Antimicrobial blue light inactivation of pathogenic microbes: State of the art

Abstract

As an innovative non-antibiotic approach, antimicrobial blue light in the spectrum of 400-470nm has demonstrated its intrinsic antimicrobial properties resulting from the presence of endogenous photosensitizing chromophores in pathogenic microbes and, subsequently, its promise as a counteracter of antibiotic resistance. Since we published our last review of antimicrobial blue light in 2012, there have been a substantial number of new studies reported in this area. Here we provide an updated overview of the findings from the new studies over the past 5 years, including the efficacy of antimicrobial blue light inactivation of different microbes, its mechanism of action, synergism of antimicrobial blue light with other angents, its effect on host cells and tissues, the potential development of resistance to antimicrobial blue light by microbes, and a novel interstitial delivery approach of antimicrobial blue light. The potential new applications of antimicrobial blue light are also discussed.

Keywords: Antibiotic resistance; Antimicrobial blue light; Bacterium; Endogenous photosensitizer; Fungus; Infection; Microbe; Non-antibiotic approach.

Copyright © 2017 Elsevier Ltd. All rights reserved.

Figures

Figure 1

HPLC chromatograms of porphyrin extracts from A. baumannii (A) and P. aeruginosa (B) (Wang et al., 2016).

Figure 2

Reduction of CFU (log10 CFU) of A. baumannii in different cycles of sub-lethal bacterial inactivation by aBL at 415 nm followed by bacterial regrowth (Zhang et al., 2014).

Fig. 3

Design principle of the OMNA (Kim et al., 2016). (a) Schematics of a microneedle array and microlens array. (b) Illustration of an assembled OMNA. The microlens array focuses incident light through the microneedles. (c) Illustration of light delivery into a porcine muscle tissue slice. The design has been optimized to achieve uniform and maximal light intensity at a target depth.

Fig. 4

Enhanced light penetration into tissues by OMNA (Kim et al., 2016). (a–c) Light penetration through a 3.1-mm-thick bovine tissue slice: (a) Camera image of the tissue; Transmission intensity maps without (b) and with the OMNA (c). (d–f) Light transmission through a 2.7-mm-thick porcine tissue slice: (d) Camera image; Transmission intensity maps without (e) and with (f) the OMNA. The magnitudes of transmission are indicated in (c), (d), (e), and (f).

Figure 5

Arrayed micro-well comets with varying exposure times to UV irradiation (340–380 nm) and blue light (460–500 nm), respectively (Ge et al., 2013). Monochrome images were collected from microscope camera and colored with Red Hot lookup Table using Image J. Bars=100 μm.

Figure 6

TUNEL assay of apoptotic cells in mouse skin before, 0 h, and 24 h after aBL exposure (540 J/cm2) (Wang et al., 2016). The positive control was treated with DNase I. Nuclei were stained blue with DAPI.