Light-Quality-Adapted Carotenoid Photoprotection in the Photosystem of Roseiflexus castenholzii.

The photosystem of filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii comprises a light-harvesting (LH) complex encircling a reaction center (RC), which intensely absorbs blue-green light by carotenoid (Car) and near-infrared light by bacteriochlorophyll (BChl). To explore the influence of light quality (color) on the photosynthetic activity, we compared the pigment compositions and triplet excitation dynamics of the LH-RCs from Rfl. castenholzii was adapted to blue-green light (bg-LH-RC) and to near-infrared light (nir-LH-RC). Both LH-RCs bind γ-carotene derivatives; however, compared to that of nir-LH-RC (12%), bg-LH-RC contains substantially higher keto-γ-carotene content (43%) and shows considerably faster BChl-to-Car triplet excitation transfer (10.9 ns vs 15.0 ns). For bg-LH-RC, but not nir-LH-RC, selective photoexcitation of Car and the 800 nm-absorbing BChl led to Car-to-Car triplet transfer and BChl-Car singlet fission reactions, respectively. The unique excitation dynamics of bg-LH-RC enhances its photoprotection, which is crucial for the survival of aquatic anoxygenic phototrophs from photooxidative stress.

Stimulus-Responsive Hydrogels as Drug Delivery Systems for Inflammation Targeted Therapy.

Deregulated inflammations induced by various factors are one of the most common diseases in people's daily life, while severe inflammation can even lead to death. Thus, the efficient treatment of inflammation has always been the hot topic in the research of medicine. In the past decades, as a potential biomaterial, stimuli-responsive hydrogels have been a focus of attention for the inflammation treatment due to their excellent biocompatibility and design flexibility. Recently, thanks to the rapid development of nanotechnology and material science, more and more efforts have been made to develop safer, more personal and more effective hydrogels for the therapy of some frequent but tough inflammations such as sepsis, rheumatoid arthritis, osteoarthritis, periodontitis, and ulcerative colitis. Herein, from recent studies and articles, the conventional and emerging hydrogels in the delivery of anti-inflammatory drugs and the therapy for various inflammations are summarized. And their prospects of clinical translation and future development are also discussed in further detail.

Daphnia magna uptake and excretion of luminescence-labelled polystyrene nanoparticle as visualized by high sensitivity real-time optical imaging.

The environmental and ecological consequences of nanoplastics (NPs) draw increasing research interests and social concerns. However, the in situ and real-time detection of NPs from living organisms and transferring media remains as a major technical obstacle for scientific investigation. Herein we report a novel time-gated imaging (TGI) strategy capable of real-time visualizing the intake of NPs by an individual living organism, which is based on the polystyrene NPs labelled with lanthanide up-conversion luminescence. The limit of detection (LOD) of the TGI apparatus was 600 pg (SNR = 3) in a field of view of 2.4 × 3.8 mm. Taking Daphnia magna as the aquatic model, we investigated the dynamics of uptake and accumulation of NPs (500 µg/L) for 24 h, and the subsequent excretion process (in clean medium) for 48 h, and quantitively analyzed the distribution and the overall mass of NPs deposited in D. magna. The uptake of NPs via filter-feeding occurred in a few minutes, whereas a longer accumulation was found, in a timescale of several hours. And similar behaviors (bi-phase elimination) were also seen in the excretion, indicating the migration of NPs into the circulatory system. The average mass of NPs accumulated in an individual D. magna was ∼12 ng after 24 h exposure, indicating that D. magna as a filter feeder tends to retain NPs. The observed NPs accumulation in D. magna exemplifies the potential risk of aquatic ecosystem on exposure to NP contamination.

Rhodobacter sphaeroides as a model to study the ecotoxicity of 1-alkyl-3-methylimidazolium bromide.

The purple non-sulfur bacterium Rhodobacter sphaeroides was selected as a biological model to investigate its response to the toxicity of 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br), a type of ionic liquid (IL), with different alkyl chain lengths (n describes the number of carbon atoms in the alkyl chain). The inhibition of bacterial growth by [Cnmim]Br was positively correlated with n. Morphological characterization revealed that [Cnmim]Br caused cell membrane perforation. The signal amplitude of the electrochromic absorption band shift of endogenous carotenoids showed a negatively linear correlation with n, and the amplitude of the blue-shift of the B850 band in light-harvesting complex 2 showed a positively linear correlation with n. Furthermore, an increase in blocked ATP synthesis and increase in antioxidant enzyme activity were observed in chromatophores treated with ILs containing longer alkyl chains. In summary, the purple bacterium can be developed as a model to monitor ecotoxicity and examine the mechanism of IL toxicity.

Photoinduced chlorophyll charge transfer state identified in the light-harvesting complex II from a marine green alga Bryopsis corticulans.

