Simple synthesis of multifunctional photosensitizers for mitochondrial and bacterial imaging and photodynamic anticancer and antibacterial therapy

Synthesis of versatile fluorescent isoquinolinium salts and their applications

Isoquinolinium salts are well-known N-heterocyclic cationic compounds that have been applied in various research fields, such as materials chemistry and pharmaceutical applications. In particular, isoquinolinium salts with polyaromatic structures have been widely investigated due to their intrinsic photophysical properties, including fluorescence emission maxima, fluorescence lifetime, and quantum yield. Notably, fluorescent isoquinolinium salts have been synthesized via various synthetic strategies, such as alkylation of isoquinoline, oxidation of dihydropyridines, rearrangement reactions, and transition-metal-catalyzed C-H activation. In this review, we summarize the synthetic methodologies for diverse fluorescent isoquinolinium salts and their applications in pharmaceutical applications, materials chemistry, theranostics, DNA binding, fluorescent sensing, and bioimaging.

A Dual-Channel Fluorescent Probe for Accurate Diagnosis and Precise Photodynamic Killing of Bacterial Infections by Employing Dual-Mechanism Responses

Bacterial infections pose a huge challenge to global public health, exacerbated by the growing threat of antibiotic resistance due to overuse of antibiotics, and there is an urgent need to develop epidemiological control methods that enable accurate detection and precise treatment. In this study, we present an innovative dual-response integrated probe, Nap-CefTTPy, which is capable of dual-channel fluorescence imaging, synergizing with photodynamic therapy for the accurate diagnosis and precise treatment of bacterial infections. The probe has excellent selectivity for bacteria and can produce two independent spectral responses to bacteria through two different response mechanisms under a single laser excitation, achieving accurate diagnosis of dual-channel bacterial infections. At the same time, it can also produce reactive oxygen species for synergistic photodynamic therapy, which ensures the accuracy of diagnosis and treatment. In a mouse bacterial infection model, it largely promoted the wound healing of S. aureus-infected mice. This platform represents a significant advancement in the field, providing a novel approach for the dual-code mutual correction diagnosis and photodynamic therapy of bacterial infections.

Biomimetic Cancer-Targeting Nanoplatform Boosting AIEgens-Based Photodynamic Therapy and Ferroptosis by Disrupting Redox-Homeostasis

Photodynamic therapy (PDT) using aggregation-induced emission photosensitizer (AIE-PS) holds tremendous potential but is limited by its inherent disadvantages and the high concentrations of reduced glutathione (GSH) in tumor cells that can neutralize ROS to weaken PDT. Herein, we designed a nanodelivery system (CM-HSADSP@[PS-Sor]) in which albumin was utilized as a carrier for hydrophobic drug AIE-PS and Sorafenib, cross-linkers with disulfide bonds were introduced to form a nanogel core, and then cancer cell membranes were wrapped on its surface to confer homologous tumor targeting ability. A two-way strategy was employed to disturb redox-homeostasis through blocking GSH synthesis by Sorafenib and consuming excess GSH via abundant disulfide bonds, thereby promoting the depletion of GSH, which in turn increased the ROS levels in cancer cells to amplify the efficacy of ferroptosis and PDT, achieving an efficient in vivo antibreast cancer effect. This study brings a new strategy for ROS-based cancer therapy and expands the application of an albumin-based drug delivery system.

Preparation and evaluation of oxidized-dextran based on antibacterial hydrogel for synergistic photodynamic therapy

Skin trauma is a widespread, extremely susceptible health issue that affects people all over the world. In this study, an innovative antibacterial hydrogel (ODAA hydrogel) with photosensitizer and antibiotics was developed. Oxidized dextran (ODEX) was used as a carrier to prepare a pH-responsive hydrogel by loading the antibiotic amikacin (AMK) and the photosensitizer hexyl 5-aminolevulinate (HAL) via imine bonds. The ODAA hydrogel has a uniformly distributed cavity structure. The cumulative release rates of HAL and AMK in a simulated inflammatory environment at pH 5.0 were approximately 62.3 % and 71.9 % during 15 days. These results demonstrate the ODAA hydrogel's ability to deliver antibiotics on demand, where the antibiotic content is reduced within the effective range. Regarding the in vitro antibacterial behavior, the combination of HAL and AMK synergistically destroyed the majority of Gram-positive and Gram-negative bacteria through several pathways with broad-spectrum antibacterial effects. ODAA hydrogel has been shown to be biocompatible, nearly non-cytotoxic, and capable of promoting wound healing. It is anticipated that the simultaneous targeted delivery of multiple drugs to lesions in the same carrier at ideal dose ratios for particular therapeutic combinations will produce the most synergistic effects.

