Inhibitory Effects of Shikonin Dispersion, an Extract of Lithospermum erythrorhizon Encapsulated in ß-1,3-1,6 Glucan, on Streptococcus mutans and Non-Mutans Streptococci.

Shikonin is extracted from the roots of Lithospermum erythrorhizon, and shikonin extracts have been shown to have inhibitory effects on several bacteria. However, shikonin extracts are difficult to formulate because of their poor water solubility. In the present study, we prepared a shikonin dispersion, which was solubilized by the inclusion of ß-1,3-1,6 glucan, and analysed the inhibitory effects of this dispersion on Streptococcus mutans and non-mutans streptococci. The shikonin dispersion showed pronounced anti-S. mutans activity, and inhibited growth of and biofilm formation by this bacterium. The shikonin dispersion also showed antimicrobial and antiproliferative effects against non-mutans streptococci. In addition, a clinical trial was conducted in which 20 subjects were asked to brush their teeth for 1 week using either shikonin dispersion-containing or non-containing toothpaste, respectively. The shikonin-containing toothpaste decreased the number of S. mutans in the oral cavity, while no such effect was observed after the use of the shikonin-free toothpaste. These results suggest that shikonin dispersion has an inhibitory effect on S. mutans and non-mutans streptococci, and toothpaste containing shikonin dispersion may be effective in preventing dental caries.

Inhibitory Effect of Adsorption of Streptococcus mutans onto Scallop-Derived Hydroxyapatite.

Hydroxyapatite adsorbs various substances, but little is known about the effects on oral bacteria of adsorption onto hydroxyapatite derived from scallop shells. In the present study, we analyzed the effects of adsorption of Streptococcus mutans onto scallop-derived hydroxyapatite. When scallop-derived hydroxyapatite was mixed with S. mutans, a high proportion of the bacterial cells adsorbed onto the hydroxyapatite in a time-dependent manner. An RNA sequencing analysis of S. mutans adsorbed onto hydroxyapatite showed that the upregulation of genes resulted in abnormalities in pathways involved in glycogen and histidine metabolism and biosynthesis compared with cells in the absence of hydroxyapatite. S. mutans adsorbed onto hydroxyapatite was not killed, but the growth of the bacteria was inhibited. Electron microscopy showed morphological changes in S. mutans cells adsorbed onto hydroxyapatite. Our results suggest that hydroxyapatite derived from scallop shells showed a high adsorption ability for S. mutans. This hydroxyapatite also caused changes in gene expression related to the metabolic and biosynthetic processes, including the glycogen and histidine of S. mutans, which may result in a morphological change in the surface layer and the inhibition of the growth of the bacteria.

Hydrostatic Pressure-Regulated Cellular Calcium Responses.

Hydrostatic pressure control has attracted much attention and presents a still challenging objective from mechanobiological viewpoints. Herein, we reveal the calcium entry processes in HeLa cells by means of hydrostatic pressure spectroscopy. The steady-state fluorescence spectral data comprehensively elucidated the factors controlling the outcomes of the hydrostatic pressure-stimulated calcium entry behavior. The present work leads to a new perspective on ion regulations in living cells and an attractive alternative to conventional mechanostimuli.

Solubilization of poorly water-soluble bioactive molecules in neutral aqueous media by complexation with renatured ß-1,3-1,6-glucan nanoparticles.

The design of scaffolds for solubilizing/dispersing poorly water-soluble bioactive molecules in neutral aqueous media is a major challenge of functional food, pharmaceuticals, and cosmetics development, as highlighted by the plethora of corresponding solubilization/dispersion strategies. Herein, renatured ß-1,3-1,6-glucan (r-glucan) nanoparticles prepared by neutralization of alkali-denatured ß-1,3-1,6-glucan and subsequent centrifugation are used as a host to disperse water-insoluble bioactive molecules (curcumin, all-trans-retinoic acid, and rebamipide) by simple mixing of host and guest solutions. Curcumin in the r-glucan cavity is found to be stacked in the form of J-aggregates and twisted along the helix, and is demonstrated to be retained for significantly longer than curcumin in the corresponding γ-cyclodextrin (γ-CD) complex. Specifically, curcumin incorporated in γ-CD is released within 5.5 hours, whereas that in the r-glucan complex is released very slowly, with 12% of curcumin in the latter complex retained after 31-day incubation at 37°C. Thus, inclusion protocol simplicity and slow release ability make r-glucan nanoparticles a potential carrier scaffold for various applications.

Structural effect of amine N-oxides on the facilitation of α-glucosidase-catalyzed hydrolysis reactions.

