Content uploaded by André Rolim Baby
Author content
All content in this area was uploaded by André Rolim Baby on Jul 07, 2017
Content may be subject to copyright.
cosmetics
Review
In Vitro Methodologies to Evaluate the Effects of Hair
Care Products on Hair Fiber
Robson Miranda da Gama 1,2,3,*, André Rolim Baby 1and Maria Valéria Robles Velasco 1
1Laboratório de Cosmetologia, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo,
05508-000 São Paulo, Brazil; andrerb@usp.br (A.R.B.); mvrobles@usp.br (M.V.R.V.)
2Laboratório de Pesquisa do Curso de Farmácia, Faculdade de Medicina do ABC,
09060-870 Santo André, Brazil
3LESIFAR—Laboratório Escola Semi Industrial de Farmácia, Universidade Santo Amaro,
04829-300 São Paulo, Brazil
*Correspondence: robson.gama@fmabc.br; Tel.: +55-11-4993-7277; Fax: +55-11-4993-5400
Academic Editor: Won-Soo Lee
Received: 30 August 2016; Accepted: 23 December 2016; Published: 3 January 2017
Abstract:
Consumers use different hair care products to change the physical appearance of their hair,
such as shampoos, conditioners, hair dye and hair straighteners. They expect cosmetics products to
be available in the market to meet their needs in a broad and effective manner. Evaluating efficacy of
hair care products
in vitro
involves the use of highly accurate equipment. This review aims to discuss
in vitro
methodologies used to evaluate the effects of hair care products on hair fiber, which can
be assessed by various methods, such as Scanning Electron Microscopy, Transmission Electron
Microscopy, Atomic Force Microscopy, Optical Coherence Tomography, Infrared Spectroscopy, Raman
Spectroscopy, Protein Loss, Electrophoresis, color and brightness, thermal analysis and measuring
mechanical resistance to combing and elasticity. The methodology used to test hair fibers must be
selected according to the property being evaluated, such as sensory characteristics, determination
of brightness, resistance to rupture, elasticity and integrity of hair strain and cortex, among others.
If equipment is appropriate and accurate, reproducibility and ease of employment of the analytical
methodology will be possible. Normally, the data set must be discussed in order to obtain conclusive
answers to the test.
Keywords: hair; hair care; in vitro methodologies
1. Introduction
Human hair does not have a vital function, but is an important element of body image, because it
has a psychological and social importance as part of one’s identity. The hair is one of the few physical
characteristics of the human body that can be altered according to fashion trends, culture or social
values [1].
Consumers make use of different hair care products to change the physical appearance of hair,
such as shampoos, conditioners, styling products, hair dye and hair straighteners [2].
A healthy, beautiful and strong hair is broadly desired. It is a fiber composed of spindle cells,
made of a complex composition and contains mainly ↵-keratin which, depending on the type of hair,
can equate to 65% to 95% of its mass [3,4].
The hair can be divided into two components: Root and shaft. Inside the follicle is the hair root,
while the part which protrudes from the skin surface is called the hair shaft [
3
]. The hair shaft has
three main structures: Cuticle, Cortex and Medulla, from outside to inside. The external layer of the
hair shaft is the cuticle. Its core function is to protect the hair shaft against environmental and chemical
damages. Adherence and the orientation of cuticle scale is responsible for surface properties such as
Cosmetics 2017,4, 2; doi:10.3390/cosmetics4010002 www.mdpi.com/journal/cosmetics
Cosmetics 2017,4,2 2 of 10
brightness and resistance to combing. The Cortex is the layer located just below the cuticle. It lends
mechanical properties, such as tensile strength and elasticity to the hair fiber. In this layer, the melanin
responsible for hair color is located. The inside layer (Medulla) is present only in thick hair. Its function
has not been clearly defined [1–4].
Consumers are increasingly concerned about their appearance, either for aesthetic or health
reasons. They expect cosmetic products to meet their needs in a broad and effective manner. Nowadays,
there is great ease of access to information and this makes consumers aware and more demanding
regarding the acclaimed benefits described in product labels.
Evaluating efficacy of hair care products
in vitro
involves use of normally highly accurate
equipment. Tests are generally specific and provide information of only one hair attribute for
each assay.
Those techniques have advantages over subjective evaluations: They will not demand a group of
volunteers, they frequently demand only a short period of time, they use specific hair locks and must
meet standards.
