Stretching single polysaccharide molecules using AFM: A potential method for the investigation of the intermolecular uronate distribution of alginate?

Illustrative examples of the way in which the molecular force-extension behaviour of polysaccharides is governed by the nature of the linkage between their constituent pyranose rings are presented for a series of standard homopolymers. These results agree with previously proposed general hypotheses regarding the possibility of generating force-induced conformational transitions, and with the predictions of a model in which the inter-conversion of pyranose conformers is assumed to be an equilibrium process on the timescale of the molecular stretching. Subsequently, we investigate the potential of the technique in the characterisation of co-polymeric polysaccharides in which the nature of the glycan linkages is different between the two distinct residue types. Specifically, we explore the possibility that the ratio of mannuronic acid (M) to guluronic acid (G) in alginate chains will be reflected in their single molecule stretching behaviour, owing to their contrasting equatorial and axial linkages. Furthermore, as the technique described interrogates the sample one polymer at a time we outline the promise of, and the obstacles to, obtaining a new level of characterisation using this methodology where differences observed in the single molecule stretching curves obtained from single alginate samples reflectsomething of the real intermolecular distribution of the M / G ratio

Gels and gelled emulsions prepared by acid-induced gelation of mixtures of faba bean (Vicia faba) protein concentrate and λ-carrageenan

In this study, gels were successfully prepared at room temperature from mixtures of dry fractionated faba bean protein concentrate (FPC) and λ-carrageenan (λ-CGN), through acidification with glucono-δ-lactone (GDL). At neutral pH, the mixtures were shear thinning liquids, although the shear viscosity increased dramatically with λ-CGN addition. After adding GDL, the gelling kinetics were followed through small amplitude oscillatory rheology for 19 hours, at which point all gels had reached a gel modulus plateau. Elastic moduli for the prepared gels were in the range of 1500 – 4500 Pa, dependent on FPC:λ-CGN ratio and concentrations, and final pH (3.5 – 4). Rheological data further indicated the gels had properties typical of aggregated particle gels, e.g., low yield strains (∼1%). All gels showed some syneresis upon centrifugation (2000g), with the least amount of syneresis (15 – 20%) at the highest λ-CGN concentrations (1.5 – 2%). FPC is a good emulsifier, and gelled emulsions were successfully prepared. Inclusion of emulsion droplets had significant impact on the gel network, with ∼40% and ∼60% increased gel storage modulus at 20% and 30% oil, respectively. Preparing similar formulations using a more extensively processed commercial faba bean protein isolate was also attempted, but this resulted in poor gels with very high syneresis. This indicates that dry fractionation methods may be beneficial to preserve native protein functionality.Gels and gelled emulsions prepared by acid-induced gelation of mixtures of faba bean (Vicia faba) protein concentrate and λ-carrageenanpublishedVersio

Housing First – veien inn i bolig?

