Ion-pair based Molecular Imprinted Polymers for bioanalysis and sustainable use of organocatalysts

  • Federica Pessagno

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

This thesis presents the development and application of ion-pair functional monomers as a new concept in stoichiometric molecular imprinting, as well as a proof-of-concept application of urea and thiourea based monomers in the development of an assay of thyroxine in patient blood samples.

The development of ion-pairs where only the anionic partner is polymerisable, is discussed in the first part of Chapter 4, and an in-depth investigation of the performance of the new recognition motif in the binding of a sulfonylurea drug, glibenclamide, both in solution and post-polymerisation, is presented. It is shown that under certain conditions, the acidic sulfonylurea drug is deprotonated by the basic anion of the ion-pair monomer, resulting in a charge transfer complex, followed by release of the non-polymerisable cationic partner, and eventual deactivation of the binding sites. Despite the need for a reactivation after each extraction cycle, the polymers showed excellent stability and were able to recover up to 92% of the drug from blood samples. Expanding on this work in the second part of Chapter 4, ion-pairs where both anionic and cationic partners are polymerisable where subsequently prepared and applied to the same problem. These materials exhibited excellent stability while they did not require reactivation after each extraction cycle and achieved even higher recovery of the drug of up to 98%, from blood samples.

In Chapter 5, the application of the optimised ion-pair monomers in the recovery and recycling of urea and thiourea organo-catalysts from common catalytic reactions, such as the Baylis-Hillman, Diels-Alder, Strecker and Michael addition reactions, is presented. In all cases, catalyst recoveries of up to 100% in very high purity were achieved, an achievement not matched by the commercially available resins which were used as controls. The recovered catalysts were reused for as many as 7 reaction cycles and polymer cartridges for as many as 100 extraction cycles without a loss in performance, confirming the validity of the hypothesis that molecular imprints can play a key role in the sustainability of organocatalytic processes. Lastly, in Chapter 6, the comparison of a new thiourea based monomer with an established urea monomer in the stoichiometric imprinting of thyroxine, with a view to offer a viable replacement to the current gold-standard immunoassay method for T3/T4 analysis, is discussed. Despite excellent binding performance in solution and in the solid phase, and the development of a LC-MS method for the trace level analysis of T3/T4, it is shown that excessive template bleeding prohibits the application of the prepared materials as an alternative to the immunoassay. However, it is proven that MIPs can be a viable concept for T3/T4 hormone analysis if an improved template removal or a template analogue strategy is applied.

The results of Chapter 4 have been published as two manuscripts, and the results of Chapter 5 are being drafted into an additional publication. The preliminary results of Chapter 6 are being expanded by a follow-on PhD project and will be published upon completion of the work.
Date of AwardJul 2020
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsQueen's University Belfast
SupervisorPanagiotis Manesiotis (Supervisor) & Mark Muldoon (Supervisor)

Keywords

  • Molecular imprinting
  • supramolecular chemistry
  • ion-pair monomers
  • bioanalysis
  • separation science
  • organocatalysis

Cite this

Ion-pair based Molecular Imprinted Polymers for bioanalysis and sustainable use of organocatalysts
Pessagno, F. (Author). Jul 2020

Student thesis: Doctoral ThesisDoctor of Philosophy