Construction of gelatin/alginate hydrogels doped hemicyanine derivatives for photodynamic antibacterial application.

Hydrogel systems based on natural polymer materials have provided alternative opportunities for preparing antimicrobial dressings. A composite antibacterial hydrogel system containing gelatin (Gel), alginate (Alg) and hemicyanine derivatives with different chain lengths (C3, C6 and C10) was constructed. The composite hydrogels have excellent swelling ability and low degradability due to the classical three-dimensional network structure. Because of the photosensitization ability of C3, C6 and C10, hydrogels containing these molecules can also effectively produce reactive oxygen species (ROS) under light. Importantly, the hydrogel containing C3 molecules that have higher spatial extension structure and shorter alkyl chain than C6 and C10 shows better photo-responsive antibacterial effect against drug-resistant Escherichia coli. The bacterial killing activity of the composite hydrogel system could be regulated by changing the alkyl chain length of the photosensitizers. This effective and photo-responsive composite hydrogel system is expected to be used for bacteria-infected wound repair and promoting wound healing.

Construction of Electrostatic Spinning Membranes Based on Conjugated Hemicyanine Derivatives for Photodynamic Antibacterial Application.

The preparation of efficient antibacterial membrane materials is one of the important strategies to fight against bacterial infection and alleviate drug resistance. Herein, hemicyanine derivatives with different chain lengths (C3, C6, and C10) that exhibit excellent photodynamic antibacterial activity were doped into spinnable polyvinyl alcohol solution (PVA, 8%) to obtain composite fiber membrane Cn/PVA (C3/PVA, C6/PVA, and C10/PVA) by a simple "one-pot" method using electrospinning technology. The antibacterial nanofiber membrane has a dense fiber structure which has a good interception effect, high thermal stability, and great biocompatibility. Importantly, Cn/PVA nanofibers could efficiently sensitize oxygen to generate reactive oxygen species (ROS), leading to high photokilling efficacy against drug-resistant bacteria. The variation of structure for hemicyanines causes the difference of Cn/PVA nanofibers in the effects of antibacterial performance, and it is found that C3/PVA and C10/PVA with three and ten carbons in the alkyl chain could kill more than 97% of ampicillin-resistant E. coli, which is much better than that of C6/PVA. Moreover, C3/PVA and C10/PVA exhibited killing efficiencies of 98.6 and 90.6% against MRSA, respectively. The construction of Cn/PVA composite fibers provides research ideas for the development of structure-dependent antimicrobial surface materials and is expected to be applied as superficial medical antibacterial protection materials.

Regulation of Antimicrobial Effect of Hemicyanine-Based Photosensitizer via Supramolecular Assembly.

An intelligent "antimicrobial switch" has been constructed to reduce prolonged exposure of pathogenic bacteria to antibiotics, which could reversibly "turn off" or "turn on" the antimicrobial activity of hemicyanines through self-assembly or dis-assembly of cucurbit[7]uril (CB[7]). This assembly effectively inhibited the production of ROS under light, shielding the active site of hemicyanines and achieving on-demand antimicrobial ability. Moreover, CB[7] differentially inhibits ROS of molecules with different alkyl chain lengths, which provided reference for the subsequent design of materials with antimicrobial activity regulation, and could effectively delay or even prevent the development of pathogens resistance.

Design and structural regulation of AIE photosensitizers for imaging-guided photodynamic anti-tumor application.

In recent years, photodynamic therapy (PDT) has become one of the important therapeutic methods for treating cancer. Aggregation-induced emission (AIE) photosensitizers (PSs) overcome the aggregation-caused quenching (ACQ) effects of conventional PSs in aggregation or high concentration states, showing enhanced reactive oxygen species (ROS) generating capacity and improved therapeutic efficiency. Meanwhile, connecting different donor and acceptor groups gives the PSs a lower energy level and the absorption/emission of a long wavelength, which makes the PSs produce more ROS and penetrate deeper into the tissue for imaging. As a promising tool for achieving efficient PDT applications, numerous studies have demonstrated the advantages and potential medical applications of AIE PSs in the diagnosis and treatment of various diseases. Herein, we outline the research progress of AIE PSs with different representative structures in fluorescence imaging and photodynamic anti-tumor therapy, and expound the design strategy of the donor-acceptor (D-A) framework for constructing practical AIE PSs in the past three years. Furthermore, this review addresses the underlying challenges and opportunities of AIE PSs in PDT, aiming to grasp the striving directions of the next generation of AIE PSs.

Bipolar Hemicyanine-Based Photodynamic Modulation of Type I Pathway for Efficient Sterilization and Real-Time Monitoring.

The development of photosensitizers with low oxygen dependence for generating type I ROS is in high demand to be able to treat pathogenic infections in hypoxic conditions. Here, we report a series of cationic bipolar hemicyanines (C3, C6, and C10) with alkyl linkers of varying lengths that are found to exclusively produce hydroxyl radicals and superoxide radicals with the aid of white light and that have different antibacterial abilities toward a variety of pathogens. Furthermore, hemicyanines could differentiate live from dead bacteria to track the status of pathogens in real time. It is expected that hemicyanines could be applied for combatting various microbial infections in hypoxia and real-time tracking.

Design and Application of Conjugated Polymer Nanomaterials for Detection and Inactivation of Pathogenic Microbes.

Infectious deaths due to drug resistance of pathogens caused by the abuse of antibiotics have seriously endangered public health in the world. Therefore, it is urgent to develop diversified methods for rapid detection of pathogens and antimicrobial drugs that are not prone to develop resistance. Conjugated polymers (CPs) are macromolecular compounds composed of many luminescent units through covalent bond. They have high molar extinction coefficient and strong light absorption capacity. In addition, they have good photo stability and excellent biocompatibility. In recent years, conjugated polymer nanomaterials (CPNs) have stimulated the research enthusiasm of many researchers because of the materials' small size, high fluorescence intensity, and easy modification. This article reviews the recent research progress of conjugated polymer nanomaterials in the detection and killing of pathogenic microbes.