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1.
Proc Natl Acad Sci U S A ; 119(1)2021 01 04.
Article in English | MEDLINE | ID: mdl-34969854

ABSTRACT

Disentangling the roles of the external environment and internal biotic drivers of plant population dynamics is challenging due to the absence of relevant physiological and abundance information over appropriate space and time scales. Remote observations of giant kelp biomass and photosynthetic pigment concentrations are used to show that spatiotemporal patterns of physiological condition, and thus growth and production, are regulated by different processes depending on the scale of observation. Nutrient supply was linked to regional scale (>1 km) physiological condition dynamics, and kelp forest stands were more persistent where nutrient levels were consistently high. However, on local scales (<1 km), internal senescence processes related to canopy age demographics determined patterns of biomass loss across individual kelp forests despite uniform nutrient conditions. Repeat measurements of physiology over continuous spatial fields can provide insights into complex dynamics that are unexplained by the environmental drivers thought to regulate abundance. Emerging remote sensing technologies that provide simultaneous estimates of abundance and physiology can quantify the roles of environmental change and demographics governing plant population dynamics for a wide range of aquatic and terrestrial ecosystems.


Subject(s)
Macrocystis/metabolism , Nutrients/metabolism , Biomass , Ecosystem , Macrocystis/chemistry , Macrocystis/growth & development , Photosynthesis , Population Dynamics , Remote Sensing Technology
2.
Molecules ; 26(8)2021 Apr 18.
Article in English | MEDLINE | ID: mdl-33919590

ABSTRACT

Seaweed processing generates liquid fraction residual that could be used as a low-cost nutrient source for microbial production of metabolites. The Rhodotorula strain is able to produce antimicrobial compounds known as sophorolipids. Our aim was to evaluate sophorolipid production, with antibacterial activity, by marine Rhodotorula rubra using liquid fraction residual (LFR) from the brown seaweed Macrocystis pyrifera as the nutrient source. LFR having a composition of 32% w/w carbohydrate, 1% w/w lipids, 15% w/w protein and 52% w/w ash. The best culture condition for sophorolipid production was LFR 40% v/v, without yeast extract, artificial seawater 80% v/v at 15 °C by 3 growth days, with the antibacterial activity of 24.4 ± 3.1 % on Escherichia coli and 21.1 ± 3.8 % on Staphylococcus aureus. It was possible to identify mono-acetylated acidic and methyl ester acidic sophorolipid. These compounds possess potential as pathogen controllers for application in the food industry.


Subject(s)
Macrocystis/chemistry , Oleic Acids/chemistry , Plant Extracts/pharmacology , Rhodotorula/drug effects , Aquatic Organisms/chemistry , Oleic Acids/pharmacology , Plant Extracts/chemistry , Rhodotorula/pathogenicity
3.
Molecules ; 26(5)2021 Feb 28.
Article in English | MEDLINE | ID: mdl-33671085

ABSTRACT

Seaweeds have a long history of use as food, as flavouring agents, and find use in traditional folk medicine. Seaweed products range from food, feed, and dietary supplements to pharmaceuticals, and from bioenergy intermediates to materials. At present, 98% of the seaweed required by the seaweed industry is provided by five genera and only ten species. The two brown kelp seaweeds Laminaria digitata, a native Irish species, and Macrocystis pyrifera, a native New Zealand species, are not included in these eleven species, although they have been used as dietary supplements and as animal and fish feed. The properties associated with the polysaccharides and proteins from these two species have resulted in increased interest in them, enabling their use as functional foods. Improvements and optimisations in aquaculture methods and bioproduct extractions are essential to realise the commercial potential of these seaweeds. Recent advances in optimising these processes are outlined in this review, as well as potential future applications of L. digitata and, to a greater extent, M. pyrifera which, to date, has been predominately only wild-harvested. These include bio-refinery processing to produce ingredients for nutricosmetics, functional foods, cosmeceuticals, and bioplastics. Areas that currently limit the commercial potential of these two species are highlighted.


