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Efeito de diferentes concentrações de quitosana na dieta de novilhos Nelore / Effect of different levels of chitosan in Nellore steers dietAraújo, Ana Paula Chaves de 15 December 2011 (has links)
O objetivo do presente trabalho foi avaliar os efeitos de diferentes concentrações de quitosana nas dietas de novilhos Nelore canulados no rúmen sobre o consumo e digestibilidade aparente total da matéria seca e nutrientes, fermentação e síntese de proteína microbiana ruminal, concentrações de parâmetros sangüíneos, e os balanços de energia e de nitrogênio. Foram utilizados 8 novilhos canulados da raça Nelore. Os animais foram distribuídos aleatoriamente em 2 quadrados latinos 4 x 4 balanceados e contemporâneos, para receber as seguintes rações experimentais: 1) Controle (Q0), composta por ração sem a inclusão de quitosana; 2) Q50, com a inclusão de 50 mg/kg de peso corporal de quitosana; 3) Q100, com a inclusão de 100 mg/kg de peso corporal de quitosana; e 4) Q150, com a inclusão de 150 mg/kg de peso corporal de quitosana. Diariamente foram realizadas pesagens das quantidades dos volumosos e concentrados fornecidos e das sobras de cada animal, para estimativa do consumo. As amostras de sobras, silagem e fezes foram coletadas do 15° ao 18° dias de cada período experimental, armazenadas em sacos plásticos em freezer à 20°C, e posteriormente submetidas a análises químico-bromatológicas dos principais nutrientes. Na determinação da digestibilidade aparente total dos nutrientes a quantidade total de matéria seca fecal excretada foi estimada pela concentração de fibra em detergente ácido indigestível (FDAi). As amostras de líquido ruminal foram coletadas no último dia de cada período, sendo uma coleta realizada antes da alimentação (0 hora), e seis coletas com intervalos de 2 horas após a alimentação (2, 4, 6, 8, 10 e 12 horas). Foram determinados no líquido ruminal o pH, as concentrações de nitrogênio amoniacal e as concentrações dos ácidos graxos de cadeia curta. As amostras spot de urina foram obtidas de no 16º dia de cada período experimental, quatro horas após a alimentação matinal, durante micção espontânea. As amostras de sangue foram coletadas em tubos vacuolizados (vacutainer) por punção da veia jugular. Houve efeito quadrático com menores valores sobre o consumo de FDN, expressos em kg/dia e porcentagem de peso vivo (PV) para o tratamento Q150 (P<0,05). A inclusão de quitosana na dieta proporcionou aumento linear crescente (P<0,05) da digestibilidade da matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), carboidratos totais (CT), FDN e nutrientes digestíveis totais (NDT). Houve efeito quadrático (P<0,05) sobre a concentração de N-NH3 com redução no tratamento Q150. A inclusão de quitosana na dieta não causou diferenças nas concentrações totais de AGCC (P>0,05), porém alterou as proporções molares de AGCC individualmente. Houve efeito linear crescente (P>0,05) das concentrações e porcentagens molares de propionato (mmol/L) à medida que se elevou as concentrações de quitosana na dieta. Houve diminuição (P>0,05) da relação acetato: propionato, principalmente para o tratamento Q150. Foi observado efeito linear decrescente para as proporções molares de acetato e butirato com a inclusão de quitosana. Houve efeito linear crescente sobre as concentrações plasmáticas de glicose com os tratamentos. As concentrações de quitosana utilizadas não influenciaram a síntese de proteína microbiana. O balanço de energia não foi influenciado pelos tratamentos. Não houve efeito dos tratamentos sobre o balanço de nitrogênio, porém ocorreu decréscimo na excreção do nitrogênio total (NT) nas fezes em porcentagem de NT. A quitosana quando utilizada como aditivo modulador da fermentação ruminal, resultou em alterações que possibilitam sua utilização como alternativa ao uso de ionóforos para bovinos. / The aim of this study was to evaluate the effect of different levels of chitosan on intake, digestibility, ruminal fermentation, ruminal microbial protein, balance of energy and nitrogen and blood parameters. Eight Nellore steers cannulated in the rumen were divided into two 4 x 4 balanced Latin squares. The daily doses of chitosan were 0, 50, 100 and 150 mg/kg BW respectively the treatments Q0 (Control), Q50, Q100 and Q150. The diets consisted of corn silage and concentrate in ratio 60:40 and the chitosan were inserted directly through the ruminal cannula, twice a day before feeding. Daily weights of the amounts of corn silage and concentrated