against biofilm-associated infections.

Keywords: Antibacterial; Biofilm microenvironment; Charge reversal; Gasotransmitter; Photothermal therapy.

Graphical abstract

Fig. 1

Schematic illustrations of surface charge adaptable NO nanogenerator for BAI treatment. a) Design and preparation of surface charge adaptable NO nanogenerator. b) Schematic illustration of NO nanogenerator with surface charge adaptability for NO enhanced PTT to eradicate BAI.

Fig. 2

Synthesis and characterization of PDG. a) Schematic illustration for preparation of PDG. b) SEM and TEM images of PDA, PDNG and PDG. c) XPS O1s and d) N1s binding energy spectra of PDA and PDG nanoparticles. e) MALDI-TOF MS spectra of PDA and PDG nanoparticles. f) The non-covalent interaction of glucosamine moiety with DA monomer.

Fig. 3

Synthesis and characterization of PDG@Au–NO/PBAM nanogenerator. a) SEM and TEM images of PDG@Au nanocomposite. b) The average hydrodynamic sizes of PDG@Au and PDG@Au/PBAM at pH 7.4 and 5.5. c) The zeta potential of PDG@Au/PBAM at pH 7.4 and 5.5. d) UV–Vis spectra of PDG@Au and PDG@Au/PBAM. e) The heating-cooling curve of PDG@Au with varying concentrations under NIR light irradiation (808 nm 1.0 W cm⁻²). f) The on/off generation of NO from PDG@Au–NO/PBAM under NIR light irradiation (808 nm, 1 W cm⁻²). g) The relatively long-term NO generation profiles of PDG@Au–NO and PDG@Au–NO/PBAM.

Fig. 4

In vitro hemocompatibility towards rabbit red blood cells and cytocompatibility towards mouse embryonic fibroblast NIH3T3 cells. a) Hemolysis rates of different nanocomposites and 0.1% of Triton X-100 (positive control). b) Cell viability of NIH3T3 fibroblasts at different concentrations of nanocomposites.

Fig. 5

In vitro antibacterial activity of PDG@Au–NO/PBAM nanogenerator. The log reduction of a) MRSA and b) TREC after treated by different nanocomposites with or without 10 min NIR light irradiation (808 nm, 1.0 W cm⁻²). c) Photographs of surviving bacterial colonies on agar plates under different treatments. d) SEM morphologies of MRSA and TREC under different treatments. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, and not significant (NS).

Fig. 6

In vitro biofilm dispersal ability of PDG@Au–NO/PBAM nanogenerator. Quantitative calculation of biofilm biomass of a) MRSA and b) TREC by the crystal violet staining assay. c) SEM images of MRSA and TREC biofilms before and after treatment by different nanocomposites. d) Schematic illustrations of biofilm dispersal by PDG@Au–NO/PBAM nanogenerator. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, and not significant (NS).

Fig. 7

In vitro anti-biofilm ability of PDG@Au–NO/PBAM nanogenerator. The log reduction of MRSA biofilm a) and TREC biofilm b) after treated by different nanocomposites with or without 10 min NIR light irradiation (808 nm, 1.0 W cm⁻²). c) 3D confocal images of fluorescent stained MRSA and TREC biofilms under different treatments. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, and not significant (NS).

Fig. 8

In vitro anti-biofilm efficiency of PDG@Au–NO/PBAM nanogenerator in a subcutaneous implant-associated biofilm infection model. a) Schematic illustration of subcutaneous implant-associated biofilm infection model. b) Representative photographs of the implanted site every 12 h. Quantitative evaluation of bacterial counts on the c) implanted PDMS and d) tissue after different treatments. e) H&E staining of the vicinity tissues on the implanted site. f) The pro-inflammatory cytokines (IL-6 and TNF-α) analysis by immunohistochemistry. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 and not significant (NS).