Experimental design and investigation of how cosmetic proteins affect bacteria found on the skin

Salvage, Hannah 2022. Experimental design and investigation of how cosmetic proteins affect bacteria found on the skin. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Skin care companies have started to invest in products which are microbe friendly or promote and support ‘good’ microbes. Cosmetic proteins are proteolysates used in cosmetic formulations for their hydration and moisturization properties. This thesis investigates how cosmetic proteins could affect skin bacteria and the steps required to take the research from in vitro to in vivo. The preservatives in the cosmetic proteins had varied inhibitory effects on the three chosen species, Staphylococcus aureus, Staphylococcus epidermidis and Corynebacterium jeikeium. The three species were also able to utilize the peptides and amino acids found in the cosmetic proteins to aid in both planktonic growth and formation of biofilms. The low pH of the cosmetic proteins controlled S. aureus from dominating when in a mixed biofilm culture model. Once skin cells were included in the experiments, it was clear how S. aureus elicited an immune response, significantly greater than any of the cosmetic protein were able to elicit. S. epidermidis however, was able to reduce the amount of inflammation and stop over proliferation of S. aureus. Planning future experiments in vivo required investigations of different swab types and buffers for collection of the skin microbiota, as well as choosing suitable swab sites for bacterial studies. The research also found that past cosmetic skin study protocols may not be appropriate for microbial investigations, as the differences in bacterial communities and mass across different skin sites had not been previously considered. In conclusion, in vitro, cosmetic proteins are ingredients which can both promote and harm the bacteria that live on our skin. The amino acids can provide nutrients, while the preservatives have a bacteriostatic or bactericidal effects. Using dry cosmetic proteins would remove the need for preservatives, however this has the potential to cause over-proliferation of undesirable species. Further work using skin panel testing, launching from the final chapters of this thesis, would help conclude whether the answers from the in vitro work would be repeated in the in vivo experiments.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	6 September 2022
Date of Acceptance:	6 September 2022
Last Modified:	05 Jan 2024 08:17
URI:	https://orca.cardiff.ac.uk/id/eprint/152391

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