Subject(s)
Aquaculture/methods , Complex Mixtures/chemistry , Laminaria/chemistry , Macrocystis/chemistry , Seaweed/chemistry , Animals , Dietary Supplements , Europe , Food , Humans , Legislation as Topic , Pharmaceutical Preparations , Polysaccharides/chemistry , Proteins/chemistry , Social Control, Formal , United States
4.
Int J Biol Macromol ; 180: 547-558, 2021 Jun 01.
Article in English | MEDLINE | ID: mdl-33741372

ABSTRACT

A fuciodan (Mw = 11.1 kDa) was obtained and purified from Macrocystis pyrifera (MPF). MPF was an acid heteropolysaccharide including fucose, mannose, xylose, galactose, rhamnose, glucuronic acid, and glucose in a molar ratio of 3.1:1.0:0.86:0.63:0.25:0.33:0.11. Sulfate content in MPF was 28.6%, and the molar ratio of fucose to sulfate (Fuc:SO42-) was 1.0:0.58. The structure of MPF was mainly consist of repeating →3)-ß-L-Fucp (2SO3-)-(1→ and →4)-ß-D-Xylp-(1→3)-ß-L-Fucp(2SO3-)-(1→ and with α-L-Fucp-(1→ and →6)-α-D-Galp-(1→ in branches. Moreover, the effects of different MPF concentrations on plant salt tolerance were investigated. The results indicated that MPF could improve the salt tolerance of wheat seedlings. Among the five concentrations (0.05, 0.1, 0.5, 1, and 2 mg/ml), 0.5 and 1 mg/ml MPF were optimal for effective plant salt-resistance activity. These results suggested that MPF extracted from brown seaweed show potential as plant stimulators that may be used to improve salt resistance of plants.


Subject(s)
Macrocystis/chemistry , Polysaccharides/chemistry , Salt Stress/physiology , Salt Tolerance/physiology , Seedlings/physiology , Triticum/physiology , Antioxidants/metabolism , Dose-Response Relationship, Drug , Fucose/analysis , Hydrogen Peroxide/metabolism , Lipid Peroxidation/drug effects , Magnetic Resonance Spectroscopy , Microscopy, Electron, Scanning , Polysaccharides/isolation & purification , Polysaccharides/pharmacology , Salt Stress/drug effects , Salt Tolerance/drug effects , Seedlings/drug effects , Seedlings/metabolism , Spectroscopy, Fourier Transform Infrared , Sulfates/analysis , Superoxide Dismutase/metabolism , Triticum/drug effects , Triticum/metabolism
5.
Int J Biol Macromol ; 174: 477-484, 2021 Mar 31.
Article in English | MEDLINE | ID: mdl-33513426

ABSTRACT

Brown seaweed is an important source of fucoidan, which displays immunomodulatory effects by activating various immune cells. However, these effects of fucoidans from various sources of brown seaweed have not yet been explored in human blood dendritic cells. We studied fucoidans extracted from Ecklonia cava, Macrocystis pyrifera, Undaria pinnatifida, and Fucus vesiculosus for their effects on human monocyte-derived dendritic cells (MODC) and human peripheral blood DC (PBDC) activation. Ecklonia cava fucoidan (ECF) strongly upregulated co-stimulatory molecules, major histocompatibility complex class I and II, and the production of proinflammatory cytokines in MODCs and PBDCs compared to those by the other three fucoidans. Moreover, ECF elicited the strongest effect in the induction of syngeneic T cell proliferation and IFN-γ production compared to those of other fucoidans. These results suggest that ECF could be a suitable candidate molecule for enhancing immune activation in humans compared to that with the other three fucoidans.


