Recent Advances in Polymer-Based Photothermal Materials for Biological Applications

Abstract

The photothermal effect, which is a phenomenon of converting light energy into thermal energy using photothermal conversion materials, has recently attracted significant attention in biological applications because of the minimal invasiveness to healthy tissues, high specificity, and easy operation. Polymer-based photothermal materials have emerged as a promising category of photothermal agents in biological applications because they show superiorities in tailorable molecular structures, high photothermal conversion efficiencies, and excellent biocompatibility. In this Review, we summarize the recent progresses achieved in polymer-based photothermal materials for biological applications. To have a better understanding of the working mechanism and the design of polymer-based photothermal materials, this Review starts with the fundamental description of photothermal conversion mechanism of polymer-based photothermal materials. According to their structures and compositions, the polymer-based photothermal materials can be classified into three types: conjugated polymers, polymer-modified carbon nanomaterials, and polymer-modified metals and metal compounds. Then we present the recent advances of the polymer-based photothermal materials in a diversity of biological areas such as photothermal therapy and photothermal sterilization. In the last section, we summarize the critical existing issues in polymer-based photothermal materials for biological applications and propose some perspectives that are related to the design and synthesis of polymer-based photothermal materials for biological applications.

Synthesis of Magnetic Ferrocene-Containing Polymer with Photothermal Effects for Rapid Degradation of Methylene Blue

“…The reason might be attributed the Fc, which as an excellent electron-donating unit can inhibit singlet-oxygen ( 1 O 2 ) production and quench fluorescence emission by a photo-induced electron transfer (PET) process, and thus improve the nonradiative transition of thermal energy release [ 29 ]. Furthermore, it has also been proven that iron-containing polymer is considered as a new class of photothermal agents [ 30 ].…”

Light‐Activated Conjugated Polymers for Antibacterial Photodynamic and Photothermal Therapy

“…The useful characteristics of photoresponsive agents have their origin in the mechanisms by which materials can release energy following excitation: The light energy absorbed by a material can be converted into photoluminescence (radiative de‐excitation) and heat (nonradiative de‐excitation). [ 52–54 ] The light emission (fluorescence or phosphorescence) and the generation of heat following light absorption can be illustrated according to the Jablonski diagram ( Figure 3 ). Briefly, the absorption of light with appropriate energy leads to a transition from the ground state to an excited singlet state (S n ), generally with one electron holding its opposed spinning configuration occupying higher vibrational levels.…”

“…Energy release in the form of light emission or that in the form of heat are complementary in a way that a material with a high fluorescence quantum yield would generate low heat. [ 53,54 ] As a consequence, good fluorescence emitters find use in bioimaging, [ 16 ] while lower photoluminescence emitters have been used as probes for photoacoustic imaging [ 16 ] and as PTT agents capable of tumor ablation [ 13,57 ] and microorganism inactivation. [ 9,23,58 ] As fluorescence and phosphorescence are competing radiative de‐excitation pathways, successful PDT agents would typically present a low fluorescence quantum yield and long‐standing triplet states.…”

“…[ 69 ] The many useful characteristics of conjugated polymers are also related to their easy processability, enabling the assembly of electromechanically active devices, [ 70 ] manufacture of solar cells [ 71 ] and flexible light‐emitting displays, [ 72,73 ] and the preparation of nanoparticles with biomedical application. [ 74,75 ] Their organic composition and good biocompatibility have boosted the interest for biomedical use, [ 54 ] with one of the earliest biological applications exploring their excellent fluorescence for biosensing. [ 76,77 ] Since then, their biomedical application has greatly expanded [ 63 ] as conjugated polymer–based materials have excelled as bioimaging probes, [ 16 ] theranostic agents for cancer treatments, [ 57,78,79 ] drug delivery systems, [ 74,80 ] and light‐responsive antimicrobial agents.…”

“…[ 18–20 ] In fact, conjugated polymers with a sequence of electron‐donating and electron‐accepting units (donor–acceptor structures) have shown enhanced performance as aPDT and aPTT agents. [ 24,54,81,95 ] In this context, conjugated polymers with the same backbone structure but functionalized with electron‐donating and withdrawing groups outperformed the ROS generation and antimicrobial activity of their counterpart functionalized with two strong electron‐accepting groups. [ 20 ] In addition, conjugated polymers with increasing electron‐withdrawing benzothiadiazole (BT) units presented a decrease in their fluorescence emission, augmented singlet oxygen ( 1 O 2 ) generation, and greater antibacterial activity under visible light irradiation.…”