supplied, and the orts refused of each animal, were recorded for estimate the nutrient intake. Samples of orts and feedstuffs were analyzed for composition and subsequent nutrient intake calculation. For determination of total apparent digestibility of nutrients, the total amount of fecal dry matter excreted was estimate by indigestible detergent acid fiber (ADFi). The feces were collected in the 15th until the 18th day of each experimental period, and frozen in freezer at -20°C. In the end of the collection period it was made composed sample by animal with base in the dry matter, and analyzed. Samples of ruminal fluid were collected at 0 (before feeding) and 2, 4, 6, 8, 10 and 12 hours after feeding. Spot urine samples were collected on day 16 of the experimental period. The estimation of microbial protein synthesis was performed by the method of total excretion of purine derivatives. Blood samples were collected by puncture of jugular vein. Intakes (kg/d) of DM, OM, CP, ether extract , total carbohydrates , non-fiber carbohydrates and TDN were not different, however, NDF intake decresead quadratically (P<0,05) when expressed as kg/d and percent of BW. Digestibility in the total digestive tract increased linearly to NDF, DM, OM as well as improved the digestibility of CP and TC, accordingly there was a positive effect on TDN with the inclusion of chitosan. All the ruminal fermentation parameters were influenced by the time after feeding. The NH3-N concentration decreased quadractically with Q150 treatment and there were no difference in total VFA concentration, however the individual VFA proportions were affected. Propionate concentration was higher with Q150 and similarly increasing linearly the proportion of propionate (P<0,05) which means an increase of 7.47% (Q0 vs. Q150). Chitosan decreased linearly the molar proportion of acetate and butyrate .Was observed linear and quadratic decrease effect on acetate: propionate ratio. The plasmatic metabolites and enzymes had no effect by the treatments, nevertheless the glucose concentration was markedly superior with the supplementation corresponding to an increase of 18.58%, 26.35%, 23.68% for Q0 versus Q50, Q100 e Q150 respectively. The energy and nitrogen balance had no effect with the treatments, however there was a decrease of fecal total nitrogen (%) excretion. Chitosan when used as modulator of ruminal fermentation resulted in changes that allow its use as an alternative to the use of ionophores for cattle without showing damage to the health of the animal.
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Co-delivery of cationic polymers and adenovirus in immunotherapy of prostate cancerGraham, Jessica Beth 01 May 2010 (has links)
Prostate cancer is the most common non-skin cancer in America, and the most commonly diagnosed cancer among males. When metastatic, the disease can ultimately be incurable. Consequently, alternative strategies to current treatments are sought, especially in the area of immunotherapy. Vaccine immunotherapy using a specific antigen, such as prostate specific antigen (PSA) seeks to stimulate both the innate and adaptive immune system to destroy tumor cells in the body. PSA is an ideal target antigen given that it has a narrow distribution in tissues and is expressed in virtually all prostate cancer cases. An adenovirus encoding for PSA (Ad-PSA) can be used to deliver the genomic data encoding for PSA production and secretion to the target cell. This type of viral gene delivery system has already been shown to have the potential to stimulate anti-tumor activity.
To enhance this activity and increase transfection efficiency, we proposed the combination of a viral system with a non-viral system, in the form of a cationic polymer such as poly(ethyl)enimine (PEI) or chitosan. Cationic polymers complex with the negatively charged adenovirus to form nanoparticles that can be used in gene delivery. Delivery in nanoparticle form can give enhanced uptake by the antigen-presenting cells necessary to initiate the targeted immune response. To further augment this response, previous research has shown that CpG sequences act as an adjuvant to enhance the efficacy of the Ad-PSA vaccines' tumor protection. CpG delivered in particulate form has also been shown to be more effective than delivery in solution. The objective of this proposal was to test the hypothesis that co-delivery of this targeted viral/non-viral gene delivery system will enhance tumor protection in a mouse model of prostate cancer.
