Design, synthesis, and biological evaluation of 5-(1H-indol-5-yl)isoxazole-3-carboxylic acids as novel xanthine oxidase inhibitors.

Xanthine oxidase (XO) is a key enzyme for the production of uric acid in the human body. XO inhibitors (XOIs) are clinically used for the treatment of hyperuricemia and gout, as they can effectively inhibit the production of uric acid. Previous studies indicated that both indole and isoxazole derivatives have good inhibitory effects against XO. Here, we designed and synthesized a novel series of N-5-(1H-indol-5-yl)isoxazole-3-carboxylic acids according to bioisosteric replacement and hybridization strategies. Among the obtained target compounds, compound 6c showed the best inhibitory activity against XO with an IC50 value of 0.13 µM, which was 22-fold higher than that of the classical antigout drug allopurinol (IC50 = 2.93 µM). Structure-activity relationship analysis indicated that the hydrophobic group on the nitrogen atom of the indole ring is essential for the inhibitory potencies of target compounds against XO. Enzyme kinetic studies proved that compound 6c acted as a mixed-type XOI. Molecular docking studies showed that the target compound 6c could not only retain the key interactions similar to febuxostat at the XO binding site but also generate some new interactions, such as two hydrogen bonds between the oxygen atom of the isoxazole ring and the amino acid residues Ser876 and Thr1010. These results indicated that 5-(1H-indol-5-yl)isoxazole-3-carboxylic acid might be an efficacious scaffold for designing novel XOIs and compound 6c has the potential to be used as a lead for further the development of novel anti-gout candidates.

Corrigendum: Improving yields by switching central metal ions in porphyrazine-catalyzed oxidation of glucose into value-added organic acids with SnO2 in aqueous solution.

[This corrects the article DOI: 10.3389/fchem.2023.1114454.].

Boronic acid-functionalized magnetic porphyrin-based covalent organic framework for selective enrichment of cis-diol-containing nucleosides.

In this study, a novel boronic acid-functionalized magnetic porphyrin-based covalent organic framework (COF) with a core-shell structure was designed and synthesized for the selective enrichment and detection of nucleosides. Firstly, brominated porphyrin-based COF was in situ grown on Fe3O4-NH2 nanospheres (denoted as Fe3O4@Br-COF), then a post-synthetic modification strategy was used to introduce boronic acid into the framework via Suzuki-Miyaura cross-coupling reaction to obtain boronic acid functionalized magnetic COF (denoted as Fe3O4@BA-COF). Suzuki-Miyaura cross-coupling possesses the advantages of mild synthesis conditions, high tolerance to functionalities, and ease of handling and separation, which is considered as a promising candidate for functionalizing COF. It is worth mentioning that the porphyrin-based COF possesses a unique nitrogen-rich skeleton and "trap" structure formed by four pyrrole rings, which can provide hydrogen bond and make it more suitable for trapping analytes than other types of COF. The boronic acid group provides boronate affinity, which enables better selective enrichment of cis-diol-containing nucleoside. The morphology and structure of the prepared Fe3O4@BA-COF was characterized by various methods. Based on the Fe3O4@BA-COF, a facile magnetic solid phase extraction coupled with high performance liquid chromatography method (MSPE-HPLC) was used to extract and detect adenosine, guanosine, uridine, and cytidine in urine samples. This work not only provides a mild and feasible post-synthetic modification method for fabrication of boronic acid-functionalized magnetic COF, but also provides an efficient and rapid method to selectively enrich and detect hydrophilic nucleosides.

Highly luminescent nitrogen and sulfur co-doped carbon dots for Sn2+ and S2- sensing and dual-mode anti-counterfeiting.