Subject(s)
Dendritic Cells/immunology , Leukocytes, Mononuclear/cytology , Monocytes/cytology , Phaeophyceae/classification , Polysaccharides/pharmacology , Cells, Cultured , Cytokines/metabolism , Dendritic Cells/cytology , Dendritic Cells/drug effects , Fucus/chemistry , Gene Expression Regulation/drug effects , Histocompatibility Antigens Class I/metabolism , Histocompatibility Antigens Class II/metabolism , Humans , Interferon-gamma/metabolism , Leukocytes, Mononuclear/drug effects , Leukocytes, Mononuclear/immunology , Macrocystis/chemistry , Monocytes/drug effects , Monocytes/immunology , Phaeophyceae/chemistry , Polysaccharides/chemistry , Polysaccharides/isolation & purification , Seaweed , T-Lymphocytes/metabolism , Undaria/chemistry , Up-Regulation
6.
J Appl Microbiol ; 127(4): 1069-1079, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31237965

ABSTRACT

AIMS: To evaluate an aqueous extract of Macrocystis pyrifera as a nutrient source for the production of carotenoids by a marine Rhodotorula mucilaginosa isolated from seaweed samples. MATERIALS AND RESULTS: The effect of different culture conditions on the concentration of biomass and total pigments was evaluated using a Box-Behnken experimental design. The seaweed extract contained 15% w w-1 of protein and 20% w w-1 of carbohydrate; the main sugar in this fraction was trehalose (78%). The culture conditions that maximize the total pigment concentration (1·84 ± 0·03 mg l-1 ) were initial pH equal to 7, yeast extract as nitrogen source at a concentration of 4 g l-1 , seaweed extract concentration at 25% v v-1 , incubation performed at 25°C and 150 rev min-1 during 6 days. Under optimal growth conditions, three carotenoids were identified among the pigments produced by R. mucilaginosa, lycopene (38·4 ± 9·4%), ß-carotene (21·8 ± 1·5%) and astaxanthin (1·8 ± 0·3%). CONCLUSIONS: Carotenoids of commercial interest (lycopene, ß-carotene and astaxanthin) can be produced using a marine R. mucilaginosa cultivated with an aqueous extract of M. pyrifera as nutrient source. The total pigment concentration in the culture ranged between 0·82 and 1·84 mg l-1 , and was significantly affected by the concentration of the seaweed extract, and yeast extract. SIGNIFICANCE AND IMPACT OF THE STUDY: This work demonstrates that M. pyrifera can be used as a nutrient source for the production of carotenoids by the marine yeast.


Subject(s)
Carotenoids , Macrocystis/chemistry , Rhodotorula , Biomass , Bioreactors , Carotenoids/analysis , Carotenoids/metabolism , Culture Media , Rhodotorula/metabolism , Rhodotorula/physiology
7.
Food Chem ; 237: 312-319, 2017 Dec 15.
Article in English | MEDLINE | ID: mdl-28764002

ABSTRACT

Phlorotannins are secondary metabolites produced by brown seaweed, which are known for their nutraceutical and pharmacological properties. The aim of this work was to determine the type of macroporous resin and the conditions of operation that improve the purification of phlorotannins extracted from brown seaweed, Macrocystis pyrifera. For the purification of phlorotannins, six resins (HP-20, SP-850, XAD-7, XAD-16N, XAD-4 and XAD-2) were assessed. The kinetic adsorption allowed determination of an average adsorption time for the resins of 9h. The highest level of purification of phlorotannins was obtained with XAD-16N, 42%, with an adsorption capacity of 183±18mgPGE/g resin, and a desorption ratio of 38.2±7.7%. According to the adsorption isotherm the best temperature of operation was 25°C, and the model that best described the adsorption properties was the Freundlich model. The purification of phlorotannins might expand their use as a bioactive substance in the food, nutraceutical and pharmaceutical industries.


Subject(s)
Macrocystis/chemistry , Acrylic Resins , Adsorption , Polystyrenes , Resins, Plant
8.
Toxins (Basel) ; 9(6)2017 06 12.
Article in English | MEDLINE | ID: mdl-28604648