Using the OVA model antigen system, we found that the adenovirus encoding OVA (AdOVA), coupled with the polymer PEI, enhanced tumor protection in vivo compared to AdOVA alone. To move towards our therapeutic model, these experiments were repeated using chitosan as the cationic polymer carrier, delivering AdOVA, and incorporating CpG into some particles. In this set of experiments, we found that AdOVA + CpG gave the best tumor protection in challenge studies. AdOVA + chitosan + CpG showed a decrease in protective levels and numbers of antigen-specific immune cells.
Further experiments focused on elucidating the mechanisms by which chitosan and CpG modulate the immune response. Using the therapeutic AdPSA model, chitosan was not found to enhance tumor protection or numbers of antigen-specific immune cells. Additional experiments found that this depression was not due to problems with viral infectivity or secretion due to chitosan complexation. A series of kinetics studies were performed which showed that peak levels of effector T cells were present 14 days later in AdPSA + CpG immunized mice than in AdPSA alone. This delayed effect may explain the increased levels of protection in AdPSA + CpG mice, and be useful in future vaccine design concerning the timing of peak response.
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Chitosan and improved pigment ink jet printing on textilesMomin, Nasar, nasarhm@gmail.com January 2008 (has links)
The purpose of this research was to explore two ways of the application of chitosan, a biopolymer, for ink jet printing of textiles. 1) To apply chitosan as a post-treatment on the fabric ink jet printed with pigment based inks for the fixation of pigments on the fabric. 2) To incorporate chitosan as a binder in pigment based ink jet ink formulations. The incorporation of chitosan was carried out in two ways. 1) Direct addition of chitosan into the ink formulations containing surface modified pigments. 2) Preparation of chitosan encapsulated pigment nanoparticles using complex coacervation technique and using these nanoparticles for the formulation of ink jet ink. The degree of deacetylation (DD) was determined using FTIR spectroscopy. Various protocols proposed by researchers were used to determine the DD of chitosan samples used in the present study. The protocol proposed by Raut was found to be fairly accurate in determining the DD of chitosan samples. The molecular weight of chitosan was estimated using dilute solution viscometry method. The characterisation of the film forming ability of chitosan was evaluated using scanning electron microscopy (SEM). The colour strength (K/S), colour difference, colour characteristics and colour fastness to laundering and rubbing of ink jet printed fabrics post treated with chitosan were evaluated using standard methods. Post-treatment (pad-dry-cure method) of cotton fabric ink jet printed with pigment based inks revealed that chitosan could effectively fix the pigments on cotton compared to the commercial textile binders and the water-soluble derivative of chitosan. The chemical interaction between chitosan and cotton fabric was illustrated by FTIR-ATR analysis and through determination of carboxyl group content. The ink jet printed cotton fabric post treated with 3gpl chitosan (MW 156,156) maintained almost 86% of bacterial reduction against Klebsiella Pneumoniae even after 50 launderings. Inks containing chitosan were formulated and were found to be stable in terms of mean particle size and viscosity over a period of one month and for 4 freeze/thaw cycles. A magenta ink containing chitosan was selected for ink jet printing of cotton fabric. It was found that the DF was around 97% for magenta ink containing chitosan compared to around 53% fixation for magenta ink without chitosan on cotton fabric. Surface modified carbon black pigment with carboxylated (COO-) surface functionality was selected to prepare chitosan encapsulated pigment nanoparticles by complex coacervation technique. Chitosan encapsulated pigment nanoparticles with mean particle size diameter of 876 nm and 742 nm were formed when 5 ml of 0.1% w/v pigment was mixed with 2ml and 3ml of 0.1% w/v chitosan, respectively. However, no correlation was found between the particle size of the nanoparticles formed and the concentration of chitosan. The DF with ink containing chitosan encapsulated pigment nanoparticles was found to be around 98% while the blank ink with only surface modified carbon black pigment showed 44% fixation.
