Conjugated Polymer-Based Photothermal Therapy for Killing Microorganisms

Abstract

Microbial infections pose major threats to human health, and such a situation is further exasperated by microbial resistance to conventional antibiotics. It is therefore highly imperative to develop antimicrobial agents or strategies to achieve effective microbicidal effects. Recently, conjugated polymers (CPs) have shown their capacity to serve as effective photothermal agents (PTAs) for antimicrobial photothermal therapy (PTT). In this review, we first introduce the latest advances in the development of CPs as PTAs for combating microbes. We focus on the most-investigated polydopamine (PDA)-based PTT for killing microorganisms, in which the PDA-based PTAs are mainly in the formulations of nanoparticles, hydrogels, and surface coatings. Meanwhile, we present antimicrobial PTT based on the other CPs, including polypyrrole, polyaniline, and poly (3,4-ethylenedioxythiophene). Finally, we discuss both the current limitations and future directions of the CP-derived antimicrobial PTT.

Low-Temperature Photothermal Therapy: Strategies and Applications

“…It is widely recognized that the mechanism of employing hyperthermia for killing microorganisms is destroying diverse life-fundamental molecules or structures, including protein denaturation, lipid evaporation, and cell membrane breakage [ 2 , 52 ]. To date, many kinds of PTAs, such as carbon-based nanomaterials [ 53 , 54 ], noble metal nanomaterials [ 55 , 56 ], other metal-containing nanocomposites [ 57 ], and conjugated polymers [ 35 , 36 ], have been used for antimicrobial applications and have established their unique advantages. Moreover, owing to the uneven heat distribution in the bacterial biofilms, it is difficult to completely eradicate the bacteria within the biofilms via PTT alone.…”

“…The inorganic PTAs include metal or metal-containing nanomaterials including gold nanostructures [ 11 , 12 ], palladium-based nanostructures [ 13 – 15 ], iron or copper-containing nanoparticles (NPs) [ 16 – 19 ], transition metal chalcogenides [ 20 ], and quantum dots [ 21 , 22 ]. On the other hand, organic materials [ 23 ] including near-infrared (NIR) dyes represented by cyanine dyes [ 24 – 32 ], conjugated polymers (e.g., polydopamine (PDA), polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene)) [ 33 – 36 ], and some carbon-based nanomaterials (most of them are organic materials; as represented by graphite-related nanostructures) [ 37 – 41 ] have also been utilized for PTT.…”

Smart Asymmetric Hydrogel with Integrated Multi‐Functions of NIR‐Triggered Tunable Adhesion, Self‐Deformation, and Bacterial Eradication

“…[29][30][31] Compared with chemotherapy, the PTT has broadspectrum sterilizing ability and would not lead to the formation of drug-resistant pathogens as a non-resistant and minimally invasive process. [32][33][34] Therefore, multifunctional hydrogels incorporating photothermal agents have great potential as an antibacterial wound dressing to prevent infection and promote wound healing.…”

Intramolecular Charge Transfer-Based Conjugated Oligomer with Fluorescence, Efficient Photodynamics, and Photothermal Activities

“…Conjugated polymers/oligomers have emerged as a competitive class of photoactive agents for phototriggered inactivation of cancer cells or microorganisms. − Due to its large π-conjugated structure, conjugated polymers/oligomers possess strong light-harvesting abilities which can motivate a cascade of photochemical reactions. Through radiative transition from singlet excited state, they display favorable fluorescence properties with high quantum yields, which makes them excellent probes for biological imaging and diagnosis. − Meanwhile, the excited triplet state formed by intersystem crossing can interact with the surrounding oxygen and other substrates to produce toxic ROS. − Moreover, their capacity to serve as photothermal agents has also been explored, which mainly focus on nonfluorescent polydopamine (PDA), polyaniline (PANI), polypyrrole (PPy), and poly­(3,4-ethyl-enedioxythiophene) (PEDOT), as well as some conjugated polymers/oligomers with a narrow bandgap that shifted their absorption into the NIR region. ,− In these cases, photon energy has been transferred into heat through nonradiative transition, and the radiative channel and ISC process are inhibited. Up to now, only a few examples of conjugated polymers/oligomers have been developed as photoactive agents integrating both PDT and PTT effects. , Since the radiative transition, singlet-to-triplet intersystem crossing, and nonradiative transition are the three main decay processes of a photoexcited fluorophore and are competitive with one another, how to balance these three processes and acquire a multifunctional photoactive agent is still a big challenge.…”