Fordypningsoppgave i videreutdanning rus, avhengighet og psykiske lidelser, 2016Innledning: Å eie eller leie bolig er en selvfølge for de fleste mennesker i Norge, et av verdens rikeste land med et godt utbygd velferdssystem. De fleste av innbyggerne i Norge bor godt, men dette gjelder ikke alle. I den nasjonale strategien for boligsosialt arbeid, «Bolig for velferd» (Kommunal- og moderniseringsdepartementet, 2014) blir det anslått at om lag 150 000 personer er vanskeligstilte på boligmarkedet, og at rundt 6200 av disse personene mangler et fast sted å bo. Grunnen til at de er vanskeligstilte er at de ofte mangler økonomiske ressurser til å komme seg inn på boligmarkedet, og/eller at de har tilleggsproblemer i form av rusproblemer, atferd og funksjonsnivå (Økland, 2012). I veilederen «Sammen om mestring» (Helsedirektoratet, 2014) blir det slått fast at personer med rusproblemer og/eller psykiske lidelser er overrepresentert blant de vanskeligstilte på boligmarkedet og blant de bostedsløse. I ROP-retningslinjen (Helsedirektoratet, 2012) blir det uttalt at 60 prosent av de bostedsløse har rusproblemer og 32 prosent har psykiske lidelser, og om lag 25 prosent har samtidig ruslidelse og psykisk lidelse (ROP-lidelser). Jeg jobber i en liten kommune, og vi har for så vidt få bostedsløse, men vi har en forholdsvis stor gruppe personer med rusproblemer som har/har hatt problemer med å komme inn på det private boligmarkedet, problemer med å beholde bolig og holde boligen i orden. Bosituasjonen til denne gruppen er preget av utkastelse på grunn av manglende betaling av husleie, bråk, uro og hærverk, søppel og rot i leilighetene og de blir stigmatisert av nærmiljøet. I en liten kommune/bygd kjenner alle hverandre, og de fleste vet hvem disse personene er. De blir ganske synlige i et lite og tett lokalsamfunn, og mange private utleiere vil ikke leie ut til personer med rusproblemer. Pr. i dag bor derfor de fleste i kommunale leiligheter rundt omkring i kommunen. Mange av dem er ikke særlig interessert i å ta imot bistand i form av boveiledning og hjemmetjenester, med det resultat at kommunen med jevne mellomrom må foreta storopprydning og kaste containere fulle med søppel og rot. Ofte må en også foreta diverse reparasjoner og vedlikehold forårsaket av hard bruk, hærverk og forsøpling. Manglende betaling av husleie medfører også utkastelser, men innebærer kanskje bare at de må flytte til en annen kommunal leilighet fordi vi i henhold til loven er forpliktet til å bidra med å fremskaffe bolig til vanskeligstilte personer. Mange har også pådratt seg store husleierestanser, og fått strømmen avstengt ved flere anledninger. Dette er en utfordrende gruppe å jobbe med, og en opplever ikke å komme i posisjon i forhold til å få dem til å ta imot hjelp. Ved tildeling av kommunale boliger er det ikke lov til å stille vilkår om at de skal ta imot for eksempel hjemmetjenester, en kan bare oppfordre dem til å gjøre det. Mange i denne gruppen er inkludert i LAR (legemiddelassistert rehabilitering), men mange har et stort sidemisbruk og er i aktiv rus. Deres situasjon er derfor preget av ustabilitet (både i forhold til rus, men også psykisk helse, f.eks. gjentatte rusutløste psykoser), kaos, dårlig økonomi, kriminalitet og uverdige boforhold preget av forsøpling, bråk/uro/naboklager og rot. Vi som jobber i det offentlige hjelpeapparatet føler oss ofte maktesløse i forhold til å hjelpe denne gruppen, og jeg har ofte lurt på hva som skal til for å komme i posisjon og gjøre bosituasjonen bedre for personer med omfattende rusproblemer og/eller psykiske lidelser. Gjennom deltakelse på diverse konferanser/seminarer, artikler i aviser/fagtidsskrifter og kontakt med andre kommuner har vi stadig hørt om vellykkede boligsosiale prosjekter, og sist var det Housing First-prosjekter (også kalt HF) som vekket min interesse. Dette er en tilnærming/modell grunnlagt i USA for bostedsløse med alvorlig psykisk lidelse og/eller rusproblemer. Etter hvert som jeg leste om denne modellen ble jeg klar over at Housing First-programmet i Lisboa høster anerkjennelse rundt omkring i verden, de er også konsulenter for norske Housing First-prosjekter. Jeg kontaktet organisasjonen AEIPS i Lisboa som driver dette programmet (Casas Primerio heter det der), og spurte om jeg fikk gjennomføre min praksisperiode hos dem, og var så heldig at jeg fikk lov til det. Jeg var hos AEIPS i nesten syv uker høsten 2015, og ble mektig imponert over hva de får til ovenfor denne gruppen, der mange har alvorlig psykisk lidelse som for eksempel schizofreni i tillegg til rusproblematikk, spesielt med tanke på at Portugal fremdeles sliter etter finanskrisen, har stor arbeidsledighet og ikke i nærheten av vårt norske velferdssystem. 1.1 Problemstilling og avgrensning Etter å ha vært i praksis i Lisboa begynte jeg å tenke «hva kan vi lære av dette? Er denne innsikten og erfaringen noe jeg kan dra nytte av i min egen jobb?», og «er det mulig å overføre dette til en norsk kontekst, spesielt i en liten kommune?». Jeg vil derfor i denne oppgaven undersøke om det er mulig å bruke denne kunnskapen og erfaringen i min egen jobb. Jeg kom etter dette frem til følgende problemstilling: Hvordan kan bruk av prinsippene i Housing First-modellen bedre den boligsosiale oppfølgingen av personer med omfattende rusproblemer og/eller psykiske lidelser i norske kommuner? Dette har jeg forsøkt å svare på i oppgaven, og jeg har valgt å avgrense meg til å ta for meg hovedprinsippene i Housing First-modellen

