A natural molecular approach for hair treatments: Silab has created a high molecular weight quaternized soy protein polymer that is capable of binding to the hair and forming a cohesive film on the surface.

Whether maintaining healthy hair or improving damaged tresses, consumer interest in effective hair care products has never been greater. Demand for these products is on the rise due to the growing use of chemical treatments such as permanents and bleaching or mechanical stresses such as styling and repeated drying (Zviak, 1987). Furthermore, environmental aggressions, especially UV radiation, are particularly harmful to hair. The most visible effect of UV rays is bleaching (Santos Nogueira, 2004), but it also damages the hair cuticle and reduces intercellular adhesion. The morphologic changes increase the coefficient of friction as well as the fragility of the cuticle and the porosity of the fiber (Signori, 2004). When subjected to these stresses, hair becomes dry, dull and rough due to the opening of the scales and has more static electricity; thus becoming brittle and difficult to style.

In order to recover or preserve the surface properties responsible for maintaining hair structure and its esthetic qualities, the industry has developed an array of hair treatments that coat the hair. The coating property of a product is characterized by a substantive effect, its ability to bind to the hair, its film-forming effect and its capacity to spread on the hair surface.

Typical hair coating products are primarily composed of polymers such as silicone derivatives (Leidreiter, 1994), gum and starch (Syed, 1998) as well as cellulose derivatives (Jones, 1988). These products are the best among lipids, vitamins and protein derivatives since they provide excellent coating properties. However, these traditional polymers are sticky and are difficult to eliminate, which weighs hair down (Syed, 1998).

Because of its experience in the area of protein polymers used to develop its tensor products, Silab has created a polymer of high molecular weight from quaternized soy proteins. This polymer is capable of binding to the hair and forming a cohesive film on the hair surface at the same time. Developing this active ingredient requires two steps: one, quaternization of soy monomeric proteins of perfectly defined size, structure and solubility, selected and controlled by an enzymatic hydrolysis of native soy proteins and two, obtain a three-dimensional protein network of high molecular weight using an original and patented technology of protein polymerization in order to improve the substantive effect of quaternized peptides.

Materials and Methods

In a study of the substantive effect of the quaternized soy peptides, natural blond hair tresses (Secher-Fesnoux, France) were soaked for 10 minutes in 50 ml of a solution containing 2% soy peptides or 2% quaternized soy peptides. The tresses were rinsed under running water for one minute. The substantive effect of soy peptides towards locks of natural blond hair was evaluated with the Rubine test modified (Jones, 1988). Hair tresses previously treated with soy peptides were soaked for 20 minutes in a 0.5% solution of Red 80 (Ref 36554-8, Sigma) adjusted to pH 3.5 with sulphuric acid. The tresses were rinsed under water for one minute, dried using a hair dryer and placed in a 60[degrees]C incubator for one hour. Colorant elution was realized from 150 mg hair taken from each locks in 10 ml of a solution containing 2% of SDS for 15 minutes. Color intensity was measured with a spectrophotometer at 528 nm. Substantivity of the tested products toward hair tresses was measured (mg of bounded colorant per g of hair) and then expressed as a percentage of fixed colorant compared to the control.

The substantivity of quaternized soy polymer was measured in a study whereby natural blond hair was soaked for 10 minutes in 50 ml of a solution containing 2% of quaternized soy peptides or 2% of quaternized soy polymer. Tresses were rinsed under running water for one minute. The substantive effect of soy molecules toward locks of natural blond hair was carried out with the Rubine test modified and detailed above.

The build-up effect of the quaternized soy polymer was evaluated using locks of natural blond locks in three different treatments, control was not treated and rinsed, positive control was quaternized cellulose (RITA Polyquat-400):

* Locks of natural blond hair were soaked for 10 minutes in 50 ml of a solution containing 2% of quaternized soy polymer or 2% of quaternized cellulose (125 g/l). The hair was rinsed under running water for one minute.

