Proteomic and mechanical perspectives on keratin fibre damage and recovery

Conventional haircare treatments that modify hair characteristics, such as bleaching, use chemicals which can irreversibly damage hair fibres and be hazardous to the health of the user and the environment. Consumer desire for healthy hair and environmentally-conscious haircare products has created a niche within the haircare industry for products that do not rely on harsh chemicals. The successful use of biological agents, particularly peptides, in haircare formulations to repair or even mitigate hair damage caused by chemicals has been reported for over a decade, and products containing synthetic peptides are a reality today. Despite this, the effects of damage on hair fibres are not fully understood. Furthermore, the action mechanisms via which restorative agents interact with hair fibres have not been elucidated. Additionally, hair fibre research has traditionally focused on a limited range of hair types, often neglecting the diversity inherent across populations, despite evidence that hair fibre response to damage and restorative treatments are not consistent across different hair types.
This thesis provides a comprehensive characterisation of African, Asian, Caucasian, and Latin American hair fibres under consistent experimental conditions. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), morphological tests, and tensile testing, were used to explore the structural and chemical differences between hair types and their responses to bleaching. Findings reveal type-specific characteristics and highlight how bleaching affects these types differently, including unique type-bleaching interactions. Novel density data for each hair type are also presented, shedding light on previously unquantified structural properties. In addition to characterising hair and bleaching effects, this thesis evaluates [REDACTED]- and [REDACTED]- derived peptides as sustainable hair treatments. While these peptides show potential in enhancing hair strength and hydration, their efficacy was inconsistent and type-dependent, and their mechanisms of interaction with hair fibres remain unclear.
By integrating chemical, thermal, and mechanical analyses, this work contributes to fundamental knowledge of hair fibre science and provides insights for developing personalised and sustainable haircare solutions tailored to diverse hair types.