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Investigation of film forming properties of β-chitosan from jumbo squid pens (Dosidicus gigas) and improvement of water solubility of β-chitosan / Investigation of film forming properties of beta-chitosan from jumbo squid pens (Dosidicus gigas) and improvement of water solubility of beta-chitosanChen, Jeremy L. 27 April 2012 (has links)
The objectives of this project were to investigate the critical factors impacting the physicochemical and antibacterial properties of β-chitosan based films derived from jumbo squid (Dosidicus gigas) pens, and to evaluate the feasibility of improving water solubility of β-chitosan through Maillard reaction. The studies examined the effect of molecular weight (1,815 and 366 kDa), acid (formic, acetic, propionic, and lactic acid), and plasticizer (glycerol and sorbitol) on the film properties, as well as reducing sugar (fructose and glucosamine) and heat treatment (high temperature short time (HTST), low temperature long time (LTLT)) on water solubility of chitosan. Results on β-chitosan were compared with α-chitosan in both studies.
Tensile strength (TS) and elongation (EL) of β-chitosan films were influenced by molecular weight (Mw), acid and plasticizer types (P < 0.05). High molecular weight (Hw) β-chitosan films had an overall TS of 44 MPa, 53% higher than that of low
molecular weight (Lw) β-chitosan films (29 MPa) across all acid types used. The mean TS of β-chitosan acetate and propionate films (43 and 39 MPa) were higher (P < 0.05) than that of β-chitosan formate and lactate films (34 and 29 MPa). Films incorporated with plasticizer (32 MPa) had lower TS than those without plasticizer (48 MPa). Mean EL of Hw β-chitosan films was 10% versus approximately 4% in Lw β-chitosan films. Formate and acetate films had higher EL than that of propionate film. Glycerol and sorbitol increased (P < 0.001) EL 151% and 106% compared with the films without plasticizer, respectively. Water vapor permeability (WVP) of the films was affected by acid and plasticizer. Formate films (34 g mm/m² d KPa) had higher WVP than other acid films. Adding plasticizer increased (11% to 31%) WVP of propionate films except the Lw β-chitosan propionate film with sorbitol. The antibacterial activity of Lw β-chitosan and α-chitosan films delayed (P < 0.05) the proliferation of E. coli, where lactate films showed the strongest effect. The growth of L. innocua at 24 h was completely (P < 0.05) inhibited by chitosan films except Hw β-chitosan acetate film.
A soft and cotton-like water soluble chitosan with mesopores was acquired after freeze-drying the Maillard reacted chitosan-sugar solution. The yield of β-chitosan-derivatives (8.48%) was 1.21 times higher than that of α-chitosan products (7.00%) (P < 0.01). Heat treatment only affected the yield of chitosan-glucosamine derivatives. Sugar type did not indicate any impact on the yield of the chitosan-derivative products in general (P > 0.05). The solubility was affected by sugar type (P < 0.01) only occurred in the β-chitosan products prepared with LTLT (P<0.05), where β-chitosan-fructose derivatives (9.56 g/L) had higher solubility than the glucosamine (5.19 g/L).LTLT
treatment had given all chitosan-derivatives a higher solubility (8.44 g/L) than HTST (3.83 g/L) did (P<0.001).
