Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations,since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modu...Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations,since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modulated and specific properties that meet specific therapeutic needs.Objective:In this work the influence of polymer ratio and cross-linking process on the swelling and the mechanism driving the drug release from swellable matrix tablets prepared with this excipient was investigated.Methods:Cross-linked samples were characterized by their micromeritic properties(size and shape,density,angle of repose and flow rate)and liquid uptake ability.Matrix tablets were evaluated according their physical properties and the drug release rates and mechanisms were also investigated.Results:Cross-linked samples demonstrated size homogeneity and irregular shape,with liquid uptake ability insensible to pH.Cross-linking process of samples allowed the control of drug release rates and the drug release mechanism was influenced by both polymer ratio and cross-linking process.The drug release of samples with minor proportion of pectin was driven by an anomalous transport and the increase of the pectin proportion contributed to the erosion of the matrix.Conclusion:The cross-linked mixtures of high amylose and pectin showed a suitable excipient for slowing the drug release rates.展开更多
The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starc...The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starch react with glyoxal via formation of acetal bonds;hence crosslinking could take place. The cross-linking of glyoxal is observed in various analytical methods such as DSC and FTIR. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile shear strength, pencil hardness and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the cross-linking is directly proportional to starch, since the starch hydroxyl groups are easily accessible for reacting. The cross-linked blend showed better cohesion between its chains, thereby increasing glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.展开更多
This research paper describes the synthesis of thermo-reversible cross-linking of sago starch by grafting a furan pendant group(methyl 2-furoate)onto the starch backbone,followed by a Diels-Alder(DA)reaction of the fu...This research paper describes the synthesis of thermo-reversible cross-linking of sago starch by grafting a furan pendant group(methyl 2-furoate)onto the starch backbone,followed by a Diels-Alder(DA)reaction of the furan functional group with 1,1′-(methylenedi-4,1-phenylene)bismaleimide(BM).The proof of principles was provided by FTIR and 1H-NMR analyses.The relevant FTIR peaks are the carbonyl peak(υC=O sym)at 1721 cm^(−1);the two peaks appeared after DA cross-linking,i.e.,at 1510 cm^(−1)(corresponding toυCH=CH BM aromatic rings,stretching vibrations),and at 1173 cm^(−1)(assigned to cycloadduct(C-O-C,δDA ring))while the^(1)H-NMR result shows evidence for the presence of a furan ring in the starch matrices(in the range ofδ6.3-7.5 ppm).The crosslinked starch product is indeed thermally reversible,as is evident from the appearance of exothermal(DA,temperature range of 50℃-70℃)and endothermal(retro DA,temperature range of 125℃-150℃)transitions in the DSC thermograms.This paper not only proves the thermal reversibility but also demonstrates that the final product properties(chemical,morphology,and thermal stability)can be tuned by varying the annealing temperature,BM intake,and reaction time.展开更多
In this workα-amylase was immobilized on magnetic Fe3O4 nanoparticles with polyethylenimine(PEI)/polydopamine(PDA)coating or 3-aminopropyl triethoxysilane(APTES)for the first time via adsorption–precipitation–cross...In this workα-amylase was immobilized on magnetic Fe3O4 nanoparticles with polyethylenimine(PEI)/polydopamine(PDA)coating or 3-aminopropyl triethoxysilane(APTES)for the first time via adsorption–precipitation–cross-linking.Compared with the freeα-amylase,the resultant magnetic cross-linkedα-amylase aggregates(PEI/PDA-M-CLEAs and N-M-CLEAs)exhibited excellent thermal and storage stability as well as pH stability.After storage at 25°C for 60 days,freeα-amylase only retained 60%of its initial activity,while PEI/PDA-M-CLEAs and N-M-CLEAs retained 80%and 78%of their initial activities,respectively.Furthermore,N-M-CLEAs and PEI/PDA-M-CLEAs showed good reusability.After 6 repeated uses,PEI/PDA-M-CLEAs and N-M-CLEAs still maintained 65%and 62%of their initial activities,respectively.Especially,PEI/PDA-M-CLEAs and N-M-CLEAs exhibited higher starch hydrolysis efficiency than freeα-amylase.The maximum dextrose equivalent(DE)values of starch hydrolysis by PEI/PDA-M-CLEAs and N-M-CLEAs reached 29.24%and 28.79%within 90 min,respectively.However,the maximum DE values of starch hydrolysis by the freeα-amylase was only 27.89%even in 150 min.The magnetic cross-linkedα-amylase aggregates could be introduced as effective biocatalyst for industrial applications in production of maltose syrups.展开更多
Increasing global energy crisis and scarcity of petroleum resources has shifted focus of chemical industries to look for alternative raw material resources. The main focus of raw materials in wood adhesives, such as p...Increasing global energy crisis and scarcity of petroleum resources has shifted focus of chemical industries to look for alternative raw material resources. The main focus of raw materials in wood adhesives, such as petroleum and natural gas [1] [2], would be gradually replaced by renewable biopolymers. Starch is a relatively inexpensive and renewable product from abundant plants, easy processing and it has been extensively used as binders, sizing materials, glues and pastes [3], but its bonding capacity is not strong enough to glue wood [4]. Extensive research has been carried out on improving the cohesive properties, especially water resistance, of starch-based adhesives. In starch-based wood adhesive many new approaches have come forward for effective use it in wood/wood composite adhesive giving comparable performance as synthetic adhesives. This review of starch-based adhesives is made with the focus on starch modification methods for improving properties of starch-based adhesives.展开更多
基金Coordenac¸a˜o de Aperfei-c¸oamento de Pessoal de Nı´vel Superior(CAPES)and Fundac¸a˜o de Amparo a`Pesquisa do Estado de Sa˜o Paulo(FAPESP)is acknowledged.F.M.C.thanks FAPESP for a M.Sci.scholarship.
