Children born with congenital heart valve defects require open-heart surgery to implant an artificial replacement valve. These valves are unable to grow with the developing child and need replacing every 5 years. Tissue engineered heart valves, capable of growing with the patient, would alleviate the need for repeat surgery. I hypothesize chitosan and collagen possess advantageous qualities as scaffolding for a tissue engineered heart valve. This study evaluated chitosan and collagen hydrogels as potential scaffold materials. Chitosan scaffolds had suitable pore size/distribution and scaffold strength; however, they were unable to sustain cell attachment or viability. Collagen gels were assessed for compaction, mechanical properties and expression of matrix metalloproteases in the presence or absence of biochemical and mechanical stimuli. Pressure increased the remodeling potential. This was augmented further in the presence of TGF-β. In conclusion, both materials have potential as scaffolding substrate in a tissue engineered heart valve.

No description available.

Foram realizados estudos buscando otimizar as condições reacionais para obtenção de um sal (QN) de naproxeno (NAP) e o biopolímero quitosana (QP). Essa matriz (QN) foi utilizada para o estudo do equilíbrio de dissociação do anti-inflamatório. Para tanto, foram estudadas as melhores condições em relação aos parâmetros tempo reacional, temperatura de reação e razão molar dos reagentes. Os produtos foram caracterizados por ressonância magnética nuclear de hidrogênio e carbono 13, 1H e 13C RMN, espectroscopia vibracional na região do infravermelho com transformada de Fourier, FTIR, espectroscopia eletrônica na região do ultravioleta-visível na modalidade reflectância difusa, UV-vis, difração de raios X (DRX) e técnicas termoanalíticas: termogravimetria (TG), análise térmica diferencial (DTA) e calorimetria exploratória diferencial (DSC). Além disso, estudou-se a evolução dos gases por termogravimetria acoplada a espectroscopia vibracional na região do infravermelho (TG-FTIR). Verificou-se que o maior rendimento de sal foi obtido nas seguintes condições reacionais: 24 horas, temperatura de 60°C e razão molar de 1 mol de QP para 1,05 mol de NAP. Este produto de reação foi chamado de QN1. Neste caso, quando calculado o grau de substituição (GS) por meio da técnica de RMN 13C, observou-se um GS de 19,1 %, sugerindo uma neutralização do grupo NH2 ligado ao C2 do biopolímero com o grupo COOH presente no fármaco. Nos espectros de FTIR foram observadas bandas que correspondem a formação de um produto diferente de QP e NAP, corroborando com a hipóstese de formação do sal QN1. No espectro do UV-vis notou-se as três bandas referentes à absorção dos grupos cromóforos pressentes no sal. Nos difratogramas, verificou-se um pico na região de ~22Ø em QN1, sendo esse já observado como um ombro em QP, porém houve um incremento, além disso, alterações no índice de cristalinidade da quitosana, sugeriram modificações na sua estrutura semicristalina após reação com o NAP. As curvas TG/DTG/DTA mostraram alterações no comportamento térmico do QN1 em relação à QP, evidenciou que a modificação leva a mudanças no comportamento térmico e sugerem a presença de NAP na matriz biopolimérica. A caracterização corroborou hipótese de formação do sal, QN1, pois houveram modificações nos intervalos de perda de massa, assim como, pela razão entre a terceira e segunda perda de massa, pode-se verificar um ganho de estabilidade. Com objetivo de melhorar a capacidade de interação NAP-QP, realizou-se a reticulação das cadeias de quitosana com epicloridrina. No entanto, a reação teve um menor rendimento quando comparada com o sal não reticulado. Verificou-se pelas diferentes técnicas de caracterização, sobretudo, por RMN 13C que, ao invés de organizar e deixar os grupos amino