Photoinduced Reactive Oxygen Species Research Articles

Singlet oxygen species induced by colloidal crystalline carbon nitride induced for efficient H2O2 synthesis with in situ antibacterial effect

Solar-driven hydrogen (H2) and hydrogen peroxide (H2O2) generation over visible-light responsive carbon nitride (CN) photocatalysts for in situ efficient sterilization is a promising and eco-friendly strategy. Herein, a colloidal potassium-ion (K+) intercalated crystalline CN nanosheets (KCCN) photocatalyst was constructed for boosting synergetic H2O2 synthesis with isopropanol (IPA) oxidation and in situ antibacterial effect. The surface hydroxyl (−OH) and cyano (−CN) groups induced by molten salt (KCl)-assisted thermal treatments contributed to the colloidal nature of CN, facilitating for high wettability of KCCN in aqueous solution to gain active hydrogen (H+) from water sustainably. Meaningfully, the enhanced high-energy singlet oxygen species (1O2) produced by KCNN-2 were verified by electron paramagnetic resonance (EPR) and 9,10-anthracenediyl-bis(methylene)-dimalonic acid (ABDA)-fluorescent probe, significantly contributing to H2O2 production and antibacterial effect. Consequently, the optimal KCCN-2 exhibited a much enhanced H2 generation of 4.11 mmol g−1 h−1, and H2O2 production activity of 1.82 mmol L−1 h−1 with acetone yield rate of 47.3 mmol g−1 h−1 under visible-light (λ > 420 nm) irradiation in 10 vol% IPA solution. The in-situ generated H2O2 can be activated to produce reactive oxygen species (ROS), especially 1O2, to effectively kill the Escherichia coli, reaching an improved an antibacterial rate of 89.7% under stimulated sunlight irradiation in 1 h. This work could offer a new insight into the photoinduced ROS for aqueous H2O2 photosynthesis and antibacterial application.

Atomically dispersed magnesium enhancing reactive oxygen species generation over g-C3N4 nanosheets for efficient photocatalytic NO removal

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification.

Photochemically Inert Broad-Spectrum Sunscreen by Metal-Phenolic Network Coatings of Titanium Oxide Nanoparticles.

Titanium dioxide (TiO2) nanoparticles are extensively used as a sunscreen filter due to their long-active ultraviolet (UV)-blocking performance. However, their practical use is being challenged by high photochemical activities and limited absorption spectrum. Current solutions include the coating of TiO2 with synthetic polymers and formulating a sunscreen product with additional organic UV filters. Unfortunately, these approaches are no longer considered effective because of recent environmental and public health issues. Herein, TiO2-metal-phenolic network hybrid nanoparticles (TiO2-MPN NPs) are developed as the sole active ingredient for sunscreen products through photochemical suppression and absorption spectrum widening. The MPNs are generated by the complexation of tannic acid with multivalent metal ions, forming a robust coating shell. The TiO2-MPN hybridization extends the absorption region to the high-energy-visible (HEV) light range via a new ligand-to-metal charge transfer photoexcitation pathway, boosting both the sun protection factor and ultraviolet-A protection factor about 4-fold. The TiO2-MPN NPs suppressed the photoinduced reactive oxygen species by 99.9% for 6 h under simulated solar irradiation. Accordingly, they substantially alleviated UV- and HEV-induced cytotoxicity of fibroblasts. This work outlines a new tactic for the eco-friendly and biocompatible design of sunscreen agents by selectively inhibiting the photocatalytic activities of semiconductor nanoparticles while broadening their optical spectrum.

Utilizing Hairy Hollow Conjugated Microporous Polymers and Native Enzymes for Precise Aerobic Photocatalysis Under Near‐Infrared Wavelengths

