Light Irradiation of Mouse Spermatozoa: Stimulation of In Vitro Fertilization and Calcium Signals

Irradiation of mouse spermatozoa by 630 nm He-Ne laser was found to enhance the intracellular calcium levels and fertilizing potential of these cells. The effect of light on calcium transport and on fertilization rate was abrogated in the absence of Ca²⁺during the irradiation time, indicating that the effect of light is Ca²⁺dependent. The stimulatory effect of light on Ca²⁺uptake was abolished in the presence of a voltage-dependent Ca²⁺-channel inhibitor nifedipine, indicating the involvement of a plasma membrane voltage-dependent Ca²⁺channel. Furthermore, the stimulatory effect of light was completely inhibited by the mitochondrial uncoupler FCCP, indicating that laser irradiation might affect the mitochondrial Ca²⁺transport mechanisms. A causal association between laser irradiation, reactive oxygen species (ROS) generation and sperm function was indicated by studies with ROS scavengers, superoxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide. The SOD treatment, which enhanced H₂O₂ production, resulted in increased Ca²⁺uptake and enhanced fertilization rate. On the other hand, catalase, which decomposes H₂O₂, impaired the light-induced stimulation in Ca²⁺uptake and the fertilization rate. Taken together, the data suggest that H₂O₂ might be involved in the irradiation effects, and indeed laser irradiation enhances the production of H₂O₂, by spermatozoa. These results indicate that the effect of 630 nm He-Ne laser irradiation is mediated through the generation of H₂O₂ by the spermatozoa and that this effect plays a significant role in the augmentation of the sperm cells' capability to fertilize metaphase H-arrested eggs in vitro.     

Ag@TiO2 Nanoprisms with Highly Efficient Near‐Infrared Photothermal Conversion for Melanoma Therapy

Melanoma is a primary reason of death from skin cancer and associated with high lethality. Photothermal therapy (PTT) has been developed into a powerful cancer treatment technique in recent years. Here, we created a low‐cost and high‐performance PTT agent, Ag@TiO₂ NPs, which possesses a high photothermal conversion efficiency of ≈65 % and strong near‐infrared (NIR) absorption about 808 nm. Ag NPs were synthesized using a two‐step method and coated with TiO₂ to obtain Ag@TiO₂ NPs by a facile sol‐gel method. Because of the oxide, Ag@TiO₂ NPs exhibit remarkable high photothermal conversion efficiencies and biocompatibility in vivo and in vitro. Cytotoxicity and therapeutic efficiency of photothermal cytotoxicity of Ag@TiO₂ NPs were tested in B16‐F10 cells and C57BL/6J mice. Under light irradiation, the elevated temperature causes cell death in Ag NPs‐treated (100 μg mL^?1) cells in vitro (both p<0.01). In the case of subcutaneous melanoma tumor model, Ag@TiO₂ NPs (100 μg mL^?1) were injected into the tumor and irradiated with a 808 nm laser of 2 W cm^?2 for 1 minute. As a consequence, the tumor volume gradually decreased by NIR laser irradiation with only a single treatment. The results demonstrate that Ag@TiO₂ NPs are biocompatible and an attractive photothermal agent for cutaneous melanoma by local delivery.     

Research Note: Ultraviolet Irradiation (UVB) Interrupts Calcium Cell Signaling in Lens Epithelial Cells

