66 HAIR CARE
retention properties from 20°C to 180°C. Thanks to its advanced water-retention
properties, PQ33-starch emulsion locks moisture into the hair fibre, minimizing evaporation for long-lasting hydration. With just 2% of PQ33-starch emulsion, hair hydration increases by 7% (Figure 5).
Bleaching protection Permanent hair colouring, or oxidation colouring, makes up over 80% of the hair colouration market. It requires mixing with an oxidizing agent, usually hydrogen peroxide, for application and colour development. When hair is damaged, disulfide bonds
may be altered. Free thiols can play a role in repairing these bonds, helping to restore the hair’s structure and prevent breakage. Free thiols levels are associated with keratin and hair quality. Free thiols quantification was assessed
by Oxiproteomics. 2% of active polymer PQ33-starch emulsion was applied on virgin Caucasian hair tress (0,25g product/g of hair) before dipping in a H2
O2 solution (2% or 6
volumes) for 1h15. Hair tresses were rinsed and dried.
The free thiols were quantified using a specific fluorometric assay kit (Abcam / ab112158) according to the manufacturer’s guideline. Hair proteins were extracted by using the OxiProteomics extraction buffer. Total protein quantification (μg/μl) was assessed by the Bradford method to normalize the thiols-free quantification for each sample of the experience. A fluorometric assay was used to quantify
the free thiols in each sample by specific fluorescence signal detection (lEx/lEm = 490/520nm). The quantity of free thiols in extracted proteins from hair shafts was determined thanks to a series of thiol (GSH) standards at known concentrations. The interpolation of the fluorescence values
of unknown samples to the standard curve allowed to obtain the concentrations of free thiols in each sample (μM). A value (nmol/mg proteins) of free thiols per experimental group is obtained by normalization on the protein concentration. The quantification of free thiols normalized
over the control group is reported in the bar graph representation (mean % versus control ± sd) (Figure 6). As expected, the levels of free thiols significantly decreased upon stress (bleaching, H2
O2
active ingredient PQ-33 starch significantly contrasted the stress (H2
). These results indicate the beneficial
protective and reparative effects of the PQ33- starch emulsion in maintaining optimal levels of free thiols, key precursors of disulfide bonds in hair, which are associated with hair strength, suggesting its potential for haircare products.
Restoration of superficial damage The scanning electron microscopy (SEM) technique allows the evaluation of the surface of the hair fibres about to prevent and repair damage caused by straightening procedures, dyeing, bleaching, successive combability,
PERSONAL CARE June 2025
) exposure. The presence of O2
Stress (H2 O2 ) Control 50 60 70 80 90 100 110 120 130
Figure 6: Quantification of free thiols levels, mean ± std N=3. * Level of Free thiols is significantly higher compared to the stress. Method: One-way ANOVA and Dunnett’s post-hoc test for multi- comparisons versus stress group (alpha=0.05)
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2% (active) Natursol EMI REV in water
ΔHvap water (J/g) 168.48* +7% of hair hydration
Brazilian benchmark for thermal protection
2% (active) Natursol EMI REV in water
Control shampoo SLES 10% ΔHD (J/g) +33% of thermal protection 3.140*
+40% of thermal protection
3.297*
2.359 0.000 0.500 1.000 1.500 2.000 2.500 3.000 3.500
Figure 4: Denaturation enthalpy by DSC, mean ± std N=3. * ΔHD values significantly higher compared to the control. Method: One-way ANOVA summary followed by Dunnett’s post test. Confidence interval: 95%
157.46 Control shampoo SLES 10% 145 150 155 160 165 170 175
Figure 5: Water vaporization enthalpy, mean ± std N=3. * ΔH value significantly higher compared to the control. Method: Bimodal, unpaired, Student’s t-test. Confidence interval: 95%
(vs control; nmol/mg proteins) Free thiols level (%) Natursol EMI REV + Stress *
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