AbstractUtilizing photoregenerated cofactors in conjunction with enzymes in a sequential manner presents an effective approach for the synthesis of targeted compounds in gentle reaction conditions. Nevertheless, the integration of enzymes and photocatalysts has faced challenges due to the swift breakdown of biomaterials caused by high‐energy or blue lights and photoinduced reactive oxygen species, leading to the denaturation and deactivation of enzymatic materials. This study details the deliberate development and production of hairy hollow conjugated microporous polymers (S‐hPrTZ‐P HCMPs), achieved via Sonogashira–Hagihara coupling on SiO2 templates, followed by sulfonation, polymer grafting and ultimately eliminating the SiO2 cores. This technique leverages the distinctive characteristics of low‐energy near‐infrared light, such as its superior penetration ability, to effectively regenerate the enzymatic cofactor NAD+ from NADH. It can accomplish this feat even when faced with synthetic or biological barriers that are impermeable to visible light. Simultaneously, photogenerated reactive oxygen species are captured and neutralized by the hydrophilic polymer brushes, safeguarding the integrity of the enzymatic material. The adaptability of S‐hPrTZ‐P with photocatalytic properties is showcased alongside glucose 1‐dehydrogenase and glycerol dehydrogenase. This structure and morphology‐controlled strategy offers a promising pathway for various enzymatic photobiocatalysis employing stable, efficient, and reusable hairy HCMPs.

Confined semiconducting polymers with boosted NIR light-triggered H2O2 production for hypoxia-tolerant persistent photodynamic therapy.

Hypoxia featured in malignant tumors and the short lifespan of photo-induced reactive oxygen species (ROS) are two major issues that limit the efficiency of photodynamic therapy (PDT) in oncotherapy. Developing efficient type-I photosensitizers with long-term ˙OH generation ability provides a possible solution. Herein, a semiconducting polymer-based photosensitizer PCPDTBT was found to generate 1O2, ˙OH, and H2O2 through type-I/II PDT paths. After encapsulation within a mesoporous silica matrix, the NIR-II fluorescence and ROS generation are enhanced by 3-4 times compared with the traditional phase transfer method, which can be attributed to the excited-state lifetime being prolonged by one order of magnitude, resulting from restricted nonradiative decay channels, as confirmed by femtosecond spectroscopy. Notably, H2O2 production reaches 15.8 μM min-1 under a 730 nm laser (80 mW cm-2). Further adsorption of Fe2+ ions on mesoporous silica not only improves the loading capacity of the chemotherapy drug doxorubicin but also triggers a Fenton reaction with photo-generated H2O2 in situ to produce ˙OH continuously after the termination of laser irradiation. Thus, semiconducting polymer-based nanocomposites enables NIR-II fluorescence imaging guided persistent PDT under hypoxic conditions. This work provides a promising paradigm to fabricate persistent photodynamic therapy platforms for hypoxia-tolerant phototheranostics.

The cyano positional isomerism strategy for constructing mitochondria-targeted AIEgens with type I reactive oxygen species generation capability.

In this work, a series of cationic luminogens (designated as PSMP isomers) were developed based on the cyano positional isomerism strategy. The isomerism of the cyano substituent on the molecular skeleton can finely regulate the optical behaviour, the type of photoinduced reactive oxygen species (ROS), and mitochondria-targeted capability of isomers. Interestingly, PSMP-4, with the cyano group installed at an appropriate location, exhibits a special aggregation-induced emission effect and potent O2˙- generation efficacy through the type I photochemistry pathway. Notably, PSMP-4 can accumulate in mitochondria with high specificity. Taking advantage of its excellent photostability, PSMP-4 realizes in situ mitochondria imaging in a washing-free manner and sensitive response to the change of mitochondrial membrane potential. The integration of comprehensive photophysical properties and mitochondrial specificity enable PSMP-4 to successfully trigger the death of cancer cells through an efficient type I photodynamic therapy process both in vitro and in multicellular tumor spheroid models.

Precise ligand engineering of Ir(III)-based photosensitizer with aggregation-induced emission for image-guided photodynamic therapy.

Photodynamic therapy (PDT), which relies on the production of reactive oxygen species (ROS) induced by a photosensitizer to kill cancer cells, has become a non-invasive approach to combat cancer. However, the conventional aggregation-caused quenching effect, as well as the low ROS generation ability of photosensitizers, restrict their biological applications. In this work, a new Ir(III) complex with a dendritic ligand has been strategically designed and synthesized by ingenious modification of the ancillary ligand of a reported Ir(III) complex (Ir-1). The extended π-conjugation and multiple aromatic donor moieties endow the resulting complex Ir-2 with obvious aggregation-induced emission (AIE) activity and bathochromic emission. In in vitro experiments, importantly, Ir-2 nanoparticles exhibit the excellent photoinduced ROS generation capabilities of O2 •- and 1 O2 , as well as excellent biocompatibility and the lipid droplets (LDs) targeting feature. This study would provide useful guidance to design efficient Ir(III)-based photosensitizers used in biological applications in the future.