A preliminary study was undertaken to establish whether low-dose UV irradiation (UVB) affects calcium cell signaling in rabbit lens epithelia. In a suspension of lens epithelial cells (line NN1003A), changes in intracellular Ca2+ were measured by Fura-2 fluorescence in response to exogenously added ATP. The cellular response to ATP, referred to as the calcium signal, is characterized by a brief increase and subsequent decrease in cytosolic Ca2+ levels. Ultraviolet B irradiation (1.8-9 mJ/cm2) was found to reduce the magnitude of the Ca2+ signal in a dose-dependent manner. A 5 min UVB exposure (9 mJ/cm2) completely altered the biphasic nature of the calcium signal, causing only an immediate and steady rise in cytosol Ca2+ levels. Lower fluences of UVB irradiation (2 min exposure times or 3.6 mJ/cm2) induced a 50% reduction in the calcium signal. When irradiated cells were returned to culture for 3 h after irradiation, calcium signals induced by ATP were normal. In view of the photooxidative nature of UVB irradiation, the oxidative state of cells was assessed by measuring glutathione (GSH) levels. Ultraviolet B irradiation caused a rapid 20% decline in GSH levels that returned to near-control values after a 3 h postirradiation incubation. The results of this study indicate that fluences lower than previously found to be cataractogenic can perturb calcium cell signaling in cultured lens epithelial cells.     

Interaction of trialkyltin(IV) chlorides with sarcoplasmic reticulum calcium ATPase

The interaction of the organotin compounds trimethyltin(IV) and tributyltin(IV) chlorides with the calcium pump from sarcoplasmic reticulum membranes was studied. It was found that the presence of calcium fully protects against the inhibitory effect of both organotin compounds. However, the apparent affinity of the protein for tributyltin chloride is two orders of magnitude higher than for trimethyltin chloride (K_0.5 values of 14 µ m and 1.4 m m , respectively). Studies of intrinsic fluorescence of the Ca²⁺‐ATPase and enzyme phosphorylation by ATP and Pi support the hypothesis that the inhibitory properties of trialkyltin compounds are due to the inhibition of calcium binding to the high‐affinity binding sites of the Ca²⁺‐ATPase. This suggests that there is a specific interaction between the trialkyltin compounds and the calcium binding sites of the protein. The effect of trialkyltin compounds on Ca²⁺‐ATPase was also addressed by differential scanning calorimetry to assess the thermal transition of the protein denaturation, and by infrared spectroscopy in the absorption region corresponding to the amide I band (1600–1700 cm^?1) to observe changes in the secondary structure of the protein. We conclude that the interaction of trialkyltin compounds with Ca²⁺‐ATPase reduces the affinity and cooperativity for calcium binding and, consequently, the inhibition of ATPase activity. These events are accompanied by changes in the secondary structure of the protein, including loss of α‐helix structure and a concomitant increase in protein aggregation or unfolding. The activity of trialkyltin compounds on the Ca²⁺‐ATPase is discussed in relation to their solubility in water and in the lipid phase. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

Actual Isothermal Effects of Water‐Filtered Infrared A‐Irradiation

In this study, the athermal effects of water‐filtered infrared A (wIRA)‐irradiation (780–1400 nm) on human dermal fibroblasts were investigated. For this purpose, cells were exposed to wIRA‐irradiation (178 mW cm^?2 for 1 h), while a sophisticated experimental setup prevented warming of the samples exceeding 0.1°C. The investigated parameters were the formation of reactive oxygen species (ROS), mitochondrial membrane potential and superoxide release, protein oxidation, proliferation rate, as well as intracellular Ca²⁺‐release in single cells, most of them quantified via fluorescence microscopy and fluorimetric techniques. The existence of actual athermal wIRA‐effects is still intensively discussed, since their detection requires a careful experimental setup and both efficient and powerful temperature regulation of the exposed samples. Here, we can definitively show that some of the supposed athermal wIRA‐effects may be rather artifacts, since wIRA did not reveal any impact on the above mentioned parameters—as long as the temperature of the exposed cells was carefully maintained. Though, we were able to identify an athermal DNA‐protective wIRA‐effect, since the induced DNA damage (quantified via 8‐Oxo‐G‐formation) was significantly decreased after a subsequent UVB‐exposure. These results suggest that many of the supposed athermal wIRA‐effects can be induced by pure warming of the samples, independent from any wIRA‐irradiation.     

