Preparation and recognition performance of creatinine-imprinted material prepared with novel surface-imprinting technique

By adopting the novel surface molecular imprinting technique put forward by us not long ago, a creatinine molecule-imprinted material with high performance was prepared. The functional macromolecule polymethacrylic acid (PMAA) was first grafted on the surfaces of micron-sized silica gel particles in the manner of “grafting from” using 3-methacryloxypropyltrimethoxysilane (MPS) as intermedia, resulting in the grafted particles PMAA/SiO₂. Subsequently, the molecular imprinting was carried out towards the grafted macromolecule PMAA using creatinine as template and with ethylene glycol diglycidyl ether (EGGE) as crosslinker by right of the intermolecular hydrogen bonding and electrostatic interaction between the grafted PMAA and creatinine molecules. Finally, the creatinine-imprinted material MIP-PMAA/SiO₂ was obtained. The binding character of MIP-PMAA/SiO₂ for creatinine was investigated in depth with both batch and column methods and using N-hydroxysuccinimide and creatine as two contrast substances, whose chemical structures are similar to creatinine to a certain degree. The experimental results show that the surface-imprinted material MIP-PMAA/SiO₂ has excellent binding affinity and high recognition selectivity for creatinine. Before imprinting, PMAA/SiO₂ particles nearly has not recognition selectivity for creatinine, and the selectivity coefficients of PMAA/SiO₂ for creatinine relative to N-hydroxysuccinimide and creatine are only 1.23 and 1.30, respectively. However, after imprinting, the selectivity coefficients of MIP-PMAA/SiO₂ for creatinine in respect to N-hydroxysuccinimide and creatine are remarkably enhanced to 11.64 and 12.87, respectively, displaying the excellent recognition selectivity and binding affinity towards creatinine molecules.     

Study of the cytotoxicity and particle action in human cancer cells of titanocene-functionalized materials with potential application against tumors

Titanocene dichloride [Ti(η⁵-C₅H₅)₂Cl₂] (1), has been grafted onto dehydrated hydroxyapatite (HAP), Al₂O₃ and two mesoporous silicas MSU-2 (Michigan State University Silica type 2) and HMS (Hexagonal Mesoporous Silica), to give the novel materials HAP/[Ti(η⁵-C₅H₅)₂Cl₂] (S1) (1.01 wt.% Ti), Al₂O₃/[Ti(η⁵-C₅H₅)₂Cl₂] (S2) (2.36 wt.% Ti), HMS/[Ti(η⁵-C₅H₅)₂Cl₂] (S3) (0.75 wt.% Ti) and MSU-2/[Ti(η⁵-C₅H₅)₂Cl₂] (S4) (0.74 wt.% Ti), which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear magic angle spinning NMR spectroscopy, IR spectroscopy, thermogravimetry analysis, UV spectroscopy, scanning electronic microscopy and transmission electronic microscopy. The cytotoxicity of the titanocene-functionalized materials toward human cancer cell lines from five different histogenic origins: 8505 C (anaplastic thyroid cancer), A253 (head and neck cancer), A549 (lung carcinoma), A2780 (ovarian cancer) and DLD-1 (colon cancer) has been determined. M₅₀ values (quantity of material needed to inhibit normal cell growth by 50%) and Ti-M₅₀ values (quantity of anchored titanium needed to inhibit normal cell growth by 50%) indicate that the activity of S1-S4 against studied human cancer cells depended on the surface type as well as on the cell line. In addition, studies on the titanocene release and the interaction of the materials S1-S4 with DNA show that the cytotoxic activity may be due to particle action, because no release of titanium complexes has been observed in physiological conditions, while electrostatic interactions of titanocene-functionalized particles with DNA have been observed.     