Toward Type I/II ROS Generation Photoimmunotherapy by Molecular Engineering of Semiconducting Perylene Diimide.

As prospective phototheranostic agents for cancer imaging and therapy, semiconducting organic molecule-based nanomedicines are developed. However, near-infrared (NIR) emission, and tunable type I (O2 • -) and type II (1O2) photoinduced reactive oxygen species (ROS) generation to boost cancer photoimmunotherapy remains a big challenge. Herein, a series of D-π-A structures, NIR absorbing perylene diimides (PDIs) with heavy atom bromide modification at the bay position of PDIs are prepared for investigating the optimal photoinduced type I/II ROS generation. The heavy atom effect has demonstrated a reduction of molecular ∆EST and promotion of the intersystem crossing processes of PDIs, enhancing the photodynamic therapy (PDT) efficacy. The modification of three bromides and one pyrrolidine at the bay position of PDI (TBDT) has demonstrated the best type I/II PDT performance by batch experiments and theoretical calculations. TBDT based nanoplatforms (TBDT NPs) enable type I/II PDT in the hypoxic tumor microenvironment as a strong immunogenic cell death (ICD) inducer. Moreover, TBDT NPs showing NIR emission allow in vivo bioimaging guided phototherapy of tumor. This work uses novel PDIs with adjustable type I/II ROS production to promote antitumor immune response and accomplish effective tumor eradication, consequently offering molecular guidelines for building high-efficiency ICD inducers.

Nuclear PARP1-Targeted Photosensitizer as a Dual-Mode DNA-Damaging Agent and Immune Activator for Tumor Ablation.

Photodynamic therapy is a promising cancer therapeutic method that can damage DNA via photoinduced reactive oxygen species production. However, tumor cells can initiate DNA repair pathways to resist oxidative damage. In this study, a nuclear-targeted photosensitizer PARP-PS with a poly (ADP-ribose) polymerase 1 (PARP1) inhibitory effect is developed based on the reported PARP1 inhibitor, rucaparib. As a dual-mode DNA-damaging agent, PARP-PS damages DNA upon photoirradiation and enhances oxidative DNA damage by blocking the DNA repair pathway via PARP1 inhibition and degradation. Both in vitro and in vivo investigations demonstrate that PARP-PS exhibits high antitumor activity with few side effects in breast cancer. In addition, PARP-PS can act as an immunogenic cell death inducer to activate immune responses characterized by the promotion of cytotoxic T lymphocyte activation and tumor infiltration. Therefore, PARP-PS is a potential multimodal antitumor agent with synergistic phototherapeutic, chemotherapeutic, and immunotherapeutic effects.

Metal-Coordination-Mediated H-Aggregates of Cyanine Dyes for Effective Photothermal Therapy.

Integration of cyanine dyes and metal ions into one nanoplatform via metal-coordination interactions is an effective strategy to build multimodality phototheranostics. The multifunctionalities of the formed nanoscale metal-organic particles (NMOPs) have been widely explored. However, the effect of metal-coordination interaction on the aggregation behavior of cyanine dyes is rarely reported. Herein, we reported the H-aggregation behavior of cyanine dye Cy-3COOH induced by different metal ions M (Fe2+ or Mn2+). Moreover, the extent of H-aggregates varied with different metal-coordination interactions. Upon NIR irradiation, H-aggregates of Cy-3COOH remarkably promoted photothermal conversion efficiency. Interestingly, we also find that H-aggregates of Cy-3COOH induced by metal ions can generate the reactive oxygen species (ROS) involving singlet oxygen (1O2) and superoxide anion radical (O2-·) upon light irradiation. And the ROS efficiency varies depending on the extent of H-aggregates. Additionally, the photoinduced ROS could disassemble aggregates and decompose cyanine dye Cy-3COOH, which limits the photothermal capability of Cy-3COOH/M NPs. Therefore, the photothermal performance of Cy-3COOH/M NPs could be manipulated by the degree of H-aggregation. This would provide a new insight to develop efficient phototheranostics NMOPs for cancer treatment.

