Polylactic acid/thermoplastic starch/montmorillonite nanocomposite : morphological, tensile properties, water absortion and degradation behavior

Polylactic acid/ Tapioca starch/ Montmorillonite nanocomposites were prepared with different loadings of nanoclay (MMT) via twin screw extruder then compressed into plates for using in various tests. The effects of different loadings of MMT on mechanical, thermal, morphological properties, water absorption and biodegradation behavior of nancocomposites were investigated. Tensile properties were studied as some mechanical properties through this research. The thermal properties were characterized by using differential scanning calorimeter (DSC). Morphological properties of nanocomposites were studied through field emission scanning electron microscope (FESEM) and x-ray diffraction (XRD). Tensile strength increased by increasing the percentage of MMT in polymer matrix. Optimum amount for Young’s modulus and percentage of elongation at break were determined among the five samples and these results are in fine agreement with XRD results that prove the intercalated and exfoliated structure of nanocomposites. The results of DSC showed that MMT increased melting temperature and crystallization temperature of matrix but reduction in glass transition temperature was observed. During the water absorption test, amount of water intake decreased by increasing the content of MMT in nanocomposite structure. Biodegradation study exhibited that incorporation of this type of nanoclay has growing effect on degradation rate of nanocomposites

Vaginal Administration of Contraceptives

While contraceptive drugs have enabled many people to decide when they want to have a baby, more than 100 million unintended pregnancies each year in the world may indicate the contraceptive requirement of many people has not been well addressed yet. The vagina is a well-established and practical route for the delivery of various pharmacological molecules, including contraceptives. This review aims to present an overview of different contraceptive methods focusing on the vaginal route of delivery for contraceptives, including current developments, discussing the potentials and limitations of the modern methods, designs, and how well each method performs for delivering the contraceptives and preventing pregnancy

Hydrogels For Biomedical Applications: From Bio-adhesive to Drug Delivery

There is a need for materials to replace the use of sutures and staples in surgical procedures. Amongst all the alternatives, special attention has been paid to hydrogels because of their unique and interesting mechanical and physiochemical properties which can meet the requirements of an ideal wound sealant. Specifically, a wound sealant may attach to tissue by molecular cross-linking or through mechanical interlocking with the underlying tissue. Commercially available adhesive sealants are limited by inadequate adhesion, biocompatibility and degradability. So, it is desired to introduce a novel biodegradable and biocompatible surgical adhesive with high strength and minimal immune or inflammatory response. The first part of this dissertation (Chapter 2 and 3) focuses on the use of novel hydrogels as bio-adhesives. For this purpose, various polymers were employed and characterized with different characterization techniques such as 1H, 13C NMR, GPC, FTIR analysis. In order to increase the adhesion of these materials to the target tissue, a positively charged functional group, guanidinium, was immobilized on to the polymer backbones. The electrostatic interactions of these cationic groups on polymers with negatively charged molecules presenting at the tissue surface and cell membrane might cause strong adhesion. Hydrogels were prepared in-situ, simply by mixing two different polymer solutions without the need for any catalyst or initiator. The mechanical properties of the gels were studied which showed not enough strength of these hydrogels for being used as surgical glues. Some approaches were taken to improve the mechanical properties; however, this area of biomedical application needs more investigation. Another biomedical application of hydrogels investigated in this study was drug delivery. Controlled drug release enhances the safety and efficiency of drug administration. Using hydrogels as delivery platforms is a new technology which can improve and control the release rate of bioactive compounds. Hydrogels closely resemble living tissues due to their high water content. So, these networks exhibit a reduced risk of toxicity and inflammation which is ideal for a drug carrier. The second part of this thesis (Chapter 4 and 5) describes the ability of hydrogels in sustained/controlled release studies applying two different model drugs. The hydrogels were formed in-situ, with different levels of cross-linking by Schiff-base chemistry, which is a reversible reaction, and could be hydrolysed and result in degradation of the cross-linked matrices. The cross-linking density was the key factor in the characteristics of the gels such as degradation rate, swelling and rheological behaviour. The precursors of the hydrogels were injectable fluids which can be presented into the body in a minimally invasive manner followed by solidification at the target site/tissue. Release of a hydrophilic model drug was studied in Chapter 4, where the drug was dissolved into the precursor solution and then entrapped inside the cross-linked system during the hydrogel formation. However, current polymeric systems (e.g. the gels made in Chapter 4) encounter difficulties with loading hydrophobic molecules into their aqueous networks and the subsequent release of the drug from the gel matrices. Cyclodextrins offer a potential solution to the hydrophobic drug delivery challenge. These supramolecules possess internal hydrophobic cavities which can partially or entirely accommodate hydrophobic molecules. Chapter 5 explores the ability of cyclodextrin-based hydrogels in encapsulation and release of a hydrophobic model drug. The interaction of cyclodextrin-functionalized polymers with the hydrophobic drug was analyzed using 1H NMR, FTIR, DSC and SEM and showed the capacity of these polymers in encapsulation of the model drug. Overall, different types of cross-linking chemistry were studied in this project to produce hydrogels with potential application in the biomedical area. Some of the hydrogels showed weak mechanical properties and need to be studied in greater detail in order to make a stronger surgical adhesive. Some other hydrogels exhibited good properties which make them interesting materials in drug delivery and the subject of further in vivo studies