ABSTRACT

The saxitoxin-group (STX-group) corresponds to toxic metabolites produced by cyanobacteria and dinoflagellates of the genera Alexandrium, Gymnodinium, and Pyrodinium. Over the last decade, it has been possible to extrapolate the areas contaminated with the STX-group worldwide, including Chile, a phenomenon that has affected ≈35% of the Southern Pacific coast territory, generating a high economic impact. The objective of this research was to study the toxicity of the STX-group in all aquatic organisms (bivalves, algae, echinoderms, crustaceans, tunicates, cephalopods, gastropods, and fish) present in areas with a variable presence of harmful algal blooms (HABs). Then, the toxic profiles of each species and dose of STX equivalents ingested by a 60 kg person from 400 g of shellfish were determined to establish the health risk assessment. The toxins with the highest prevalence detected were gonyautoxin-4/1 (GTX4/GTX1), gonyautoxin-3/2 (GTX3/GTX2), neosaxitoxin (neoSTX), decarbamoylsaxitoxin (dcSTX), and saxitoxin (STX), with average concentrations of 400, 2800, 280, 200, and 2000 µg kg-1 respectively, a species-specific variability, dependent on the evaluated tissue, which demonstrates the biotransformation of the analogues in the trophic transfer with a predominance of α-epimers in all toxic profiles. The identification in multiple vectors, as well as in unregulated species, suggests that a risk assessment and risk management update are required; also, chemical and specific analyses for the detection of all analogues associated with the STX-group need to be established.


Subject(s)
Food Contamination/analysis , Saxitoxin/analysis , Seafood/analysis , Animals , Cyanobacteria , Dinoflagellida , Food Chain , Invertebrates/chemistry , Invertebrates/metabolism , Macrocystis/chemistry , Macrocystis/metabolism , Salmon/metabolism , Saxitoxin/metabolism
9.
Mar Drugs ; 13(3): 1084-104, 2015 Feb 19.
Article in English | MEDLINE | ID: mdl-25706632

ABSTRACT

Fucoidan, a sulfated polysaccharide purified from brown algae, has a variety of immune-modulation effects, such as promoting activation of dendritic cells (DCs), natural killer (NK) cells and T cells, and enhancing anti-viral and anti-tumor responses. However, the immune-modulatory effect of fucoidan from different seaweed extracts has not been thoroughly analyzed and compared. We analyzed fucoidans obtained from Ascophyllum nodosum (A. nodosum), Macrocystis pyrifera (M. pyrifera), Undaria pinnatifida (U. pinnatifida) and Fucus vesiculosus (F. vesiculosus) for their effect on the apoptosis of human neutrophils, activation of mouse NK cells, maturation of spleen DCs, proliferation and activation of T cells, and the adjuvant effect in vivo. Fucoidans from M. pyrifera and U. pinnatifida strongly delayed human neutrophil apoptosis at low concentration, whereas fucoidans from A. nodosum and F. vesiculosus delayed human neutrophil apoptosis at higher concentration. Moreover, fucoidan from M. pyrifera promoted NK cell activation and cytotoxic activity against YAC-1 cells. In addition, M. pyrifera fucoidan induced the strongest activation of spleen DCs and T cells and ovalbumin (OVA) specific immune responses compared to other fucoidans. These data suggest that fucoidan from M. pyrifera can be potentially useful as a therapeutic agent for infectious diseases, cancer and an effective adjuvant for vaccine.


Subject(s)
Immunologic Factors/pharmacology , Macrocystis/chemistry , Phaeophyceae/chemistry , Polysaccharides/pharmacology , Animals , Apoptosis/drug effects , Cell Line , Cell Proliferation/drug effects , Dendritic Cells/drug effects , Dendritic Cells/metabolism , Humans , Immunologic Factors/isolation & purification , Killer Cells, Natural/drug effects , Killer Cells, Natural/immunology , Mice , Mice, Inbred C57BL , Neutrophils/drug effects , Neutrophils/metabolism , Ovalbumin/immunology , Polysaccharides/isolation & purification , T-Lymphocytes/drug effects , T-Lymphocytes/metabolism
10.
J Biomed Mater Res A ; 100(11): 2939-47, 2012 Nov.
Article in English | MEDLINE | ID: mdl-22700168

