Indirect detection of photosensitizer ex vivo

Water-soluble AIE photosensitizer in short-wave infrared region for albumin-enhanced and self-reporting phototheranostics

Organic photosensitizers (PSs) play important roles in phototheranostics, and contribute to the fast development of precision medicine. However, water-soluble and highly emissive organic PSs, especially those emitting in the short-wave infrared region (SWIR), are still challenging. Also, it's difficult to prepare self-reporting PSs for visualizing the treatment via stimulated emission depletion (STED) nanoscopy. Thus, in this work, a water-soluble molecule of DTPAP-TBZ-I with aggregation-induced emission features is designed for the self-reporting photodynamic therapy (PDT) in an ultra-high resolution. In contrast to single molecule, its complex (DTPAP-TBZ-I@BSA) shows much enhanced fluorescence properties and reactive oxygen species (ROS) generation in SWIR window. Their photoluminescence quantum yield is determined to be ∼20.6 % and the enhancement of ROS generation is ∼18-fold. During the PDT, immigration of the complex from cytoplasm to nucleus is also observed via STED nanoscopy with a resolution of 66.11 nm, which allows self-report in the PDT treatment. DTPAP-TBZ-I@BSA is finally utilized for the imaging-guided PDT in vivo with a tumor inhibition rate of 84 %. This is the first work in albumin-enhanced water-soluble organic PSs in SWIR window for self-reporting phototheranostics at ultra-high resolutions, providing an ideal solution for the next generation of photosensitizers for precise medicine.

Comparative response to PDT with methyl-aminolevulinate and temoporfin in cutaneous and oral squamous cell carcinoma cells

Cutaneous and Head and Neck squamous cell carcinoma (CSCC, HNSCC) are among the most prevalent cancers. Both types of cancer can be treated with photodynamic therapy (PDT) by using the photosensitizer Temoporfin in HNSCC and the prodrug methyl-aminolevulinate (MAL) in CSCC. However, PDT is not always effective. Therefore, it is mandatory to correctly approach the therapy according to the characteristics of the tumour cells. For this reason, we have used cell lines of CSCC (A431 and SCC13) and HNSCC (HN5 and SCC9). The results obtained indicated that the better response to MAL-PDT was related to its localization in the plasma membrane (A431 and HN5 cells). However, with Temoporfin all cell lines showed lysosome localization, even the most sensitive ones (HN5). The expression of mesenchymal markers and migratory capacity was greater in HNSCC lines compared to CSCC, but no correlation with PDT response was observed. The translocation to the nucleus of β-catenin and GSK3β and the activation of NF-κβ is related to the poor response to PDT in the HNSCC lines. Therefore, we propose that intracellular localization of GSK3β could be a good marker of response to PDT in HNSCC. Although the molecular mechanism of response to PDT needs further elucidation, this work shows that the most MAL-resistant line of CSCC is more sensitive to Temoporfin.

Reconstituting Low-Density Lipoprotein with NIR-Absorbing Organic Photothermal Agents for Targeted Killing of Cancer Cells

Photothermal therapy (PTT) systems typically do not possess intrinsic tumor-targeting capability, resulting in indiscriminate thermal damage to both cancer and normal cells. Herein, a low-density lipoprotein (LDL)-based nanosystem (denoted as MTTQ@LDL) is reported for targeted photothermal killing of cancer cells. Such a nanosystem is fabricated by reconstituting the lipophilic core of LDL with an organic photothermal agent MTTQ. The reconstitution process improves the supramolecular photothermal effects of MTTQ assemblies, which contributes to the significantly enhanced photothermal conversion efficiency (41.3% vs. 16.2%). MTTQ@LDL can actively target LDL receptor-overexpressed cancer cells via receptor-mediated endocytosis, enabling the selective killing of cancer cells over normal cells (98% vs. 7%) post-NIR irradiation. Reconstituted LDL can serve as a promising platform for targeted delivery of functional materials, holding great promise in tumor eradication in vivo.

Photodynamic Hydrogen-Bonded Biohybrid Framework: A Photobiocatalytic Cascade Nanoreactor for Accelerating Diabetic Wound Therapy

A diabetic wound causes thousands of infections or deaths around the world each year, and its healing remains a critical challenge because of the ease of multidrug-resistant (MDR) bacterial infection, as well as the intrinsic hyperglycemic and hypoxia microenvironment that inhibits the therapeutic efficiency. Herein, we pioneer the design of a photobiocatalytic cascade nanoreactor via spatially organizing the biocatalysts and photocatalysts utilizing a hydrogen-bonded organic framework (HOF) scaffold for diabetic wound therapy. The HOF scaffold enables it to disperse and stabilize the host cargos, and the formed long-range-ordered mesochannels also facilitate the mass transfer that enhances the cascade activity. This integrated HOF nanoreactor allows the continuous conversion of overexpressed glucose and H₂O₂ into toxic reactive oxygen species by the photobiocatalytic cascade. As a result, it readily reverses the microenvironment of the diabetes wound and exhibits an extraordinary capacity for wound healing through synergistic photodynamic therapy. This work describes the first example of constructing an all-in-one HOF bioreactor for antimicrobial diabetes wound treatment and showcases the promise of combined biocatalysis and photocatalysis achieved by using an HOF scaffold in biomedicine applications.

