Synthesis and characterization of chitosan based sponges for wound dressings

Matsvaire, Taguma Noble (2017-03)

Thesis

ENGLISH ABSTRACT: The work presented in this study focused on the development of chitosan based sponges for the possible use as wound dressings. The sponges were to be modified to try and overcome some of the flaws associated with the use of natural polymers, that is, the poor mechanical properties. The important parameters that had to be met were a continuously porous morphology, to have a good absorption capability, good thermal properties, increase the mechanical strength and to maintain and/or increase the antimicrobial properties inherently in the chitosan. The two crosslinking agents that were used in this study to crosslink the chitosan sponges were genipin and tannic acid (TA). These are both natural crosslinking agents as this provided a platform to create a possible non-toxic wound dressing. The mechanical properties of the chitosan sponges resulting from these two crosslinking agents were compared to that when a synthetic crosslinking agent, namely glutaraldehyde (glut), was used. In an attempt to further enhance the mechanical properties, microcrystalline cellulose (MCC) was incorporated into the sponges as a reinforcing agent. The antimicrobial nature of a wound dressing is of high importance as it aids the healing processes in wounds. Certain properties that were imparted on the sponges by the different synthesis parameters were analysed in order to determine how to best enhance these properties as they play a vital role in the wound healing process. The sponges were synthesized using the bubbling technique and freeze–drying. The temperature used during the synthesis was of importance as the interaction between the chitosan and the crosslinking agents differs at different temperatures. The time taken to crosslinking time allowed during synthesis of the sponges was also of significance as this variable also had an important influence on the resultant properties of the sponges. The crosslinking of the sponges was confirmed using FTIR spectroscopy where the characteristic shifts and peaks that have occurred due to the crosslinking could be seen. These shifts are due to the chemical reactions that occur when the chitosan and the crosslinking agents react. The morphology of the sponges was determined using SEM where the porosity of the sponges could then be analysed and gave better understanding of some of certain other properties. The homogeneous distribution of MCC in the chitosan sponges was confirmed using confocal microscopy. The thermal properties of all the sponges were investigated using TGA and DSC. The TGA and DSC results showed that the crosslinking using either genipin or TA improved the thermal properties of the sponges. Absorbance tests were done to determine the absorption properties of the sponges which were also improved by the crosslinking when using either one of the involved crosslinking agents. For testing of the mechanical strength, compressional tests were done and these showed that there was an increase in the strain percentage in comparison to the uncrosslinked sponges but was, however, less than those for the sponges crosslinked with glutaraldehyde. The antimicrobial properties of the samples were analysed using the alamar assay technique. This assay showed that the antimicrobial properties were sensitive to crosslinking temperature, MCC loadings, Gramicidin S treatment and the crosslinking agent used. The samples crosslinked with genipin at 0.5 weight percent concentrations showed the greatest enhancement in antimicrobial properties.

AFRIKAANSE OPSOMMING: Hierdie studie fokus op die ontwikkeling van chitosan gebaseerde sponse vir die moontlike gebruik as wondbedekkings. Die sponse is aangepas om te probeer om sommige van die tekortkominge wat verband hou met die gebruik van natuurlike polimere te oorkom, dit wil sê die swak meganiese eienskappe. Die belangrikste eienskappe waaraan voldoen moes word was 'n deurlopende poreuse morfologie, 'n goeie absorpsie vermoë, goeie termiese eienskappe, verhoogde die meganiese sterkte en handhawing en of verhoging van die antimikrobiese eienskappe inherent tot die chitosan. Die twee kruisbindingsagente wat in hierdie studie gebruik was om die chitosan sponse te kruisbind, is genipin en tanniensuur (TA). Beide kruisbindingsagente is natuurlike verbindings aangesien dit ‘n platform voorsien om 'n moontlike nie-toksiese wondbedekking te skep. Die meganiese eienskappe van die sponse wat met behulp van die twee kruisbindingsagente gesintetiseer is, is vergelyk met dié wat met behulp van 'n sintetiese kruisbindingsagent, naamlik glutaraldehied (glut), gesintetiseer is. Om die meganiese eienskappe van die sponse verder te versterk, is mikrokristallyne sellulose (MCC) in die sponse geïnkorporeer as 'n versterking van die agent. Die antimikrobiese aard van 'n wondbedekking is van groot belang, aangesien dit die helende prosesse in wonde aanhelp. Sekere eienskappe wat aan die sponse oorgedra is deur middel van die verskillende sintese parameters is geanaliseer om sodoende te bepaal hoe om hierdie eienskappe die beste te verbeter, aangesien dit ‘n belangrike rol speel in wondgenesing. Die sponse is gesintetiseer deur middel van ‘n borreltegniek en vries-droging. Die temperatuur tydens die sintese was van belang aangesien die interaksie tussen die chitosan en die kruisbindingsagente verskil by verskillende temperature. Die tyd wat dit neem om die monsters te kruisbind was ook van belang, aangesien dit ook 'n invloed het op die resulterende eienskappe van die sponse. Die kruisbinding van die sponse is bevestig met behulp van FTIR spektroskopie waartydens die karakteristieke verskuiwings en pieke wat plaasgevind het as gevolg van die kruisbinding sigbaar geword het. Hierdie verskuiwings is die gevolg van die chemiese reaksies wat plaasvind wanneer die chitosan en die kruisbinding agente reageer. Die morfologie van die sponse is bepaal met behulp van SEM waartydens die porositeit van die sponse ontleed is en dit het 'n beter begrip van sommige van die ander eienskappe gebied. Die MCC is homogeen in die spons versprei en dit is bevestig met behulp van konfokale mikroskopie. Die termiese eienskappe is ondersoek met behulp van TGA en DSC. Die TGA en DSC resultate het getoon dat kruisbinding wat met behulp van geninpin of TA plaasgevind het hierdie eienskappe verbeter het. Daar is absorbsie toetse gedoen om die absorberingseienskappe van die sponse wat ook verbeter word deur die kruisbinding te bepaal. Vir die meganiese sterkte, was saamdrukbaarheidsweerstand toetse gedoen en dit het getoon dat daar 'n toename was in die druk persentasie in vergelyking met die kruisgebinde sponse, maar was egter minder as dié van die sponse wat kruisgebind was met glutaraldehyde. Die antimikrobiese eienskappe van die monsters is ontleed met behulp van die alamar toets tegniek. Hierdie toets het getoon dat die antimikrobiese eienskappe was sensitief vir temperatuur, MCC beladings, gramisidien S behandeling en die kruisbinding agent gebruik. Die kruisgebind met genipin monsters het die grootste toename in die antimikrobiese eienskappe op 0,5 gewig persent konsentrasies.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101331
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