The results from this study demonstrated the feasibility of creating β-chitosan based film from jumbo squid pens with similar mechanical, water barrier and antibacterial properties compare to α-chitosan films as a food wrap and controlled the properties with several important factors, and developing water soluble chitosan through Maillard reaction that possess the potential as functional substance in a wider range of applications. / Graduation date: 2012
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Physical Characteristics and Metal Binding Applications of Chitosan FilmsJones, Joshua B 01 August 2010 (has links)
Chitosan films are an excellent media for binding metal ions due to the electrostatic nature of the chitosan molecules. Addition of cross-linking or plasticizing agents alters texture of the films, but their effect on metal-binding capacity has not been fully characterized. The objective of this research was to determine effects of plasticizers and cross-linkers on physical and metal-binding properties of chitosan films and coatings prepared by casting and by spincoating. Chitosan films were prepared using 1% w/w chitosan in 1% acetic acid with or without (control) additives. Plasticizing agents were tetraethylene glycol (TEG) and glycerol while citric acid, ethylenediamine tetraacetic acid (EDTA), and tetraethylene glycol diacrylate (TEGDA) were used as cross-linkers. The additives were applied in concentrations of 0.10%, 0.25%, and 0.50% w/w of film-forming solution. The films were prepared by casting and by spincoating. Films were cast at ambient conditions for tests within one week (fresh films) and eight weeks (aged) after casting. The cast films were evaluated for thickness, residual moisture (by the Karl Fischer method), Cr(VI) binding capacity, puncture strength, and puncture deformation while the chitosan coatings were tested for thickness, Cr(VI) binding capacity, solubility in aqueous solution, and surface morphology (using atomic force microscopy). Cast films with cross-linkers showed an increase in resistance to puncture while plasticized films become more elastomeric. Control films bound 97.2% Cr(VI) ions from solution (0.56 mg Cr(VI)/g film), and addition of plasticizers did not affect chromium binding, tying up to 96.7% Cr(VI) ions from solution (0.56 mg Cr(VI)/g film). Films containing cross-linkers yielded binding capabilities ranging from 42.3% to 94.3% bound Cr(VI) ions (0.26-0.52 mg Cr(VI)/g film). Ultrathin coatings also possess the ability to bind Cr(VI) from solution, though only a maximum of 7.4% of Cr(VI) ions could be bound from solution, the thin films had the ability to bind up to 224 mg Cr(VI)/g ultrathin film. These coatings use less chitosan, but they display greater binding per mass. Overall, plasticizers do not alter, while cross-linkers may reduce, the binding capacity of chitosan films, but physical properties of the films can be controlled by inclusion of additives.
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Depolymerization of Chitosan by High-Pressure Homogenization and the Effect on Antimicrobial PropertiesLyons, Deidra Shannon 01 August 2011 (has links)
The focus of this study was to look at relationship between polydispersity caused by high pressure homogenization and molecular weight dependent antimicrobial activity of chitosan. It has been shown that chitosan has antimicrobial activity against bacteria, fungi, and viruses. Chitosan is obtained by partial de-N-acetylation of chitin which, consists of a ß 1-4 copolymer of glucosamine and N-acetylglucosamine residues. In this experiment we compared chitosan of sixteen different molecular weights after being processed through a high pressure homogenizer. Processed chitosan (420 kDa average molecular weight, 30% of acetylation) was dissolved in a 1% (v/v) acetic acid in water to a final concentration of 1% (w/v) and apparent viscosity of 183 MPa. The chitosan solution was passed through a high pressure homogenizer with 0-5 passes at pressure levels 0, 100, 200, and 300 MPa. After processing, the chitosan acetate was investigated to determine the effect on polydispersity in terms of molecular weight and the antimicrobial properties of chitosan at different molecular weights. All compounds were tested against Escherichia coli K-12 to determine antimicrobial activity. There is growing interest in the application of chitosan in food industry due to its wide range of desirable properties including being non-toxic and biodegradability. However, as a hydrophobic material, it is very challenging to work with. Though chitosan is a challenge to work my findings indicated a strong antimicrobial relationship with chitosan at 1% concentration with a molecular weight of 200 kDa and lower against E. coli. In conclusion chitosan has viable application with a variety of foods and can be used as a preservative that decrease bacterial activity below detection level’s and helps to prolong shelf-stable products.
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Growth of phytopathogenic fungi in the presence of partially acetylated chitooligosaccharidesOliveira Jr, E. N., Gueddari, Nour E. El, Moerschbacher, Bruno M., Peter, Martin, Franco, Telma January 2008 (has links)
Four phytopathogenic fungi were cultivated up to six days in media containing chitooligosaccharide mixtures differing in average DP and FA. The three different mixtures were named Q3 (which contained oligosaccharides ofDP2–DP10, withDP2–DP7 asmain components), Q2 (which contained oligosaccharides of DP2–DP12, with DP2–DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5–DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixtures of oligosaccharides with different and known composition on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concentrations. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concentrations of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, respectively.