The preparation of nitrogen and sulfur co-doped carbon dots (N, S-CDs) with highly bright orange-red fluorescence is reported through a facile solvothermal approach with naphthalenetetracarboxylic dianhydride as starting material. The N, S-CDs exhibited superior properties, including intense long-wavelength emission with a narrow full width at half maxima (FWHM) of 33 nm, high fluorescence quantum yield (QY) of 60.5% in aqueous solution, excitation-independent emission behavior, and excellent water dispersibility. In addition, sulfide ions (S2-) could selectively recover the fluorescence of N, S-CDs quenched by Sn2+. The selective experiment suggested that the N, S-CDs/Sn2+ complex could be used as a fluorescence-enhancement sensor for sulfide ions (S2-), with the linear range of 5-50 µM and the LOD of 0.35 µM. The practicality and feasibility of this sensor for the determination of sulfide ions in tap and lake water were verified with good recoveries. Furthermore, because of their highly bright fluorescence and strong water solubility, the N, S-CDs could be easily fabricated into fluorescent ink and transparent films, demonstrating the promising application in anti-counterfeiting. Therefore, the designed N, S-CDs exhibited the advantages of facile preparation, intense fluorescence, high stability, easy processing, and selective fluorescence change for specific analytes, which showed high potential in fluorescence detection and anti-counterfeiting.

Coffee grounds-derived carbon quantum dots as peroxidase mimetics for colorimetric and fluorometric detection of ascorbic acid.

In this study, we reported the eco-responsible synthesis of iron-doped carbon quantum dots (Fe-CQDs) from waste coffee grounds through a simple hydrothermal method. The Fe-CQDs exhibited high peroxidase-like activity, which could convert 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB in the presence of H2O2. After adding ascorbic acid (AA) to above system, the blue solution faded. Based on this phenomenon, a colorimetric method for visual monitoring of H2O2 and AA was developed. Meanwhile, the fluorescence of Fe-CQDs can be quenched by the formed ox-TMB via inner filter effect (IFE), followed by the recovery upon the addition of AA. Therefore, Fe-CQDs can be acted as a fluorescent probe to detect H2O2 and AA through the "on-off-on" mode. Furthermore, the dual-recognition methods based on Fe-CQDs were used to measure AA content in beverage samples. Thus, this work would shed much light on converting waste into biomass CQDs and their potential applications in biomolecular detection.

Improving yields by switching central metal ions in porphyrazine-catalyzed oxidation of glucose into value-added organic acids with SnO2 in aqueous solution.

Photocatalysis has exhibited huge potential in selective conversion of glucose into value-added chemicals. Therefore, modulation of photocatalytic material for selective upgrading of glucose is significant. Here, we have investigated the insertion of different central metal ions, Fe, Co, Mn, and Zn, into porphyrazine loading with SnO2 for access to more efficient transformation of glucose into value-added organic acids in aqueous solution at mild reaction conditions. The best selectivity for organic acids containing glucaric acid, gluconic acid, and formic acid of 85.9% at 41.2% glucose conversion was attained by using the SnO2/CoPz composite after reacting for 3 h. The effects of central metal ions on surficial potential and related possible factors have been studied. Experimental results showed that the introduction of metalloporphyrazine with different central metal ions on the surface of SnO2 has a significant effect on the separation of photogenerated charges, changing the adsorption and desorption of glucose and products on the catalyst surface. The central metal ions of cobalt and iron contributed more to the positive effects toward enhancing conversion of glucose and yields of products, and manganese and zinc contributed more to the negative effects, resulting in the poor yield of products. The differences from the central metals may attribute to the surficial potential change of the composite and the coordination effects between the metal and oxygen atom. An appropriate surficial potential environment of the photocatalyst may achieve a better interactive relationship between the catalyst and reactant, while appropriate ability of producing active species matched with adsorption and desorption abilities would gain a better yield of products. These results have provided valued ideas for designing more efficient photocatalysts in selective oxidation of glucose utilizing clean solar energy in the future.

In situ growth of porous organic framework on iron wire for microextraction of polycyclic aromatic hydrocarbons.

In this work, a novel spherical metal organic framework (MOF) was first in situ grown on the surface of iron wire (IW), in which IW served as the substrate and metal source for MOF (type NH2-MIL88) growth without adding additional metal salts in the process, while spherical NH2-MIL88 provided more active sites for further construction of multifunctional composites. Subsequently, a covalent organic framework (COF) was covalently bonded to the surface of the NH2-MIL88 to obtain the IW@NH2-MIL88@COF fibers, which were used for headspace solid-phase microextraction (HS-SPME) of polycyclic aromatic hydrocarbons (PAHs) in milk samples prior to determination by gas chromatography-flame ionization detection (GC-FID). Compared with the fiber prepared by physical coating, the IW@NH2-MIL88@COF fiber prepared by in situ growth and covalent bonding exhibits better stability and possesses more uniform layer. The extraction mechanism of the IW@NH2-MIL88@COF fiber for PAHs was discussed, which mainly owed to π-π interactions and hydrophobic interactions. After optimization of the primary extraction conditions, the SPME-GC-FID method was established for five PAHs with a wide linear range (1-200 ng mL-1), good linearity coefficient (0.9935-0.9987) and low detection limits (0.017-0.028 ng mL-1). The relative recoveries for PAHs detection in milk samples ranged from 64.69 to 113.97%. This work not only provides new ideas for the in situ growth of other types of MOF, but also provides new methods for the construction of multifunctional composites.