Metal–organic framework- and graphene quantum dot-incorporated nanofibers as dual stimuli-responsive platforms for day/night antibacterial bio-protection

Development of advanced antibacterial nanomaterials is important to prevent pathogenic microbial contamination and achieve bioprotection. Herein, we developed dual-stimuli-responsive nanoplatforms with efficient antibacterial activity based on electrospun polycaprolactone/hydroxypropyltrimethylammonium chloride chitosan (PQ) nanofiber membranes (NFMs) incorporated with naringenin-loaded zeolitic imidazolate framework-8 (NAR@ZIF-8) and graphene quantum dots (GQDs). These NFM nanoplatforms could simultaneously be used as “smart” pH-responsive controlled-release and photocatalytic systems. NAR was encapsulated in the microporous structure of the ZIF-8 channel, with a loading capacity of 22.57%. NAR@ZIF-8- and GQD-incorporated PQ (PQZG) nanofibers exhibited enhanced thermal stability and mechanical properties. The release kinetics and microstructure of the nanocarriers demonstrated that the acid-sensitive cleavable crystal structure of ZIF-8 resulted in the pH-responsive release of NAR from PQZG NFMs. Moreover, the presence of GQDs significantly enhanced the photoinduced reactive oxygen species (ROS) generation by NFMs. pH-triggered NAR release and photoinduced ROS generation improved the antibacterial efficacy of PQZG NFMs, forming the synergetic chemical-photodynamic strategies of the dual stimuli-responsive nanoplatforms. Additionally, cytotoxicity experiments revealed that the PQZG NFMs were non-toxic and had good biocompatibility. Therefore, the designed composite nanomaterials combined with the two antibacterial strategies can aid in the development of biosafe nanofibrous membranes for antibacterial or multifunctional bio-protection.

Unravelling the role of reactive oxygen species in ultrathin Z-scheme heterojunction with surface zinc vacancies for photocatalytic H2O2 generation and CTC degradation

Photo-induced reactive oxygen species (ROS) produced by molecular oxygen activation and oxidization of H2O/OH− during photocatalytic reaction are extremely important in environmental remediation. Herein, a dual pathway to improve ROS formation was designed through establishing ultrathin 2D/2D Z-scheme heterojunction and defect engineering in O-doped g-C3N4/ZnIn2S4-Zn (ZIS-Z/OCN) composite. The results of experiment and density functional theory (DFT) calculation indicate that the charge-carriers are spatially separated in composite driven by different work functions and ultrathin 2D/2D interface, boosting charge-transfer efficiency from 42.05 % (ZnIn2S4-Zn) to 59.93 % (40ZIS-Z/OCN). Benefiting by this fact, improving molecular oxygen activation capacity can induce more ROS generation. In consequence, 40ZIS-Z/OCN reveals optimal chlortetracycline hydrochloride (CTC) removal efficiency (88.43 %) and hydrogen peroxide (H2O2) yield (168.67 μmol/L) under visible light irradiation. The results of control experiments show that H2O2 is generated via two-step electron reduction route and singlet oxygen (1O2) conversion. This study provides new views on the construction of cost-effective and reusable photocatalysts for environmental remediation and energy conversion.

Inorganic-organic Synergy in Nano-hybrids Makes a New Class of Drug with Targeted Delivery: Glutamate Functionalization of Iron Nanoparticles for Potential Bone Marrow Delivery and X-ray Dynamic Therapy.

The direct delivery of therapeutic molecules is generally inefficient and has several problems. Hence, nanomedicines with targeted and controlled delivery applications have been an exciting field of research for the past decade. In this regard, the adjustable properties of inorganic nanoparticles like particle size distribution, ability to change the targeting ligand to have a higher affinity towards the pathologic cell, and controlled delivery properties have made them indispensable for targeted drug delivery applications. Changing the ligand on the surface of the inorganic nanoparticle can direct different therapeutic molecules to different organs like the liver, spleen, kidney, bone, and even brain. However, while the other targeted nanomedicines are well-reported, the targeting of therapeutics to bone marrow cells is sparse in the literature. Hence, the administration of therapeutics for bone-related disorders, like bone metastases, leads to several problems, such as severe systemic toxicity and suboptimal efficacy. In this direction, we have shown our successful effort to functionalise a model inorganic nanoparticle (Fe2O3) by glutamate ligand which is reported to have a high affinity towards the NMDA receptors of the bone cells. We have performed spectroscopic studies to characterize the nano-hybrid. We have shown that the cargo or the Fe2O3 nanoparticle possesses the ability to generate photo-induced reactive oxygen species (ROS), thereby leading to a therapeutic opportunity for bone metastases. In addition, the nanoparticle also possesses the ability to generate enhanced ROS on X-ray irradiation, which may provide a new strategy for bone metastases and cancer therapy. Also, this paper reviews the advancement in the drug delivery applications of inorganic nanoparticles and highlights the crosstalk between the inorganic nanoparticles with the conjugated targeting ligand for efficient delivery applications.