Study of intragastric structuring ability of sodium alginate based o/w emulsions under in vitro physiological pre-absorptive digestion conditions

In the present work, the intragastric structuring ability of o/w emulsions either stabilised (1–4%, w/w of sodium alginate (SA)) or structured with sheared ionic gel (1–3%, w/w of SA crosslinked with Ca2+) in the absence (saliva and gastric phases constituted of deionised water) or presence of in vitro pre-absorptive conditions (physiological simulated saliva and gastric fluids) was investigated. Visualisation of the morphological aspects of the gastric chymes, in the absence of multivalent counterions, demonstrated that SA stabilised systems underwent a remarkable swelling in the pH range of 2–3, whilst at the same pH range, ionic SA gel structured systems maintained their major structure configuration. When the aforementioned systems were exposed to physiological intragastric fluids, a reduction of the length and the hydrodynamic volume of the alginate fibres was detected regardless the structuring approach. On their exposure to physiological intragastric conditions (pH = 2), SA stabilised emulsions underwent sol–gel transition achieving a ca. 3- to 4-order increase of storage modulus (at 1 Hz). In the case of ionic sheared gel structured emulsions, exposure to physiological intragastric fluids resulted in a 10-fold reduction ability of their acid structuring ability, most likely due to the dialysis of egg-box dimer conformations by monovalent cations and protons and the sterical hindering of hydrogen bonding of MM and GG sequences under acidic conditions. Using of non-physiological simulated intragastric fluids was associated with overestimated structuring performance of SA regardless its physical state

Daily ingestion of alginate reduces energy intake in free-living subjects

Sodium alginate is a seaweed-derived fibre that has previously been shown to moderate appetite in models of acute feeding. The mechanisms underlying this effect may include slowed gastric clearance and attenuated uptake from the small intestine. In order to assess whether alginate could be effective as a means of appetite control in free-living adults, 68 males and females (BMI range: 18.50-32.81 kgl M-2) completed this randomised, controlled two-way crossover intervention to compare the effects of 7 day daily ingestion of a strong-gelling sodium alginate formulation against a control. A sodium alginate with a high-guluronate content was chosen because, upon ingestion, it forms a strong gel in the presence of calcium ions. Daily preprandial ingestion of the sodium alginate formulation produced a significant 134.8 kcal (7%) reduction in mean daily energy intake. This reduced energy intake was underwritten by significant reductions in mean daily carbohydrate, sugar, fat, saturated fat and protein intakes. The absence of any significant interaction effects between the main effect of preload type and those of gender, BMI classification and/or timing of preload delivery indicates the efficacy of this treatment for individuals in different settings. These findings suggest a possible role for a strong-gelling sodium alginate formulation in the future management of overweight and obesity. (C) 2008 Elsevier Ltd. All rights reserved