Efficient Preparation of Enantiopure D-Phenylalanine through Asymmetric Resolution Using Immobilized Phenylalanine Ammonia-Lyase from Rhodotorula glutinis JN-1 in a Recirculating Packed-Bed Reactor

An efficient enzymatic process was developed to produce optically pure D-phenylalanine through asymmetric resolution of the racemic DL-phenylalanine using immobilized phenylalanine ammonia-lyase (RgPAL) from Rhodotorula glutinis JN-1. RgPAL was immobilized on a modified mesoporous silica support (MCM-41-NH-GA). The resulting MCM-41-NH-GA-RgPAL showed high activity and stability. The resolution efficiency using MCM-41-NH-GA-RgPAL in a recirculating packed-bed reactor (RPBR) was higher than that in a stirred-tank reactor. Under optimal operational conditions, the volumetric conversion rate of L-phenylalanine and the productivity of D-phenylalanine reached 96.7 mM h⁻¹ and 0.32 g L⁻¹ h⁻¹, respectively. The optical purity (ee _D) of D-phenylalanine exceeded 99%. The RPBR ran continuously for 16 batches, the conversion ratio did not decrease. The reactor was scaled up 25-fold, and the productivity of D-phenylalanine (ee _D>99%) in the scaled-up reactor reached 7.2 g L⁻¹ h⁻¹. These results suggest that the resolution process is an alternative method to produce highly pure D-phenylalanine.     

Understanding DP receptor antagonism using a CoMSIA approach

A Comparative Molecular Similarity Indices Analysis (CoMSIA) was performed for 2,6-substituted-4-monosubstituted aminopyrimidine antagonists of prostaglandin D₂ receptor (DP). Both two-component (Q² = 0.63, R² = 0.82, SEE = 0.47 pIC₅₀) and three-component (Q² = 0.70, R² = 0.91, SEE = 0.36 pIC₅₀) CoMSIA models were established. Two hydrogen-bond acceptors with spatial separation of about 8 Å are shown as optimal for binding. A large hydrophobic center that separates the two acceptors confers to the potency of the 2,6-substituted-4-monosubstituted aminopyrimidine. The models were used to predict IC₅₀ values for compounds which had functional groups different from those in the training set.     

A fluorescence spectroscopy assay for real-time monitoring of enzyme immobilization into mesoporous silica particles

Mesoporous silica particles are used as support material for immobilization of enzymes. Here we investigated a fluorescence-based assay for real-time monitoring of the immobilization of lipase, bovine serum albumin, and glucose oxidase into micrometer-sized mesoporous silica particles. The proteins are labeled with the dye epicocconone, and the interaction with the particles is observed as an increase in emission intensity of the protein–dye conjugates that can be quantified if correcting for a comparatively slow photobleaching. The immobilization occurs in tens of minutes to hours depending on particle concentration and type of protein. In the limit of excess particles over proteins, the formation of the particle–protein complexes can be described by a single exponential growth for all three investigated proteins, and the fitted pseudo-first-order rate constant increases linearly with particle concentration for each protein type. The derived second-order rate constant k varies with the protein hydrodynamic radius according to k ∼ R_H^{−4.70±0.01}, indicating that the rate-limiting step at high particle concentrations is not the diffusional encounter between proteins and particles but rather the entry into the pores, consistent with the hydrodynamic radii of the three proteins being smaller but comparable to the pore radius of the particles.     

Toxicity Assessment of Silica Coated Iron Oxide Nanoparticles and Biocompatibility Improvement by Surface Engineering

We have studied in vitro toxicity of iron oxide nanoparticles (NPs) coated with a thin silica shell (Fe₃O₄/SiO₂ NPs) on A549 and HeLa cells. We compared bare and surface passivated Fe₃O₄/SiO₂ NPs to evaluate the effects of the coating on the particle stability and toxicity. NPs cytotoxicity was investigated by cell viability, membrane integrity, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) assays, and their genotoxicity by comet assay. Our results show that NPs surface passivation reduces the oxidative stress and alteration of iron homeostasis and, consequently, the overall toxicity, despite bare and passivated NPs show similar cell internalization efficiency. We found that the higher toxicity of bare NPs is due to their stronger in-situ degradation, with larger intracellular release of iron ions, as compared to surface passivated NPs. Our results indicate that surface engineering of Fe₃O₄/SiO₂ NPs plays a key role in improving particles stability in biological environments reducing both cytotoxic and genotoxic effects.     