Adenosine triphosphate-activated prodrug system for on-demand bacterial inactivation and wound disinfection

The prodrug approach has emerged as a promising solution to combat bacterial resistance and enhance treatment efficacy against bacterial infections. Here, we report an adenosine triphosphate (ATP)-activated prodrug system for on-demand treatment of bacterial infection. The prodrug system benefits from the synergistic action of zeolitic imidazolate framework-8 and polyacrylamide hydrogel microsphere, which simultaneously transports indole-3-acetic acid and horseradish peroxidase in a single carrier while preventing the premature activation of indole-3-acetic acid. The ATP-responsive characteristic of zeolitic imidazolate framework-8 allows the prodrug system to be activated by the ATP secreted by bacteria to generate reactive oxygen species (ROS), displaying exceptional broad-spectrum antimicrobial ability. Upon disruption of the bacterial membrane by ROS, the leaked intracellular ATP from dead bacteria can accelerate the activation of the prodrug system to further enhance antibacterial efficiency. In vivo experiments in a mouse model demonstrates the applicability of the prodrug system for wound disinfection with minimal side effects.

Prodrugs are increasingly promising in tackling bacterial resistance and efficacy of treatment. Here, the authors encapsulated horseradish peroxidase and zeolitic imidazolate framework-8 loaded with indole-3-acetic acid in polyacrylamide hydrogel microspheres for ATP-activated wound disinfection.

A receptor-targeting AIE photosensitizer for selective bacterial killing and real-time monitoring of photodynamic therapy outcome

A receptor-targeting AIE photosensitizer (CE-TPA) is synthesized by conjugating cephalothin with a cationic D-A type AIE photosensitizer for selective killing of Gram-positive bacteria over Gram-negative bacteria and normal mammalian cells. By virtue of the strong photosensitization capability, CE-TPA exhibits efficient killing against Gram-positive methicillin-resistant Staphylococcus aureus. More importantly, the photodynamic bactericidal outcome can be conveniently reflected in a real-time fashion by the polarity-sensitive property of CE-TPA.

A cell membrane-targeting AIE photosensitizer as a necroptosis inducer for boosting cancer theranostics

The exploration of cellular organelle-specific anchoring photosensitizers with both prominent fluorescence imaging behavior and extraordinary reactive oxygen species (ROS) production capability is highly in demand but remains a severe challenge for effective cancer theranostics involving photodynamic therapy (PDT). In this contribution, we developed a cell membrane-targeting and NIR-emission photosensitizer having an aggregation-induced emission (AIE) tendency. The AIE photosensitizer, namely TBMPEI, is capable of lighting up and ablating cancer cells by means of a necroptosis procedure enabling cell membrane rupture and DNA degradation upon light irradiation, endowing TBMPEI with impressive performance for both in vitro and in vivo fluorescence imaging-guided PDT.

Bridging D-A type photosensitizers with the azo group to boost intersystem crossing for efficient photodynamic therapy

Photodynamic therapy (PDT) has attracted much attention in disease treatments. However, the exploration of a novel method for the construction of outstanding photosensitizers (PSs) with stimuli-responsiveness remains challenging. In this study, we, for the first time, report a novel and effective strategy to boost reactive oxygen species (ROS) generation by bridging donor-acceptor (D-A) type PSs with the azo group. In contrast to the counterpart without azo-bridging, the azo-bridged PSs exhibit remarkably enhanced ROS generation via both type-I and type-II photochemical reactions. Theoretical calculations suggest that azo-bridging leads to a prominent reduction in ΔE ST, thereby enabling enhanced ROS generation via efficient intersystem crossing (ISC). The resulting azo-bridged PS (denoted as Azo-TPA-Th(+)) exhibits a particularly strong bactericidal effect against clinically relevant drug-resistant bacteria, with the killing efficiency up to 99.999999% upon white light irradiation. Since azo-bridging generates an azobenzene structure, Azo-TPA-Th(+) can undergo trans-to-cis isomerization upon UV irradiation to form emissive aggregates by shutting down the ISC channel. By virtue of the fluorescence turn-on property of unbound Azo-TPA-Th(+), we propose a straightforward method to directly discern the effective photodynamic bactericidal dose without performing the tedious plate-counting assay. This study opens a brand-new avenue for the design of advanced PSs with both strong ROS generation and stimuli-responsiveness, holding great potential in high-quality PDT with rapid prediction of the therapeutic outcome.

Conjugation of Antimicrobial Peptide to Zinc Phthalocyanine for an Efficient Photodynamic Antimicrobial Chemotherapy

Photodynamic antimicrobial chemotherapy is an attractive and novel therapeutic approach to treat microbial infections. Antimicrobial peptides (AMPs) have the potential to specifically target and kill the microorganism while showing no effect toward mammalian cells. In the current study, antimicrobial peptide (GGG(RW)3), an analogue of MP-196, was conjugated to a zinc phthalocyanine (ZnPc) photosensitizer (PS) for photoinactivation assay to enhance the bacterial killing efficacy of the peptide. The AMPs showed selectivity toward the Gram-positive strain of bacteria. We observed that the conjugate ZnPc-GGG(RW)3 also displayed a photoinactivation effect against the Gram-positive strains of S. aureus. The results showed that ZnPc-GGG(RW)3 induced a 6-log reduction (i.e., 99.999% cell killing) in Gram-positive S. aureus at a light dose of 22 J/cm2 upon illumination under red light, while the peptide did not exhibit such a significant effect when tested alone at the same concentration. The conjugate also showed 50% inhibition of the bacterial strain in the dark at a higher concentration. Furthermore, the addition of potassium iodide salt to the PS at lower concentrations also significantly killed the Gram-negative E. coli strain and killed the E. coli strain with up to a 5-log reduction at a light dose of 22 J/cm2 under red light illumination. We demonstrated the efficacy of antimicrobial peptide (GGG(RW)3 enhanced by conjugation to a ZnPc photosensitizer.