ainda mais suscetíveis à reação, a estrutura da quitosana organizou-se de forma que houve menos interação com o fármaco. Portanto, para os sais QN1 e QPEPIN1 foi realizado o estudo do equilíbrio de dissociação por HPLC, em diferentes pHs 2,00 e 7,00, simulando condições do intestino e estômago, afim de verificar o seu perfil de dissociação e comportamento nessas soluções. Desse modo, verificou-se que em pH 2,00 para QN1 ocorre a dissociação mais rapidamente quando comparada com pH 7,00. Já o sal reticulado QPEPIN1, sua dissociação em pH 2,00 é mais lenta quando comparada com pH 7,00. / Studies were carried out to optimize the reaction conditions to obtain a naproxen (NAP) salt (QN) and the chitosan biopolymer (QP). This matrix (QN) was used for the study of anti-inflammatory dissociation equilibrium. For this, the best conditions were studied in relation to the parameters reaction time, reaction temperature and molar ratio of the reactants. The products were characterized by nuclear magnetic resonance of hydrogen and carbon 13, 1H and 13C NMR, Fourier transform infrared vibration spectroscopy, FTIR, ultraviolet-visible electronic spectroscopy in the diffuse reflectance, UV-vis, diffraction (XRD) and thermoanalytical techniques: thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). In addition, the evolution of gases by thermogravimetry coupled to infrared vibrational spectroscopy (TG-FTIR) was studied. It was found that the higher salt yield was obtained under the following reaction conditions: 24 hours, temperature of 60 ° C and molar ratio of 1 mol of QP to 1.05 mol of NAP. This reaction product was called QN1. In this case, when calculating the degree of substitution (GS) by the 13C NMR technique, a GS of 19.1% was observed, suggesting a neutralization of the NH2 group bound to the C2 of the biopolymer with the COOH group present in the drug. In the FTIR spectra were observed bands corresponding to the formation of a product different than QP and NAP, corroborating with the hypothesis of QN1 salt formation. In the UV-vis spectrum the three bands were observed for the absorption of the chromophore groups present in the salt. In the diffractograms, there was a peak in the region of ~22Ø in QN1, which was already observed as a shoulder in QP, but there was an increase, in addition, changes in the index of crystallinity of chitosan, suggested modifications in its semicrystalline structure after reaction with the NAP. The TG / DTG / DTA curves showed changes in the thermal behavior of QN1 in relation to QP, showing that the modification leads to changes in the thermal behavior and suggest the presence of NAP in the biopolymer matrix. The characterization confirmed the hypothesis of salt formation, QN1, because there were modifications in the intervals of mass loss, as well as, by the ratio between the third and second loss of mass, a stability gain can be verified. In order to improve the NAP-QP interaction capacity, the chitosan chains were crosslinked with epichlorohydrin. However, the reaction had a lower yield when compared to the uncrosslinked salt. It was verified by the different characterization techniques, mainly by 13C NMR that, instead of organizing and leaving the amino groups even more susceptible to reaction, the chitosan structure was organized in a way that there was less interaction with the drug. Therefore, for the salts QN1 and QPEPIN1 the study of the equilibrium of dissociation by HPLC, at different pHs 2,00 and 7,00, was carried out, simulating conditions of the intestine and stomach, in order to verify their profile of dissociation and behavior in these solutions. Thus, it was found that at pH 2.00 for QN1 dissociation occurs more rapidly when compared to pH 7.00. Already the crosslinked salt QPEPIN1, its dissociation at pH 2.00 is slower when compared to pH 7.00.

