Iskanje po katalogu digitalne knjižnice

Opis: The derivatization of the polysaccharide dextran with N-protected amino acids (Boc-L-Phenylalanine, BocGlycine, Boc-L-Cysteine, and Boc-L-Cysteine-S-Trt) and peptides (Boc-L-DiPhenylalanine, Boc DiGlycine, and 2,5-diketopiperazine) as the basis for biomaterial preparation is presented in this Doctoral Dissertation. Such prepared dextran derivatives are intended to mimic the proteoglycan complex (PGs), one of the most important structural and functional biomacromolecules in the extracellular matrix (ECM) of tissue. Nowadays, developments in biomaterials are focusing increasingly on the preparation and use of biomimetic molecular structures to achieve positive results in tissue engineering (TE) and drug delivery. Designing and synthesizing these biomimetic materials, however, requires sophisticated chemical and material preparation methods, knowledge that is, currently, unexplored. In this work, we developed a suitable procedure for dextran derivatization, and investigated the most optimal reaction or deprotection conditions (temperature and time) and isolation/purification methods. The structures of the obtained BocPhe-Dex, BocGly-Dex, BocCys-Dex, and BocSTLC-Dex were analyzed with FTIR, NMR, SEC-MALS, and EA. The results showed that dextran derivatization was successful in all cases except in the case of dextran derivatization with BocCys. Investigation of the effect of the derivatization conditions and purification on the stability, purity, and other important chemical and physical properties of the obtained product, showed that the temperature and time of derivatization do not have a bigger effect on the products' properties, while the purification method, on the other hand, has. Its effect is visible in the product's purity and mass yields of products prepared under the same reaction conditions. Derivatization of dextran with peptides (Boc-L-DiPhenylalanine, BocDiGlycine, and 2,5-diketopiperazine) was performed using the CDI coupling agent or Amberlite-IR 120 as a catalyst. The products were analyzed with FTIR and 1H and 13C NMR. The results showed successful dextran derivatization in the case of BocDiPhenylalanine and BocDiGlycine, while, in the case of 2,5-diketopiperazine, a reaction covalent bond with the dextran was not confirmed. BocPhe-Dex and BocSTLC-Dex were selected as the most optimal amino acid-dextran derivatives for further preparation of 3D formulations in the shape of nanoparticles (NPs). Nanoparticles were prepared with the emulsion/solvent evaporation method from the obtained BocPhe-Dex and BocSTLC-Dex products (prepared in the first stage of this Doctoral Dissertation). SEM analysis showed that the prepared NPs were homogeneous and nicely spherical, with an average dry diameter of 325 ± 118 nm in the case of BocSTLC-Dex, and 1039 ± 382 nm in the case of NPs prepared from BocPhe-Dex. All the prepared NPs retained their proper spherical shape and stability during the acidic treatment, and so confirmed their potential for further functionalization and applications for drug delivery. The BocSTLC-Dex NPs were also evaluated with cell viability tests, which showed that the prepared NPs were not cytotoxic, one of the most important characteristics for the drug delivery applications of NPs. This work serves as a basis for further studies on the derivatization of polysaccharides with amino acids and peptides, and their application in tissue engineering or drug delivery.
Ključne besede: Amino Acid-Dextran derivatives, Peptide-Dextran derivatives, Proteoglycan complex, 3D formulation, Nanoparticles, Drug delivery
Objavljeno v DKUM: 18.10.2024; Ogledov: 0; Prenosov: 25
Celotno besedilo (9,08 MB)