Luminescent carbon dots with excellent peroxidase mimicking property for fluorometric and colorimetric detection of glucose.

The luminescent carbon dots with peroxidase mimicking property had attracted considerable attention in biomedical field. In this work, iron-doped carbon dots (Fe-CDs) were prepared by one-pot hydrothermal method with 5, 10, 15, 20-tetra (4-borate phenyl)-21H, 23H-porphyrin Fe (II) (Fe-TBPP) as precursor. The obtained Fe-CDs emitted intense blue luminescence under ultraviolet light irradiation. Moreover, the Fe-CDs exhibited remarkable peroxidase mimicking property, which can efficiently catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) into blue ox-TMB in the presence of hydrogen peroxide (H2O2). More importantly, the emission of Fe-CDs could be gradually quenched with the addition of H2O2. Based on these phenomena, a new optical dual-mode (colorimetric and fluorometric) method for the detection of H2O2 and glucose was successfully established. The detection limits of glucose were calculated to be 3.86 and 7.27 µM (S/N = 3) respectively based on the colorimetric and fluorometric methods. Furthermore, we combined this dual-mode detection method with smartphone imaging. The colorimetric and fluorescent images were collected by recognition software of smartphone, which were then transformed into the corresponding HSL values for quantitative determination of glucose. Finally, the dual-mode approach based on Fe-CDs was used for the detection of glucose content in human serum, demonstrating the potential application of carbon dots in the biological area.

Fabrication of highly fluorinated porphyrin-based covalent organic frameworks decorated Fe3O4 nanospheres for magnetic solid phase extraction of fluoroquinolones.

A highly fluorinated porphyrin-based covalent organic frameworks magnetic adsorbent (FPy-COF@PDA@Fe3O4) was fabricated by using polydopamine (PDA) grafting Fe3O4 nanospheres as magnetic core and FPy-COF as shell for magnetic solid phase extraction (MSPE) of fluoroquinolones (FQs). FPy-COF was constructed by using 5,15-bis(4-aminophenyl)-10,20-bis(perfluorophenyl)porphyrin and 4,4'-biphenyldicarboxaldehyde as two building blocks. PDA as a bridge grafting on the surface of Fe3O4 nanospheres facilitated the growth of FPy-COF. The morphology and structure of FPy-COF@PDA@Fe3O4 adsorbent were characterized in detail. The prepared magnetic adsorbent exhibited good extraction capability to amphiphilic FQs due to their superior chemical affinities such as fluorophilic interaction and hydrogen-bond interaction from nitrogen-rich skeleton. Under the optimized conditions, the MSPE method combined with high performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed to sensitively quantify trace level of six FQs in milk samples. The developed MSPE-HPLC method showed good linearity with wide concentration range, precision, and low limits of detection (S/N = 3) for six FQs as low as 2.3 ngꞏmL-1 in milk. The extraction recoveries of different spiked concentrations were in the range 77.8-110.4% for milk samples with RSD less than 9.7%.

Self-Assembled BODIPY Derivative with A-D-A Structure as Organic Nanoparticles for Photodynamic/Photothermal Cancer Therapy.

