Monitoring glycation through the intrinsic fluorescence of biological fluorophores

The high blood glucose levels associated with diabetes affect various cells and proteins in the body. In response to high blood glucose the proteins collagen, keratin, and human serum albumin (HSA) experience glycation, and the cofactor reduced nicotinamide adenine dinucleotide (NADH) is also known to be affected in some way. This work aims to establish if the intrinsic fluorescence of these compounds could be used to monitor the impact of glucose, and thus offer an alternative method to monitoring long term glycaemic control. We have studied the evolution of the intrinsic fluorescence of four compounds in response to glucose in vitro using steady state and time-resolved fluorescence spectroscopy techniques. For NADH, although significant changes were seen in the sample when in a phosphate buffered saline (PBS) buffer, no similar changes in fluorescence were observed when a Trizma buffer was used. As such, we conclude that glycation does not have an impact on the intrinsic fluorescence of NADH. Changes in the intrinsic fluorescence of collagen, keratin, and HSA however were observed. For collagen, TRES revealed changes in the intrinsic fluorescence kinetics, caused by both collagen aggregation and glycation. In keratin, the addition of glucose caused an increase in the fluorescence intensity at the characteristic wavelength of 460 nm, due to faster formation of new cross-links, and glucose may also cause the formation of two new fluorescent complexes that emit at longer wavelengths. For HSA, fluorescence intensity decay analysis indicates that glycation can be detected through a decrease in the short lifetime component when decays are fitted to a 2-exponential model, however fitting to a non-Debye model more clearly highlights the impact of glucose. We also studied the intrinsic fluoresce of mouse skin and human fingernails. In an initial pilot study on mouse skin, our results suggested that collagen, keratin, and NADH can be detected from a skin autofluorescence (AF) measurement, and that there may be a relationship between skin AF and blood glucose. Using fingernails, it appeared that although both the peak emission wavelengths, and the fitted exponential parameters indicated that we can detect keratin fluorescence, there was no evidence that glycated keratin can be sensed through a nail clipping. Furthermore, neither our steady state or time resolved analysis exposed a correlation between any of the extracted fluorescence parameters and glycated haemoglobin (HbA1c). In conclusion, monitoring the intrinsic fluorescence of particular biological proteins in vitro suggests that this method could be used as a method to monitor long term glycaemic control in patients with diabetes. Further studies would be required to translate these findings into an in vivo environment.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2023

Author dc:creator

• Muir, Rhona

Advisor dc:contributor.advisor

• Rolinski, Olaf

DOI

10.48730/26wv-z566

Identifier

T16657

Author Identifier

201862155

OAI identifier oai:identifier

oai:strathclyde:8910jv148