ABSTRACT

Microbeads of alginate crosslinked with Ca(2+) and/or Ba(2+) are popular matrices in cell-based therapy. The aim of this study was to quantify the binding of barium in alginate microbeads and its leakage under in vitro and accumulation under in vivo conditions. Low concentrations of barium (1 mM) in combination with calcium (50 mM) and high concentrations of barium (20 mM) in gelling solutions were used for preparation of microbeads made of high-G and high-M alginates. High-G microbeads accumulated barium from gelling solution and contained higher concentrations of divalent ions for both low- and high-Ba exposure compared with high-G microbeads exposed to calcium solely and to high-M microbeads for all gelling conditions. Although most of the unbound divalent ions were removed during the wash and culture steps, leakage of barium was still detected during storage. Barium accumulation in blood and femur bone of mice implanted with high-G beads was found to be dose-dependent. Estimated barium leakage relevant to transplantation to diabetic patients with islets in alginate microbeads showed that the leakage was 2.5 times lower than the tolerable intake value given by WHO for high-G microbeads made using low barium concentration. The similar estimate gave 1.5 times higher than is the tolerable intake value for the high-G microbeads made using high barium concentration. To reduce the risk of barium accumulation that may be of safety concern, the microbeads made of high-G alginate gelled with a combination of calcium and low concentration of barium ions is recommended for islet transplantation.


Subject(s)
Alginates/chemistry , Barium/blood , Barium/chemistry , Cross-Linking Reagents/chemistry , Gels/chemistry , Animals , Barium/metabolism , Calcium/chemistry , Cross-Linking Reagents/metabolism , Femur/metabolism , Glucuronic Acid/chemistry , Hexuronic Acids/chemistry , Laminaria/chemistry , Macrocystis/chemistry , Male , Mice , Mice, Inbred BALB C , Microspheres
11.
Mar Pollut Bull ; 62(12): 2619-32, 2011 Dec.
Article in English | MEDLINE | ID: mdl-22030107

ABSTRACT

This study introduces an innovative method for biomonitoring using giant kelp (Macrocystis pyrifera) sieve tube sap (STS) metal concentrations as an indication of pollution influence. STS was sampled from fronds collected from 10 southern California locations, including two reference sites on Santa Catalina Island. Using ICP-MS methodology, STS concentrations of 17 different metals were measured (n=495). Several metals associated with pollution showed the highest STS concentrations and most seasonal variation from populations inside the Port of Los Angeles/Long Beach. Lowest concentrations were measured at less-urbanized areas: Santa Catalina Island and Malibu. Some metals showed a spatial gradient in STS metal concentration with increasing distance from point sources (i.e. Los Angeles River). Cluster analyses indicate that polluted seawater may affect kelp uptake of metals essential for cellular function. Results show that this method can be useful in describing bioavailable metal pollution with implications for accumulation within an important ecosystem.


Subject(s)
Environmental Monitoring/methods , Macrocystis/chemistry , Metals/metabolism , Spectrophotometry, Atomic/methods , Water Pollutants, Chemical/metabolism , Analysis of Variance , California , Cluster Analysis , Ecosystem , Kelp/chemistry , Kelp/drug effects , Los Angeles , Macrocystis/drug effects , Metals/toxicity , Phloem/chemistry , Phloem/drug effects , Seasons , Seawater/analysis , Seawater/chemistry , Water Pollutants, Chemical/toxicity
12.
J Environ Sci (China) ; 23(11): 1778-86, 2011.
Article in English | MEDLINE | ID: mdl-22432300

ABSTRACT

This study investigated the adsorption of Hg(II) on Macrocystis pyrifera and Undaria pinnatifida in monometallic system in the presence of Zn(II), Cd(II) and Ni(II). The two biosorbents reached the same maximum sorption capacity (q(m) = 0.8 mmol/g) for mercury. U. pinnatifida showed a greater affinity (given by the coefficient b of the Langmuir equation) for mercury compared to M. pyrifera (4.4 versus 2.7 L/mmol). Mercury uptake was significantly reduced (by more than 50%) in the presence of competitor heavy metals such as Zn(II), Cd(II) and Ni(II). Samples analysis using an environmental scanning electron microscopy equipped with an energy dispersive X-ray microanalysis showed that mercury was heterogeneously adsorbed on the surface of both biomaterials, while the other heavy metals were homogeneous distributed. The analysis of biosorbents by Fourier transform infrared spectrometry indicated that Hg(II) binding occurred on S = O (sulfonate) and N-H (amine) functional groups.