Physicochemical properties and in vitro intestinal permeability properties and intestinal cell toxicity of silica particles,performed in simulated gastrointestinal fluids

Background

Amorphous silica particles with the primary dimensions of a few tens of nm, have been widely applied as additives in various fields including medicine and food. Especially, they have been widely applied in powders for making tablets and to coat tablets. However, their behavior and biological effects in the gastrointestinal tracts associated with oral administration remains unknown.

Methods

Amorphous silica particles with diameters of 50, 100, and 200 nm were incubated in the fasted-state and fed-state simulated gastric and intestinal fluids. The sizes, intracellular transport into Caco-2 cells (model cells for intestinal absorption), the Caco-2 monolayer membrane permeability, and the cytotoxicity against Caco-2 cells were then evaluated for the silica particles.

Results

Silica particles agglomerated in fed-state simultaneous intestinal fluids. The agglomeration and increased particles size inhibited the particles' absorption into the Caco-2 cells or particles' transport through the Caco-2 cells. The in vitro cytotoxicity of silica particles was not observed when the average size was larger than 100 nm, independent of the fluid and the concentration.

Conclusion

Our study indicated the effect of diet on the agglomeration of silica particles. The sizes of silica particles affected the particles' absorption into or transport through the Caco-2 cells, and cytotoxicity in vitro, depending on the various biological fluids.

General significance

The findings obtained from our study may offer valuable information to evaluate the behavior of silica particles in the gastrointestinal tracts or safety of medicines or foods containing these materials as additives.     

Novel method for aroma recovery from the bioconversion of lutein to β-ionone by Trichosporon asahii using a mesoporous silicate material

In this work, we report on the synthesis and ability of the mesoporous material MCM-41 to adsorb the norisoprenoid β-ionone. This compound, with a violet aroma note, can be produced from lutein by the yeast Trichosporon asahii through a bioconversion process. We found that β-ionone inhibited the yeast growth and constrained aroma formation. Growth inhibition was overcome using silicate MCM-41 as sorbent device in a fermentation system that allowed product removal from the culture medium by headspace manipulation. Compared to a commercial silica gel, the mesoporous material exhibited a 4.5-fold higher β-ionone adsorption. Contrasting to cultures without the sorbent device, the presence of MCM-41 allowed a marked increase (14-fold) in β-ionone production. Our results suggested that confinement of the norisoprenoid into the sorbent material bypassed its toxicity which allowed a better β-ionone production. This study represents the first report on the use of MCM-41 to recover an aroma produced by fermentation and therefore, a novel application for a mesoporous material.     

Synthesis of functionalized polyethylenimine-grafted mesoporous silica spheres and the effect of side arms on lipase immobilization and application

In the present study, silicate mesoporous materials (MCM-41), MCM-41-grafted polyethylenimine (MCM-41@PEI), and succinated PEI containing amine, amide, and acid groups were successfully synthesized and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy. Thermomyces lanuginosa lipase (TLL) was then immobilized onto MCM-41 and polymer-grafted MCM-41 by physical adsorption. Besides, for enzyme immobilization via covalent bonding, glutaraldehyde (GLU), and hexamethylene diisocyanate (HMDI) were used as the bridges for binding the enzyme to supports. The best result was obtained with the immobilized lipase on MCM-41@PEI-GLU. In the study of the enzyme reusability, it was shown that about 83% of the initial activity could be retained after 12 cycles of uses. The immobilized lipase on the selected support was also applied for the synthesis of ethyl valerate. Following 24 h incubation in n-hexane and solvent free media, the esterification percentages were 79% and 67%, respectively.     