Organic nanomaterials have attracted considerable attention in the area of photodynamic and photothermal therapy, owing to their outstanding biocompatibility, potential biodegradability, well-defined chemical structure, and easy functionalization. However, it is still a challenge to develop a single organic molecule that obtains both photothermal and photodynamic effects. In this contribution, we synthesized a new boron-dipyrromethene (BODIPY)-based derivative (DPBDP) with an acceptor-donor-acceptor (A-D-A) structure by coupling 3,6-di(2-thienyl)-2,5-dihydropyrrolo [3,4-c] pyrrole-1,4-dione (DPP) and BODIPY. To enhance the hydrophilicity of the BODIPY derivative, the polyethylene glycol (PEG) chains were introduced to the meso- position of BODIPY core. The amphiphilic DPBDP was then self-assembled into related nanoparticles (DPBDP NPs) with improved hydrophilicity and enhanced absorbance in the NIR region. DPBDP NPs could simultaneously generate the singlet oxygen (1O2) and heat under the irradiation of a single laser (690 nm). The 1O2 quantum yield and photothermal conversion efficiency (PCE) of DPBDP NPs were calculated to be 14.2% and 26.1%, respectively. The biocompatibility and phototherapeutic effect of DPBDP NPs were evaluated through cell counting kit-8 (CCK-8) assay. Under irradiation of 690 nm laser (1.0 W/cm2), the half maximal inhibitory concentration (IC50) of DPBDP NPs was calculated to be 16.47 µg/mL. Thus, the as-prepared DPBDP NPs could be acted as excellent candidates for synergistic photodynamic/photothermal therapy.

Iron porphyrin-based porous organic polymer with high peroxidase-like activity as colorimetric sensor for glutathione and ascorbic acid assay.

A new iron porphyrin-based organic polymer (Fe-POP) was synthesized through the William ether reaction. The as-prepared Fe-POP presented high chemical stability, wide pore distribution, high iron content, and strong affinity with 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), which contributed to its excellent peroxidase-mimicking performance. In the presence of H2O2, Fe-POP could catalyze the transparent TMB into blue ox-TMB, which could be easily distinguished by the naked eyes. Moreover, glutathione (GSH) and ascorbic acid (AA) could convert blue ox-TMB into colorless TMB due to the inhibitory effect of GSH/AA to the catalytic oxidation of TMB. Based on this phenomenon, a rapid and sensitive colorimetric method for the assay of H2O2, GSH, and AA was developed using Fe-POP as sensor. The detection limits of H2O2, GSH, and AA  were 1.37, 0.44, and 0.33 µM, respectively. Finally, the colorimetric method based on Fe-POP was used to evaluate the GSH and AA content in real samples, which provided the guidance for GSH and AA supplements in our daily diet, suggesting the significant potential of Fe-POP in practical applications.

Exploration of N-Arylsulfonyl-indole-2-carboxamide Derivatives as Novel Fructose-1,6-bisphosphatase Inhibitors by Molecular Simulation.

A series of N-arylsulfonyl-indole-2-carboxamide derivatives have been identified as potent fructose-1,6-bisphosphatase (FBPase) inhibitors (FBPIs) with excellent selectivity for the potential therapy of type II diabetes mellitus. To explore the structure-activity relationships (SARs) and the mechanisms of action of these FBPIs, a systematic computational study was performed in the present study, including three-dimensional quantitative structure-activity relationship (3D-QSAR) modeling, pharmacophore modeling, molecular dynamics (MD), and virtual screening. The constructed 3D-QSAR models exhibited good predictive ability with reasonable parameters using comparative molecular field analysis (q2 = 0.709, R2 = 0.979, rpre2 = 0.932) and comparative molecular similarity indices analysis (q2 = 0.716, R2 = 0.978, rpre2 = 0.890). Twelve hit compounds were obtained by virtual screening using the best pharmacophore model in combination with molecular dockings. Three compounds with relatively higher docking scores and better ADME properties were then selected for further studies by docking and MD analyses. The docking results revealed that the amino acid residues Met18, Gly21, Gly26, Leu30, and Thr31 at the binding site were of great importance for the effective bindings of these FBPIs. The MD results indicated that the screened compounds VS01 and VS02 could bind with FBPase stably as its cognate ligand in dynamic conditions. This work identified several potential FBPIs by modeling studies and might provide important insights into developing novel FBPIs.

Red-Emissive Sulfur-Doped Carbon Dots for Selective and Sensitive Detection of Mercury (II) Ion and Glutathione.