Photosensitizer with High Efficiency Generated in Cells via Light-Induced Self-Oligomerization of 4,6-Dibromothieno[3,4-b]thiophene Compound Entailing a Triphenyl Phosphonium Group

Photodynamic therapy (PDT) has emerged as an attractive alternative in cancer therapy, but therapeutic effects suffer from low photosensitizing efficiency and poor retention of photosensitizes in cancer cells. This paper reports the photosensitizers which show absorption and emission in the long-wavelength region and high photosensitizing efficiency can be formed in situ in cells from 4,6-dibromothieno[3,4-b]thiophene derivative (TT-5-P) after white light irradiation. The self-oligomerization of TT-5-P is uptaken in cells upon light irradiation-induced cell apoptosis simultaneously and efficiently. In addition, the formation of oligomers (TT-5-Ps) enhances the retention time in cells remarkably, which is advantageous for boosting the photodynamic therapy efficiency. Moreover, the selectivity toward tumor cells of TT-5-P can be improved obviously via the formation of complex of TT-5-P with albumin. This in situ photoinduced self-oligomerization strategy can be utilized to design effective biomaterials for long-term imaging and improved therapy.

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

To develop efficient photoactive agents with satisfactory fluorescence, photodynamic, and photothermal effects is crucial for a phototherapeutic strategy to combat cancer diseases and pathogenic microbes. Herein, a water-soluble donor-acceptor-donor (D-A-D) structured conjugated oligomer was designed and synthesized, consisting of two cyclopenta-dithiophene (CDT) units as the electron donor and boron dipyrromethene (BODIPY) as the electron acceptor. Upon excitation, dual emission was observed for CDT-BODIPY with blue and red fluorescence peaks at 463 nm and at 730 nm, respectively, which was ascribed to intramolecular charge transfer (ICT). Due to the ICT effect, the singlet-to-triplet intersystem crossing rate of CDT-BODIPY was also enhanced, leading to an outstanding photodynamic behavior to produce reactive oxygen species (ROS). Meanwhile, its low bandgap also enabled it a moderate photothermal capability with a conversion efficiency of 33.1%. Taking advantage of its phototriggered activities, this conjugated oligomer exhibited an effective inhibition behavior on the pathogenic growth of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans), which can be guided by dual-wavelength fluorescence imaging. This D-A-D type conjugated oligomer with balanced photophysical characteristics provides a promising strategy to imaging-guided photoactive therapy.

Tumor Microenvironment Modulation Platform Based on Composite Biodegradable Bismuth-Manganese Radiosensitizer for Inhibiting Radioresistant Hypoxic Tumors

Solid tumors possess a unique internal environment with high-level thiols (mainly glutathione), over-expressed H₂ O₂ , and low oxygen partial pressure, which severely restrict the radiotherapy (RT) efficacy. To overcome the imperfections of RT alone, there is vital to design a multifunctional radiosensitizer that simultaneously achieves multimodal therapy and tumor microenvironment (TME) regulation. Bismuth (Bi)-based nanospheres are wrapped in the MnO₂ layer to form core-shell-structured radiosensitizer (Bi@Mn) that can effectively load docetaxel (DTX). The solubility of Bi@Mn-DTX is further improved via folic acid-modified amphiphilic polyethylene glycol (PFA). Bi@Mn-DTX-PFA can specifically respond to the TME to realize multimodal therapy. Primarily, the outer MnO₂ layer responds with H₂ O₂ and glutathione to release oxygen and generate •OH, thereby alleviating hypoxia and achieving chemodynamic therapy (CDT). Afterward, the strong coordination between Bi³⁺ and deprotonated thiol groups in glutathione allows the mesoporous Bi-containing core bonding with glutathione to form a water-soluble complex. These actions conduce Bi@Mn-DTX-PFA degradation, further releasing DTX to implement chemotherapy (CHT). In addition, the degradation in vivo and tumor enrichment of Bi@Mn-PFA are explored via T₁ -weighted magnetic resonance and computed tomography imaging. The biodegradable composite Bi@Mn-DTX-PFA can simultaneously modulate the TME and achieve multimodal treatment (RT/CDT/CHT) for hypoxic tumors.