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Films and composites based on chitosan, wheat gluten or whey proteins -Their packaging related mechanical and barrier propertiesGällstedt, Mikael January 2004 (has links)
No description available.
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Analysis and entrapment of select antioxidants from chokecherry and Saskatoon berry fruitsKonecsni, Kelly Alyson 03 June 2011
The major objectives of this research were to produce a phenolic rich isolate from two locally grown Saskatchewan fruits, chokecherries and saskatoons, develop an encapsulation system for the phenolic isolate, and test this system for the delivery of the phenolic isolate in an animal (rat) model.
Natural phenolic compounds present in plants such as fruits have antioxidant and free radical scavenging activities, which have been proposed to have health benefits. The extraction of these compounds from plants is commonly performed using methanol despite being toxic to both humans and animals. As such, ethanol was investigated for its ability to extract phenolics from plants as a food safe alternative to methanol. Phenolic extraction from chokecherries with ethanol:formic acid:water (EFW) resulted in higher concentrations (9.83 mg gallic acid equivalents (GAE)/g fresh weight) than with methanol:formic acid:water (MFW) (7.97 mg GAE/g fresh weight). Results from saskatoons showed similar phenolic levels of 4.26 and 4.21 mg GAE/g fresh weight with MFW and ethanol (EFW), respectively. These results showed that EFW was a suitable substitute for MFW in phenolic compound isolation from chokecherries and saskatoons, and could be used to produce extracts that were safe for use in foods and feeds.
High performance liquid chromatography with photodiode array detection (HPLC-PDA) was used to determine the phenolic compound composition of the raw fruits and their phenolic rich isolates. Chlorogenic acid was identified in both chokecherry and saskatoon samples, and rutin was also shown to be present in saskatoons. These identifications were based on the relative retention time and ultra violet-visual spectra comparisons to standards. Solid phase extraction (SPE) using Amberlite XAD-16 was employed to produce phenolic isolates from chokecherries and saskatoons. HPLC-PDA results determined that there was a ~2.7x and ~1.6x increase in peak area for chokecherries and saskatoons, respectively when SPE was employed. The antioxidant activity of the extracts and isolates was determined using in vitro radical scavenging tests including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2´-azinobis-3-ethylbenzthiazoline-sulphonic acid (ABTS). The EFW chokecherry extract and isolate had the highest overall free radical scavenging activity. Crude fruit extracts exhibited lower free radical scavenging values compared to the isolate samples in both of the assays performed.
The fruit phenolic isolates were encapsulated in chitosan (CH) sodium tripolyphosphate (TPP) nanoparticles at a ratio of 4.0:1.0 (CH:TPP). HPLC-PDA was used to determine the entrapment efficiency of phenolic isolates to be 15.9 ± 2.7% and 23.0 ± 7.1% for chokecherries and saskatoons, respectively. Characteristics such as the size, surface potential and phenolic release were determined for the two fruit isolate containing nanoparticles. The size of the nanoparticles were 527.90 ± 74.57 nm and 443.03 ± 15.79 nm for chokecherries and saskatoons, respectively. Both of the nanoparticle systems had positive surface charges at 52.70 ± 2.93 mV and 54.43 ± 1.27 mV for chokecherries and saskatoons, respectively. The release properties of the CH:TPP nanoparticles containing fruit phenolics were examined in enzymatic simulated intestinal fluid and resulted in ~23% and ~28% release of chokecherry and saskatoon phenolics, respectively.