Subject(s)
Macrocystis/chemistry , Mercury/isolation & purification , Undaria/chemistry , Adsorption , Binding, Competitive , Biodegradation, Environmental , Electron Probe Microanalysis , Hydrogen-Ion Concentration , Metals, Heavy/chemistry , Spectroscopy, Fourier Transform Infrared , Thermodynamics
13.
Int J Biol Macromol ; 44(4): 365-71, 2009 May 01.
Article in English | MEDLINE | ID: mdl-19428468

ABSTRACT

In this work, three methods (ethanol, HCl, and CaCl(2) routes) of sodium alginate extraction-purification from brown seaweeds (Macrocystis pyrifera) were used in order to study the influence of process conditions on final properties of the polymer. In the CaCl(2) route, was found that the precipitation step in presence of calcium ions followed by proton-exchange in acid medium clearly gives alginates with the lowest molecular weight and poor mechanical properties. It is well known that the acid treatment degrade the ether bonds on the polymeric chain. Ethanol route displayed the best performance, where the highest yield and rheological properties were attained with the lowest number of steps. Although the polymer I.1 showed a molar mass and polydispersity index (M(w)/M(n)) similar to those of commercial sample, its mechanical properties were lower. This performance is related to the higher content of guluronic acid in the commercial alginate, which promotes a more successful calcium chelation. Moreover, the employment of pH 4 in the acid pre-treatment improved the yield of the ethanol route, avoiding the ether linkage hydrolysis. Therefore, samples I.2 and I.3 displayed a higher M(w) and a narrower distribution of molecular weights than commercial sample, which gave a higher viscosity and better viscoelastic properties.


Subject(s)
Alginates/chemistry , Alginates/isolation & purification , Macrocystis/chemistry , Calcium/chemistry , Gels/chemistry , Glucuronic Acid/chemistry , Glucuronic Acid/isolation & purification , Hexuronic Acids/chemistry , Hexuronic Acids/isolation & purification , Magnetic Resonance Spectroscopy , Rheology , Water/chemistry
14.
J Sep Sci ; 30(14): 2332-40, 2007 Sep.
Article in English | MEDLINE | ID: mdl-17683047

ABSTRACT

The coupling of the flow field-flow fractionation (FlFFF) to differential refractive index (DRI) and multiangle laser light scattering (LS) detectors is a powerful tool for characterizing charged polysaccharides such as alginate. However, the correct interpretation of the experimental results and extrapolation of meaningful molecular parameters by using an analytical tool with such a level of complexity requires improvement of the knowledge of the alginate behavior in the channel and careful optimization of the operating conditions. Therefore, the influence of the critical operating parameters, such as crossflow rate, carrier composition and concentration, and sample load, on the alginate retention was carefully evaluated. Combined information obtained simultaneously by DRI and LS detectors over the wide range of the crossflow rate, carrier liquid concentration, and injected amount, allowed to set the appropriate combination of optimal parameters. It was found that the crossflow rate of 0.25 mL/min, carrier solution containing 5x10(-2 )mol/L ammonium or sodium chloride, and 50-100 microg of injected sample mass were necessary to achieve complete separation and determination of the meaningful molecular characteristics. The values of the weight-average hydrodynamic radius (R(Hw)), radius of gyration (R(G)), and molar mass (M), obtained under the optimal conditions were in good agreement to those found for alginates in the literature.