AIEgen-loaded nanofibrous membrane as photodynamic/photothermal antimicrobial surface for sunlight-triggered bioprotection

The outbreak of infectious diseases such as COVID-19 causes an urgent need for abundant personal protective equipment (PPE) which leads to a huge shortage of raw materials. Additionally, the inappropriate disposal and sterilization of PPE may result in a high risk of cross-contamination. Therefore, the exploration of antimicrobial materials possessing both microbe interception and self-decontamination effects to develop reusable and easy-to-sterilize PPE is of great importance. Herein, an aggregation-induced emission (AIE)-active luminogen-loaded nanofibrous membrane (TTVB@NM) sharing sunlight-triggered photodynamic/photothermal anti-pathogen functions are prepared using the electrospinning technique. Thanks to its porous nanostructure, TTVB@NM shows excellent interception effects toward ultrafine particles and pathogenic aerosols. Benefiting from the superior photophysical properties of the AIE-active dopants, TTVB@NM exhibits integrated properties of wide absorption in visible light range, efficient ROS generation, and moderate photothermal conversion performance. A series of antimicrobial evaluations reveal that TTVB@NM could effectively inactivate pathogenic aerosols containing bacteria (inhibition rate: >99%), fungi (~88%), and viruses (>99%) within only 10 min sunlight irradiation. This study represents a new strategy to construct reusable and easy-to-sterilize hybrid materials for potential bioprotective applications.

Two-photon active nucleus-targeting carbon dots: enhanced ROS generation and photodynamic therapy for oral cancer

Novel conjugated carbon dots (CDs) were synthesized as two-photon active photosensitisers to unleash lethal reactive oxygen species (ROS) for nucleus-targeting photodynamic therapy (PDT). To enhance the therapeutic efficiency and preclude non-specific CD uptake, we employed a combination of folic acid and curcumin for two-photon NIR-triggered ROS generation and enhanced internalization in the nucleus. Consequently, enhanced destruction of cancer cells occurred by directly attacking the DNA. The intrinsic ROS generation and nucleus-targeting ability of CDs introduced multifunctional two-photon active nanoprobes within a single platform for enhanced PDT in oral cancer theranostics.

Enhanced photodynamic inactivation for Gram-negative bacteria by branched polyethylenimine-containing nanoparticles under visible light irradiation

Antibiotic pollution has been a serious global public health concern in recent years, photodynamic inactivation is one of the most promising and innovative methods for antibacterial applications that avoids antibiotic abuse and minimizes risks of antibiotic resistance. However, limited by the weak interaction between the photosensitizers and Gram-negative bacteria, the effect of photodynamic inactivation cannot be fully exerted. Herein, photosensitizer chlorin e6-loaded polyethyleneimine-based micelle was constructed. The synergy of electrostatic and hydrophobic interactions between the nanoparticles and the bacterial surface promoted the anchoring of nanoparticles onto the bacteria, resulting in enhanced photoinactivation activities on Gram-negative bacteria. As expected, an eminent antibacterial effect was also observed on the Gram-positive bacteria Staphylococcus aureus. The cellular uptake results showed that photosensitizer was firmly anchored to the bacterial cell surface of Escherichia coli or Staphylococcus aureus by the introduction of branched polyethylenimine-containing nanoparticles. The light-triggered generation of reactive oxygen species, mainly singlet oxygen, from the membrane-bound nanoparticles caused irreversible damage to the bacterial outer membrane, achieving enhanced bactericidal efficiency than free photosensitizer. The study would provide an efficient and promising antimicrobial alternative to prevent overuse of antibiotics and have enormous potential for human healthcare and the environment remediation.

Synthesis of Ag@CuO nanohybrids and their photo-enhanced bactericidal effect through concerted Ag ion release and reactive oxygen species generation

Ag and CuO in the form of nanoparticles have been widely used in our daily life as antibacterial agents, through releasing Ag ions and generating reactive oxygen species (ROS). In this work, we demonstrate that by synthesizing Ag@CuO nanohybrids with core-shell configurations, their bactericidal activity can be synergistically enhanced compared to the respective constituents. Upon AM 1.5G light illumination for short durations, the measured minimum inhibitory concentrations of the Ag@CuO nanohybrids show a significant decrease against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacterial strains, requiring only 7% and 34% of those when conducted in the dark. The spread plate results demonstrate that with nanohybrid concentrations of 11.0 and 21.9 mg L^-1, at least 7 orders of magnitude decrease in Escherichia coli and Staphylococcus aureus colony forming units is achieved, when the Ag@CuO nanohybrids are exposed to light illumination for 10 min. The effect of illumination is found to induce Ag⁺ release and enhance ¹O₂ generation, which act concertedly to facilitate the remarkable photo-enhanced bactericidal effect.

Theranostic Nanoparticles with Aggregation-Induced Emission and MRI Contrast Enhancement Characteristics as a Dual-Modal Imaging Platform for Image-Guided Tumor Photodynamic Therapy

Introduction

Advanced tumor-targeted theranostic nanoparticles play a key role in tumor diagnosis and treatment research. In this study, we developed a multifunctional theranostic platform based on an amphiphilic hyaluronan/poly-(N-ε-carbobenzyloxy-L-lysine) derivative (HA-g-PZLL), superparamagnetic iron oxide (SPIO) and aggregation-induced emission (AIE) nanoparticles for tumor-targeted magnetic resonance (MR) and fluorescence (FL) dual-modal image-guided photodynamic therapy (PDT).