Saskatoon phenolic isolates and isolates encapsulated in CH:TPP were gavage fed to rats (six animals in each of the two groups) at a dosage rate of 276.36 ± 9.74 mg/kg body weight. The saskatoon isolate contained 12.44 ± 0.44 mg/kg body weight anthocyanins (~3.30 mg anthocyanin per rat). These animals were sacrificed after 1 h and all stomach tissue samples in each of the treatment groups contained detectable levels of anthocyanins. In the small intestine tissues all six of the saskatoon isolate and three of the encapsulated isolate groups had detectable amounts of anthocyanins, while in the large intestine tissue, only one sample from the isolate group showed detectable amounts of anthocyanins. Although other tissues were tested (brain, heart, kidney and liver), anthocyanins were not detected. Therefore anthocyanins were detected in the gastrointestinal tract of both of the treatment groups.
The research performed therefore illustrated that phenolic compounds can be extracted from fruit sources using EFW and can be successfully encapsulated in chitosan tripolyphosphate capsules allowing for targeted delivery in an animal model.
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Chitosan-Sericin Blend Membranes for Controlled Release of DrugsEslami, Shahabedin 22 December 2011 (has links)
The peak and valley problems caused by oral administration, injection or other conventional methods, call for developing systems that can deliver therapeutics more effectively. As one of the techniques, diffusion-controlled drug release membranes have significant interest due to great ease with which they can be designed to achieve near-zeroth-order release kinetics. Since diffusion is the rate-limiting step in these systems, determining the permeability and diffusivity of drug molecules in the membrane is therefore important in evaluating drug release performance.
This study focuses on the Membrane Permeation Controlled Release (MPC) system, which involves a non-porous (dense) membrane, comprising of two biopolymers, sericin and chitosan. Ciprofloxacin hydrochloride and (+)-cis-diltiazem hydrochloride were used as hydrophilic model drugs, and nitro-2-furaldehyde semicarbazone (Nitrofurazon) was used as a hydrophobic model drug. Permeation experiments were carried out in a semi-infinite reservoir/receptor system to simulate in-vitro drug release.
The intrinsic permeability and diffusivity (P, D) of the drugs through the membranes were determined using a modified time-lag method based on short time permeation and mass balance method based on long time permeation. The partition coefficients Kd of the drugs in the membranes and the swelling degree of the membranes were determined by sorption/desorption experiments. The diffusivities of the drugs were also determined from the sorption/desorption kinetics. Over the experimental ranges tested, the drug concentration and membrane cross-linking did not have significant effects on these parameters presumably due to the relatively low drug concentrations and mild crosslinkings of the membranes. The diffusivity coefficients of ciprofloxacin hydrochloride, (+)-cis-diltiazem hydrochloride and nitrofurazon in the membranes were found to be in the range of (2.0-2.6)×〖10〗^(-9)±2.6×〖10〗^(-10) cm2/s, (2.5-2.6) ×〖10〗^(-9)±1.1×〖10〗^(-10) and (38-134) ×〖10〗^(-9)±33.1×〖10〗^(-9) (cm2/s), respectively, and their permeability coefficients were in the range of (24-29)×〖10〗^(-8),(51-52) ×〖10〗^(-8) and (131-169) ×〖10〗^(-8) (cm2/s), respectively. The partition coefficients were determined to be around 0.91±0.21, 25±0.12 and 26±0.31, respectively. The diffusivity coefficients determined from sorption experiments for ciprofloxacin hydrochloride, diltiazem hydrochloride and nitrofurazon were found to be in the range of (3.2-7.6) ×〖10〗^(-9)±6.3×〖10〗^(-8), (6-10) ×〖10〗^(-9)±2.6×〖10〗^(-8) and (15-18) ×〖10〗^(-9)±2.7×〖10〗^(-7) (cm2/s), respectively. Also the diffusivity coefficients determined from sorption experiments for ciprofloxacin hydrochloride, diltiazem hydrochloride and nitrofurazon were in the range of (20-47) ×〖10〗^(-9), (12-24) ×〖10〗^(-9) and (11-20) ×〖10〗^(-9) (cm2/s), respectively. Nonetheless the differences in the diffusivities calculated from permeation and sorption/desorption experiments are considered to be acceptable, in view of the different experimental techniques used in this work, for the purpose of comparison of the membrane diffusivity and permeability.
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