Orientador: Marisa Masumi Beppu / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-22T08:45:44Z (GMT). No. of bitstreams: 1 Godoi_FernandaCondide_D.pdf: 6019663 bytes, checksum: 38baf78eef2e8c653a42f1495127a3c1 (MD5) Previous issue date: 2013 / Resumo: Dentre os biopolímeros que têm maior capacidade em formar complexos metálicos, a quitosana (QUI) ocupa posição de destaque. Os materiais feitos de quitosana-metal podem ter aplicações em diferentes campos, tais como: na engenharia ambiental, na medicina, na catálise e até no desenvolvimento de biosensores. A quitosana pode atuar como um agente redutor e estabilizante de nanopartículas metálicas. O presente estudo aborda o tema que envolve o estudo de nanopartículas metálicas tendo como suporte quitosana. Escolheu-se como metal o cobre, pois a adsorção deste pela quitosana já é bem conhecida pela comunidade científica. Neste contexto, objetivou-se: (1) Sintetizar e caracterizar membrana QUI contendo nanopartículas de cobre; (2) avaliar o comportamento higroscópico e a (3) influência da presença de nanopartículas de cobre na adsorção de Cr(VI) e V(V) em membrana QUI. As nanopartículas de cobre foram sintetizadas pela reação de oxi-redução entre os cátions Cu(II), adsorvidos previamente à membrana de quitosana, e o agente redutor NaBH4. Verificou-se, por meio da técnica Espectroscopia de Absorção de Raios X Dispersiva (DXAS), que ao final do processo de redução as espécies de cobre eram compostas por 63% de Cu(0) e 37% de Cu(I). O comportamento higroscópico das membranas de quitosana com e sem cobre foi avaliado por curvas isotérmicas (25 °C) de sorção de água em equipamento DVS. As curvas foram analisadas pelo Modelo GAB e pela teoria de Zimm-Lundberg. De acordo com a segunda teoria, a formação de "clusters" de água ocorre para umidade relativa > 60% na estrutura das membranas testadas. A obtenção da curva isotérmica sob atmosfera de ar sintético mostrou que a quitosana previne ou retarda a oxidação do cobre. Além disso, avaliou-se o efeito do cobre na adsorção de Cr(VI) e V(V) em membrana de quitosana, por meio de curvas cinéticas e isotérmicas (pHs 4 e 6) e ensaios de caracterização (XPS, FTIR, EDX, ESEM e TEM). Diferentemente do Cr(VI), o comportamento cinético para o V(V) foi caracterizado pelo período de difusão interna. Para as membranas com cobre, observou-se existência de dois sítios de adsorção associados a: (1) reações de oxi-reduções entre os pares Cr(VI)/Cu(I) ou Cu(0) e V(V)/Cu(I) ou Cu(0) e (2) atração eletrostática entre os ânions cromato/vanadato e a quitosana. Nas melhores condições testadas (pH=4), a membrana com cobre apresentou capacidade máxima de adsorção igual a 4,36 e 12,2 mmol g-1 para a adsorção de Cr(VI) e V(V), respectivamente, segundo o modelo de Langmuir Duplo-sítio. A membrana de quitosana com nanopartículas de cobre mostrou-se um produto com promissora aplicação como adsorvente em soluções de Cr(VI) e V(V) / Abstract: Among the biopolymers that have better capacity to form metal complexes, chitosan (CHI) occupies a prominent position. Materials made from chitosan-metal may have applications in different fields such as: engineering environment, medicine, catalysis and even the development of biosensors. Chitosan can act as a reducing agent and stabilizer for metal nanoparticles. The present study reports about the study of metal nanoparticles supported by chitosan. The objectives can be summarized as follows: (1) to synthesize and characterize membrane CHI containing copper nanoparticles, (2) to explore the hygroscopic behavior and (3) the influence of the presence of copper nanoparticles in the adsorption of Cr(VI) and V(V) on CHI membrane. Copper nanoparticles were synthesized by oxidation-reduction reaction between Cu(II), previously adsorbed on CHI membrane and the reducing agent NaBH4. It was found, by DXAS technique, that the copper species were composed of 63% Cu(0) and 37% Cu(I) after the reduction process. The hygroscopic behavior of CHI membrane, with and without copper, was evaluated by isotherms (25 ° C) of water sorption in DVS equipment. The curves were analyzed by the GAB model and the theory of Zimm-Lundberg. According to the second theory, the formation of water clusters occurs at relative humidity > 60%. The attainment of isothermal curve under synthetic air atmosphere showed that chitosan prevents or delays the oxidation of copper. In addition, we evaluated the effect of copper on the adsorption of Cr(VI) and V(V) on CHI membrane by means of kinetic/isothermal (pH 4 to 6) curves and laboratory characterization (XPS, FTIR, EDX , ESEM and TEM). Differently of Cr(VI), the kinetic behavior for V(V) was characterized by internal diffusion. For membranes with copper it was observed the existence of two adsorption sites that were associated with: (1) redox reactions between pairs Cr(VI)/Cu(I) or Cu(0) and V(V)/Cu(I) or Cu(0) and (2) electrostatic attraction between the anions chromate/vanadate and chitosan. Under the best conditions tested (pH = 4), the membrane with copper showed maximum adsorption capacity equal to 4.36 and 12.2 mmol g-1 for the adsorption of Cr(VI) and V(V), respectively, according to the Bi-site Langmuir model. The CHI membrane with copper nanoparticles can be a promising product with application as an adsorbent for Cr(VI) and V(V) metallic solutions / Doutorado / Engenharia de Processos / Doutora em Engenharia Quimica