Materials and Methods

The amphiphilic hyaluronan acid (HA) derivative HA-g-PZLL was synthesized by grafting hydrophobic poly-(N-ε-carbobenzyloxy-L-lysine) (PZLL) blocks onto hyaluronic acid by a click conjugation reaction. The obtained HA-g-PZLLs self-assembled into nanoparticles in the presence of AIE molecules and SPIO nanoparticles to produce tumor-targeted theranostic nanoparticles (SPIO/AIE@HA-g-PZLLs) with MR/FL dual-modal imaging ability. Cellular uptake of the theranostic nanoparticles was traced by confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining. The intracellular reactive oxygen species (ROS) generation characteristics of the theranostic nanoparticles were evaluated with CLSM and flow cytometry. The effect of PDT was evaluated by cytotoxicity assay. The dual-mode imaging ability of the nanoparticles was evaluated by a real-time near-infrared fluorescence imaging system and magnetic resonance imaging scanning.

Results

The resulting theranostic nanoparticles not only emit red fluorescence for high-quality intracellular tracing but also effectively produce singlet oxygen for photodynamic tumor therapy. In vitro cytotoxicity experiments showed that these theranostic nanoparticles can be efficiently taken up and are mainly present in the cytoplasm of HepG2 cells. After internalization, these theranostic nanoparticles showed serious cytotoxicity to the growth of HepG2 cells after white light irradiation.

Discussion

This work provides a simple method for the preparation of theranostic nanoparticles with AIE characteristics and MR contrast enhancement, and serves as a dual-modal imaging platform for image-guided tumor PDT.

Mitochondria-anchoring and AIE-active photosensitizer for self-monitored cholangiocarcinoma therapy

An AIE-active photosensitizer, TTVPHE, can fast penetrate into cancer cells and efficiently trigger mitochondria-dependent apoptotic pathway with self-monitoring ability.

Hollow ferric-tannic acid nanocapsules with sustained O2 and ROS induction for synergistic tumor therapy

HFe-TA nanoparticles, with a fine hollow microstructure, are synthesized and incorporated with ICG for synergistic photo/chemodynamic therapy with enhanced efficacy.

DNA interaction and photodynamic antitumor activity of transition metal mono-hydroxyl corrole

A series of iron(III), manganese(III) and copper(III) mono-hydroxyl corrole complexes had been prepared and well characterized by UV-vis, ¹H NMR, ¹⁹F NMR and HR-MS. These metallocorroles may bind to CT-DNA through external binding mode. Metallocorrole Fe-2c exhibited significant phototoxicity and low toxicity toward A549 tumor cells. While manganese (III) and copper (III) corroles showed hypotoxicity to A549, MCF-7 and HepG-2 tumor cells, whether under dark or illumination conditions. All tested metallocorroles exhibited non-toxicity to human normal cells (GES-1) with or without irradiation at 625 nm. Cell cycle analysis indicated that metallocorrole Fe-2c arrested the cell cycle at G2/M phase and increased the Sub-G1 phase in A549 cell lines. It was mainly localized at mitochondria and could significantly reduce mitochondrial membrane potential after photodynamic treatment, which would further induce tumor cell apoptosis.

Enhancing singlet oxygen generation in semiconducting polymer nanoparticles through fluorescence resonance energy transfer for tumor treatment

Photosensitizers (PSs) are of particular importance for efficient photodynamic therapy (PDT). Challenges for PSs simultaneously possessing strong light-absorbing ability, high 1O2 generation by effective intersystem crossing from the singlet to the triplet state, good water-solubility and excellent photostability still exist. Reported here are a new kind of dual-emissive semiconducting polymer nanoparticles (SPNs) containing fluorescent BODIPY derivatives and near-infrared (NIR) phosphorescent iridium(iii) complexes. In the SPNs, the BODIPY units serve as the energy donors in the fluorescence resonance energy transfer (FRET) process for enhancing the light absorption of the SPNs. The NIR emissive iridium(iii) complexes are chosen as the energy acceptors and efficient photosensitizers. The ionized semiconducting polymers can easily self-assemble to form hydrophilic nanoparticles and homogeneously disperse in aqueous solution. Meanwhile, the conjugated backbone of SPNs provides effective shielding for the two luminophores from photobleaching. Thus, an excellent overall performance of the SPN-based PSs has been realized and the high 1O2 yield (0.97) resulting from the synergistic effect of BODIPY units and iridium(iii) complexes through the FRET process is among the best reported for PSs. In addition, owing to the phosphorescence quenching of iridium(iii) complexes caused by 3O2, the SPNs can also be utilized for O2 mapping in vitro and in vivo, which assists in the evaluation of the PDT process and provides important instructions in early-stage cancer diagnosis.