Activation and stabilization of enzymes is an important issue in their industrial application. We recently reported that synthetic betaines, derived from cellular metabolites, structure-dependently increased the activity and stability of various enzymes including hydrolases, oxidases, and synthetases simply by mixing them into the reaction buffer. In this report, we focus on amine N-oxides, which are similarly important metabolites in cells with a highly polarized N-oxide bond, and investigate their enzyme stabilization and activation behavior. It was revealed that synthetic amine N-oxides structure-dependently activate α-glucosidase-catalyzed hydrolysis reactions similarly to betaines. The subsequent comparison of the kinetic parameters, the optimal concentration range for activation, and the maximal activity, suggested that amine N-oxides facilitate hydrolysis reactions via the same mechanism as betaines, because no differences were confirmed. However, the enzyme stabilization effect of amine N-oxides was slightly superior to that of betaines and the temporal stability of the enzyme in aqueous solutions was higher in the low amine N-oxide concentration range. The rheological properties, CD spectra, and dynamic fluorescence quenching experiments suggested that the suppression of unfavorable conformational perturbation was related to the difference in the hydration environments provided by the surrounding water molecules. Thus, we clarified that amine N-oxides facilitate enzyme reactions as a result of their similarity to betaines and provide a superior stabilizing effect for enzymes. Amine N-oxides show potential for application in enzyme storage and long-term reactions.

Turn-on fluorescence and photodynamic activity of ß-(1,3-1,6)-d-glucan-complexed porphyrin derivatives inside HeLa cells.

Fluorescence intensities of water-soluble ß-(1,3-1,6)-d-glucan (ß-1,3-glucan)-complexed porphyrin derivatives were very weak as a result of self-quenching. However, ß-1,3-glucan-complexed tetra(aminophenyl)porphyrin exhibited 'off-state' to 'on-state' fluorescence switching activity by intracellular uptake. Furthermore, the internalised complex showed a high level of photodynamic activity toward HeLa cells under photoirradiation at long wavelengths.

Lipid-membrane-incorporated arylboronate esters as agents for boron neutron capture therapy.

Arylboronate esters bearing methyl groups in both of their ortho positions were stably incorporated into lipid membranes at high concentrations without undergoing hydrolysis to the corresponding boronic acids. This method could be used in combination with previous methods to increase the maximum ratio of boron atoms in liposomal boron carriers.

Formation of ß-(1,3-1,6)-d-glucan-complexed [70]fullerene and its photodynamic activity towards macrophages.

[70]Fullerene was dissolved in water by complexation with ß-1,3-glucan using a mechanochemical high-speed vibration milling apparatus. The photodynamic activity of ß-1,3-glucan-complexed C70 was highly dependent on the expression level of dectin-1 on the cell surfaces of macrophages. The photodynamic activity increased as a result of a synergistic effect between ß-1,3-glucan-complexed 1'-acetoxychavicol acetate and the C70 complex.

Correction: Formation of ß-(1,3-1,6)-d-glucan-complexed [70]fullerene and its photodynamic activity towards macrophages.

Correction for 'Formation of ß-(1,3-1,6)-d-glucan-complexed [70]fullerene and its photodynamic activity towards macrophages' by Atsushi Ikeda et al., Org. Biomol. Chem., 2017, 15, 1990-1997.

Increased yield of ß-glucosidase-catalyzed hydrolysis reactions in the presence of betaine-type metabolite analog.

ß-Glucosidases (EC 3.2.1.21), abundant enzymes distributed in animals, plants and microorganism, has been generating lots of attentions for bioethanol production from cellulosic biomass. In this study, using three different origins of ß-glucosidases, glucose productivity of ß-glucosidase-catalyzed hydrolysis reactions in the presence of synthetic betaine-type metabolite analog (2-N,N,N-tri-n-butylammonium) acetate, was investigated. By the addition of the analog, the hydrolysis yields for all ß-glucosidases was highly improved from 4-13 to 64-100 %. To understand the factors affecting on the yield enhancements, the kinetic parameters, inhibition constants of end-product and temporal stability of ß-glucosidases were compared. As a result, enhancement of the yields is mainly related to the increase in the temporal stability of ß-glucosidases in the presence of the analog. The present findings lead to not only improve the glucose productivity of ß-glucosidase-catalyzed hydrolysis reaction toward bioethanol production but also apply to a new stabilization method for various unstable enzymes.

Enhanced Immunostimulating Activity of Lactobacilli-Mimicking Materials by Controlling Size.