The light-harvesting complex II of Bryopsis corticulans (B-LHCII), a green alga, differs from that of spinach (S-LHCII) in chlorophyll (Chl) and carotenoid (Car) compositions. We investigated ultrafast excitation dynamics of B-LHCII with visible-to-near infrared time-resolved absorption spectroscopy. Absolute fluorescence quantum yield (Φ FL) of LHCII and spectroelectrochemical (SEC) spectra of Chl a and b were measured to assist the spectral analysis. Red-light excitation at Chl Qy-band, but not Car-band, induced transient features resembling the characteristic SEC spectra of Chl a ⋅+ and Chl b ⋅-, indicating ultrafast photogeneration of Chl-Chl charge transfer (CT) species; Φ FL and 3Car∗ declined whereas CT species increased upon prolonging excitation wavelength, showing positive correlation of 1Chl∗ deactivation with Chl-Chl CT formation. Moreover, ultrafast Chl b-to-Chl a and Car-to-Chl singlet excitation transfer were illustrated. The red-light induction of Chl-Chl CT species, as also observed for S-LHCII, is considered a general occurrence for LHCIIs in light-harvesting form.

A Possible Mechanism for Aggregation-Induced Chlorophyll Fluorescence Quenching in Light-Harvesting Complex II from the Marine Green Alga Bryopsis corticulans.

The light-harvesting complex II of a green alga Bryopsis corticulans (B-LHCII) is peculiar in that it contains siphonein and siphonaxathin as carotenoid (Car). Since the S1 state of siphonein and siphonaxathin lies substantially higher than the Qy state of chlorophyll a (Chl a), the Chl a(Qy)-to-Car(S1) excitation energy transfer is unfeasible. To understand the photoprotective mechanism of algal photosynthesis, we investigated the influence of temperature on the excitation dynamics of B-LHCII in trimeric and aggregated forms. At room temperature, the aggregated form showed a 10-fold decrease in fluorescence intensity and lifetime than the trimeric form. Upon lowering the temperature, the characteristic 680 nm fluorescence (F-680) of B-LHCII in both forms exhibited systematic intensity enhancement and spectral narrowing; however, only the aggregated form showed a red emission extending over 690-780 nm (F-RE) with pronounced blueshift, lifetime prolongation, and intensity boost. The remarkable T-dependence of F-RE is ascribed to the Chl-Chl charge transfer (CT) species involved directly in the aggregation-induced Chl deactivation. The CT-quenching mechanism, which is considered to be crucial for B. corticulans photoprotection, draws strong support from the positive correlation of the Chl deactivation rate with the CT state population, as revealed by comparing the fluorescence dynamics of B-LHCII with that of the plant LHCII.

Inflammation-Triggered Supramolecular Nanoplatform for Local Dynamic Dependent Imaging-Guided Therapy of Rheumatoid Arthritis.

The aging of population has resulted in a significant increase in the prevalence of rheumatoid arthritis (RA), which is a persistent and recurrent synovial inflammation caused by abnormal immune activation. Herein, the authors designed an inflammation-triggered disassembly (ITD) nanoplatform by a supramolecular assembly method, which controls the decomposition and drug release through changes in cytokine concentrations and redox potentials during the onset of arthritis, and its dual-targeted synergistic effect on collagen-induced arthritis (CIA) rats resulted in higher cell death rate and immunosuppressive rate. Meanwhile, they propose the local dynamic dependent imaging (LDDI) technology to diagnose the disease status, which may produce corresponding changes with the fluctuation of inflammatory activity and improve the accuracy of dual-target therapy by monitoring the synovial changes through in situ photoactivation of the second near infrared light (NIR-II). Very importantly, histological analysis shows that ITD strategy relieved joint destruction and cartilage degeneration and its clinical score is similar to that of the healthy group. Their work provides an effective strategy for the early diagnosis and treatment of acute and chronic inflammation diseases, which can interfere to abnormal immune activation, rather than affecting the normal function of immune system.

Spatial effects of photosensitization on morphology of giant unilamellar vesicles.

Singlet oxygen (1O2) formed through photosensitization may initiate oxidative destruction of biomembranes, however, the influence from the spatial organization of photosensitizers (PS) relative to membranes remains unclear. To clarify this issue, we loaded riboflavin 5'-(dihydrogen phosphate) monosodium (FMN-Na) as a hydrophilic PS into the lumen of halloysite nanotubes (HNTs), and attached the nanoassemblies (FMN-Na@HNTs), via Pickering effects, to the outer surfaces of giant unilamellar vesicles (GUVs) of phospholipids. We also prepared GUVs dopped with lumiflavin (LF) as a lipophilic PS having a 1O2 quantum yield comparable to FMN-Na. FMN-Na capsulated in HNT was characterized by a longer triplet excited state lifetime (12.1 µs) compared to FMN-Na free in solution (7.5 µs), and FMN-Na in both forms efficiently generated 1O2 upon illumination. The spatio-effects of PS on the photosensitized morphological changes of membranes were studied using conventional optical microscopy by monitoring GUV morphological changes. Upon light exposure (400-440 nm), the GUVs attached with FMN-Na@HNT merely experienced membrane deformation starting from the original spherical shape, ascribed to Type II photosensitization with 1O2 as oxidant. In contrast, photooxidation of LF dopped GUVs mainly led to membrane coarsening and budding assigned to Type I photosensitization. The spatial effects of PS on photosensitized morphological changes were related to the different lipid oxidation products generated through Type I and Type II photosensitized lipid oxidation.