Construction of perfluorohexane/IR780@liposome coating on Ti for rapid bacteria killing under permeable near infrared light

Near infrared (NIR) light induced photodynamic antibacterial therapy (PDAT) is a promising antibacterial technique in rapid in situ disinfection of bacterially infected artificial implants due to its penetration ability into tissues. However, the lower oxygen content in vivo may restrict the yields of reactive oxygen species (ROS), thus reducing the antibacterial efficacy of PADT significantly. Herein, liposome encapsulated photosensitizers (PS), IR780 and perfluorohexane (PFH), have been constructed on the surface of Ti implants via a covalent linkage to overcome this issue. Thanks to the high oxygen capacity of PFH, more ROS can be generated during NIR irradiation regardless of the low content of oxygen in vivo. As a result, in vitro tests demonstrated that 15 minutes of 808 nm near-infrared irradiation could achieve a high antibacterial efficacy of 99.62% and 99.63% on the implant surface against Escherichia coli and Staphylococcus aureus, respectively. By contrast, the PDAT system without PFH modification shows a lower antibacterial efficacy (only 66.54% and 48.04%, respectively). In addition, this enhanced PDAT system also possesses great biocompatibility based on the in vitro and in vivo subcutaneous assays. This surface system makes it possible for rapid bacteria-killing in artificial implants that have been implanted in vivo under local conditions with lower oxygen content.

Protoporphyrin-IX conjugated cellulose nanofibers that exhibit high antibacterial photodynamic inactivation efficacy

Towards the development of anti-infective nanoscale materials employing a photodynamic mechanism of action, we report the synthesis, physical properties (SEM, mechanical strength, water contact angle), spectroscopic characterization (infrared, Raman, DRUV), and evaluation of antibacterial efficacy of porphyrin-conjugated regenerated cellulose nanofibers, termed RC-TETA-PPIX-Zn. Cellulose acetate was electrospun to produce nanofibers, thermally treated to enhance mechanical strength, and finally hydrolyzed to produce regenerated cellulose (RC) nanofibers that possessed a high surface area and nanofibrous structure. Covalent grafting of a protoporphyrin IX (PPIX) photosensitizer using epichlorohydrin/triethylenetetramine (TETA), followed by zinc chelation, afforded RC-TETA-PPIX-Zn. The high surface area afforded by the nanofibers and efficient photosensitizer conjugation led to a very high loading of 412 nmol PPIX/mg material, corresponding to a degree of substitution of 0.1. Antibacterial efficacy was evaluated against Staphylococcus aureus (ATCC-6538) and Escherichia coli (ATCC-8099), with our best results achieving detection limit inactivation (99.999+%) of both bacteria after only 20 min illumination (Xe lamp, λ ≥ 420 nm). No statistically significant loss in antibacterial activity was observed when using nanofibers that had been 'photo-aged' with 5 h of pre-illumination to simulate the effects of photobleaching. Post aPDI, scanning electron microscopy revealed that the bacteria had undergone cell membrane leakage, consistent with oxidative damage caused by photo-generated reactive oxygen species. Taken together, the conjugation strategy employed here provides a scalable, facile and efficient route to creating nanofibrous materials from natural polymers with a high photosensitizer loading, enabling the use of commercially-available neutral porphyrin photosensitizers, such as PPIX, in the design and synthesis of potent anti-infective nanomaterials.

Unprecedented chemosensing behavior of novel tetra-substituted benzimidazole zinc(II) phthalocynine for selective detection of Bi3+ ion: Synthesis, characterization and ROS generation

In this work, synthesis of novel symmetrical 4-(2-bromo-4-(5-bromo-1H-benzo[d] imidazol-2-yl) phenoxy) tetra substituted zinc phthalocyanine has been reported. The novel benzimidazole zinc phthlocynine compound (3) has been characterized by MALDI-TOF MS, FT-IR, UV-vis, and ¹H NMR spectroscopy. This new compound 3 displayed excellent selectivity towards Bi³⁺ ion in the presence of other competitive ions including Ca²⁺, Cd²⁺, Co²⁺ Cu²⁺, Fe³⁺, Hg²⁺, Sn²⁺, Mg²⁺, Na⁺, Ni²⁺ and Pb²⁺ respectively. Upon addition of Bi³⁺ into the solution of compound 3 in DMSO, dramatic change was observed in the Q- and the B-bands in UV-visible spectra as a result of donor acceptor interactions. Reactive oxygen species (ROS) were also studied using 2,7-dichlorofluorescin diacetate (DCFH-DA) a fluorescent probe which is converted to highly fluorescent dichlorofluorescein (DCF) in the presence of ROS. This property of non-aggregating zinc phthalocyanine is promising as a photosensitizer in photodynamic therapy of cancer.

Achieving efficient photodynamic therapy under both normoxia and hypoxia using cyclometalated Ru(ii) photosensitizer through type I photochemical process

Photodynamic therapy (PDT) through the generation of singlet oxygen utilizing photosensitizers (PSs) is significantly limited under hypoxic conditions in solid tumors. So it is meaningful to develop effective PSs which can maintain excellent therapeutic effects under hypoxia. Here we reported a coumarin-modified cyclometalated Ru(ii) photosensitizer (Ru2), which exhibits lower oxidation potential and stronger absorption in the visible region than the coumarin-free counterpart. The evaluation of the PDT effect was performed under both normoxia and hypoxia. The results showed that Ru2 has a better therapeutic effect than the coumarin-free counterpart in in vitro experiments. Especially under hypoxia, Ru2 still retained an excellent PDT effect, which can be attributed to the direct charge transfer between the excited PS and an adjacent substrate through a type I photochemical process, forming highly-oxidative hydroxyl radicals to damage tumor cells. The anti-tumor activity of Ru2 was further proven to be effective in tumor-bearing mice, and tumor growth was inhibited remarkably under PDT treatment.