Hydrogels For Biomedical Applications: From Bio-adhesive to Drug Delivery

There is a need for materials to replace the use of sutures and staples in surgical procedures. Amongst all the alternatives, special attention has been paid to hydrogels because of their unique and interesting mechanical and physiochemical properties which can meet the requirements of an ideal wound sealant. Specifically, a wound sealant may attach to tissue by molecular cross-linking or through mechanical interlocking with the underlying tissue. Commercially available adhesive sealants are limited by inadequate adhesion, biocompatibility and degradability. So, it is desired to introduce a novel biodegradable and biocompatible surgical adhesive with high strength and minimal immune or inflammatory response. The first part of this dissertation (Chapter 2 and 3) focuses on the use of novel hydrogels as bio-adhesives. For this purpose, various polymers were employed and characterized with different characterization techniques such as 1H, 13C NMR, GPC, FTIR analysis. In order to increase the adhesion of these materials to the target tissue, a positively charged functional group, guanidinium, was immobilized on to the polymer backbones. The electrostatic interactions of these cationic groups on polymers with negatively charged molecules presenting at the tissue surface and cell membrane might cause strong adhesion. Hydrogels were prepared in-situ, simply by mixing two different polymer solutions without the need for any catalyst or initiator. The mechanical properties of the gels were studied which showed not enough strength of these hydrogels for being used as surgical glues. Some approaches were taken to improve the mechanical properties; however, this area of biomedical application needs more investigation. Another biomedical application of hydrogels investigated in this study was drug delivery. Controlled drug release enhances the safety and efficiency of drug administration. Using hydrogels as delivery platforms is a new technology which can improve and control the release rate of bioactive compounds. Hydrogels closely resemble living tissues due to their high water content. So, these networks exhibit a reduced risk of toxicity and inflammation which is ideal for a drug carrier. The second part of this thesis (Chapter 4 and 5) describes the ability of hydrogels in sustained/controlled release studies applying two different model drugs. The hydrogels were formed in-situ, with different levels of cross-linking by Schiff-base chemistry, which is a reversible reaction, and could be hydrolysed and result in degradation of the cross-linked matrices. The cross-linking density was the key factor in the characteristics of the gels such as degradation rate, swelling and rheological behaviour. The precursors of the hydrogels were injectable fluids which can be presented into the body in a minimally invasive manner followed by solidification at the target site/tissue. Release of a hydrophilic model drug was studied in Chapter 4, where the drug was dissolved into the precursor solution and then entrapped inside the cross-linked system during the hydrogel formation. However, current polymeric systems (e.g. the gels made in Chapter 4) encounter difficulties with loading hydrophobic molecules into their aqueous networks and the subsequent release of the drug from the gel matrices. Cyclodextrins offer a potential solution to the hydrophobic drug delivery challenge. These supramolecules possess internal hydrophobic cavities which can partially or entirely accommodate hydrophobic molecules. Chapter 5 explores the ability of cyclodextrin-based hydrogels in encapsulation and release of a hydrophobic model drug. The interaction of cyclodextrin-functionalized polymers with the hydrophobic drug was analyzed using 1H NMR, FTIR, DSC and SEM and showed the capacity of these polymers in encapsulation of the model drug. Overall, different types of cross-linking chemistry were studied in this project to produce hydrogels with potential application in the biomedical area. Some of the hydrogels showed weak mechanical properties and need to be studied in greater detail in order to make a stronger surgical adhesive. Some other hydrogels exhibited good properties which make them interesting materials in drug delivery and the subject of further in vivo studies

Shear thinning/self-healing hydrogel based on natural polymers with secondary photocrosslinking for biomedical applications

Injectable hydrogel systems are useful in many biomedical applications, including drug or cell delivery carriers and scaffolds. Here, we describe the design and characterization of a shear thinning hydrogel that undergoes a disassembly when shear forces are applied during injection and is self-healing once the shear forces are removed. This hydrogel is based on a cyclodextrin modified alginate, and a methacrylated gelatin which initially forms through a weak guest-host interaction between hydrophobic cyclodextrin cavities and the aromatic residue of gelatin. Methacrylated gelatin possesses photocrosslinkable functionalities which can go through a light-initiated polymerization to create secondary crosslinking sites and further crosslink the matrix. The shear thinning and self-healing behavior of these gels monitored in low and high strain range, viscosity of the hydrogels components and gelation kinetic were studied. The rheological analyses showed the formation of shear thinning gels which were further stabilized by visible light exposure. The cytotoxicity of the hydrogels towards human mesenchymal stem cells were assessed and the rate of mass loss over a week period was studied. © 2018 Elsevier Ltdinfo:eu-repo/semantics/publishe

In situ-forming and pH-responsive hydrogel based on chitosan for vaginal delivery of therapeutic agents

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Biofabrication of Bacterial Constructs: New Three-Dimensional Biomaterials

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Functional Polysaccharides for Biomedical Applications: Green synthesis of polysaccharide-based inorganic nanoparticles and biomedical aspects

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Processing, thermal behavior and tensile properties of pla/thermoplastic starch/montmorillonite nanocomposites

Thermoplastic starch, polylactic acid glycerol and maleic anhydride (MA) were compounded with natural montmorillonite (MMT) through a twin screw extruder to investigate the effects of different loading of MMT on tensile properties and thermal behavior of the nanocomposites. Tensile results showed an increased in modulus, tensile strength and elongation at break. However, beyond 3phr of MMT the modulus of samples decreased because the MMT particles agglomerated. The thermal properties were characterized by using differential scanning calorimeter (DSC). The results showed that MMT increased melting temperature and crystallization temperature of matrix but reduction in glass transition temperature was observed.</jats:p

The role of microbiota in tissue repair and regeneration

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