Carbon dots (CDs) show great potential in bioimaging and biosensing because of their good biocompatibility and excellent optical properties. However, CDs with intense red emissions for sensitive and selective detection are rarely reported. Herein, we prepared the red-emissive carbon dots (RCDs) through a facile hydrothermal method using tetra (4-carboxyphenyl) porphyrin (TCPP) and thiourea as starting materials. The obtained RCDs were characterized by TEM, XRD, and XPS. RCDs exhibited high water solubility and strong red emission (λem = 650 nm), with the fluorescence quantum yield as high as 26.7%, which was greatly higher than that of TCPP. Moreover, the as-prepared RCDs could be acted as a highly selective and sensitive probe for the detection of Hg2+ and glutathione (GSH) through the fluorometric titration method. The detection limits of Hg2+ and GSH were calculated to be 1.73 and 1.6 nM, respectively. The cellular experiments demonstrated the good biocompatibility of RCDs and their feasibility in bioimaging. Thus, this work provided a simple strategy to design and synthesize the highly red-emissive carbon dots, which showed promising application in biological and environmental assays.

Boronic acid grafted metal-organic framework for selective enrichment of cis-diol-containing compounds.

This study constructed boronic acid grafted Zr-MOF (BA-Zr-MOF) by a simple pre-installation strategy through mixed organic ligands. Typically, BA-Zr-MOF was prepared by one-step hydrothermal method used for enrichment of cis-diol-containing nucleosides through pipette tip solid-phase extraction (PT-SPE) followed by detection of high-performance liquid chromatography. It is worth mentioning that BA is well assembled into MOF and cis-diol-containing compounds can be efficiently and selectively enriched by abundant boronic acid groups. Three groups of different types of compounds were used to evaluate their selectivity and the results showed the excellent selectivity to cis-diol-containing compounds of as-prepared adsorbent. The BA-Zr-MOF adsorbent possesses a high adsorption capacity, which can reach 86.40 mg g-1 for adenosine. Under the optimal extraction condition, a PT-SPE-HPLC method based on BA-Zr-MOF for analysis of nucleosides was established. The linear range of the four nucleosides is 0.01 to 50 µg mL-1 with R2 ≥ 0.99 and the detection limits (LODs) are estimated at between 0.005-0.012 µg mL-1. The recoveries in urine were used to test the reliability of the analytical methods, which ranged from 82.8% to 117.1%, with intra-day relative standard deviations (RSDs) ranged from 0.1% to 4.2% and the inter-day RSDs ranged from 0.2% to 6.2%. All the results show that the pre-installation strategy based on dual ligands is an alternative to fabricate MOF composite material and BA-Zr-MOF is a promising material for the analysis of cis-diol-containing biomolecules.

In-situ growth of boronic acid-decorated metal-organic framework on Fe3O4 nanospheres for specific enrichment of cis-diol containing nucleosides.

In this study, a novel core-shell structured magnetic metal-organic framework nanospheres (Fe3O4@PD@BA-Zr-MOF) were fabricated by in-situ growth of boronic acid-decorated porphyrin-based metal-organic frameworks on polydopamine (PD) functionalized Fe3O4 nanospheres for highly efficient enrichment of cis-diol containing nucleosides by magnetic solid phase extraction (MSPE). PD as a molecular linker promotes the nucleation and crystal growth of boronic acid-decorated porphyrin-based metal-organic framework (BA-Zr-MOF), which was synthesized via a dual-ligand strategy by using Zr4+ as a metal unit as well as meso-tetra (4-carboxylphenyl) porphyrin (TCPP) and 1, 4-phenylenebisboronic acid (BA) as dual organic ligands. It is worth noting that the nitrogen-rich skeleton of TCPP and abundant boric acid groups in MOF allows for effective and selective enrichment of cis-diol containing compounds by hydrophilic interaction and boron affinity. Also, Zr4+ well assembled into the MOF is beneficial to extraction via metal oxide affinity interaction due to reversible covalent complex formation/dissociation between Zr and cis-diol compounds. The morphology, structure and saturation magnetization of Fe3O4@PD@BA-Zr-MOF were systematically characterized. The as-prepared adsorbent coupled with high performance liquid chromatography was used for analysis of four nucleosides including cytidine, uridine, guanosine, and adenosine in urine sample with the detection limits in range of 0.002-0.005 µg mL-1 and the quantitative limits in range of 0.008-0.018 µg mL-1. The as-fabricated Fe3O4@PD@BA-Zr-MOF nanospheres shows high selectivity, low detection limit, excellent reusability and reproducibility for nucleosides enrichment. The large specific surface area and quick magnetic response performance endow the affinity magnetic nanospheres with outstanding enrichment capability for rapid extraction. The adsorbent of Fe3O4@PD@BA-Zr-MOF nanospheres has great potential for identification and analysis of trace cis-diol containing nucleosides in biological samples.