Functional fluorescent nanomaterials for the detection, diagnosis and control of bacterial infection and biofilm formation: Insight towards mechanistic aspects and advanced applications

Infectious diseases resulting from the high pathogenic potential of several bacteria possesses a major threat to human health and safety. Traditional methods used for screening of these microorganisms face major issues with respect to detection time, selectivity and specificity which may delay treatment for critically ill patients past the optimal time. Thus, a convincing and essential need exists to upgrade the existing methodologies for the fast detection of bacteria. In this context, increasing number of newly emerging nanomaterials (NMs) have been discovered for their effective use and applications in the area of diagnosis in bacterial infections. Recently, functional fluorescent nanomaterials (FNMs) are extensively explored in the field of biomedical research, particularly in developing new diagnostic tools, nanosensors, specific imaging modalities and targeted drug delivery systems for bacterial infection. It is interesting to note that organic fluorophores and fluorescent proteins have played vital role for imaging and sensing technologies for long, however, off lately fluorescent nanomaterials are increasingly replacing these due to the latter's unprecedented fluorescence brightness, stability in the biological environment, high quantum yield along with high sensitivity due to enhanced surface property etc. Again, taking advantage of their photo-excitation property, these can also be used for either photothermal and photodynamic therapy to eradicate bacterial infection and biofilm formation. Here, in this review, we have paid particular attention on summarizing literature reports on FNMs which includes studies detailing fluorescence-based bacterial detection methodologies, antibacterial and antibiofilm applications of the same. It is expected that the present review will attract the attention of the researchers working in this field to develop new engineered FNMs for the comprehensive diagnosis and treatment of bacterial infection and biofilm formation.

A biomineralized bi-functional hybrid nanoflower to effectively combat bacteria via a glucose-powered cascade catalytic reaction

The bacterial resistance due to the abuse of conventional antibiotics is regarded as a major problem for bacterial-induced infections and chronic wound healing. There is an urgent need to explore alternative antimicrobial strategies and functional materials with excellent antibacterial efficacy. Herein, guanosine monophosphate (GMP) and glucose oxidase (GOD) were coordinated with copper ions to obtain a bi-functional hybrid nanoflower (Cu-GMP/GODNF) as a cascade catalyst for promoting antibacterial efficacy. Besides the efficient conversion of glucose to hydrogen peroxide, the produced gluconic acid by loading GOD can supply a compatible catalytic environment to substantially improve the peroxidase activity for generating more toxic reactive oxygen species (ROS). So, the glucose-powered cascade catalytic reaction effectively killed bacteria. Moreover, H₂O₂ self-supplied by glucose can reduce harmful side effects of exogenous H₂O₂. Meanwhile, the adhesion between the Cu-GMP/GODNF and the bacterial membrane can enhance the antibacterial efficacy. Therefore, the achieved bi-functional hybrid nanoflower exhibited high efficiency and biocompatibility for killing bacteria in diabetes-related infections.

Synergistically Enhancing Tumor Chemotherapy Using an Aggregation-Induced Emission Photosensitizer on Covalently Conjugated Molecularly Imprinted Polymer Nanoparticles

Due to the polygenic and heterogeneous nature of the tumorigenesis process, traditional chemotherapy is far from desirable. Fabricating multifunctional nanoplatforms integrating photodynamic effect can synergistically enhance chemotherapy because they can make the cancer cells much sensitive to chemotherapeutics. However, how to assemble different units in nanoplatforms and minimize side effects caused by chemodrugs and photosensitizers (PSs) still needs to be explored. Herein, a nanoplatform CPP/PS-MIP@DOX is developed using a simultaneously covalently conjugated new aggregation-induced emission (AIE) PS and a cell-penetrating peptide (CPP) on the surface of silica-based molecularly imprinted polymer (MIP) nanoparticles, prepared with doxorubicin (DOX) as the template in the water system via a sol-gel technique. CPP/PS-MIP@DOX has good biocompatibility, high DOX-loading ability, promoted cellular uptake, and sustained and pH-sensitive drug release capability. Furthermore, it can efficiently penetrate into tumor tissue, accurately home to, and accumulate at the tumor site. As a result, a better efficacy with lower cytotoxicity is achieved with a smaller dosage of DOX by utilizing either the photodynamic effect or unique characteristics of the MIP. It is the first nanoplatform fabricated by chemically conjugating AIE PSs directly on the surface of the scaffold via the surface-decorated strategy and successfully applied in cancer therapy. This work provides an effective strategy by constructing AIE PS-based cancer nanomedicines with MIPs as scaffolds.