* Same treatment as a) but the step of rinse was repeated five times.

* Same treatment as a) but the two steps of treatment and rinse were repeated five times.

The substantive effect of peptides towards locks of natural blond hair was carried out with the Rubine test modified.

In a study to determine the coating efficacy of the quaternized soy polymer, a lock of dry and damaged hair, about 20 cm long, was divided into four equal parts which were treated as follow:

Lock 1: untreated, not rinsed control, then dried using a hair dryer at low temperature.

Lock 2: test sample treated with 50 ml of a 2% solution of quaternized soy polymer, not rinsed and dried using a hair dryer at low temperature.

Lock 3: untreated, rinsed (under running water for one minute) control, then dried using a hair dryer at low temperature.

Lock 4: test sample treated with 50 ml of a 2% solution of quaternized soy polymer, rinsed under running water for one minute and dried using a hair dryer at low temperature.

Hair surface topography measurements were carried out with an interference microscope Phoenix (Eotech, France) and a 10x objective. This method enables the three-dimensional acquisition of the surface topography image of hair, as well as nanometric measurements of its softness or roughness. Ten hair shafts per treatment were analyzed and three zones per hair were acquired. Three parameters were calculated to determine the state of hair scales along the shaft axis:

* Gap thickness corresponding to the ratio of scale opening over the mean differences between peaks and valleys;

* Length corresponding to the length of the scales; and

* Roughness corresponding to the surface state of the hair.

Results

Standard statistical methods were employed to analyze the results. Student tests for non-paired data were used for statistical analysis.

The substantive effect was evaluated by measuring the quantity of colorant fixed on the hair tresses. In order to determine the benefit of the quaternization technology, the substantive effect of soy peptides, quaternized or not, was carried out on natural blond hair with the Rubine test modified by Jones (Figure 1). Tested at 2% and compared to the control, the soy peptides had an affinity of 118% toward natural blond hair. Quaternization of the soy peptides increased the substantive effect by 45% in comparison with the non-quaternized soy peptides.

The film-forming effect of the quaternized polymer, tested at 2%, was studied with the Rubine test and compared to that of the quaternized soy peptides (Figure 2). The substantive effects of quaternized peptides and quaternized polymer, tested at 2%, were 163% and 196% respectively. Thus, the step of quaternization increased by 33% the substantive effect of the polymer towards locks of natural blond hair. This three-dimensional protein network of high molecular weight, obtained by cross-linking of monomeric soy proteins, is able to spread on the surface hair and to form a cohesive film providing elevated elasticity and flexibility properties.

The build-up effect was determined with the Rubine colorimetric method after several applications of the active ingredient, tested at 2% in solution on locks of natural blond hair. This effect was compared to that of a solution of quaternized cellulose at 2% (Figure 3).

After a single application and a single rinse, the rate of colorant deposited on locks treated with 2% quaternized cellulose (103%) was close to that of locks treated with 2% quaternized soy polymer (96%). After one application and five rinses, the deposit of colorant on locks was significantly higher after the quaternized cellulose treatment (136%) than after the quaternized polymer treatment (74%). Finally, after one application and one rinse repeated five times, there was a significant difference in the level of fixed colorant on locks between the treatment with quaternized cellulose (134%) and quaternized polymer (89%).

Thus, our active ingredient was significantly easier to eliminate than quaternized cellulose. Moreover, repeated applications of the quaternized soy polymer did not lead to a deposit effect on the surface of hair.

Interference microscopy analysis of damaged hair, treated with quaternized polymer at 2% in solution and not rinsed, resulted in a significant decrease in the roughness of hair by 9.8% (Figure 4). Moreover, the treatment induced a significant reduction in the length of hair scales by 8.7% and tended to decrease scale gap. On the other hand, the quaternized polymer tested at 2% and then rinsed also presented a significant effect on the smoothing of hair surface, also visualized by three-dimensional iconography (Figure 5). Both roughness and the scale opening of the hair were significantly reduced by 7.5% and 8.4% respectively. Finally, the pronounced smoothing of scales and consequently the smoothing of the hair microrelief tended to decrease the hair scale length by 13.1%.

