Human Hair Fibers: Structural and Thermodynamic Analysis under Multiple Physical and Chemical Stresses and Exploration of Nano-Based Modulation Strategies

• Grant number: 25/18704-1
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Cristiano Luis Pinto de Oliveira
• Grantee: Larissa Verena Figueiredo de Oliveira
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 23/10843-7 - Synthesis and characterisation of multi-functional lipid-based nano particles, with potential biomedical application in Cancer and Atherosclerosis: a multidisciplinary approach, AP.TEM

Abstract

Human hair is increasingly subjected to multiple types of chemical and physical stress, including bleaching, straightening, repeated use of heat-styling tools, and exposure to adverse environmental conditions. The combination of these factors leads to progressive structural degradation, reducing mechanical strength and thermal stability. Understanding how such damage occurs through a multifactorial approach that realistically simulates usage conditions is essential for developing more effective protection and repair strategies. This project proposes an integrated and innovative approach to investigate the combined effect of chemical treatments and physical stresses on hair fibers. Virgin and previously damaged samples, subjected to chemical treatments such as bleaching and straightening, will be studied under various physical stress conditions. Using SAXS (Small-Angle X-ray Scattering) measurements in situ, the samples will be evaluated under different levels of temperature, humidity, and mechanical tension, conditions that mimic real-life scenarios, such as heat styling in varying humid environments. This approach, combined with thermal, mechanical, and microscopic analyses, will provide insights into how these factors interact to intensify or alter pre-existing structural damage in the fiber, generating novel information not yet reported in the literature. In a second stage, the application of chitosan-functionalized silica nanoparticles will be assessed as a strategy to reinforce and protect the keratin matrix. Silica was chosen for its well-established role as a reinforcing agent in polymer matrices, enhancing mechanical strength and thermal stability, while chitosan, widely used in cosmetic formulations, will serve as a stabilizing agent and binder to the fiber. The study will evaluate different deposition and coating conditions, characterizing the distribution and possible penetration of the particles into the fiber, as well as their effect on mechanical, thermal, and structural properties after exposure to aggressive chemical treatments. The multifactorial nature of the proposed approach, integrating combined damage conditions with advanced real-time characterization, represents a significant innovation compared to existing studies. Ultimately, this research aims to establish reproducible protocols for hair degradation assessment and to provide data that may support the development of new protection and repair strategies with potential applications in cosmeceutical and clinical formulations.