Direct and mediated electron transfer between intact succinate:quinone oxidoreductase from Bacillus subtilis and a surface modified gold electrode reveals redox state-dependent conformational changes

Succinate:quinone oxidoreductase (SQR) from Bacillus subtilis consists of two hydrophilic protein subunits comprising succinate dehydrogenase, and a di-heme membrane anchor protein harboring two putative quinone binding sites, Q_p and Q_d. In this work we have used spectroelectrochemistry to study the electronic communication between purified SQR and a surface modified gold capillary electrode. In the presence of two soluble quinone mediators the midpoint potentials of both hemes were revealed essentially as previously determined by conventional redox titration (heme b_H, E_m = + 65 mV, heme b_L, E_m = − 95 mV). In the absence of mediators the enzyme still communicated with the electrode, albeit with a reproducible hysteresis, resulting in the reduction of both hemes occurring approximately at the midpoint potential of heme b_L, and with a pronounced delay of reoxidation. When the specific inhibitor 2-n-heptyl-4 hydroxyquinoline N-oxide (HQNO), which binds to Q_d in B. subtilis SQR, was added together with the two quinone mediators, rapid reductive titration was still possible which can be envisioned as an electron transfer occurring via the HQNO insensitive Q_p site. In contrast, the subsequent oxidative titration was severely hampered in the presence of HQNO, in fact it completely resembled the unmediated reaction. If mediators communicate with Q_p or Q_d, either event is followed by very rapid electron redistribution within the enzyme. Taken together, this strongly suggests that the accessibility of Q_p depended on the redox state of the hemes. When both hemes were reduced, and Q_d was blocked by HQNO, quinone-mediated communication via the Q_p site was no longer possible, revealing a redox-dependent conformational change in the membrane anchor domain.     

Low-temperature electron transfer suggests two types of QA in intact photosystem II

The correlation between the reduction of Q_A and the oxidation of Tyr_Z or Car/Chl_Z/Cyt_b559 in spinach PSII enriched membranes induced by visible light at 10 K is studied by using electron paramagnetic resonance spectroscopy. Similar g = 1.95-1.86 Q_A^-•EPR signals are observed in both Mn-depleted and intact samples, and both signals are long lived at low temperatures. The presence of PPBQ significantly diminished the light induced EPR signals from Q_A^-•, Car^+•/Chl^+• and oxidized Cyt_b559, while enhancing the amplitude of the S₁Tyr_Z• EPR signal in the intact PSII sample. The quantification and stability of the g = 1.95-1.86 EPR signal and signals arising from the oxidized Tyr_Z and the side-path electron donors, respectively, indicate that the EPR-detectable g = 1.95-1.86 Q_A^-• signal is only correlated to reaction centers undergoing oxidation of the side-path electron donors (Car/Chl_Z/Cyt_b559), but not of Tyr_Z. These results imply that two types of Q_A^-• probably exist in the intact PSII sample. The structural difference and possible function of the two types of Q_A are discussed.     

Cationic screening of charged surface groups (carboxylates) affects electron transfer steps in photosystem-II water oxidation and quinone reduction

The functional or regulatory role of long-distance interactions between protein surface and interior represents an insufficiently understood aspect of protein function. Cationic screening of surface charges determines the morphology of thylakoid membrane stacks. We show that it also influences directly the light-driven reactions in the interior of photosystem II (PSII). After laser-flash excitation of PSII membrane particles from spinach, time courses of the delayed recombination fluorescence (10 μs–10 ms) and the variable chlorophyll-fluorescence yield (100 μs–1 s) were recorded in the presence of chloride salts. At low salt-concentrations, a stimulating effect was observed for the S-state transition efficiency, the time constant of O₂-formation at the Mn₄Ca-complex of PSII, and the halftime of re-oxidation of the primary quinone acceptor (Q_a) by the secondary quinone acceptor (Q_b). The cation valence determined the half-effect concentrations of the stimulating salt effect, which were around 6 μM, 200 μM and 10 mM for trivalent (LaCl₃), bivalent (MgCl₂, CaCl₂), and monovalent cations (NaCl, KCl), respectively. A depressing high-salt effect also depended strongly on the cation valence (onset concentrations around 2 mM, 50 mM, and 500 mM). These salt effects are proposed to originate from electrostatic screening of negatively charged carboxylate sidechains, which are found in the form of carboxylate clusters at the solvent-exposed protein surface. We conclude that the influence of electrostatic screening by solvent cations manifests a functionally relevant long-distance interaction between protein surface and electron-transfer reactions in the protein interior. A relation to regulation and adaptation in response to environmental changes is conceivable.     