[FIGURE 5 OMITTED]

Conclusion

During this study, we have shown that quaternized peptides obtained from natural soy proteins increased the substantive effect of the monomeric molecules toward locks of natural blond hair. Moreover, the film-forming effect of these peptides was optimized by using an innovative technology of protein polymerization. Because of its elevated substantive and film-forming properties, this three-dimensional protein network improves the hair surface coating properties. Thus it induced the advantages of usual polymers without presenting a build-up effect, the major drawback of some coating products like quaternized cellulose, also tested in this study. Despite this high molecular weight, this active ingredient is easy to formulate since it is soluble in both water and diluted alcoholic solutions.

The capacity of quaternized soy polymer to spread on hair with a protective film and thus to improve styling was confirmed with a sensorial test realized by a trained hair stylist on 20 volunteers having unspoiled natural hair (no perms, no coloring, no bleaching). Tested at 2% in solution and compared to the placebo, the active ingredient significantly increased the ease of styling, the hair shine as well as the coating effect by 15%, 17% and 15% respectively. That is why the coating ingredient could be used in hair care products, rinsed or not, because of its capacity to form on the hair fiber a cohesive film with important elasticity and flexibility properties.

According to published data, a cationic product is more efficient in product for damaged hair, as they would be able to induce a self-regulation of hair repair. In the future, it may be interesting to evaluate the quaternized soy polymer on damaged hair in order to study thoroughly its whole properties.

References

Jones RT, Brown CA. The behavior of cationic cellulose derivatives containing fatty quat groups. Int J Cosmet Sci, 10, (1988) 219-229

Leidreiter HI, Jenni K, Jorbandt. Comparative evaluation of modern conditionning agents by tests on hair tresses. SOFW-Journal, 120, 14 (1994)

Santos Nogneira AC, Joekes I. Hair color changes and protein damage caused by ultraviolet radiation. J Photochem Photobiol B. 27;74 (2004) 109-17

Signori V. Review of the current understanding of the effect of UV and visible irradiation on hair structure and option for photoprotection. J Cosmet Sci, 55, 1 (2004) 95-113

Syed AL, Habib WW, Kuhajda AM. Water soluble polymers in hair care, prevention and repair of damage during hair relaxing. Water soluble polymer (1998)

Zviak C. The science of hair care. Editions Masson, Paris, 198

C. Lenaers, E. Le Dudal, M. Dana, B. Closs

R&D Department

Silab

Fig. 1: Influence of quaternization on substantivity

Locks + water                          100
Locks + 2% peptides                    118
Locks + 2% quaternized peptides        163

Note: Table made from bar graph.

Fig. 2: Influence of polymerization on substantivity

Locks + water                          100
Locks + 2% peptides                    118
Locks + 2% quaternized peptides        163

Note: Table made from bar graph.

Fig. 3: Quaternized cellulose vs. Polymer deposit effect

                     Locks + 2% quarternized        Locks + 2%
                           cellulose            quaternized polymer

1 bath/1 rinse              103                       96
1 bath/5 rinse              136                       74 *
5 x (1 bath/1rinse)         134                       89

* Significant differences between quaternized cellulose and
qauternized polymer according to student tests (p<0.05)

Note: Table made from bar graph.

Fig. 4: Effect on hair roughness, gap and scale length

                         Treated locks,     Treated locks,
                           not rinsed          rinsed

Hair roughness               -9.8 **            -7.5 **
Gap of hair scales           -7                 -8.4 *
Length of hair scales        -8.7 *            -13.1

* Significant results according to student tests (p<0.05)

** Significant results according to student tests (P<0.10)

Note: Table made from bar graph.