Opis: In this study, we explored the development of cationized 2-hydroxyethyl cellulose (HEC) and succinylated polyallylamine (PAA) in conjunction with polyvinyl alcohol (PVA) for potential applications as antimicrobial wound dressings. Quaternary ammonium compounds are known for their broad-spectrum antimicrobial properties against both Gram-negative and Gram-positive bacteria, but their non-selectivity can lead to high cytotoxicity. To improve the biocompatibility of the cationic materials investigates two distinct approaches. The first approach involves reducing the cationic nature of protonated PAA at a pH below 8.3 through amidation reaction with succinic anhydride. Gradual reduction of the cationic charge is achieved by varying the molar ratios of succinic anhydride during the reaction process. Notably, this reaction can be carried out in an aqueous solution, eliminating potential issues associated with solvent removal. The second part of this thesis focuses on introducing cationic charge by covalently binding naturally occurring quaternary ammonium compounds, such as betaine hydrochloride (BET HCl), choline chloride (ChCl), and carnitine hydrochloride (carnitine). Using 1,1′-carbonyldiimidazole (CDI), we quaternized HEC in anhydrous DMSO, with a detailed investigation of the reaction mechanism by isolating and characterizing intermediate products. This same procedure was applied to form a cationic dimer between BET HCl and ChCl. The chemical structures of the resulting materials were characterized using attenuated total reflectance infrared spectroscopy (ATR-IR) and nuclear magnetic resonance (NMR). The quantification of cationic and total charge was determined through polyelectrolyte and potentiometric titration, respectively. While succinylated PAA exhibited the anticipated biological properties associated with the reduction of cationic characteristics, the same behaviour was not observed for quaternized materials. High cytotoxicity and low antimicrobial properties in the derivatized HEC may be attributed to inadequate purification and the sensitivity of fibroblasts. We produced electrospun non-woven mats incorporating PVA and these derived materials using a single-needle electrospinning machine. The average diameter of the fibres was determined through scanning electron microscopy (SEM) images. Despite the cytotoxicity and the absence of significant antimicrobial properties in these materials, they exhibit potential as effective cationic flocculants for wastewater treatment. Further investigations are pending to address purification issues and make slight adjustments to the procedure to potentially scale up production. These materials still hold promise for applications in both biomedical and environmental chemistry.
Ključne besede: cellulose, quaternary ammonium compounds, antimicrobial, cytotoxicity, electrospinning
Objavljeno v DKUM: 11.07.2024; Ogledov: 127; Prenosov: 36
Celotno besedilo (16,36 MB)

Ključne besede: assays, degradation, porosity, scaffolds, 3D printing
Objavljeno v DKUM: 09.04.2024; Ogledov: 238; Prenosov: 18
Celotno besedilo (9,95 MB)
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Opis: Biocompatible polysaccharide scaffolds with controllable pore size, good mechanical properties, and no hazardous chemical crosslinkers are desirable for long-term tissue engineering applications. Despite decades of development of novel scaffolds, there are still many challenges to be solved regarding their production and optimization for specifically engineered tissues. Herein, we have fabricated several three-dimensional (3D) scaffolds using polysaccharide or polysaccharide-protein composite hydrogels or inks for 3D printing, featuring strong shear thinning behavior and adequate printability. The inks, composed of various combinations of chitosan, nanofibrillated cellulose, carboxymethyl cellulose, collagen, and citric acid, were 3D printed, freeze-dried, and dehydrothermally heat-treated to obtain dimensionally and mechanically stable scaffolds. The heat-assisted step induced the formation of covalent amide and ester bonds between the functional groups of chosen polysaccharides and protein collagen. Citric acid was chosen as a non-hazardous and „green” crosslinker to further tailor the mechanical properties and long-term stability of the scaffolds. We have investigated how the complexation conditions, charge ratio, dehydrothermal treatment, and degree of crosslinking influence the scaffolds' chemical, surface, swelling, and degradation properties in the dry and hydrated states. The compressive strength, elastic modulus, dimensional stability and shape recovery of the (crosslinked) scaffolds increased significantly with balanced charge ratio, dehydrothermal treatment, and increased concentrations of citric acid crosslinker and collagen concentrations. The prepared crosslinked scaffolds promoted (clustered) cell adhesion and showed no cytotoxic effects, as determined by cell viability assays and live/dead staining with human bone tissue-derived osteoblasts and human adipose tissue-derived mesenchymal stem cells. The water-based and non-hazardous crosslinking methods presented here can be extended to all polysaccharide- or polysaccharide-protein-based materials to develop cell-friendly scaffolds with tailored properties suitable for various tissue engineering applications.
Ključne besede: chitosan, carboxymethyl cellulose, nanofibrillated cellulose, citric acid, collagen, freeze drying, 3D printing, dehydrothermal treatment
Objavljeno v DKUM: 11.10.2022; Ogledov: 675; Prenosov: 156
Celotno besedilo (33,63 MB)

Opis: The introduction of the Laboratory Manual gives the theoretical bases on cellulose and its derivatives, which are used as starting polymers for the preparation of multifunctional polymers with three different advanced techniques - spin coating, electrospinning and 3D printing. In the following, each technique is presented in a separate Lab Exercise. Each exercise covers the theoretical basics on techniques for polymer processing and methods for their characterisation, with an emphasis on the application of prepared materials. The experimental sections contain all the necessary information needed to implement the exercises, while the added results provide students with the help to implement correct and successful exercises and interpret the results.
Ključne besede: multifunctional polymers, polysaccharides, cellulose, electrospun, spin coating, 3D printing, nanofibers, thin films, multifunctional materials, laboratory manuals
Objavljeno v DKUM: 09.03.2021; Ogledov: 965; Prenosov: 25
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