Au/TiO<Subscript>2</Subscript>/Graphene Composite with Enhanced Photocatalytic Activity Under Both UV and Visible Light Irradiation

Au/TiO₂/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO₂ and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e ^?/h ⁺ pairs. Under UV irradiation, photogenerated electrons of TiO₂ are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO₂ and then transfer further to graphene sheets. As a result, compared with pure TiO₂, Au/TiO₂/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO₂, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules.     

The Role of Calcium in UVB-lnduced Damage in Irradiated Ocular Lenses

Abstract— The purpose of this study was to evaluate the role of altered calcium homeostasis in the development of irreversible membrane damage in the UVB-irradiated ocular lens. In particular, experiments were designed to determine whether restricting calcium influx could prevent membrane damage that typically leads to ion imbalances and lens opacification following short-term exposure to ultraviolet light (UVB). The influx of calcium was reduced by culturing lenses in a low-calcium culture medium containing 0.3 mM Ca²+ rather than physiological concentrations of 1.6 mM. This low-calcium protocol retarded calcium accumulation in UVB-irradiated lenses for 2 days of culture, and opacification was delayed by 24 h. Loss of transparency did occur during the second day of culture, but more slowly than in irradiated lenses cultured in normal-calcium medium. Membrane damage was assessed by evaluating loss in cation transport activity, assessed by measuring ⁸⁶Rb uptake into cultured lenses. Uptake was markedly inhibited in UVB-irradiated lenses and low-calcium culture did not prevent this inhibition of cation transport, a finding that explains why low-calcium protocol did not help maintain sodium homeostasis in irradiated lenses. Inhibition of cation transport and sodium accumulation eventually caused lens hydration and light scattering during extended culture in the absence of significant calcium elevation. Additional experiments were done to establish whether initial damage sustained by membranes could be repaired through the biosynthesis of new membrane proteins. Incorporation of ¹⁴C-histidine in membranes of the UVB-exposed lens was measured to assess membrane synthesis essential for repairing membrane damage. The rate of membrane protein synthesis, assessed by measuring incorporation of labeled amino acids, declined in UVB cataract, despite the prevention of calcium accumulation. These results suggest that one explanation for irreversible gain in sodium and calcium content accompanying opacification is the inability of lenses to replenish damaged membrane proteins comprising ion channels or transporters.     

Correlation of the Catalytic Activity for Oxidation Taking Place on Various TiO2 Surfaces with Surface OH Groups and Surface Oxygen Vacancies

Three catalytic oxidation reactions have been studied: The ultraviolet (UV) light induced photocatalytic decomposition of the synthetic dye sulforhodamine B (SRB) in the presence of TiO₂ nanostructures in water, together with two reactions employing Au/TiO₂ nanostructure catalysts, namely, CO oxidation in air and the decomposition of formaldehyde under visible light irradiation. Four kinds of TiO₂ nanotubes and nanorods with different phases and compositions were prepared for this study, and gold nanoparticle (Au‐NP) catalysts were supported on some of these TiO₂ nanostructures (to form Au/TiO₂ catalysts). FTIR emission spectroscopy (IES) measurements provided evidence that the order of the surface OH regeneration ability of the four types of TiO₂ nanostructures studied gave the same trend as the catalytic activities of the TiO₂ nanostructures or their respective Au/TiO₂ catalysts for the three oxidation reactions. Both IES and X‐ray photoelectron spectroscopy (XPS) proved that anatase TiO₂ had the strongest OH regeneration ability among the four types of TiO₂ phases or compositions. Based on these results, a model for the surface OH group generation, absorption, and activation of molecular oxygen has been proposed: The oxygen vacancies at the bridging O^2? sites on TiO₂ surfaces dissociatively absorb water molecules to form OH groups that facilitate adsorption and activation of O₂ molecules in nearby oxygen vacancies by lowering the absorption energy of molecular O₂. A new mechanism for the photocatalytic formaldehyde decomposition with the Au/TiO₂ catalysts is also proposed, based on the photocatalytic activity of the Au‐NPs under visible light. The Au‐NPs absorb the light owing to the surface plasmon resonance effect and mediate the electron transfers that the reaction needs.     