Electrochemiluminescence Based on a Dual Carbon Ultramicroelectrode with Confined Steady-State Annihilation.

Developing novel microelectronic devices for electrochemical measurements and electrochemiluminescence (ECL) study is of great importance. Herein, we fabricated a submicrometer-sized dual carbon electrode (DCE) and investigated its annihilation ECL behavior under steady-state conditions for the first time. The oxidation and reduction of the model luminophore, [Ru(bpy)3]2+, occurred separately at the two sides of the DCE, and the electrogenerated ions then diffused to the gap between the two electrodes to generate the excited-state intermediate [Ru(bpy)3]2+* and ECL emission. Compared with other types of two-electrode systems, the prepared DCE possesses a smaller total size and an ultrasmall interelectrode distance of 60 nm or less, which could result in a shorter diffusion time and an amplified ECL signal without the purification of the solvent and supporting electrolytes. On the basis of the constructed ECL microscopic platform, we successfully obtained a stable and confined ECL signal in the vicinity of the electrode tip. Furthermore, a two-dimensional finite element method simulation of this model system was performed to quantitively analyze the concentration profiles of the electrogenerated species around the tip of the DCE and predict the concentrations of [Ru(bpy)3]2+* with various gap distances. The simulation results also proved that the higher concentrations of [Ru(bpy)3]2+* could be achieved with a smaller distance with a possible amplification factor of 6 (compared with the concentration when the gap distance is greater than 300 nm). This work provides an experimental model for further improvement of ECL efficiency and broadens the availability for annihilation ECL applications in small confined spaces.

A Spontaneous Membrane-Adsorption Approach to Enhancing Second Near-Infrared Deep-Imaging-Guided Intracranial Tumor Therapy.

Herein, a functional class of microenvironment-associated nanomaterials is reported for improving the second near-infrared (NIR-II) imaging and photothermal therapeutic effect on intracranial tumors via a spontaneous membrane-adsorption approach. Specific peptides, photothermal agents, and biological alkylating agents were designed to endow the nanogels with high targeting specificity, photothermal properties, and pharmacological effects. Importantly, the frozen scanning electron microscopy technology (cryo-SEM) was utilized to observe the self-association of nanomaterials on tumor cells. Interestingly, the spontaneous membrane-adsorption behavior of nanomaterials was captured through direct imaging evidence. Histological analysis showed that the cross-linking adhesion in intracranial tumor and monodispersity in normal tissues of the nanogels not only enhanced the retention time but also ensured excellent biocompatibility. Impressively, in vivo data confirmed that the microenvironment-associated nanogels could significantly enhance brain tumor clearance rate within a short treatment timeframe (only two weeks). In short, utilizing the spontaneous membrane-adsorption strategy can significantly improve NIR-II diagnosis and phototherapy in brain diseases while avoiding high-risk complications.

Promotion effects of flavonoids on browning induced by enzymatic oxidation of tyrosinase: structure-activity relationship.

Tyrosinase, widely distributed in nature, is a copper-containing polyphenol oxidase involved in the formation of melanin. Flavonoids are most often considered as tyrosinase inhibitors but have also been confirmed to be tyrosinase substrates. Four structure-related flavonoids including flavones (apigenin and luteolin) and flavonols (kaempferol and quercetin) are found to promote not inhibit browning induced by tyrosinase catalyzed oxidation both in model systems and in mushrooms under aerobic conditions. A comparison with enzymatic oxidation and autooxidation of flavonoids alone has helped to clarify why flavonoids function as a substrate rather than an inhibitor. Flavonoids almost do not affect the kinetics of melanin formation from enzymatic oxidation of l-dopa in excess. In addition, a new brown complex formed during the reaction of flavonoid quinone and dopaquinone is suggested to enhance the browning effects by competing with isomerization and autooxidation. Structure-activity relationships of the four flavonoids in melanin formation leading to browning induced by autooxidation and enzymatic oxidation confirm the enzymatic nature of the browning.

Microenvironment-Triggered Degradable Hydrogel for Imaging Diagnosis and Combined Treatment of Intraocular Choroidal Melanoma.