文摘Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations,since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modulated and specific properties that meet specific therapeutic needs.Objective:In this work the influence of polymer ratio and cross-linking process on the swelling and the mechanism driving the drug release from swellable matrix tablets prepared with this excipient was investigated.Methods:Cross-linked samples were characterized by their micromeritic properties(size and shape,density,angle of repose and flow rate)and liquid uptake ability.Matrix tablets were evaluated according their physical properties and the drug release rates and mechanisms were also investigated.Results:Cross-linked samples demonstrated size homogeneity and irregular shape,with liquid uptake ability insensible to pH.Cross-linking process of samples allowed the control of drug release rates and the drug release mechanism was influenced by both polymer ratio and cross-linking process.The drug release of samples with minor proportion of pectin was driven by an anomalous transport and the increase of the pectin proportion contributed to the erosion of the matrix.Conclusion:The cross-linked mixtures of high amylose and pectin showed a suitable excipient for slowing the drug release rates.
文摘The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starch react with glyoxal via formation of acetal bonds;hence crosslinking could take place. The cross-linking of glyoxal is observed in various analytical methods such as DSC and FTIR. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile shear strength, pencil hardness and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the cross-linking is directly proportional to starch, since the starch hydroxyl groups are easily accessible for reacting. The cross-linked blend showed better cohesion between its chains, thereby increasing glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.
基金funded by the Indonesia Toray Science Foundation(No.:001/I/ITSF/SEK/2019).
文摘This research paper describes the synthesis of thermo-reversible cross-linking of sago starch by grafting a furan pendant group(methyl 2-furoate)onto the starch backbone,followed by a Diels-Alder(DA)reaction of the furan functional group with 1,1′-(methylenedi-4,1-phenylene)bismaleimide(BM).The proof of principles was provided by FTIR and 1H-NMR analyses.The relevant FTIR peaks are the carbonyl peak(υC=O sym)at 1721 cm^(−1);the two peaks appeared after DA cross-linking,i.e.,at 1510 cm^(−1)(corresponding toυCH=CH BM aromatic rings,stretching vibrations),and at 1173 cm^(−1)(assigned to cycloadduct(C-O-C,δDA ring))while the^(1)H-NMR result shows evidence for the presence of a furan ring in the starch matrices(in the range ofδ6.3-7.5 ppm).The crosslinked starch product is indeed thermally reversible,as is evident from the appearance of exothermal(DA,temperature range of 50℃-70℃)and endothermal(retro DA,temperature range of 125℃-150℃)transitions in the DSC thermograms.This paper not only proves the thermal reversibility but also demonstrates that the final product properties(chemical,morphology,and thermal stability)can be tuned by varying the annealing temperature,BM intake,and reaction time.
基金the Fundamental Research Funds for the Central Universities(grant No.226-2023-0085)the Science and Technology Program of Tianjin,China(grant No.20ZYJDJC00080)the International Collaboration Project(grant No.2020/37/K/ST8/03805).
文摘In this workα-amylase was immobilized on magnetic Fe3O4 nanoparticles with polyethylenimine(PEI)/polydopamine(PDA)coating or 3-aminopropyl triethoxysilane(APTES)for the first time via adsorption–precipitation–cross-linking.Compared with the freeα-amylase,the resultant magnetic cross-linkedα-amylase aggregates(PEI/PDA-M-CLEAs and N-M-CLEAs)exhibited excellent thermal and storage stability as well as pH stability.After storage at 25°C for 60 days,freeα-amylase only retained 60%of its initial activity,while PEI/PDA-M-CLEAs and N-M-CLEAs retained 80%and 78%of their initial activities,respectively.Furthermore,N-M-CLEAs and PEI/PDA-M-CLEAs showed good reusability.After 6 repeated uses,PEI/PDA-M-CLEAs and N-M-CLEAs still maintained 65%and 62%of their initial activities,respectively.Especially,PEI/PDA-M-CLEAs and N-M-CLEAs exhibited higher starch hydrolysis efficiency than freeα-amylase.The maximum dextrose equivalent(DE)values of starch hydrolysis by PEI/PDA-M-CLEAs and N-M-CLEAs reached 29.24%and 28.79%within 90 min,respectively.However,the maximum DE values of starch hydrolysis by the freeα-amylase was only 27.89%even in 150 min.The magnetic cross-linkedα-amylase aggregates could be introduced as effective biocatalyst for industrial applications in production of maltose syrups.
文摘Increasing global energy crisis and scarcity of petroleum resources has shifted focus of chemical industries to look for alternative raw material resources. The main focus of raw materials in wood adhesives, such as petroleum and natural gas [1] [2], would be gradually replaced by renewable biopolymers. Starch is a relatively inexpensive and renewable product from abundant plants, easy processing and it has been extensively used as binders, sizing materials, glues and pastes [3], but its bonding capacity is not strong enough to glue wood [4]. Extensive research has been carried out on improving the cohesive properties, especially water resistance, of starch-based adhesives. In starch-based wood adhesive many new approaches have come forward for effective use it in wood/wood composite adhesive giving comparable performance as synthetic adhesives. This review of starch-based adhesives is made with the focus on starch modification methods for improving properties of starch-based adhesives.