Influence of Gemini Surfactant with Modified TiO2 Nanoparticles on the Interfacial Tension of Oil/Water

The research on the impacts of modified TiO₂ nanoparticles (NPs) on interfacial tension (IFT) is in its infancy. Our work focuses on the IFT of the modified TiO₂ and Gemini surfactant N,N,N′,N′-tetramethyl-N,N′-dimyristyl-1,2-ethane diammonium dichlone (YND1233) complex solutions for reservoir stimulation purposes. The factors of YND1233, modified TiO₂ NPs, temperature, aging stability, adsorption loss, and mineralized degree were explored with the comparison of unmodified TiO₂ NPs and YND1233 as contrast samples. The results indicate that the dynamic IFTs decrease and then increase with the concentrations of YND1233 and modified TiO₂ NPs, and the minimum IFT appears at 0.200 and 0.010 wt%, respectively. YND1233/modified TiO₂ complex solutions show lower and more stable IFTs, better temperature resistance, longer aging time, and lower adsorption on the surface of quartz sand. The modified TiO₂ NPs and YND1233 in the YND1233/modified TiO₂ complex solution can be adsorbed to the interface and decrease the IFTs through synergistic effect. A mixed diffusion-kinetic mechanism is provided for the adsorption and interactions with Ca²⁺/Mg²⁺ involved in YND1233/modified TiO₂ complex solution.     

Visible‐Light‐Induced Electron Transport from Small to Large Nanoparticles in Bimodal Gold Nanoparticle‐Loaded Titanium(IV) Oxide

A key to realizing the sustainable society is to develop highly active photocatalysts for selective organic synthesis effectively using sunlight as the energy source. Recently, metal‐oxide‐supported gold nanoparticles (NPs) have emerged as a new type of visible‐light photocatalysts driven by the excitation of localized surface plasmon resonance of Au NPs. Here we show that visible‐light irradiation (λ>430 nm) of TiO₂‐supported Au NPs with a bimodal size distribution (BM‐Au/TiO₂) gives rise to the long‐range (>40 nm) electron transport from about 14 small (ca. 2 nm) Au NPs to one large (ca. 9 nm) Au NP through the conduction band of TiO₂. As a result of the enhancement of charge separation, BM‐Au/TiO₂ exhibits a high level of visible‐light activity for the one‐step synthesis of azobenzenes from nitrobenzenes at 25 °C with a yield greater than 95 % and a selectivity greater than 99 %, whereas unimodal Au/TiO₂ (UM‐Au/TiO₂) is photocatalytically inactive.     

A Photoelectrochemical Biosensor Fabricated using Hierarchically Structured Gold Nanoparticle and MoS2 on Tannic Acid Templated Mesoporous TiO2

In a tannic acid assisted synthesis of mesoporous TiO₂, tannic acid was used as a cost effective and non‐toxic template for pore formation. Meanwhile, a gold nanoparticles (Au NPs) deposited TiO₂ nanocomposite was coated on an indium tin oxide electrode for the fabrication of a photoelectrochemical (PEC) biosensing system. Upon the formation of anatase structure, the electrode was coated with MoS₂ for effective visible light absorption. The mesoporous structure led to an enhanced surface area by improving Au NPs and glucose oxidase adsorption. Incorporation of Au NPs led to an enhanced photonic efficiency due to the generation of Schottky barriers. The obtained nanocomposite was used for the light‐driven, real‐time, and selective PEC glucose sensing. Under visible light irradiation, the enzyme immobilized electrodes yielded significant photocurrent improvement owing to the releasing electron donor H₂O₂. The obtained PEC biosensor demonstrated acceptable reproducibility and stability with a sensitivity of 4.42 μA mM^?1 cm^?2 and a low detection limit of 1.2 μM glucose. Also, the linear measurement range was found to be 0.004–1.75 mM glucose. The results indicated that the proposed production method of mesoporous TiO₂ will pave the way for a green chemistry based porous material production, along with the extension of the implementation of semiconductors in PEC biosensing systems.     