Human choroidal melanoma (HCM) is one of the most common primary intraocular tumors and easily provokes liver metastases owing to the lack of sensitive and noninvasive therapeutic methods. Concerning the imaging diagnostics and therapeutic predicaments for choroidal melanoma, we designed microenvironment-triggered degradable hydrogels (RENP-ICG@PNIPAM:Dox-FA) based on ultrasmall (<5 nm) rare-earth nanoparticles (RENPs) with enhanced NIR-II luminescence. The ultrasmall diameter can significantly enhance the NIR-II luminescence performance of RENPs. RENPs were encapsulated by a dual-response PNIPAM hydrogel, which could release drug by responding to heat energy and glutathione under the tumor microenvironment. The in vitro/in vivo NIR-II imaging detection and antitumor activity were also compared systematically after different treatment conditions on ocular choroidal melanoma-1 cells and tumor-bearing mice, respectively. Besides, the degradability of the hydrogel composites under physiological conditions could be conducive to enhance the photothermal-chemotherapeutic effect and alleviate long-term biological toxicity. Our work on the microenvironment-triggered hydrogels with enhanced NIR imaging and easy metabolism may provide a promising strategy for sensitive and noninvasive imaging and phototherapy in ocular tumors.

Concentration-regulated photon upconversion and quenching in NaYF4:Yb3+,Er3+ nanocrystals: nonexponentiality revisited.

Concentration quenching of rare-earth doped upconversion nanoparticles severely limits the dopant concentration, and this greatly hinders their potential applications. Therefore, it is necessary to understand the roles of dopant concentration in photon population and luminescence quenching for materials designed with improved upconversion luminescence (UCL). Herein, the excited-state dynamics of well-accepted NaYF4:Yb3+,Er3+ nanocrystals were investigated as models based on the Kohlrausch-function. The use of the Kohlrausch-function successfully disentangled the rise and decay of dynamics data and well revealed the kinetics. Photon population and concentration quenching mechanisms depending on the sensitizer concentration are deeply revealed by the regular variations of the fitting parameters. The results indicated that high doping of sensitizers will accelerate the population of both green and red emitting energy levels, but cause significant concentration quenching in green emission and little quenching in red emission. Our work opened up new pathways of kinetics analysis, which is beneficial for further mechanism development, and established detailed photon population and concentration quenching models depending on the doping concentration of the sensitizer.

Naturally occurring nanotube with surface modification as biocompatible, target-specific nanocarrier for cancer phototherapy.

Phototherapy has drawn increasing attention including the use of nanocarriers with high drug loading capacity and delivery efficacy for target-specific therapy. We have made use of naturally-occurring halloysite nanotubes (HNTs) to build a biomimetic nanocarrier platform for target-specific delivery of phototherapeutic agents. The HNTs were decorated with poly(sodium-p-styrenesulfonate) (PSS) to enhance the biocompatibility, and were further functionalized by lumen loading the type-II photosensitizer indocyanine green (ICG). The HNT-PSS-ICG nanocarrier, without further tethering targeting groups, was shown to associate with the membrane of giant unilamellar vesicles (GUVs) via Pickering effects. Application of HNT-PSS-ICG nanocarrier to human breast cancer cells gave rise to a cell mortality as high as 95%. The HNT-PSS-ICG nanocarrier was further coated with MDA-MB-436 cell membranes to endow it with targeting therapy performance against breast cancer, which was confirmed by in vivo experiments using breast cancer tumors in mice. The membrane-coated and biocompatible nanocarrier preferentially concentrated in the tumor tissue, and efficiently decreased the tumor volume by a combination of photodynamic and photothermal effects upon near-infrared light exposure. Our results demonstrate that the HNT-based nanocarrier by virtue of facial preparation and high loading capacity can be a promising candidate for membrane-targeting nanocarriers.

Energy transfer mechanism dominated by the doping location of activators in rare-earth upconversion nanoparticles.

Research on the energy transfer mechanism of rare-earth-doped upconversion nanoparticles (UCNPs) has been an important area due to the increasing demand for tuning multicolor emission and enhancing the upconversion efficiency; however, because of large energy mismatch, many lanthanide activators, such as Eu3+, cannot realize highly efficient near infrared-to-visible upconversion by simple codoping of Yb3+. Therefore, introduction of other ions to assist the energy transfer process is required. Herein, we prepared core-shell nanoparticles with different doping locations to investigate the upconversion energy transfer mechanism. The upconversion luminescence (UCL) of core-shell nanoparticles was investigated by steady-state luminescence and time-resolved luminescence spectra. The UCL behaviors in these different multi-activator core-shell nanoparticles were observed. The results revealed different energy transfer channels influenced by the doping location of activators. This study may open up new avenues of structure design for fine-tuning of multicolor UCL for specific applications.