Nanoplatform Self-Assembly from Small Molecules of Porphyrin Derivatives for NIR-II Fluorescence Imaging Guided Photothermal-Immunotherapy.

Combinatorial photothermal and immunotherapy have demonstrated great potential to remove primary tumors, suppress metastases, and prevent tumor recurrence. However, this strategy still confronts patients with many limitations, such as complex components, sophisticated construction, and inadequate therapeutic efficacy. In this work, small molecules of porphyrin derivatives (PPor) which can self-assemble into monodispersed nanoparticles without supplement of any other ingredients or surfactants are developed. The formed PPor nanoparticles (PPor NPs) exhibit highly photothermal conversion efficiency of 70% and NIR-II luminous abilities originate from the strong intramolecular charge transfer (ICT) effect of D-A structure under 808 nm laser irradiation, thus achieving NIR-II fluorescence imaging guided photothermal therapy (PTT) against primary tumors with a high cure rate. More importantly, tumor-associated antigens (TAAs), together with damage-associated molecular patterns (DAMPs) released from PTT-treated cancer cells, are proved to elicit immune responses to some degree. After combination with programmed cell death-1 (PD-1) antibodies, a robust systematic antitumor immunity is generated to restrain both primary and abscopal tumors growth, prolong survival, and prevent pulmonary metastasis on an aggressive 4T1 murine breast tumor model. Thus, this study provides a promising therapeutic paradigm with porphyrin derivatives nano-assembly as phototheranostic agents for the treatment of aggressive tumors with high efficiency.

Organic Nanoparticles Based on D-A-D Small Molecule: Self-Assembly, Photophysical Properties, and Synergistic Photodynamic/Photothermal Effects.

Cancer is one of the major diseases threatening human health. Traditional cancer treatments have notable side-effects as they can damage the immune system. Recently, phototherapy, as a potential strategy for clinical cancer therapy, has received wide attention due to its minimal invasiveness and high efficiency. Herein, a small organic molecule (PTA) with a D-A-D structure was prepared via a Sonogashira coupling reaction between the electron-withdrawing dibromo-perylenediimide and electron-donating 4-ethynyl-N,N-diphenylaniline. The amphiphilic organic molecule was then transformed into nanoparticles (PTA-NPs) through the self-assembling method. Upon laser irradiation at 635 nm, PTA-NPs displayed a high photothermal conversion efficiency (PCE = 43%) together with efficient reactive oxygen species (ROS) generation. The fluorescence images also indicated the production of ROS in cancer cells with PTA-NPs. In addition, the biocompatibility and photocytotoxicity of PTA-NPs were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and live/dead cell co-staining test. Therefore, the as-prepared organic nanomaterials were demonstrated as promising nanomaterials for cancer phototherapy in the clinic.

Self-assembled porphyrin polymer nanoparticles with NIR-II emission and highly efficient photothermal performance in cancer therapy.

The development of new organic nanoagents with extremely high photothermal conversion efficiency and good biocompatibility has gained considerable attention in the area of photothermal cancer therapy. In this work, we designed and synthesized a new porphyrin polymer (P-PPor) with donor-acceptor (D-A) structure. P-PPor displayed intense absorbance in the near-infrared (NIR) region with the maximum peak around at 850 â€‹nm. Under excitation of 808 â€‹nm, P-PPor demonstrated the significant fluorescence in the NIR-II region (λ max â€‹= â€‹1015 â€‹nm), with the fluorescence quantum yield of 2.19%. Due to the presence of hydrophilic PEG chains and hydrophobic alkyl chains in the conjugated skeleton, the amphiphilic P-PPor could self-assemble into the nanoparticles (P-PPor NPs) with good dispersibility in water and enhanced absorption in the NIR region. Moreover, P-PPor NPs exhibited quenched fluorescence because of the aggregation-caused quenching (ACQ) effect, resulting in the distinct photothermal effect. The photothermal conversion efficiency (PCE) of P-PPor NPs was measured as 66% under 808 â€‹nm laser irradiation, higher than most of PTT agents. The remarkable photothermal effect of P-PPor NPs was further demonstrated in vitro and in vivo using 4T1 tumor mode. Meanwhile, the NIR-II fluorescence imaging in vivo indicated the high distribution of P-PPor NPs in tumor site. These results suggested that P-PPor NPs could effectively damage the cancer cells in mice under 808 â€‹nm laser irradiation, and did not cause any obvious side effects after phototherapy. Thus, P-PPor NPs could be used as a potential agent in photothermal cancer therapy with high effectiveness and safety.