Proanthocyanin-Capped Biogenic TiO2 Nanoparticles with Enhanced Penetration,Antibacterial and ROS Mediated Inhibition of Bacteria Proliferation and Biofilm Formation: A Comparative Approach

Biofunctionalized TiO₂ nanoparticles with a size range of 18.42±1.3 nm were synthesized in a single-step approach employing Grape seed extract (GSE) proanthocyanin (PAC) polyphenols. The effect of PACs rich GSE corona was examined with respect to 1) the stability and dispersity of as-synthesized GSE-TiO₂-NPs, 2) their antiproliferative and antibiofilm efficacy, and 3) their propensity for internalization and reactive oxygen species (ROS) generation in urinary tract infections (UTIs) causing Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus saprophyticus strains. State-of-the-art techniques were used to validate GSE-TiO₂-NPs formation. Comparative Fourier transformed infrared (FTIR) spectral analysis demonstrated that PACs linked functional -OH groups likely play a central role in Ti⁴⁺ reduction and nucleation to GSE-TiO₂-NPs, while forming a thin, soft corona around nascent NPs to attribute significantly enhanced stability and dispersity. Transmission electron microscopic (TEM) and inductively coupled plasma mass-spectroscopy (ICP-MS) analyses confirmed there was significantly (p<0.05) enhanced intracellular uptake of GSE-TiO₂-NPs in both Gram-negative and -positive test uropathogens as compared to bare TiO₂-NPs. Correspondingly, compared to bare NPs, GSE-TiO₂-NPs induced intracellular ROS formation that corresponded well with dose-dependent inhibitory patterns of cell proliferation and biofilm formation in both the tested strains. Overall, this study demonstrates that -OH rich PACs of GSE corona on biogenic TiO₂-NPs maximized the functional stability, dispersity and propensity of penetration into planktonic cells and biofilm matrices. Such unique merits warrant the use of GSE-TiO₂-NPs as a novel, functionally stable and efficient antibacterial nano-formulation to combat the menace of UTIs in clinical settings.     

Ultraviolet Radiation‐Induced Downregulation of SERCA2 Mediates Activation of NLRP3 Inflammasome in Basal Cell Carcinoma

Basal cell carcinomas (BCCs) account for majority of skin malignancies in the United States. The incidence of BCCs is strongly associated with exposure of ultraviolet (UV) radiation. Nucleotide‐binding domain, leucine‐rich‐repeat‐containing family, pyrin domain‐containing 3 (NLRP3) inflammasome plays an important role in innate immune responses. Different stimuli such as toxins, microorganisms and particles released from injured cells activate the NLRP3 inflammasome. Activated NLRP3 results in activation of caspase‐1, which cleaves pro‐IL‐1β to active IL‐1β. In this study, we have shown that NLRP3 is expressed in human basal cell carcinomas. The proximal steps in activation of NLRP3 inflammasome are not well understood. Here, we have attempted to elucidate a critical role for Ca²⁺ mobilization in activation of the NLRP3 inflammasome by UVB exposure using HaCaT keratinocytes. We have demonstrated that UVB exposure blocks Ca²⁺ mobilization by downregulating the expression of sarco/endoplasmic reticulum Ca²⁺‐ATPase (SERCA2), a component of store‐operated Ca²⁺ entry that leads to activation of the NLRP3 inflammasome.     