Photoinduced Carbene for Effective Photodynamic Therapy Against Hypoxic Cancer Cells

Photoinduced Carbene for Effective Photodynamic Therapy Against Hypoxic Cancer Cells

An Endoplasmic Reticulum Targeting Type I Photosensitizer for Effective Photodynamic Therapy against Hypoxic Tumor Cells.

Organelle-targeted type I photodynamic therapy (PDT) shows great potential to overcome the hypoxic microenvironment in solid tumors. The endoplasmic reticulum (ER) is an indispensable organelle in cells with important biological functions. When the ER is damaged due to the production of reactive oxygen species (ROS), the accumulation of misfolded proteins will interfere with ER homeostasis, resulting in ER stress. Here, an ER-targeted benzophenothiazine-based photosensitizer NBS-ER was presented. ER targeting modification significantly reduced the dark toxicity and improved phototoxicity index (PI). NBS-ER could effectively produce O2 - ⋅ with near-infrared irradiation, making its phototoxicity under hypoxia close to that under normoxia. Meanwhile, the photoinduced ROS triggered ER stress and induced apoptosis. In addition, NBS-ER possessed excellent photodynamic therapeutic effect in 4T1-tumor-bearing mice.

Superior photocatalytic and electrochemical activity of novel WS2/PANI nanocomposite for the degradation and detection of pollutants: Antibiotic, heavy metal ions, and dyes

The untreated discharge of noxious pollutants is drawing worldwide concern due to their irretrievable damage to the environment. Especially, pharmaceutical waste has been identified as an emerging pollutant due to its increased demand and untreated discharge into the water bodies. The elimination and detection of such persistent contaminants from wastewater have proven to be a difficult endeavor due to the constraints imposed by the materials and technologies. Therefore, in the present work “free two birds with one key” strategy was implemented to develop a novel visible-light-driven photocatalyst and the electrochemical sensor using WS2/PANI nanocomposite for the degradation and detection. The synthesized WS2/PANI nanocomposite was systematically characterized with a High-resolution transmission electron microscope (HRTEM) and Field emission scanning electron microscope (FESEM) for morphology, Energy-dispersive X-ray (EDX) spectroscopy for elemental analysis, X-ray diffractogram (XRD) for orientation planes, Fourier transform infrared (FTIR) spectroscopy for functional groups and bonds, Zeta potential for the surface charge, Tauc's plot for bandgap analysis, Photoluminescence (PL) spectroscopy study for defects, Time-Resolved Photoluminescence (TRPL) for photogenerated charge carriers, BET for surface parameters and Liquid chromatography-mass spectrometry (LC-MS) for intermediate photodegradation products. The WS2/PANI nanocomposite displayed excellent activity for the photodegradation of antibiotic (nitrofurantoin: NFT, 95%) along with the detection and also degraded textile dye (Methyl orange: MO, 97%), and heavy metal ion (Cr(VI), 99%) with good reusability up to 4 cycles. The superior photocatalytic activity demonstrated by WS2/PANI attributes to its remarkable properties such as a high photoinduced charge separation (5.76 ns) and visible-light-driven bandgap (2.6 eV). A scavenger experiment was also performed to confirm the formation of photoinduced reactive oxygen species (•OH and O2•−). In addition to photocatalytic degradation, WS2/PANI nanocomposite portrayed excellent electrochemical detection of NFT with a low limit of detection (LOD) of 0.01 µM and a wide linear range of 500–0.01 µM.

Antibacterial effect of singlet oxygen depending on bacteria surface charge

Here, we investigated the bactericidal effects of two types of photoinduced reactive oxygen species (ROS), superoxide anion and singlet oxygen, on bacteria with distinct surface charges. We fabricated photofunctional polymer films (PFPFs) capable of generating both types of ROS, and they were subjected to photodynamic inactivation tests for 12 various strains of Acinetobacter baumannii. The results showed that the type I ROS (superoxide anion) was significantly dependent on the surface charge of the bacteria owing to charge-charge repulsion, while the type II ROS (singlet oxygen) was independent of the surface charge of the bacteria. These results could be significant in enhancing treatment efficiency in the clinical field.

