Hydrogels are unique materials composed of hydrophilic gelators linked together in a three-dimensional network capable of encapsulating large amounts of water. These materials are easily adaptable to different application areas i.e. biomedical areas, agriculture, removal of heavy metals from water or in food industry. In this thesis, some eco-sustainable gelators have been selected as starting materials to develop hydrogels that possess characteristics related to the selected applications. For this purpose, zwitterionic amine oxide surfactants and polysaccharides, i.e. alginate and chitosan, were selected for their ability to form hydrogels by modulating their concentration or by adding crosslinking agents. In Section B, several common techniques were selected to fully characterize the two polysaccharides in order to determine their structural features, which can affect the hydrogels properties. In Section C, the hydrogels were prepared based on the selected application areas i.e. bioconversion, food packaging and cultural heritage. The effect of surfactants structure and immobilization into hydrogel structure on the catalytic properties of Candida rugosa lipase (CRL) was investigated. The selected amine oxide surfactants exploited an improvement of the enzymatic activity as a function of the morphology of the micellar aggregates; in particular, by varying the headgroup size and the chain length, the micelles shift from spherical to rod-like leading to an increased hydrolytic activity. Furthermore, CRL was effectively entrapped in alginate hydrogel beads formed by ionotropic gelation induced by calcium ions. Different bead formulations were prepared and the effect of their morphology on the catalytic properties of CRL was assessed by studying two model reactions. The immobilized lipase showed noticeable recyclability and improved thermostability compared to the free enzyme. Part of this study was addressed to the application of chitosan-based hydrogels to prepare membranes applicable as eco-friendly food packaging material. Chitosan-succinate films were prepared, starting by their hydrogel form, by solvent casting method using glycerol as plasticizer. The NaOH-neutralized membranes, compared to the non-neutralized ones, showed improved mechanical and physicochemical properties. The formation of amide bonds between chitosan and succinic acid, suggested by the FTIR analysis, was then confirmed by acid-base titration. The prepared membranes are currently under preliminary study as novel food packaging for pecorino cheese samples. The last part of this thesis is included in a wider project focused on “Product and process innovation for maintenance, preservation and sustainable programmed restoration of cultural heritage” (Smart Cities and Communities and Social Innovation on Cultural Heritage project). It aimed at the improvement of the restoration and maintenance intervention on stone-based cultural heritages. For this purpose, novel approaches to reduce microbial colonization from stone materials were developed using classic oxidant biocidal agents supported in alginate hydrogels. Novel ionically crosslinked alginate hydrogels, which contain oxidative biocides were developed and tested. All hydrogel formulations were able to eliminate biofilms from the stone surface, keeping the chromaticity and capillary properties of the cleaned stones unchanged. To assess the presence of residues, any type of surface alteration and to evaluate the hygroscopic behavior of the stone samples, microscopic techniques, colorimetry and 1H-NMR T2 relaxation measurements have been performed. They were applied both on a laboratory scale, using calcarenite specimens artificially colonized by filamentous cyanobacteria and green microalgae and “in situ” on stone artworks in rupestrian churches of “Sassi of Matera”.

Applicazione di idrogel: Tensioattivi e polisaccaridi impiegati come costituenti altamente versatili / Gabriele, Francesco. - (2021 May 05).

Applicazione di idrogel: Tensioattivi e polisaccaridi impiegati come costituenti altamente versatili

GABRIELE, FRANCESCO
2021-05-05T00:00:00+02:00

Abstract

Hydrogels are unique materials composed of hydrophilic gelators linked together in a three-dimensional network capable of encapsulating large amounts of water. These materials are easily adaptable to different application areas i.e. biomedical areas, agriculture, removal of heavy metals from water or in food industry. In this thesis, some eco-sustainable gelators have been selected as starting materials to develop hydrogels that possess characteristics related to the selected applications. For this purpose, zwitterionic amine oxide surfactants and polysaccharides, i.e. alginate and chitosan, were selected for their ability to form hydrogels by modulating their concentration or by adding crosslinking agents. In Section B, several common techniques were selected to fully characterize the two polysaccharides in order to determine their structural features, which can affect the hydrogels properties. In Section C, the hydrogels were prepared based on the selected application areas i.e. bioconversion, food packaging and cultural heritage. The effect of surfactants structure and immobilization into hydrogel structure on the catalytic properties of Candida rugosa lipase (CRL) was investigated. The selected amine oxide surfactants exploited an improvement of the enzymatic activity as a function of the morphology of the micellar aggregates; in particular, by varying the headgroup size and the chain length, the micelles shift from spherical to rod-like leading to an increased hydrolytic activity. Furthermore, CRL was effectively entrapped in alginate hydrogel beads formed by ionotropic gelation induced by calcium ions. Different bead formulations were prepared and the effect of their morphology on the catalytic properties of CRL was assessed by studying two model reactions. The immobilized lipase showed noticeable recyclability and improved thermostability compared to the free enzyme. Part of this study was addressed to the application of chitosan-based hydrogels to prepare membranes applicable as eco-friendly food packaging material. Chitosan-succinate films were prepared, starting by their hydrogel form, by solvent casting method using glycerol as plasticizer. The NaOH-neutralized membranes, compared to the non-neutralized ones, showed improved mechanical and physicochemical properties. The formation of amide bonds between chitosan and succinic acid, suggested by the FTIR analysis, was then confirmed by acid-base titration. The prepared membranes are currently under preliminary study as novel food packaging for pecorino cheese samples. The last part of this thesis is included in a wider project focused on “Product and process innovation for maintenance, preservation and sustainable programmed restoration of cultural heritage” (Smart Cities and Communities and Social Innovation on Cultural Heritage project). It aimed at the improvement of the restoration and maintenance intervention on stone-based cultural heritages. For this purpose, novel approaches to reduce microbial colonization from stone materials were developed using classic oxidant biocidal agents supported in alginate hydrogels. Novel ionically crosslinked alginate hydrogels, which contain oxidative biocides were developed and tested. All hydrogel formulations were able to eliminate biofilms from the stone surface, keeping the chromaticity and capillary properties of the cleaned stones unchanged. To assess the presence of residues, any type of surface alteration and to evaluate the hygroscopic behavior of the stone samples, microscopic techniques, colorimetry and 1H-NMR T2 relaxation measurements have been performed. They were applied both on a laboratory scale, using calcarenite specimens artificially colonized by filamentous cyanobacteria and green microalgae and “in situ” on stone artworks in rupestrian churches of “Sassi of Matera”.
Applicazione di idrogel: Tensioattivi e polisaccaridi impiegati come costituenti altamente versatili / Gabriele, Francesco. - (2021 May 05).
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/169020
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