A novel furo[3,2-c]pyridine-based AIE photosensitizer for specific imaging and photodynamic ablation of Gram-positive bacteria

An Rh-catalyzed tandem reaction was performed to construct an AIE-active furo[2,3-c]pyridine-based photosensitizer, named LIQ-TF. LIQ-TF showed near-infrared emission with high quantum yield, and high ¹O₂ and ˙OH generation efficiency, and could be used for specific imaging and photodynamic ablation of Gram-positive bacteria in vitro and in vivo, showing great potential for combating multiple drug-resistant bacteria.

Fabrication of Curcumin@Ag Loaded Core/Shell Nanofiber Membrane and its Synergistic Antibacterial Properties

The core/shell structure nanofiber membrane loaded with curcumin and silver nanoparticles was prepared by coaxial electrospinning technology, which is a high-efficiency combined antibacterial material composed of photodynamic antibacterial agent and metal nanoparticle. As a photosensitizer, curcumin could generate singlet oxygen under laser irradiation. Silver nanoparticles have antibacterial properties, and could also enhance the singlet oxygen production of curcumin due to the metal-enhanced singlet oxygen effect, thereby producing a synergistic antibacterial effect. Compared with the antibacterial rate of uniaxial curcumin fiber membrane (45.65%) and uniaxial silver nanoparticle-loaded fiber membrane (66.96%), the antibacterial rate of curcumin@Ag core/shell structure fiber membrane against Staphylococcus aureus is as high as 93.04%. In addition, the antibacterial experiments show that the core/shell fiber membrane also has excellent antibacterial effects on Escherichia coli.

Fluorescent styrylpyrylium probes for the imaging of mitochondria in live cells

Eight styrylpyrylium tetrafluoroborate salts have been synthesized and fully optically characterized by UV-vis absorption and fluorescence steady-state/time-resolved spectroscopies. The new dyes exhibit strong emission bands with yellow-orange colours, depending on the substituents present in the structure. Notably, the Stokes shift recorded for some of them exceeds 100 nm, a very valuable feature for biological imaging. Four of them have been assayed as biological imaging agents by confocal laser scanning microscopy (CLSM) in the human hepatoma cell line Hep3B. It has been found that all the compounds efficiently stain intracellular structures which have been identified as mitochondria through colocalization assays with MitoView (a well-known mitochondrial marker) and using carbonyl cyanide m-chlorophenyl hydrazone (CCCP) as a mitochondrial membrane potential uncoupler. Additionally, the potential ability of the studied dyes as cytotoxic drugs has been explored. The inhibitory concentration (IC50) against Hep3B was found to be in the range of 4.2 μM-11.5 μM, similar to other described anticancer drugs for the same hepatoma cell line. The combined features of a good imaging agent and potential anticancer drug make the family of the studied pyrylium salts good candidates for further theranostic studies. Remarkably, despite the extensive use of pyrylium dyes in several scientific areas (from photocatalysis to optics), there is no precedent description of a styrylpyrylium salt with potential theranostic applications.

Light-Activated Biodegradable Covalent Organic Framework-Integrated Heterojunction for Photodynamic, Photothermal, and Gaseous Therapy of Chronic Wound Infection

Chronic wound healing, impeded by bacterial infections and drug resistance, poses a threat to global human health. Antibacterial phototherapy is an effective way to fight microbial infection without causing drug resistance. Covalent organic frameworks (COFs) are a class of highly crystalline functional porous carbon-based materials composed of light atoms (e.g., carbon, nitrogen, oxygen, and borane), showing potential applications in the biomedical field. Herein, we constructed porphyrin-based COF nanosheets (TP-Por CON) for synergizing photodynamic and photothermal therapy under red light irradiation (e.g., 635 nm). Moreover, a nitric oxide (NO) donor molecule, BNN6, was encapsulated into the pore volume of the crystalline porous framework structure to moderately release NO triggered by red light irradiation for realizing gaseous therapy. Therefore, we successfully synthesized a novel TP-Por CON@BNN6-integrated heterojunction for thoroughly killing Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus in vitro. Our research identified that TP-Por CON@BNN6 has favorable biocompatibility and biodegradability, low phototoxicity, anti-inflammatory properties, and excellent mice wound healing ability in vivo. This study indicates that the TP-Por CON@BNN6-integrated heterojunction with multifunctional properties provides a potential strategy for COF-based gaseous therapy and microorganism-infected chronic wound healing.