Syntheses, spectroscopic characterization and X-ray structural studies of lanthanide complexes with adamantyl substituted 4-acylpyrazol-5-one

Synthesis and spectroscopic characterization of new lanthanide complexes [Ln(Q_AD)₃(EtOH)(H₂O)], (Ln = Tb, Eu; HQ_AD = 1-phenyl-3-methyl-4-adamantylcarbonyl-pyrazol-5-one), [H₃O][Tb(Q_AD)₄], [Ln(Q_AD)₃(N-N)] (Ln = Tb, Eu; N-N = 1,10-phenanthroline (Phen), 2,2′-bipyridyl (Bipy), 4,4′-dimethyl-2,2′-bipyridyl (4,4′-Me₂Bipy)) are reported. The crystal structures of the proligand HQ_AD and of complexes [H₃O][Tb(Q_AD)₄] and [Tb(Q_AD)₃(4,4′-Me₂Bipy)] have been determined. In both complexes the lanthanide ions are in a square antiprismatic environment, the H₃O⁺ cation in the former acid complex being stabilized by H-bonding. Luminescence studies have been performed on selected derivatives.     

Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Excitation dynamics of two spectral forms of the core complexes from photosynthetic bacterium Thermochromatium tepidum

The intact core antenna-reaction center (LH1-RC) core complex of thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum is peculiar in its long-wavelength LH1-Q_y absorption (915 nm). We have attempted comparative studies on the excitation dynamics of bacteriochlorophyll (BChl) and carotenoid (Car) between the intact core complex and the EDTA-treated one with the Q_y absorption at 889 nm. For both spectral forms, the overall Car-to-BChl excitation energy transfer efficiency is determined to be ∼20%, which is considerably lower than the reported values, e.g., ∼35%, for other photosynthetic purple bacteria containing the same kind of Car (spirilloxanthin). The RC trapping time constants are found to be 50∼60 ps (170∼200 ps) for RC in open (closed) state irrespective to the spectral forms and the wavelengths of Q_y excitation. Despite the low-energy LH1-Q_y absorption, the RC trapping time are comparable to those reported for other photosynthetic bacteria with normal LH1-Q_y absorption at 880 nm. Selective excitation to Car results in distinct differences in the Q_y-bleaching dynamics between the two different spectral forms. This, together with the Car band-shift signals in response to Q_y excitation, reveals the presence of two major groups of BChls in the LH1 of Tch. tepidum with a spectral heterogeneity of ∼240 cm⁻¹, as well as an alteration in BChl-Car geometry in the 889-nm preparation with respect to the native one.     

Fabrication of two- and three-dimensional model catalyst systems with monodispersed platinum nanoparticles as active metal building blocks

Well-defined Pt monodispersed nanoparticles within the catalytically relevant 1–10 nm size regime were synthesized in solution phase by several synthetic methods which differed in the choice of reducing agent, surface stabilizer, reaction temperature and solvent. Three-dimensional model catalysts were fabricated by incorporating the metal nanoparticles into ordered channels of high surface area mesoporous oxides such as SiO₂, Al₂O₃ and Ta₂O₅ through either sonication or direct synthesis of the oxide support around the particles. Deposition of the same nanocrystals onto silica supports by means of the Langmuir–Schaeffer technique produced two-dimensional model catalysts.     

Synthesis and in vitro screening of novel N-benzyl aplysinopsin analogs as potential anticancer agents

