Novel Donor-Acceptor Conjugated Polymer-Based Nanomicelles for Photothermal Therapy in the NIR Window

pH-responsive nanogels with enhanced antioxidant and antitumor activities on drug delivery and smart drug release

pH-responsive nanogels have played an increasingly momentous role in tumor treatment. The focus of this study is to design and develop pH-responsive benzimidazole-chitosan quaternary ammonium salt (BIMIXHAC) nanogels for the controlled release of doxorubicin hydrochloride (DOX) while enhancing its hydrophilicity. BIMIXHAC is crosslinked with carboxymethyl chitosan (CMC), hyaluronic acid sodium salt (HA), and sodium alginates (SA) using an ion crosslinking method. The chemical structure of chitosan derivatives was verified by 1H NMR and FT-IR techniques. Compared to hydroxypropyl trimethyl ammonium chloride chitosan (HACC)-based nanogels, BIMIXHAC-based nanogels exhibit better drug encapsulation efficiency and loading capacity (BIMIXHAC-D-HA 91.76 %, and 32.23 %), with pH-responsive release profiles and accelerated release in vitro. The series of nanogels formed by crosslinking with three different polyanionic crosslinkers have different particle size potentials and antioxidant properties. BIMIXHAC-HA, BIMIXHAC-SA and BIMIXHAC-CMC demonstrate favorable antioxidant capability. In addition, cytotoxicity tests showed that BIMIXHAC-based nanogels have high biocompatibility. BIMIXHAC-based nanogels exhibit preferable anticancer effects on MCF-7 and A549 cells. Furthermore, the BIMIXHAC-D-HA nanogel was 2.62 times less toxic than DOX to L929 cells. These results suggest that BIMIXHAC-based nanogels can serve as pH-responsive nanoplatforms for the delivery of anticancer drugs.

Near-Infrared Conjugated Polymers Containing Thermally Activated Delayed Fluorescence Units Enable Enhanced Photothermal Therapy

Photothermal therapy (PTT) using near-infrared (NIR) conjugated polymers as photosensitizers has exhibited enormous potential for tumor treatment. However, most NIR conjugated polymers have poor therapeutic efficacy due to their faint absorbance in the NIR region and low photothermal conversion efficiency (PCE). Herein, a valuable strategy for designing NIR polymeric photosensitizer PEKBs with an enhanced PCE accompanied by strong NIR absorbance is proposed by means of inserting TPA-AQ as a thermally activated delayed fluorescence unit into a polymeric backbone. In these PEKBs, PEKB-244 with the appropriate molar content of the TPA-AQ unit displays the strongest NIR absorbance and the highest PCE of 64.5%. Theoretical calculation results demonstrate that the TPA-AQ unit in the polymeric backbone can modulate the intramolecular charge transfer effects and the excited energy decay routes for generating higher heat. The prepared nanoparticles (PEKB-244 NPs) exhibit remarkable photothermal conversion capacities and great biocompatibility in aqueous solutions. Moreover, PEKB-244 NPs also show outstanding photothermal stability, displaying negligible changes in the absorbance within 808 nm irradiation of 1 h (800 mW cm-2). Both in vitro and in vivo experimental results further indicate that PEKB-244 NPs can substantially kill cancer cells under NIR laser irradiation. We anticipate that this novel molecular design strategy can be employed to develop excellent NIR photosensitizers for cancer photothermal therapy.

Synthesis, Optical Properties and Cellular Toxicity of Water-Soluble near Infrared-II Fluorescent Assemblies Based on Pillar[5]arene

The main challenges in second near-infrared region molecular fluorophores are poor water solubility and unknown long-term toxicity at present. Herein, new NIR-II molecular fluorophores have been designed and employed to integrate biocompatible pillar[5]arene with 10 outer triethylene oxide groups for the synthesis of rotaxane IRCR. In addition, PEGylated pillar[5]arenes have been combined for the self-assembly of two supramolecular vesicular systems, i.e., PP5-IR1 and PP5-IR2, affording aqueous solubility and lowered cellular toxicity. In aqueous solution, all these fluorophores displayed room-temperature emission with λmax at 986-1013 nm and quantum yields of 0.54-1.45%. They also exhibited good chemical stability and reasonable self-assembled sizes, which may find potential applications in NIR-II imaging. In addition, PP5-IR1 can be used as a fluorescent chemosensor for selective recognition of glutathione through the cleavage of dinitrophenyl ether and release the fluorescent dye.

