RESUMO
ß-Cyclodextrin (ß-CD)-grafted dextrans with spacer arms of different length were employed to evaluate the impact of supramolecular interactions on invertase activity. The modified dextrans were used as single additives or combined with trehalose in freeze-dried formulations containing invertase. Enzyme activity conservation was analyzed after freeze-drying and thermal treatment. The change of glass transition temperature (Tg ) was also evaluated and related to effective interactions. Outstanding differences on enzyme stability were mainly related to the effect of the spacer arm length on polymer-enzyme interactions, since both the degree of substitution and the molecular weight were similar for the two polymers. This change of effective interactions was also manifested in the pronounced reduction of Tg values, and were related to the chemical modification of the backbone during oxidation, and to the attachment of the ß-CD units with spacer arms of different length on dextran.
Assuntos
Dextranos/química , Liofilização , beta-Ciclodextrinas/química , beta-Frutofuranosidase/química , Estabilidade Enzimática , Vidro/química , Peso Molecular , Polímeros/química , Temperatura de Transição , Trealose/químicaRESUMO
Structure/function relationships of different biopolymers (alginate, dextran, or beta-cyclodextrin) were analyzed as single excipients or combined with trehalose in relation to their efficiency as enzyme stabilizers in freeze-dried formulations and compared to trehalose. Particularly, a novel synthesized polymer beta-cyclodextrin-branched alginate (beta-CD-A) was employed as excipient. During freeze-drying, the polymers or their mixtures did not confer better protection to invertase compared to trehalose. Beta-CD-A (with or without trehalose), beta-cyclodextrin (beta-CD), or dextran with trehalose were the best protective agents during thermal treatment, while beta-CD and alginate showed a negative effect on invertase activity preservation. The beta-CD linked alginate combined the physical stability provided by alginate with the stabilization of hydrophobic regions of the enzyme provided by cyclodextrin. Beta-CD-A was effective even at conditions at which trehalose lost its protective effect. A relatively simple covalent combination of two biopolymers significantly affected their functionalities and, consequently, their interactions with proteins, modifying enzyme stability patterns.
Assuntos
Dessecação/métodos , Polímeros/química , beta-Frutofuranosidase/química , Estabilidade de Medicamentos , Estabilidade Enzimática , Liofilização/métodos , Laminaria/isolamento & purificação , Polímeros/análise , Relação Estrutura-Atividade , beta-Frutofuranosidase/análiseRESUMO
Mannan and carboxymethylcellulose, previously activated by periodate oxidation, were grafted with mono-6-butylenediamino-6-deoxy-beta-cyclodextrin derivatives by reductive alkylation in the presence of sodium borohydride. The formation of supramolecular complexes between these polymers and Naproxen was confirmed by fluorescence spectroscopy. The solubility of the drug was 3.8-4.6 fold increased in the presence of the cyclodextrin-grafted polysaccharides. The in vivo anti-inflammatory property of Naproxen was 1.7 times higher after supramolecular association with beta-cyclodextrin-branched mannan.
Assuntos
Anti-Inflamatórios não Esteroides/química , Anti-Inflamatórios não Esteroides/farmacologia , Carboximetilcelulose Sódica/química , Ciclodextrinas/química , Mananas/química , Naproxeno/química , Naproxeno/farmacologia , Animais , Anti-Inflamatórios não Esteroides/síntese química , Carragenina/metabolismo , Fluorescência , Espectroscopia de Ressonância Magnética , Masculino , Naproxeno/síntese química , Ratos , Ratos Wistar , SolubilidadeRESUMO
Bovine liver catalase (EC 1.11.1.6) was chemically modified with mannan, carboxymethylcellulose, and carboxymethylchitin. The enzyme retained about 48-97% of the initial specific activity after glycosidation with the polysaccharides. The prepared neoglycoenzyme was 1.9-5.7 fold more stable against the thermal inactivation processes at 55 degrees C, in comparison with the native counterpart. Also, the modified enzyme was more resistant to proteolytic degradation with trypsin. Pharmacokinetics studies revealed higher plasma half-life time for all the enzyme-polymer preparations, but better results were achieved for the enzyme modified with the anionic macromolecules.
Assuntos
Catalase/farmacocinética , Polissacarídeos/química , Animais , Área Sob a Curva , Sequência de Carboidratos , Carboximetilcelulose Sódica/química , Carboximetilcelulose Sódica/metabolismo , Catalase/administração & dosagem , Catalase/química , Bovinos , Estabilidade Enzimática , Meia-Vida , Temperatura Alta , Concentração de Íons de Hidrogênio , Injeções Intravenosas , Fígado/enzimologia , Masculino , Dados de Sequência Molecular , Estrutura Molecular , Ratos , Ratos Wistar , Solubilidade , Espectrofotometria , Especificidade por Substrato , Água/químicaRESUMO
Saccharomyces cerevisiae invertase, chemically modified with chitosan, was immobilized on pectin-coated chitin support via polyelectrolyte complex formation. The yield of immobilized enzyme protein was determined as 85% and the immobilized biocatalyst retained 97% of the initial chitosan-invertase activity. The optimum temperature for invertase was increased by 10 degrees C and its thermostability was enhanced by about 10 degrees C after immobilization. The immobilized enzyme was stable against incubation in high ionic strength solutions and was 4-fold more resistant to thermal treatment at 65 degrees C than the native counterpart. The biocatalyst prepared retained 96 and 95% of the original catalytic activity after ten cycles of reuse and 74 h of continuous operational regime in a packed bed reactor, respectively.
Assuntos
Quitina/química , Quitosana/química , Materiais Revestidos Biocompatíveis/química , Membranas Artificiais , Pectinas/química , Saccharomyces cerevisiae/enzimologia , beta-Frutofuranosidase/química , Reatores Biológicos , Eletrólitos/química , Ativação Enzimática , Enzimas Imobilizadas/química , Glicoproteínas/química , Cinética , Teste de MateriaisRESUMO
Saccharomyces cerevisiae invertase, chemically modified with chitosan, was immobilized on a carboxymethylcellulose-coated chitin support via polyelectrolyte complex formation. The yield of immobilized protein was determined to be 72% and the enzyme retained 68% of the initial invertase activity. The optimum temperature for invertase was increased by 5 degrees C and its thermostability was enhanced by about 9 degrees C after immobilization. The immobilized enzyme was stable against incubation in high ionic strength solutions and was 12.6-fold more resistant to thermal treatment at 65 degrees C than the native counterpart. The prepared biocatalyst retained 98% and 100% of the original catalytic activity after 10 cycles of reuse and 70 h of continuous operational regime in a packed bed reactor, respectively. The immobilized enzyme retained 95% of its activity after 50 days of storage at 37 degrees C.
Assuntos
Carboximetilcelulose Sódica/química , Quitina/química , Quitosana/química , Enzimas Imobilizadas/química , beta-Frutofuranosidase/química , Quitosana/metabolismo , Estabilidade Enzimática , beta-Frutofuranosidase/metabolismoRESUMO
Dextran, mannan and carboxymethylcellulose, previously activated by periodate oxidation, were grafted with beta-cyclodextrin moieties by reductive alkylation in the presence of sodium borohydride. These polymers were used as supramolecular carriers for naproxen, improving the "in vivo" anti-inflammatory properties of this drug.