Subject(s)
Alginates/isolation & purification , Fractionation, Field Flow/methods , Glucuronic Acid/isolation & purification , Hexuronic Acids/isolation & purification , Lasers , Light , Macrocystis/chemistry , Scattering, Radiation
15.
Biomacromolecules ; 7(5): 1471-80, 2006 May.
Article in English | MEDLINE | ID: mdl-16677028

ABSTRACT

Microcapsules of alginate cross-linked with divalent ions are the most common system for cell immobilization. In this study, we wanted to characterize the effect of different alginates and cross-linking ions on important microcapsule properties. The dimensional stability and gel strength increased for high-G alginate gels when exchanging the traditional Ca2+ ions with Ba2+. The use of Ba2+ decreased the size of alginate beads and reduced the permeability to immunoglobulin G. Strontium gave gels with characteristics lying between calcium and barium. Interestingly, high-M alginate showed an opposite behavior in combination with barium and strontium as these beads were larger than beads of calcium-alginate and tended to swell more, also resulting in increased permeability. Binding studies revealed that different block structures in the alginate bind the ions to a different extent. More specifically, Ca2+ was found to bind to G- and MG-blocks, Ba2+ to G- and M-blocks, and Sr2+ to G-blocks solely.


Subject(s)
Alginates/chemistry , Barium Compounds , Calcium Chloride , Chlorides , Strontium , Alginates/isolation & purification , Alginates/radiation effects , Cations, Divalent , Circular Dichroism , Cross-Linking Reagents , Gels , Hexuronic Acids , Immunoglobulin G , Laminaria/chemistry , Macrocystis/chemistry , Permeability , Sodium Chloride , Solutions , Stress, Mechanical
16.
Appl Spectrosc ; 57(7): 768-73, 2003 Jul.
Article in English | MEDLINE | ID: mdl-14658654

ABSTRACT

Raman spectroscopy has been exploited to characterize the diffusion properties of solutes in hydrogels. Raman active vibrations were used as intrinsic probes of the solute concentration along gel cylinders. The resulting one-dimensional solute distribution, characterized as a function of both time and space, could be analyzed with a model based on Fick's diffusion law, and the mutual-diffusion coefficient (Dm) was then determined. To illustrate the potential of this approach, we measured the Dm of two polyethylene glycols (PEG) in Ca-alginate gels. In this case, the intensity of the CH stretching band was used to obtain the concentration profiles of PEGs, whereas the OH stretching band of water was used as an internal intensity standard. In addition to providing a straightforward approach to measuring diffusion coefficients, the Raman profile analysis provides information relative to the accessibility of gels to large molecules. As an example, it was found that the PEG penetration in Ca-alginate gels was restricted, a phenomenon that was dependent on PEG size. The Raman technique presented here effectively characterizes transport properties of solutes in gels, and such characterization is required for developing several technical applications of gels, such as their use as materials for controlled release of drugs.


Subject(s)
Hydrogels/chemistry , Spectrum Analysis, Raman/methods , Diffusion , Macrocystis/chemistry
17.
J Biomed Mater Res A ; 67(2): 376-88, 2003 Nov 01.
Article in English | MEDLINE | ID: mdl-14566778

ABSTRACT

Alginates are increasingly being used as medical materials (matrices for tissue regeneration, surgical sponges, hemostatic bandages, microbial and cell encapsulation, artificial bacterial biofilms, etc.). The constitution of alginate gel networks is a complex phenomenon. A great number of different kinds of polysaccharidic frameworks can come to existence depending on the conditions used for their attainment. For instance, the degree of heterogeneity and porosity of Ca-alginate beads rely on this molecular organization. The formation of structural irregularities (superficial crust, cavities, shafts, dense or light gel frameworks, ordered or chaotic domains, etc.) within the alginate gel beads are inherent to this skeletal design. Several specific staining molecules (e.g. calcon carboxylic acid, murexide, methylene blue) that are negatively or positively charged interact with the gel network. These molecules allowed us to reveal a great variety of chemical interactions shown by the pattern coloration of the internal structure of the gel. The results observed are very different for the several matrices analyzed, which could explain to a great extent the singular behavior that cells confined in these kind of matrices exhibit.


Subject(s)
Alginates/chemistry , Biocompatible Materials/chemistry , Calcium/chemistry , Biocompatible Materials/chemical synthesis , Macrocystis/chemistry , Microspheres , Staining and Labeling
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