The Regulation of the Calcium Signal by Membrane Pumps

Calcium may have a static, structure‐stabilizing role in biological organs like the bones and the teeth, or may fulfill a dynamic function in cells as a regulator of signal‐transduction pathways. This is made possible by the properties of the Ca²⁺ ion (e.g., high dehydration rate, great flexibility in coordinating ligands, largely irregular geometry of the coordination sphere). Since Ca²⁺ is a universal carrier of signals, the control of its homeostasis is of central importance for the organism. It involves exchanges between the skeleton (which is the major calcium reservoir) and the extracellular and intracellular fluids. It also involves the intestine and the kidney, the organs of Ca absorption and release, respectively. The highly integrated homeostasis process consists of a number of hormonally controlled feedback loops, and an elaborate system of membrane channels, exchangers, and pumps that control the Ca²⁺ flux into and out of cells.     

Surface-modified TiO(2) nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

We utilized three different types of TiO₂ nanoparticles (NPs) namely TiO₂‐dopamine, TiO₂‐CdS and bare TiO₂ NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α‐ and β‐casein, milk and egg white using a simplified procedure in MALDI‐TOF‐MS. Surface‐modified TiO₂ NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine‐enkephalin and methionine‐enkephalin) and proteins (cytochrome c and myoglobin) in MALDI‐TOF‐MS. In the surface‐modified TiO₂ NPs‐based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO₂‐dopamine and bare TiO₂ NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO₂‐CdS NPs efficiently acted as the matrix for background‐free detection of peptides and proteins with improved resolution in MALDI‐MS. We found that the upper detectable mass range is 17 000 Da using TiO₂‐CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI‐MS in proteome research.     

ROS and p53 in Regulation of UVB‐induced HDM2 Alternative Splicing

Alternative splicing plays an important role in proteasome diversity and gene expression regulation in eukaryotic cells. Hdm2, the human homolog of mdm2 (murine double minute oncogene 2), is known to be an oncogene as its role in suppression of p53. Hdm2 alternative splicing, occurs in both tumor and normal tissues, is believed to be a response of cells for cellular stress, and thus modulate p53 activity. Therefore, understanding the regulation of hdm2 splicing is critical in elucidating the mechanisms of tumor development and progression. In this study, we determined the effect of ultraviolet B light (UVB) on alternative splicing of hdm2. Our data indicated that UVB (50 mJ cm^?2) alone is not a good inducer of alternative splicing of hdm2. The less effectiveness could be due to the induction of ROS and p53 by UVB because removing ROS by L‐NAC (10 mm ) in p53 null cells could lead to alternative splicing of hdm2 upon UVB irradiation.     

Hierarchical TiO2 nanosheet‐assembled nanotubes with dual electron sink functional sites for efficient photocatalytic degradation of rhodamine B

A novel Pt–TiO₂/Ag nanotube photocatalyst has been synthesized successfully via a facile method. TiO₂ nanotubes are assembled with numerous ultrathin TiO₂ nanosheets and show a highly open structure. The gaps between adjacent TiO₂ nanosheets can serve as channels for the access of reactants, accelerating the mass transfer process. During the fabrication process of the Pt–TiO₂/Ag nanotube photocatalyst, high‐quality Pt–SiO₂ nanotubes are synthesized first with the structure‐directing effect of polyvinylpyrrolidone. Then a TiO₂ layer is coated on the outside surface of the silica nanotubes. The introduced titanium species can be converted into TiO₂ nanosheet structure during the subsequent hydrothermal treatment, gradually constructing nanosheet‐assembled nanotubes. Lastly, after the introduction of another electron sink function site of Ag through UV irradiation, the Pt–TiO₂/Ag nanotube photocatalyst with dual electron sink functional sites is obtained. The specially doped Pt and Ag NPs can simultaneously inhibit the recombination process of photogenerated charge carriers and increase light utilization efficiency. Therefore, the as‐synthesized Pt–TiO₂/Ag nanotube catalyst exhibits a high photocatalytic degradation performance for rhodamine B of 0.2 min^?1, which is about 3.2 and 5.3 times as high as that of Pt–TiO₂ and TiO₂ nanotubes because of the enhanced charge carrier separation efficiency. Furthermore, in the unique nanoarchitecture, the nanotubes are assembled with numerous ultrathin TiO₂ nanosheets, which can absorb abundant active species and dye molecules for photocatalytic reaction. On the basis of experimental results, a possible rhodamine B degradation mechanism is proposed to explain the excellent photocatalytic efficiency of the Pt–TiO₂/Ag nanotube photocatalyst.     