TiO2 nanorods doped with g-C3N4 – Polyethylene composite coating for self-cleaning applications

Visible-light-absorbing graphitic carbon nitride–TiO2 nanorod nanomaterials (g-C3N4@TiO2NR) were successfully immobilized using a one-step UVA-induced photocatalytic procedure on commercially obtained flexible low-density polyethylene (LDPE) films. Self-cleaning properties were evaluated in solid–liquid and solid–gas phases using malachite green as a model molecule under UV-A and visible light irradiation. For comparison purpose, LDPE films containing P25 TiO2 nanoparticles was prepared using the same synthetic strategy (P25/LDPE). Among the fabricated films, the g-C3N4@TiO2NR/LDPE films exhibited the highest photocatalytic activity both in solid–liquid and solid–gas phases after 120 min of visible light irradiation (λ > 455 nm) removing efficiently malachite green stains probably due to the attack of photoinduced reactive oxygen species (ROS) such as singlet oxygen (1O2), hydroxyl radical (•OH) and superoxide anion radical (O2−•). Furthermore, the g-C3N4@TiO2NR/LDPE films retained their visible-light-photoinduced photocatalytic properties after four reuse cycles. The g-C3N4@TiO2NR/LDPE films also exhibited significant visible-light-photoinduced hydrophilicity. The high visible-light-photoinduced photocatalytic capacity of g-C3N4@TiO2NR/LDPE films was found to be related to the textural and electronic properties, superior visible-light absorption, and surface roughness of the films.

PH-responsive phototherapeutic poly(acrylic acid)-calcium phosphate passivated TiO2 nanoparticle-based drug delivery system for cancer treatment applications

This paper reports the hydrothermal synthesis and characterization of poly(acrylic acid)-calcium phosphate passivated TiO2 nanoparticles (TiO2@PAA-CaP NPs). The efficient loading and release of doxorubicin (DOX) from the TiO2@PAA-CaP NPs was observed at pH = 7.4 and 5.2, respectively. The loading and encapsulation amount of DOX in TiO2@PAA-CaP NPs was approximately fifteen and eight times as large as that of unfunctionalized TiO2 NPs, respectively, suggesting the PAA-CaP passivation layer enhanced the interaction between DOX and TiO2@PAA-CaP NPs. The DOX-loaded TiO2@PAA-CaP (TiO2@PAA-CaP(DOX)) NPs exhibited much faster cumulative DOX release at acidic pH = 5.2 than at neutral pH = 7.4 because of the pH-responsive dissolution properties of the PAA-CaP passivation layer. TiO2@PAA-CaP(DOX) NPs showed higher cytotoxicity towards MCF-7 tumor cells than free DOX. Confocal fluorescence microscopy and flow cytometry confirmed the enhanced cellular uptake of TiO2@PAA-CaP(DOX) NPs followed by the intracellular release of DOX. Overall, TiO2@PAA-CaP(DOX) NPs demonstrated significantly higher total cytotoxicity towards MCF-7 tumor cells under UV-A irradiation, which was attributed to a synergistic effect between efficient DOX delivery and enhanced photoinduced reactive oxygen species (ROS) generation. This study provides a facile means of synthesizing TiO2-based multifunctional nanocarriers with pH-responsive drug delivery and ROS generation essential for high efficacy therapeutic applications in cancer treatments.

Stabilization of flavin mononucleotide by capturing its “tail” with porous organic polymers for long-term photocatalytic degradation of micropollutants

Flavin mononucleotide (FMN) produces photo-induced reactive oxygen species (ROS), making it a bio-based and sustainable photosensitizer for micropollutant degradation. However, the rapid self-degradation of FMN under light poses challenges in practical applications. We propose for the first time to use porous organic polymer (POP) structures as particles and in situ grown on nanofibrous membranes to capture the ribityl side chain (“tail”) of FMN by electrostatic-driven guest-host interaction. By restraining the free bending mode of FMN in POP, its self-degradation is highly inhibited, showing a prolonged half-life (102.7 and 79.7 times to that in solution and in β-cyclodextrin, respectively) without any impact on the ROS production even after 16 h of UVA irradiation. As a proof-of-concept, the photocatalytic degradation efficiency of FMN-POP complexes can be achieved at 58–93% against micropollutants under UVA. The stabilization of FMN by the “tail” capture in the POP allows its photocatalytic degradation function to be continuously online.