Photodynamic and photothermal therapies for bacterial infection treatment

Abstract

Bacteria can cause numerous infectious diseases and has been a major threat to human humans. Although antibiotics have partially succeeded in treating bacteria, owing to antibiotic abuse, the emergence of multidrug-resistant (MDR) bacteria has drastically diminished their potency. Since the invention of laser, the combination of light and photosensitizers, photodynamic therapy (PDT), has become an effective noninvasive treatment along with photothermal therapy (PTT), in which heat is generated by nonradiative relaxation. Antimicrobial PDT and PTT are emerging as effective treatments for bacterial infection, particularly against MDR bacteria. This mini review covers the recent progresses in PDT and PTT for bacterial treatment.

Keywords: AIEgens; antibacterial phototherapy; photodynamic therapy; photothermal therapy; phthalocyanine.

FIGURE 1

(a) Chemical structure of the PcA and schematic illustration of its nanostructured self‐assembly. (b) Schematic illustration of the potential mechanism of O₂ ^•− production by NanoPcA. (c) Comparison of O₂ ^•−generation by NanoPc, NanoPcA, and NanoPcA4 in aqueous solutions. Reproduced with permission from Ref. [15]. Copyright (2018) Wiley‐VCH.

FIGURE 2

(a) Chemical structure of PcN and the structure of its self‐assembly NanoPcN. (b) O₂ ^•− generation ability and (c) dynamic NanoPcN temperature after laser irradiation. (d) The potential photophysically activated NanoPcN process. Reproduced with permission from Ref. [17]. Copyright (2022) American Chemical Society.

FIGURE 3

(a) Molecule structure of PcC4. (b) Enhanced ISC process of the aggregated state. (c) Schematic illustration of the binding of PcC4‐NA to the bacterial outer membrane. (d) Schematic depiction of the self‐assembled nanostructure formation. (e) Photoinactivation of MR Staphylococcus aureus and ESBL Escherichia coli in the presence of PcN4‐NA and under laser irradiation. Reproduced from Ref. [18] with permission from The Royal Society of Chemistry.

FIGURE 4

(a) Schematic illustration of the self‐assembly of Azos–PS nanoparticles. (b) Chemical structure of the Azos–PS host–guest systems. (c) Changes in the absorption spectra of Azos–PS host–guest systems. (d) Changes in the fluorescence spectra of the Azos–PS host–guest systems. (e) Transmission electron microscopy image of the Azos–PS host–guest systems. Reproduced from Ref. [19] with permission from The Royal Society of Chemistry.

FIGURE 5

(a) Molecular structure of Pc‐pDMAEMA‐C4 and the schematic illustration of antibacterial PDT. (b) Bacterial growth inhibition using various concentrations of Pc‐pDMAEMA‐C4 with and without 680 nm light irradiation. Reproduced from Ref. [20]. Copyright (2022), with permission from Elsevier.

FIGURE 6

(a) Chemical structure of the water‐soluble porphyrin derivatives (PN3). Transmission electron microscopy images of PN3 in (b) PBS (pH 7.4) and (c) PBS (pH 5.0). (d) Fluorescence spectra, (e) photothermal performance, and (f) singlet oxygen generation by PN3 in different solutions. Reproduced with permission from Ref. [22]. Copyright (2022) Wiley‐VCH.

FIGURE 7

(a) Synthesis scheme of ePLU starting from UPy and ePL. (b) Illustration of cross‐linking system of PLU@PTc by hydrogen bonding and Schiff base linking. (c) Release of TCPP triggered by bacterial infection and wound healing process using wrapped bacterial debris with hydrogels. Reproduced from Ref. [24]. Copyright (2022) with permission from American Chemical Society.

FIGURE 8

Design strategy and schematic illustration of the NIR‐smart AIEgen, TPA‐S‐C6‐NMe ₃ ⁺ , for the inactivation of bacteria and fungi. Reproduced with permission from Ref. [29]. Copyright (2021), Chinese Chemical Society. AIEgen, aggregation‐induced emission luminogen; NIR, near‐infrared.

FIGURE 9

Schematic illustration of (a) SODS of the photo‐antimicrobial AIEgen BDPTV and (b) antibacterial therapy. (c) Plate photographs demonstrating the antibacterial effect of BDPTV on various bacteria when exposed to white light. Reproduced from Ref. [31]. Copyright (2022) with permission from Elsevier. AIEgen, aggregation‐induced emission luminogen; SODS, structure‐oriented design strategy.

FIGURE 10

Molecular structure of the CPVBP and TTVBP derivatives. Reproduced from Ref. [32]. Copyright (2022) with permission from American Chemical Society.

FIGURE 11

Synthesis of AIEgens (a) and formation of spherical AIE NPs (a, c). Least unoccupied molecular orbital and highest occupied molecular orbital (b) of the AIE NPs, which can strongly absorb NIR light (e) and photothermal effect (d). Singlet oxygen generation upon 808‐nm laser irradiation (f). Reproduced from Ref. [24]. Copyright (2022), with permission from American Chemical Society. AIEgens, aggregation‐induced emission luminogens; NIR, near‐infrared.

FIGURE 12

Chemical structure of the CS‐2I AIEgen and the application of CS‐2I@gel in the inactivation of bacteria via PDT. Reproduced with permission from Ref. [33]. Copyright (2022) Wiley‐VCH. AIEgen, aggregation‐induced emission luminogen; PDT, photodynamic therapy.

FIGURE 13

(a) Chemical structures of NBS‐N and NBSe‐N. (b) O₂ ^•− generation capability of NBS‐N. (c) Comparison of ¹O₂ generation yields of NBS‐N and NBSe‐N. (d) Antibacterial tests of NBS‐N and NBSe‐N against Staphylococcus aureus and Escherichia coli. (e) Photographs of S. aureus‐ and methicillin‐resistant S. aureus‐infected wounds in mice treated with or without NBS‐N in the absence or presence of red‐light irradiation on Day 2 and Day 6. Reproduced with permission from Ref. [34]. Copyright (2022) Wiley‐VCH.

FIGURE 14

(a) Structure of TPE‐2Py‐DTE(o) and TPE‐2Py‐DTE(c) nanoparticle and its photoswitching behavior. (b) Different antibacterial effects of TPE‐2Py‐DTE(o) and TPE‐2Py‐DTE(c) in Staphylococcus aureus‐ and Escherichia coli. Reproduced from Ref. [35]. Copyright (2022) with permission from Elsevier.