The design and synthesis of materials capable of activating the immune system in a safe manner is of great interest in immunology and related fields. Lactobacilli activate the innate immune system of a host when acting as probiotics. Here, we constructed lactobacilli-mimicking materials in which polysaccharide-peptidoglycan complexes (PS-PGs) derived from lactobacilli were covalently conjugated to the surfaces of polymeric microparticles with a wide variety of sizes, ranging from 200 nm to 3 µm. The artificial lactobacilli successfully stimulated macrophages without cytotoxicity. Importantly, we found that the size of artificial lactobacilli strongly influenced their immunostimulating activities, and that artificial lactobacilli of 1 µm exhibited 10-fold higher activity than natural lactobacilli. One major advantage of the artificial lactobacilli is facile control of size, which cannot be changed in natural lactobacilli. These findings provide new insights into the design of materials for immunology as well as the molecular biology of lactobacillus.

Synthesis and immunestimulating activity of lactobacilli-originated polysaccharide-polymeric microparticle conjugates.

The design and synthesis of biomaterials capable of activating the immune system are of interest in immunology-related fields because of their ability to tune up the immune defenses of the host. Lactobacilli are a major constituent of normal human indigenous flora, and some specific strains are known to activate the immune system of the host as probiotics. In this study, we first fabricated novel biohybrid materials in which lactobacilli (L. casei strain Shirota, LcS)-originated polysaccharide-peptidoglycan complexes (PS-PGs) are conjugated with polymeric microparticles (MPs). PS-PGs conjugated onto polymeric MPs surfaces bound its specific antibody, suggesting that PS-PGs kept their original molecular recognition ability. The PS-PGs-based hybrid MPs with an appropriate density of conjugated PS-PGs effectively induced high levels of IL-12 production from macrophages without cytotoxicity. These results suggest that LcS-originated PS-PGs could be available bio-originated materials for developing novel biomaterials capable of activating the immune system in a safe manner.

Cryoprotective ability of betaine-type metabolite analogs during freezing denaturation of enzymes.

OBJECTIVE: To evaluate an analog library of betaine-type cellular metabolites, which are naturally found in polar fish for survival in subzero temperatures, for preventing denaturation of enzymes during freezing. RESULTS: Comparison of the cryoprotective ability of reported cryoprotectants, such as dimethylsulfoxide, glycerol, ectoine, hydroxyectoine, and trehalose, with betaine-type analogs using α-glucosidase revealed that analogs introducing C3-C6 alkyl chains into an ammonium cation retained 20 % higher activity than the control cryoprotectants at the same concentration. In particular, the analog possessing triplicate n-butyl chains showed a profound effect. It allowed retention of enzyme activity to 95 % even after 100 freeze-thaw cycles, while addition of the control cryoprotectants decreased the activity to 10-20 %. The cryoprotective ability of betaine-type analogs can be applied not only to α-glucosidase but also other enzymes such as ß-glucosidase, alkaline phosphatase, lactose dehydrogenase, sulfatase, and horseradish peroxidase. CONCLUSION: Synthetic betaine-type metabolite analogs possess practicable cryoprotective ability for various enzymes, and are considerably superior to previously reported cryoprotectants.

Significance of anionic functional group in betaine-type metabolite analogs on the facilitation of enzyme reactions.

Using synthetic sulfobetaine library, the enzyme activation behavior has been investigated. Comparison of enzyme activation behavior revealed that sulfobetaines equally facilitate enzyme reactions, being consistent with that of carboxybetaines. The subsequent kinetic and solution property analyses clarified that both the kinetic parameter and hydration property changes are identical with those of carboxybetaines, indicating that the difference in the anionic functional group of the betaine structure scarcely affects the enzyme activation. On the other hand, comparison of carboxy- or sulfo-betaines with tetraalkylammonium salts, whose counteranion binds to the ammonium cation intermolecularly, revealed that the activation ability for enzymes of tetraalkylammonium salts is considerably smaller than that of carboxy- or sulfo-betaines. These findings give us a hint to design the useful betaine-type enzyme activators.

Cellular zwitterionic metabolite analogs simultaneously enhance reaction rate, thermostability, salt tolerance, and substrate specificity of α-glucosidase.

We investigated the structural effects of metabolite analogs derived from a naturally-occurring zwitterionic metabolite, glycine betaine, on the activity of several hydrolases. The initial velocities of the hydrolases were enhanced by the addition of the solutes into the buffer solution. Based on a detailed study using α-glucosidases, the acceleration efficiency of the enzymatic activity was strongly induced by solutes possessing bulky and aliphatic ammonium cations, indicating that enhancement of activity by the solutes depended on their chemical structures. Kinetic analysis revealed that the acceleration of the hydrolysis reaction was related to both the decrement of K(m) and increment of V(max) values. Furthermore, the addition of the metabolite analogs enhanced not only the rate constant but also the thermostability, salt tolerance, and substrate specificity of α-glucosidase simultaneously through the reduction of conformational perturbation of the enzyme.