A series of novel substituted (Z)-5-((1-benzyl-1H-indol-3-yl)methylene)imidazolidin-2,4-diones (3a-f) and (Z)-5-((1-benzyl-1H-indol-3-yl)methylene)-2-iminothiazolidin-4-ones (3g-o) have been synthesized utilizing microwave irradiation. These analogs were evaluated for in vitro cytotoxicity against a panel of 60 human tumor cell lines. Compound 3i exhibits potent growth inhibition against melanoma UACC-257 (GI₅₀ = 13.3 nM) and OVCAR-8 ovarian (GI₅₀ = 19.5 nM) cancer cells while possessing significant cytotoxicity (LC₅₀ = 308 nM and LC₅₀ = 851 nM, respectively) against the same cell lines within this series of compounds. A second analog, 3a, had GI₅₀ values of 307 and 557 nM against SK-MEL-2 melanoma and A498 renal cancer cell lines, and exhibited GI₅₀ values ranging from 0.30 to 6 μM against 98% of all cancer cell lines in the 60-cell panel. Thus, (Z)-5-((5-chloro-1-(4-fluorobenzyl)-1H-indol-3-yl)methylene)-2-iminothiazolidin-4-one (3i) and (Z)-methyl 1-(4-cyanobenzyl)-3-((2,5-dioxoimidazolidin-4-ylidene)methyl)-1H-indole-6-carboxylate (3a) can be regarded as useful lead compounds for further structural optimization as antitumor agents.     

Using polarization analysis to separate the coherent and incoherent scattering from protein samples

Polarization analysis was used to separate experimentally the coherent and spin-incoherent nuclear static scattering functions, from a representative set of samples of interest for protein studies. This method had so far limited application in the study of amorphous materials, despite the relevance of the information that it provides. It allows, for instance, the experimental determination of the structure factor of materials containing a significant amount of hydrogen atoms, avoiding the contamination of measurements by a non-negligible incoherent background. Knowledge of the relative importance of the coherent and incoherent terms at different Q-values is also a pre-requisite for the interpretation of quasielastic neutron scattering experiments, performed at instruments in which the total dynamic scattering function is measured, such as conventional time-of-flight and backscattering spectrometers. Combining data from different instruments, it was possible to cover a wide Q-range, from the small-angle region (0.006 < Q < 0.04 Å^− 1) to the wide-angle region (up to ≈ 2.35 Å^− 1). Quantitative information was obtained on the fraction of coherent to spin-incoherent scattering from different protein samples: deuterated and protonated protein powders at different hydration levels and solutions of protonated proteins in D₂O at different concentrations. The results obtained are discussed in the context of the validity of the assumptions generally made when interpreting quasielastic neutron scattering experiments performed without polarization analysis.     

Species-dependence of the redox potential of the primary quinone electron acceptor QA in photosystem II verified by spectroelectrochemistry

The redox potentials E_m(Q_A/) of the primary quinone electron acceptor Q_A in oxygen-evolving photosystem II complexes of three species were determined by spectroelectrochemistry. The E_m(Q_A/) values were experimentally found to be −162 ± 3 mV for a higher plant spinach, −171 ± 3 mV for a green alga Chlamydomonas reinhardtii and −104 ± 4 mV vs. SHE for a red alga Cyanidioschyzonmerolae. On the basis of possible deviations for the experimental values, as estimated to differ by 9-29 mV from each true value, plausible causes for such remarkable species-dependence of E_m(Q_A/) are discussed, mainly by invoking the effects of extrinsic subunits on the delicate structural environment around Q_A.     

Sulfated polysaccharides from Laminaria angustata: Structural features and in vitro antiviral activities

Sulfated polysaccharides potently inhibit the infectivity of herpes simplex virus (HSV) in cultured cells. In this study, we have analyzed sulfated xylogalactofucan and alginic acid containing fractions generated from Laminaria angustata, a marine alga. The xylogalactofucan that has apparent molecular mass of 56 ± 5 kDa and unusually low sulfate content contains, inter alia, 1,3-, 1,4- and 1,2-linked fucopyranosyl residues. The algin (molecular mass: 32 ± 5 kDa) contains gulo- (55.5%) and mannuronic (44.5%) acid residues. Introduction of sulfate groups enhanced the macromolecules capability to inhibit the infection of cells by HSV-1. The 50% inhibitory concentration (IC₅₀) values of these macromolecules against HSV-1 were in the range of 0.2-25 μg ml⁻¹ and they lacked cytotoxicity at concentrations up to 1000 μg ml⁻¹. The sulfate content appeared to be an important hallmark of anti-HSV-1 activity. Our results suggest the feasibility of inhibiting HSV attachment to cells by direct interaction of polysaccharides with viral particles.