No description available.

Chitosan was widely studied for applications in tissue regeneration, because of its biodegradability and biocompatibility. However, its insolubility in a neutral solution and long gelation time limit its wide application in tissue engineering. In this thesis, a new chitosan-based biomaterial was synthesized, and its chemical structure and solubility were characterized. Afterwards, the gelation properties (crosslinker, crosslink time, swelling ratio, drug release and biocompatibility) of TMC material was investigated. Results show that TMC has higher water solubility than chitosan. The TMC liquid solution can transform to a hydrogel quickly at body temperature. The formed hydrogel controlled the release of the model protein. Cytotoxicity result shows the cationic TMC hydrogel brings a toxic effect on stromal cells but it may have the potential to inhibit bacteria or cancer cells, although more studied are required to confirm its potential functions. In summary, this new TMC hydrogel has a promising potential in biomedical fields. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

This research determined the in vitro, intraperitoneal injection and dietary immunostimulatory effects on the grouper Epinephelus malabaricus of chitosan and its derivatives with different molecular weight, chitosan, polyglucosamine and N-acetyl-chitooligosaccharides. Respiratory burst activity of head-kidney phagocytes isolated from the grouper incubated in vitro with the chitosans at a range of concentrations was studied. Respiratory burst activity generally decreased with increasing dosage of chitosan products. N-acetyl-chitooligosaccharides were significantly more potent in enhancing respirtatory burst activity than the other two chitosans. Respiratory burst activity of head-kidney phagocytes of the grouper injected with three kinds of chitosans at 4 dosages was assayed. N-acetyl-chitooligosaccharides caused significantly higher respiratory burst activity than the other two chitosans. N-acetyl-chitooligosaccharides at the dosage of 10 µg/g was found to enhance the highest respiratory burst activity among treatments. In the time series assay with intraperitoneal injection by N-acetyl-chitooligosaccharides at a dosage of 10 µg/g, it was found that enhancement of NBT reduction occurred early in the time course of the study and is similar to the time series response of the glucan treatment. When the groupers (120g) were fed with diets containing 5 concentrations of N-acetyl-chitooligosaccharides including 0, 0.5, 1, 1.5, and 2 g/100g and stocked in indoor closed recirculation systems for 7 weeks, weight gain of the fish was not significantly affected by the dietary treatments. The immune status measured by respiratory burst activity, alternative complement pathway, agglutination titer, lysozyme activity and superoxide dismutase activity was not significantly affected by N-acetyl-chitooligosaccharides supplement. But feeding the grouper with N-acetyl-chitooligosaccharides at 1 g/100g diet seems to lower the immunity of the fish, although the effects were statistically insignificant.

Thesis (doctoral)--Christian-Albrechts-Universität zu Kiel, 2003.

Adenosine is currently limited in its application as a treatment for various cancers since intravenous infusion has not been successful due to enzymatic degradation. Entrapment/association of adenosine into chitosan nanoparticles offers a possible solution to this problem. Chitosan nanoparticles which are formed by ionotropic gelation. The size, zeta potential, morphology, entrapment efficiency, and in vitro drug release were investigated. In the swollen state, nanoparticle had an average size between 425 to 515 nm and a positive zeta potential, as measured by dynamic light scattering. Particle size measured by transition electron microscopy varied between 135 to 183 nm. Average entrapment efficiency in the range of 72 to 78% was achieved depending on initial adenosine loading and an average association efficiency of 84%. Release studies show that more than 98% of the adenosine remained entrapped/associated with the chitosan nanoparticles for at least 120 hours in PBS (pH 7.4).

Univ., Diss.--Würzburg, 1997.