Fluorinated polymeric micelles to overcome hypoxia and enhance photodynamic cancer therapy

Perfluoroalkyl groups-containing polymeric micelles were constructed to transport oxygen, overcome the hypoxia of tumours and enhance photodynamic cancer therapy.

Metalla-aromatic loaded magnetic nanoparticles for MRI/photoacoustic imaging-guided cancer phototherapy

In this study, metalla-aromatic agents and a cluster of superparamagnetic iron oxide nanoparticles were loaded inside a micellar carrier and used for MRI/PA imaging-guided PTT/PDT synergistic cancer therapy.

Functionalization of composite bacterial cellulose with C60nanoparticles for wound dressing and cancer therapy

A series of novel bacterial cellulose/C₆₀ (BCC₆₀) composites was prepared using a original dehydration-rehydration method. The composites were characterized to demonstrate their potential in multifunctional wound dressings for skin cancer treatment using photodynamic therapy. Raman spectroscopy revealed that the C₆₀ nanoparticles were successfully incorporated into the bacterial cellulose (BC) network. Scanning electron microscopy was used to examine the morphology and distribution of the C₆₀ particles as photosensitizers in the bacterial cellulose network, and the C₆₀ particles were uniformly distributed in the hyperfine three-dimensional BC network with diameters less than 100 nm. Reactive oxygen species (ROS) measurements indicated that the BCC₆₀ composites possessed a high ROS generation ability when exposed to light. The antibacterial assessment of the BCC₆₀ composites revealed their ability to inhibit the growth of E. coli and S. aureus and their relationship with light irradiation. In vitro cell experiments also confirmed that the BCC₆₀ composites had low cytotoxicity in the dark, while they exhibited significant cancer cell damage activity under visible light.

A series of novel BCC₆₀ composites as multifunctional wound dressings for skin cancer treatment were successfully fabricated using an original dehydration-rehydration method.

A ZnO-gated porphyrinic metal–organic framework-based drug delivery system for targeted bimodal cancer therapy

A ZnO-gated porMOF-AS1411 nanosystem was prepared and successfully used for drug delivery and synergistic bimodal cancer therapy.

Biofilm Inhibition and Elimination Regulated by Cationic Conjugated Polymers

In this work, we demonstrate that water-soluble conjugated polymers (PFP) have the ability to inhibit biofilm formation and eradicate mature established biofilm using reactive oxygen species (ROS) produced by PFP under white light irradiation. Upon addition of PFP to planktonic Staphylococcus aureus (S. aureus), electrostatic interactions bring cationic PFP to the surface of S. aureus, which possesses negative charges. As the amount of PFP coated on S. aureus becomes saturated, the interactions of bacteria to bacteria and bacteria to surface may be disrupted, resulting in reduced biofilm formation. After the biofilm matures, those PFP on the surface of the biofilm can generate ROS under white light irradiation, which has the ability to inactivate bacteria nearby. Once the biofilm is broken, PFP can penetrate throughthe biofilm and continuously generate ROS under irradiation, resulting in biofilm disruption. As a consequence, this makes conjugated polymers a very promising material for the disruption of biofilm in biomedical and industrial applications.

Supramolecular Porphyrin Photosensitizers: Controllable Disguise and Photoinduced Activation of Antibacterial Behavior

A series of supramolecular photosensitizers were fabricated from porphyrin derivatives (Por) containing quaternary ammonium groups with cucurbit[7]uril (CB[7]) based on host-guest interactions. The antibacterial activity of Por in the dark could be turned off upon binding with CB[7], whereas the antibacterial activity under white-light illumination could be turned on. In addition, its antibacterial efficiency could be greatly enhanced by introducing metal ions. When Pd(II) was introduced into porphyrin, its antibacterial efficiency was enhanced from 40 to 100%. It should be noted that these small molecules showed little to no cytotoxicity toward mammalian cells even at concentrations higher than those under the antibacterial condition studied. This line of research will provide a strategy for germicides consisting of quaternary ammonium groups to fight against bacterial accumulation in the long term and holds huge potential for application in the real world.

A New Green Titania with Enhanced NIR Absorption for Mitochondria-Targeted Cancer Therapy

A new kind of green titania (G-TiO2-x ) with obvious green color was facilely synthesized from black titania (B-TiO2-x ) through subsequently strong ultrasonication. Comparatively, this stable G-TiO2-x shows much enhanced near infrared (NIR) absorption, especially around 920 nm, which can be ascribed to the obvious change of TiO2-x lattice order owing to the effect of ultrasonication. This feature enables G-TiO2-x to be stimulated with 980 nm laser in the combined photodynamic therapy (PDT) and photothermal therapy (PTT), which is greatly beneficial for improving tissue penetration depth. Furthermore, since mitochondria are preferred subcellular organelles for PDT/PTT, G-TiO2-x was further designed to conjugate with triphenylphosphonium (TPP) ligand for mitochondria-targeted PDT/PTT to obtain precise cancer treatment. Attributing to the high mitochondria-targeting efficiency and simultaneously synergistic PDT/PTT, high phototherapeutic efficacy and safety with a much lower laser power density (980 nm, 0.72 W cm-2) and low materials dosage were achieved both in vitro and in vivo. In addition, negligible toxicity was found, indicating high biocompatibility. This novel G-TiO2-x could provide new strategies for future precise minimal/non-invasive tumor treatment.