Mechanism toward Turn-on of Polysaccharide-Porphyrin Complexes for Fluorescence Probes and Photosensitizers in Photodynamic Therapy in Living Cells.

ß-(1,3-1,6)-D-Glucan, λ-carrageenan, tamarind gum, and pullulan can dissolve various porphyrin derivatives via the formation of complexes in water using a high-speed vibration milling method. The aqueous solutions of the resulting complexes exhibit long-term stability. Despite the adverse effects of the self-quenching process, notable fluorescence and improved photodynamic activity of the polysaccharide-complexed porphyrin derivatives were observed in the presence of liposomes, micelles, cyclodextrins, and HeLa cells. It was noted that the type of porphyrins was more important than the type of polysaccharides present in the complex. Porphyrin self-aggregates were monodispersed in the lipid membranes of the liposomes and lysosomes. The polysaccharide-complexed porphyrin derivatives showed increased photodynamic activity toward HeLa cells under photoirradiation between 610 and 740 nm.

Improved Stability and Photodynamic Activity of Water-Soluble 5,15-Diazaporphyrins Incorporated in ß-(1,3-1,6)-d-Glucan with On-Off Switch.

5,15-Diazaporphyrins, which have a large absorption at wavelengths over 600 nm, were dissolved in water by complex formation with ß-(1,3-1,6)-d-glucans. Aqueous solutions of these complexes were relatively stable compared with their trimethyl-ß-cyclodextrin-complexed analogues. ß-Glucan-complexed diazaporphyrins showed quenched fluorescence and had low singlet-oxygen-generation abilities owing to random self-aggregation. However, external stimuli, such as the presence of liposomes or intracellular uptake, restored the fluorescence and singlet-oxygen-generation abilities of ß-glucan-complexed diazaporphyrins. Consequently, ß-glucan-complexed diazaporphyrins showed very high photodynamic activities toward HeLa cells.

Reversible stability switching of a hairpin DNA via a photo-responsive linker unit.

We have designed and synthesized a novel photo-responsive linker unit, 4,4'-bis(hydroxymethyl)-azobenzene, which was introduced to the loop oligonucleotide in a DNA hairpin and was able to reversibly control the stability of the whole hairpin structure via UV or visible light irradiation.

Water Solubilization of Fullerene Derivatives by ß-(1,3-1,6)-d-Glucan and Their Photodynamic Activities toward Macrophages.

Anionic and neutral fullerene derivatives were dissolved in water by using ß-(1,3-1,6)-d-glucan (ß-1,3-glucan) as a solubilizing agent. In the water-solubilized complexes, the concentrations of fullerene derivatives were ≈0.30 mm and the average particle sizes were ≈90 nm. The ß-1,3-glucan-complexed fullerene derivative with a carboxylic acid was found to have higher photodynamic activity toward macrophages under visible-light irradiation (λ>610 nm) than other ß-1,3-glucan-complexed fullerene derivatives. This result suggests that carboxylic acid moieties in the complex enhance the binding affinity with ß-1,3-glucan receptors on the surface of macrophages when the ß-1,3-glucan is recognized. In contrast, all ß-1,3-glucan-complexed fullerene derivatives showed no photodynamic activity toward HeLa cells under the same conditions.

Galactose-PEG dual conjugation of beta-(1-->3)-D-glucan schizophyllan for antisense oligonucleotides delivery to enhance the cellular uptake.

Antisense oligonucleotides (AS ODNs) are applied to silence a particular gene, and this approach is one of the potential gene therapies. However, naked oligonucleotides are easy to be degraded or absorbed in biological condition. Therefore, we need a carrier to deliver AS ODNs. This paper presents galactose moieties that were conjugated to the side chain of SPG to enhance cellular ingestion through endocytosis mediated by asialoglycoprotein receptor specifically located on parenchymal liver cells. We introduced galactose with two types of chemical bonds; amide and amine, and the amine connection showed lower ingestion and more toxicity than the amide one. Since PEG was known to induce endocytosis escape, we combined PEG and galactose aiming to provide both cellular up-take and subsequent endocytosis escape. We designed lactose or galactose moieties to attach to the end of the PEG chain that connects to the SPG side chain. When the PEG had the molecular weight of 5000-6000, the antisense effect reached the maximum. We believe that this new type of galactose and PEG dual conjugation broaden the horizon in antisense delivery.