Cobalt-Doped Carbon Quantum Dots with Peroxidase-Mimetic Activity for Ascorbic Acid Detection through Both Fluorometric and Colorimetric Methods.

In this work, we fabricated cobalt-doped carbon quantum dots (Co-CQDs) by a one-pot hydrothermal method with cobalt tetraphenylporphyrin and 1,2-ethanediamine as precursors. The morphology and structure of the Co-CQDs were characterized through transmission electron microscopy, X-ray diffraction spectra, Fourier transform infrared, and X-ray photoelectron spectra. The Co-CQDs emitted intense blue luminescence under ultraviolet irradiation and exhibited a typical excitation-dependent emission property. Moreover, they can act as a fluorescent probe for the detection of Fe3+ and ascorbic acid (AA) with high selectivity and sensitivity through an "on-off-on" mode. The limit of detection (LOD) of Fe3+ was measured as 38 µM (S/N = 3). The quenched emission of carbon quantum dots can be recovered with the addition of ascorbic acid (AA) to the Co-CQDs/Fe3+ system. The change of fluorescence was linear with the concentration of AA (0.6-1.6 mM) with the LOD of 18 µM. Furthermore, the Co-CQDs exhibited high oxidase-like catalytic behavior, which could convert transparent 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB by dissolved oxygen. After adding ascorbic acid to the Co-CQDs/TMB system, the blue color of the solution faded due to the reduction of blue ox-TMB to colorless TMB. Based on this phenomenon, the Co-CQDs were capable of detecting AA (10-400 µM) with the LOD of 0.27 µM. The fluorometric and colorimetric assays based on the Co-CQDs for the AA detection were then successfully applied in fresh fruits. Furthermore, the high biocompatibility of the Co-CQDs against HeLa cells was verified by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Thus, the Co-CQDs could be used as a powerful tool for the detection of AA in real samples through a dual-mode method.

Exploration of Novel Xanthine Oxidase Inhibitors Based on 1,6-Dihydropyrimidine-5-Carboxylic Acids by an Integrated in Silico Study.

Xanthine oxidase (XO) is an important target for the effective treatment of hyperuricemia-associated diseases. A series of novel 2-substituted 6-oxo-1,6-dihydropyrimidine-5-carboxylic acids (ODCs) as XO inhibitors (XOIs) with remarkable activities have been reported recently. To better understand the key pharmacological characteristics of these XOIs and explore more hit compounds, in the present study, the three-dimensional quantitative structure-activity relationship (3D-QSAR), molecular docking, pharmacophore modeling, and molecular dynamics (MD) studies were performed on 46 ODCs. The constructed 3D-QSAR models exhibited reliable predictability with satisfactory validation parameters, including q2 = 0.897, R2 = 0.983, rpred2 = 0.948 in a CoMFA model, and q2 = 0.922, R2 = 0.990, rpred2 = 0.840 in a CoMSIA model. Docking and MD simulations further gave insights into the binding modes of these ODCs with the XO protein. The results indicated that key residues Glu802, Arg880, Asn768, Thr1010, Phe914, and Phe1009 could interact with ODCs by hydrogen bonds, π-π stackings, or hydrophobic interactions, which might be significant for the activity of these XOIs. Four potential hits were virtually screened out using the constructed pharmacophore model in combination with molecular dockings and ADME predictions. The four hits were also found to be relatively stable in the binding pocket by MD simulations. The results in this study might provide effective information for the design and development of novel XOIs.