Properties and effects of cosmetic products on hair fiber can be assessed through many
methods, such as Scanning Electron Microscopy [
5
], Transmission Electron Microscopy [
6
], Atomic
Force Microscopy [
7
], Optical Coherence Tomography [
8
], Infrared Spectroscopy [
9
], Raman
Spectroscopy [
10
], Protein Loss [
11
,
12
], Electrophoresis [
13
], color and brightness [
14
], Thermal
Analysis [15] and measuring mechanical resistance against combing and elasticity [12,16].
2. Image Analysis
2.1. Scanning Electron Microscopy
Scanning electron microscopy (SEM) is an electron microscope capable of producing highly
amplified and sharp images (up to 300,000 times from 3 to 20 nm, according to the equipment being
used) of sample surfaces by scanning them with focused electron beams, under vacuum. SEM
images are created by interacting electrons with the sample’s atoms, resulting in various signals
transformed in three-dimensional images. They are useful in order to evaluate the sample’s surface
topography and composition [
17
,
18
]. The SEM images, gray scale mapping, secondary electron count
(SE—secondary electrons) and backscattered electrons (BSE—electron backscattering) are generated
from analyzed material [18].
If the sample is not conductive and is going to be analyzed by SEM, it must first be metalized.
Metallization consists of precipitation under vacuum, in a micrometer film of conductive material
(e.g., gold or carbon) on the surface of the sample, enabling conduction of electrical current [18].
This could be applied to access certain hair strain properties, such as overall appearance [
19
];
particle deposition over surface and affinity to incorporated ingredients in hair care products [
20
];
structural and morphological changes [
6
,
21
,
22
]. This technique enables one to see samples with
opalescent to opaque appearance, to amplify images and to measure composing parts [5].
2.2. Transmission Electron Microscopy
Transmission electron microscopy (TEM) is a technique in which a beam of electrons is transmitted
through an ultra-thin sample, interacting as it passes through it. This system consists of an emitting
electrons source where a set of electromagnetic lenses enclosed in a column evacuated at low
pressure [23] control the beam.
When passing through the sample, the electrons interact to the lower surface with a distribution
of intensity and direction controlled mainly by the diffraction laws imposed by the crystalline
arrangement of the atoms in it. Then, the angular distribution of the diffracted electron beams
leads to the formation of the image or the diffraction diagram for observation on the screen or on the
photographic plate, with an increase in size between 1000 and 300,000 times [23].
Cosmetics 2017,4,2 3 of 10
TEM can be used to assess the ultrastructures and/or morphological changes of hair fibers after
the use of cosmetic chemical treatments [6,24,25].
2.3. Atomic Force Microscopy
Atomic Force Microscopy (AFM) enables the acquisition of a wide range of information, because it
provides many imaging possibilities for different types of samples [26].
Through this method, it is possible to study material surfaces beyond the scope of electronic and
optical microscopy. Visualizing macromolecules and cell imaging with near atomic resolution is made
possible. AFM has the advantage of virtually no need to make the sample conductive, as in such
techniques as SEM [27].
AFM images are generated by measuring the forces of attraction or repulsion between the sample
surface and a very fine needle, or probe, that scans the sample in such microscopes. This scanning is
performed by means of a piezoelectric system with displacement at x, y and z coordinates with the
accuracy of a tenth of an angstrom, which occurs through the applied tension range [27].
AFM could be applied to get certain hair strain properties, such as Particle deposition over surface
and affinity to incorporated ingredients in hair care products [
20
,
24
], structural and morphological
changes [26,28–31] as well.
2.4. Optical Coherence Tomography
Optical Coherence Tomography (OCT) is a new morphological method for non-invasive
investigation in cosmetology. Internal sectional images of high resolution are enabled by this method
for investigation of internal microstructures from living tissue [8,32].
OCT uses principles of low length coherence interferometry. Biological structure images with
high resolution tomography are obtained by the reflection of photons through direct coherence by
equipment [8,32].
Optical properties of the sample, such as backscattering coefficient and refractive index variation
are very important to obtain OCT images. The background color in the image represents the
backscattering coefficient, where white color represents the high-scattering coefficient and black
color the low-scattering coefficient [32].
OCT could be utilized to evaluate structural and morphological changes on hair by hair dye [
33
]
and hair straightening [8] treatments.
3. Spectroscopy Analysis
In the spectroscopic methods based on absorption, the emission of electromagnetic radiation on
molecules happens when the movement of electrons between their energy levels occurs [34].
