Comprehensive analysis of modified hyaluronic acid by multidimensional chromatography

Viktor, Zanelle (2017-12)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Hyaluronic acid (HA) that had been modified through the hydroxyl moieties with an acrylate functional group can produce very complex and heterogeneous polymers. The substitution of the hydroxyl moieties on the HA backbone are not homogeneous, resulting in different numbers of acrylate functionalities that are present among and along the polymer chains (1st and 2nd order heterogeneity). Effectively, the samples have a chemical composition distribution (CCD) along with a molar mass distribution (MMD), inherited from the parent HA. The chemical composition and molar mass distributions of a given polymer have a close correlation to the resulting final properties of the polymer. It is therefore essential to gain knowledge about the heterogeneity with respect to CCD and MMD since these distributions can provide an insight into the structure-property relationship. The properties of the polymer subsequently determine its applications. The acrylate-functionalized HA cannot simply be characterized by a single one-dimensional LC method, for instance, gradient high performance liquid chromatography (HPLC) or size exclusion chromatography (SEC), due to the inherent complex nature of HA. It requires advanced liquid chromatographic (LC) techniques such as online two - dimensional LC (2D – LC), as it thus allows for the simultaneous determination of the degree of substitution (DS) and the molar mass distribution of the given HA sample. 2D – LC is thus a direct method to determine the CCD - MMD relationship that is present in the sample. With gradient reversed phased LC (RP – LC), as the first dimension, the modified HA was separated according to CCD i.e. DS. The resultant fractions collected from the first dimension were subjected to the second dimension, SEC, where the fractions of narrowly distributed DS were separated according to hydrodynamic volume. With the developed 2D – LC method, different structural compositions could be made apparent alongside the molar mass distribution. The developed method illustrates the heterogeneity of the modified HA samples, as bimodal molar masses were observed for narrow DS fractions.

AFRIKAANSE OPSOMMING: Die substitusie van hidroksielgroepe van hialuroniese suur (HA) met 'n aktiewe akriel groep, kan komplekse en heterogeniese polimere produseer. Die substitusie van hidroksielgroepe op die HA-ruggraat is nie homogeneen nie, wat beteken dat die hoeveelheid akriel funksionaliteit wat tussen en op die polimeerkettings (1ste en 2de orde heterogeniteit) teenwoordig is, kan wissel. Gevolglik, het die monsters beide 'n chemiese samestelling distribusie (CCD) en ‘n molêre massadistribusie (MMD). Die chemiese samestelling en molêre massadistribusie van 'n gegewe polimeer het 'n noue verband met die finale eienskappe van die polimeer. Dit is dus noodsaaklik om kennis te verkry oor die heterogeniteit van die polimeer ten opsigte van CCD en MMD. Hierdie verdelings gee insig omtrent die struktuur-eienskap verhouding, aangesien die eienskappe van die polimeer sy toepassing bepaal. Die akriel gefunksionaliseerde HA kan nie eenvoudig gekaraktariseer word deur 'n enkele een-dimensionele vloeistof chromatografiese (LC) metode nie. Dit vereis gevorderde analitiese LC tegnieke soos aanlyn twee-dimensionele LC (2D - LC) waar gradient hoë verrigting vloeistof chromatografie (HPLC) gekoppel word aan grootte uitsluiting chromatografie (SEC). Met 2D-LC kan die graad van substitusie (DS) en die molêre massa verdeling van die HA polimeer, gelyktydige bepaal word. Dit is dus 'n direkte metode om die CCD - MMD-verhouding wat binne die monster voorkom, te bepaal. Gradiënt HPLC is gebruik vir die eerste dimensie om die HA polimeer volgens die mate van substitusie te skei. Die verskeie fraksies wat vanuit die eerste dimensie versamel is, was onderworpe aan die tweede dimensie, SEC, waar die fraksies van bepaalde DS volgens hidrodinamiese volume geskei was. Met die ontwikkelde metode kan verskillende struktuursamestellings geïdentifiseer word saam met die molêre massadistribusie daarvan. Die ontwikkelde metode illustreer die heterogeniteit van die gemodifiseerde HA monsters, aangesien bimodale molêre massa vir gegewe DS fraksies waargeneem was.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102959
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