Alginate Blocks and Block Polysaccharides: A Review

AbstractAlginates consist of distinct blocks with different physical properties. This short review focuses on research carried out in Trondheim related to the early discovery of the block structure, their isolation, their different chemical and physical properties, and how they recently are utilized in diblock polysaccharides to obtain new nanostructuring properties

Intragastric structuring of anionic polysaccharide kappa-carrageenan filled gels under physiological in vitro digestion conditions

In the present work, sodium alginate (SA), low methoxyl pectin (PEC) and κ-carrageenan (κ-CAR) were evaluated for their intragastric structuring ability by means of light microscopy and dynamic oscillatory rheology. SA and PEC solutions, their Ca2+ complexed gel analogues as well as their binary blends with ionically or thermally set sheared κ-CAR gels, were subjected to in vitro orogastric conditions. SA and PEC – Ca2+ complexed sheared gels exerted the highest vulnerability to digestive fluid exposure due to the dialysis of egg-box dimer structures via proton-calcium exchange. Incorporation of SA and PEC systems to κ-CAR gels prevented the loss of mechanical strength of the gastric gels due to the ability of κ-CAR to undergo spontaneous gelation in the presence of Na+ and K+ ions. Binary blends of SA and PEC – Ca2+ complexed sheared gels with κ-CAR-Ca2+ gels exerted a significantly lower mechanical strength loss sensitivity against pH and counterion composition of the gastric fluids

Development of gelatin-alginate hydrogels for burn wound treatment

Hydrogels are interesting as wound dressing for burn wounds to maintain a moist environment. Especially gelatin and alginate based wound dressings show strong potential. Both polymers are modified by introducing photocrosslinkable functionalities and combined to hydrogel films (gel-MA/alg-MA). In one protocol gel-MA films are incubated in alg-MA solutions and crosslinked afterward into double networks. Another protocol involves blending both and subsequent photocrosslinking. The introduction of alginate into the gelatin matrix results in phase separation with polysaccharide microdomains in a protein matrix. Addition of alg(-MA) to gel-MA leads to an increased swelling compared to 100% gelatin and similar to the commercial Aquacel Ag dressing. In vitro tests show better cell adhesion for films which have a lower alginate content and also have superior mechanical properties. The hydrogel dressings exhibit good biocompatibility with adaptable cell attachment properties. An adequate gelatin-alginate ratio should allow application of the materials as wound dressings for several days without tissue ingrowth

Maintaining dimensions and mechanical properties of ionically crosslinked alginate hydrogel scaffolds in vitro

Ionically crosslinked alginate hydrogels are attractive scaffolds because of their biocompatibility and mild gelation reaction that allows for gentle cell incorporation. However, the instability of ionically crosslinked hydrogels in an aqueous environment is a challenge that limits their application. This report presents a novel method to control the dimensions and mechanical properties of ionically crosslinked hydrogels via control of the ionic concentration of the medium. Homogeneous calcium-alginate gels were incubated in physiological saline baths adjusted to specific calcium ion concentrations. Swelling and shrinking occurred at low and high ionic concentrations of the medium, respectively, while an “optimal” intermediate calcium ion concentration of the medium was found to maintain original size and shape of the hydrogel. This optimal calcium ion concentration was found to be a function of crosslinking density and polymer concentration of the hydrogel and chemical composition of the alginate. The effects of optimal and high calcium ion concentrations of the medium on swelling behavior, calcium content, dry weight, and mechanical properties of the immersed hydrogels were investigated. It was found that the resulting hydrogel composition and mechanical properties depended on not only the calcium concentration of the medium, but also the crosslinking density and polymer concentration of the gel. In an 8-week experiment, controlled dimensions and mechanical properties of alginate gels in an aqueous environment were demonstrated. This new technique significantly enhances the potential of alginate hydrogels for tissue engineering and other biomedical applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58038/1/31375_ftp.pd