Recent Strategies to Develop Conjugated Polymers for Detection and Therapeutics

The infectious diseases resulting from pathogenic microbes are highly contagious and the source of infection is difficult to control, which seriously endangers life and public health safety. Although the emergence of antibiotics has a good therapeutic effect in the early stage, the massive abuse of antibiotics has brought about the evolution of pathogens with drug resistance, which has gradually weakened the lethality and availability of antibiotics. Cancer is a more serious disease than pathogenic bacteria infection, which also threatens human life and health. Traditional treatment methods have limitations such as easy recurrence, poor prognosis, many side effects, and high toxicity. These two issues have led to the exploration and development of novel therapeutic agents (such as conjugated polymers) and therapeutic strategies (such as phototherapy) to avoid the increase of drug resistance and toxic side effects. As a class of organic polymer biological functional materials with excellent photoelectric properties, Conjugated polymers (CPs) have been extensively investigated in biomedical fields, such as the detection and treatment of pathogens and tumors due to their advantages of easy modification and functionalization, good biocompatibility and low cost. A rare comprehensive overview of CPs-based detection and treatment applications has been reported. This paper reviews the design strategies and research status of CPs used in biomedicine in recent years, introduces and discusses the latest progress of their application in the detection and treatment of pathogenic microorganisms and tumors according to different detection or treatment methods, as well as the limitations and potential challenges in prospective exploration.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

A Novel NQO1 Enzyme-Responsive Polyurethane Nanocarrier for Redox-Triggered Intracellular Drug Release

The design of nano-drug delivery vehicles responsive to tumor microenvironment stimuli has become a crucial aspect in developing cancer therapy in recent years. Among them, the enzyme-responsive nano-drug delivery system is particularly effective, as it utilizes tumor-specific and highly expressed enzymes as precise targets, leading to increased drug release at the target sites, reduced nonspecific release, and improved efficacy while minimizing toxic side effects on normal tissues. NAD(P)H:quinone oxidoreductase 1 (NQO1) is an important reductase associated with cancer and is overexpressed in some cancer cells, particularly in lung and breast cancer. Thus, the design of nanocarriers with high selectivity and responsiveness to NQO1 is of great significance for tumor diagnosis and treatment. It has been reported that under physiological conditions, NQO1 can specifically reduce the trimethyl-locked benzoquinone structure through a two-electron reduction, resulting in rapid lactonization via an enzymatic reaction. Based on this, a novel reduction-sensitive polyurethane (PEG-PTU-PEG) block copolymer was designed and synthesized by copolymerizing diisocyanate, a reduction-sensitive monomer (TMBQ), and poly(ethylene glycol). The successful synthesis of monomers and polymers was verified by nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC). Then, the PEG-PTU-PEG micelles were successfully prepared by self-assembly, and their reductive dissociation behavior in the presence of Na₂S₂O₄ was verified by dynamic light scattering (DLS), ¹H NMR, and GPC. Next, the model drug doxorubicin (DOX) was encapsulated into the hydrophobic core of this polyurethane micelles by microemulsion method. It was observed that the drug-loaded micelles could also achieve a redox response and rapidly release the encapsulated substances. In vitro cell experiments demonstrated that PEG-PTU-PEG micelles had good biocompatibility and a low hemolysis rate (<5%). Furthermore, in the presence of an NQO1 enzyme inhibitor (dicoumarol), lower drug release from micelles was observed in A549 and 4T1 cells by both fluorescence microscopy and flow cytometry assays, but not in NIH-3T3 control cells. Predictably, DOX-loaded micelles also showed lower cytotoxicity in 4T1 cells in the presence of NQO1 enzyme inhibitors. These results indicate that drug-loaded polyurethane micelles could accomplish specific drug release in the reducing environment in the presence of NQO1 enzymes. Therefore, this study provides a new option for the construction of polyurethane nanocarriers for precise targeting and reductive release, which could benefit the intracellular drug-specific release and precision therapy of tumors.

Review of quantitative and qualitative methods for monitoring photopolymerization reactions

Authomatic in-situ monitoring and characterization of photopolymerization.