3.1. Infrared Spectroscopy
Infrared spectroscopy (IRS) is based on the effects of radiation absorption. IRS is a type of
absorption spectroscopy in which absorbed energy belongs to the infrared region (wavelength between
700 and 50,000 nm) of the electromagnetic spectrum [34].
This methodology can be employed in compound identification or to investigate the composition
of a sample, which is founded on the fact that chemical bonds of chiral centers have specific vibrational
frequencies, which are equivalent to the energy levels of the molecule, also called vibrational levels.
Such frequencies depend on the form of potential energy on the molecule’s surface, molecular geometry,
molecular weight of the atoms and optionally vibrational coupling [9,34].
Near-infrared spectroscopy can be applied in hair research when one wants to analyze physical
properties, such as moisturizing action of a conditioner, structural and morphological changes on hair
by bleaching and hair dye treatments [9,35].
Cosmetics 2017,4,2 4 of 10
3.2. Raman Spectroscopy
Raman spectroscopy is a photonic technique that can provide high resolution within a few seconds,
chemical and morphological data on virtually any material, organic or inorganic compound for its
identification [34,36].
If an electromagnetic wave hits the surface of a medium, a fraction of the light is reflected while
the remainder is transmitted into the material. The portion of radiation transmitted through the surface
is absorbed as heat and another fraction is released in the form of scattered light. The emerging light
is within a small portion composed of different frequencies that occur; the process that rules this
phenomenon is called Raman scattering [34].
The Raman spectrum provides a direct measurement of the energy through normal oscillation
mode. In turn, it depends intrinsically on interactions between the constituent atoms. Thus,
the vibrational spectrum of materials will be significantly modified in the presence of compositional
and structural changes. Atomic interdiffusion quantum confinement stress effects enable Raman
Spectroscopy. This is used to investigate the mechanism leading to the reduction of tensile strength of
permanent waved human hair [
36
]; the internal structure changes in virgin human black hair keratin
fibers that undergo aging [
37
]; the influence of chemical treatments (reduction, heating, and oxidation)
on keratin fibers; and the structure of virgin white human hair resulting from a permanent hair
straightening [10,38].
3.3. Photoluminescence Spectroscopy
In photoluminescence, a medium is illuminated, then energy is absorbed. It generates an excess
of energy, an effect called photo-excitation. Photo-excitation makes the electrons of the material alter
its transition to the excited state with higher energy than those of equilibrium states. When these
electrons return to their equilibrium state, excess energy is ejected from the material and may include
light emission (radiative process) or not (non-radiative process). Energy of the emitted radiation is
related to the difference between the two electronic states involved in the transition. The amount of
light emitted depends on the relative contribution to the radiative process [34,39].
When it is desired to evaluate the effects of solar radiation on the degradation of the internal
structures of hair [
39
–
42
] or also hair photo-protection obtained by cosmetic ingredients [
40
–
43
],
photoluminescence spectroscopy analysis can be used, because in hair amino acids susceptible
to photo-degradation such as tryptophan (Trp), an intrinsic fluorophore is present. Disulphide
bonds in keratin, where significant losses in Trp, prior to any increase in photo-oxidation products,
are detected [42].
3.4. Protein Loss
The hair fiber, when exposed to physical or chemical treatments, may suffer damage to its structure
and thus may be altered in the protein composition. This can be evaluated easily by a quantitative
assay of the extracted hair amino acids [44,45].
Many spectrophotometric methods, over the years, have been suggested for the purpose of
measuring total protein from the hair; simply, there is no single universally considered methodology
in use for all media. The methods which are more used and cited in scientific literature are
Lowry [11,12,44–46], Bradford [42,47] and the bicinchoninic acid (BCA) method [48].
The Lowry assay is based on the reduction of the Folin reagent by protein previously treated with
copper in alkaline medium. A copper atom bonds to four residuals of amino acid. This complex reduces
the Folin reagent, with the solution becoming blue with maximum absorbance at about 715 nm [
11
,
12
].
The Bradford method is based on the interaction between Coomassie brilliant blue BG-250 dye and
protein macromolecules containing basic amino acids or aromatic side chains. In the pH of the reaction,
the interaction between the high molecular weight protein and BG-250 dye causes the dye to balance
the offset to the anionic form, for which maximum absorbance is at about 595 nm [42,47]. In the BCA
Cosmetics 2017,4,2 5 of 10
method, amino acids and polypeptide chains from the hair reduced the Cu
2+
ion to Cu
+
that reacts
with the BCA sodium salt. The product of this reaction is a purple complex composed of Cu
+
and two
molecules of BCA with maximum absorbance at about 562 nm [48].