Mitochondrial Responses of Normal and Injured Human Skin Fibroblasts Following Low Level Laser Irradiation—An In Vitro Study

Laser irradiation has proved to be very efficient in speeding and improving the quality of healing in pathological conditions of diverse etiologies. However, the mechanisms by which the beneficial effects are attained are not clear. Mitochondria are the primary phototargets during irradiation. The study aimed to establish if laser irradiation had an effect on hypoxic and acidotic cells. The study also aimed to use existing information regarding the possible mechanism of action (established in wounded cells) and apply these principles to acidic and hypoxic irradiated cells to determine whether laser has a stimulatory or inhibitory effect. Cell cultures were modified to simulate conditions of hypoxia (hypoxic gas mixture 95% N₂ and 5% O₂) and acidosis (pH 6.7) whereas the central scratch model was used to simulate a wound. Cells were irradiated with a helium–neon (632.8 nm, 3 mW cm^?2) laser using 5 or 16 J cm^?2 on days 1 and 4. Mitochondrial responses were measured 1 or 24 h after laser irradiation by assessing changes in mitochondrial membrane potential (MMP), cyclic AMP, intracellular Ca²⁺ and adenosine triphosphate (ATP) cell viability. Hypoxia and acidosis significantly reduced MMP when compared with normal nonirradiated control cells. Wounded, hypoxic and acidotic cells irradiated with 5 J cm^?2 showed an increase in mitochondrial responses when compared with nonirradiated cells while 16 J cm^?2 showed a significant decrease. The study confirmed that laser irradiation with 5 J cm^?2 stimulated an increase in intracellular Ca²⁺ which resulted in an increase in MMP, ATP and cAMP, which ultimately results in photobiomodulation to restore homeostasis of injured cells.     

Tuning the Surface Structure of Nitrogen‐Doped TiO2 Nanofibres—An Effective Method to Enhance Photocatalytic Activities of Visible‐Light‐Driven Green Synthesis and Degradation

Nitrogen‐doped TiO₂ nanofibres of anatase and TiO₂(B) phases were synthesised by a reaction between titanate nanofibres of a layered structure and gaseous NH₃ at 400–700 °C, following a different mechanism than that for the direct nitrogen doping from TiO₂. The surface of the N‐doped TiO₂ nanofibres can be tuned by facial calcination in air to remove the surface‐bonded N species, whereas the core remains N doped. N‐Doped TiO₂ nanofibres, only after calcination in air, became effective photocatalysts for the decomposition of sulforhodamine B under visible‐light irradiation. The surface‐oxidised surface layer was proven to be very effective for organic molecule adsorption, and the activation of oxygen molecules, whereas the remaining N‐doped interior of the fibres strongly absorbed visible light, resulting in the generation of electrons and holes. The N‐doped nanofibres were also used as supports of gold nanoparticle (Au NP) photocatalysts for visible‐light‐driven hydroamination of phenylacetylene with aniline. Phenylacetylene was activated on the N‐doped surface of the nanofibres and aniline on the Au NPs. The Au NPs adsorbed on N‐doped TiO₂(B) nanofibres exhibited much better conversion (80 % of phenylacetylene) than when adsorbed on undoped fibres (46 %) at 40 °C and 95 % of the product is the desired imine. The surface N species can prevent the adsorption of O₂ that is unfavourable for the hydroamination reaction, and thus, improve the photocatalytic activity. Removal of the surface N species resulted in a sharp decrease of the photocatalytic activity. These photocatalysts are feasible for practical applications, because they can be easily dispersed into solution and separated from a liquid by filtration, sedimentation or centrifugation due to their fibril morphology.