Synthesis of Multifunctional Cationic Poly(p-phenylenevinylene) for Selectively Killing Bacteria and Lysosome-Specific Imaging

In this work, a cationic polymer was synthesized to bear quaternized N-methyl-imidazole groups in the side chains. Positively charged PPV-M could selectively bind to Gram-negative and Gram-positive bacteria over fungi and exhibit enhanced antibacterial activity with the aid of white light because PPV-M could sensitize oxygen to generate reactive oxygen species (ROS) that would damage bacteria. In addition, green fluorescent and positively charged PPV-M has the ability to enter mammalian cells and be specifically accumulated in lysosome. Moreover, PPV-M could stay in live cells for a relatively long time, which implies that PPV-M has the potential to be a long-term imaging agent.

Flexible Antibacterial Film Based on Conjugated Polyelectrolyte/Silver Nanocomposites

In this work, we report a flexible film based on conjugated polyelectrolyte/silver nanocomposites with efficient antibacterial activity. A flexible poly(dimethylsiloxane) film served as a substrate for deposition of nanostructured silver. A light-activated antibacterial agent, based on the cationic conjugated polyelectrolyte poly({9,9-bis[6'-(N,N-trimethylamino)hexyl]-2,7-fluorenyleneethynylene}-alt-co-1,4-(2,5-dimethoxy)phenylene)dibromide (PFEMO) was self-assembled on the negatively charged substrate. By changing the thickness of the poly(l-lysine)/poly(acrylic acid) multilayers between the metal substrate and PFEMO, we obtained concomitant enhancement of PFEMO fluorescence, phosphorescence, and reactive oxygen species generation. These enhancements were induced by surface plasmon resonance effects of the Ag nanoparticles, which overlapped the PFEMO absorption band. Owing to the combination of enhanced bactericidal effects and good flexibility, these films have great potential for use as novel biomaterials for preventing bacterial infections.

Preparation of Hybrid Gold/Polymer Nanocomposites and Their Application in a Controlled Antibacterial Assay

In this work, we report a photosensitizer-loaded hybrid nanostructure that shows high antibacterial efficiency after surface interaction with a lectin protein. Gold nanoparticles were generated on the polymer nanoparticle surface through an in situ reduction method and behaved as a plasmonic amplifier. After conjugation of the photosensitizer rose bengal onto the hybrid nanoparticles, higher phosphorescence intensity and generation of reactive oxygen species (ROS) were observed. The nanocomposites showed high antibacterial efficiency toward Gram-negative Escherichia coli treated with a lectin protein concanavalin A, which caused self-assembly of the bacteria and nanoparticles. Therefore, the as-prepared nanostructure considerably improved the effectiveness of ROS toward bacteria and provides an alternative strategy for controlled antibacterial assays.

ROS-generating TiO2 nanoparticles for non-invasive sonodynamic therapy of cancer

The non-invasive photodynamic therapy has been limited to treat superficial tumours, primarily ascribed to poor tissue penetration of light as the energy source. Herein, we designed a long-circulating hydrophilized titanium dioxide nanoparticle (HTiO2 NP) that can be activated by ultrasound to generate reactive oxygen species (ROS). When administered systemically to mice, HTiO2 NPs effectively suppressed the growth of superficial tumours after ultrasound treatments. In tumour tissue, the levels of proinflammatory cytokines were elevated several fold and intense vascular damage was observed. Notably, ultrasound treatments with HTiO2 NPs also suppressed the growth of deeply located liver tumours at least 15-fold, compared to animals without ultrasound treatments. This study provides the first demonstration of the feasibility of using HTiO2 NPs as sensitizers for sonodynamic therapy in vivo.

Nano-thick calcium oxide armed titanium: boosts bone cells against methicillin-resistant Staphylococcus aureus

Since the use of systemic antibiotics for preventing acute biomaterial-associated infections (BAIs) may build up bacterial resistance and result in huge medical costs and unpredictable mortality, new precaution strategies are required. Here, it demonstrated that titanium armed with a nano-thick calcium oxide layer was effective on averting methicillin-resistant Staphylococcus aureus (MRSA) infections in rabbits. The calcium oxide layer was constructed by, firstly, injecting of metallic calcium into titanium via a plasma immersion ion implantation process, and then transforming the outer most surface into oxide by exposing to the atmosphere. Although the calcium oxide armed titanium had a relative low reduction rate (~74%) in growth of MRSA in vitro, it could markedly promote the osteogenic differentiation of bone marrow stem cells (BMSCs), restore local bone integration against the challenge of MRSA, and decrease the incidence of MRSA infection with a rate of 100% (compared to the titanium control). This study demonstrated for the first time that calcium, as one of the major elements in a human body, could be engineered to avert MRSA infections, which is promising as a safe precaution of disinfection for implantable biomedical devices.

Synthesis and characterization of photodynamic activity of an iodinated Chlorin p6copper complex

A novel iodinated copper complex of Chlorinp₆that acts as type I photosensitizer and capable of inducing phototoxicity in cancer cells under hypoxia.