Development of a microfluidic device for the in situ production of singlet oxygen for chemical and biological applications

Lumley, Emily K.

Abstract

Cancer cells are derived from cells that are termed, and recognised as being 'self', meaning that the immune system does not target them. Many treatments target the tumour through its requirement for large quantities of nutrients. However, this causes healthy cells to be destroyed and unpleasant side effects for the patient. Recently research has found that cancer cells treated ex vivo with photodynamic therapy will initiate an immune response on reintroduction to the patient. Photodynamic therapy is the use of a photosensitiser drug, in the presence of oxygen, being irradiated with light and thus producing singlet oxygen which is toxic to cells in the region.

The purpose of this work was to immobilise a photosensitiser to the glass channel walls of a microfluidic device which could be used to produce singlet oxygen in situ. This device could then be used for chemical applications, in photo-oxidation reactions, and for a specific biological application, the efficient production of a PDT-generated cancer vaccine.

A method was developed to immobilise a porphyrin, bearing an isothiocyanate group on the inner glass channels of the fluidic device, pre-silanised to present amino groups. This method was optimised using rhodamine B isothiocyanate on glass beads and within the microfluidic device before the porphyrin was used in its place. To determine the success of this reaction the porphyrin-immobilised chips were used to oxidise cholesterol and compared to the same reaction with the porphyrin in solution, both on chip, and in batch conditions. Further photo-oxidation reactions were conducted with α-terpinene and citronellol and compared to the equivalent reaction in batch conditions. It was found that the on-chip reaction gave a lower yield, but was more efficient, at producing oxidation products.

Finally the porphyrin-immobilised chip was used to determine the effect on cultured cancer cells pumped through in the presence of light. The cationic porphyrin used for the chemical applications was found to cause dark toxicity, and therefore a neutral hydrophilic porphyrin was used. This was found to give a difference between the cell death in the dark and in the light that was statistically significant. However, the expression of heat shock protein 70, a key marker for immunogenicity of cells, was not found.

The microfluidic chip was successfully functionalised with porphyrin molecules, and was found to efficiently produce singlet oxygen for the purposes of chemical oxidation reactions. The chip was capable of causing cell death to cancer cells and proven to be due to the irradiation of the porphyrin, however, it was not discerned whether they would be capable of initiating an immune response.

Citation

Lumley, E. K. Development of a microfluidic device for the in situ production of singlet oxygen for chemical and biological applications. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4219891

• Thesis Type: Thesis
• Deposit Date: Feb 12, 2018
• Publicly Available Date: Feb 23, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4219891
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Aug 1, 2012