3.5. Electrophoresis
Electrophoresis is a particle separation procedure according to its electrical charge and molecular
weight. It allows the isolation of organic molecule fractions such as RNA, DNA, proteins and enzymes
by its migration into a gel at the time of an electric potential application [49].
In this technique, a vat with two separated compartments is used where electrodes determine its
positive and negative poles. A buffer solution that conducts electricity between the chambers is placed
and the gel submerged. For the particles’ migration, a voltage and electrical current is applied to the
system and thus the lower molecular weight ionized molecules will be able to immigrate through the
gel—as opposed to the higher molecular weight ones—and will move a greater distance, getting closer
to the positive pole. The fragment distance (band) traveled from the point of application is compared
to the distance that other fragments of known sizes traversed in the same gel [49].
Electrophoresis is used to evaluate the influence of chemical cosmetic treatments, light exposure
and combinations of these processes in the modification of hair protein composition. Also, this process
is performed with untreated hair (virgin) and after cosmetic treatment, so it is possible to assess protein
amount, peptides and amino acids, due to the presence of new fractions (bands) of protein not observed
in untreated hair, indicating a degradation induced by the treatment of proteins, which originally were
not extractable in virgin hair [13,25].
3.6. Diffuse Reflectance Spectrophotometry
Diffuse reflectance spectrophotometry is based on the correlation between the energy reflectance
and absorption and scattering coefficients of a sample. The color change is obtained by diffuse
reflectance, is measured on a specific spectrophotometer and an integrating sphere can be used to
capture the scattered light from a sample. The device scans the spectral range from 360 to 740 nm,
and the diffuse light from a xenon lamp [50].
Sensing of color is subjective, and thus it is important to use analytical methods to allow discrete
measurements to be carried out. The Commission Internationale L’Eclairage, CIELAB or CIE L*a*b*,
developed and proposed in 1976 one model to measure color; in this model, color is divided onto three
axes, broadly linear to human perception. Standard L*, a*, b* measurements were collected where L*
refers to the lightness on a scale of 0 to 100, a* denotes the red-green color range (positive value denotes
higher red values) and b* represents the yellow-blue color range (positive value denotes higher yellow
values) [51].
The diffuse reflectance spectrophotometry was used for the measurement of luster and color of
hair fiber, virgin or treated, by hair care products [14,33,43,46,50].
4. Thermal Analysis
Thermal analysis is defined as a "group of techniques by which a physical property of a substance
and/or its reaction products is measured as a function of temperature and/or time while the substance
is subjected to a controlled program of temperature and under a specific atmosphere” [52].
According to Wendlandt [
53
], the thermoanalytical techniques most used are thermogravimetry
(TG), differential termogravimetry (DTG), differential thermal analysis (DTA), differential scanning
calorimetry (DSC) and thermomechanical (TMA). TG provides information with respect to changes in
mass function of time and/or under certain temperature atmosphere conditions. The experiments are
done by way of a high thermo-balance sensitivity, reproducibility and rapid answer as mass changes.
The obtained curves provide information on the composition and thermal stability of the sample,
intermediate products and residues formed [52,53].
Cosmetics 2017,4,2 6 of 10
DSC is a thermal analysis technique where energy differences are measured according to the
substance and a reference material (thermally stable), depending on temperature. The substance
and reference material are subjected to a controlled program temperature. During the heating or
cooling process, a sample may go through temperature changes due to exothermic or endothermic
events [52,53].
For better characterization of materials, it is significant to use a combination of data from TG/DTG
and DSC measurements, as the TG/DTG detects events associated with mass loss, while DSC indicates
the thermal events related to mass variation [15].
Several of the authors who researched the thermal analysis applied on human hair executed TG
and DSC analyses with the purpose of characterizing the keratin of human hair [
54
–
56
] and verifying
the effects of hair care products on keratin structure [15,57,58].
5. Mechanical Resistance
Mechanical strength of the hair can be measured by suitable equipment intended for measuring
strength properties or elasticity of hair fiber due to tension force or load.
Hair fibers have elastic and plastic property. Plastic property of the hair fiber is measurable when
a force is applied; the hair fiber extends in part, due to this force and effect, stretching about 2% of its
original length. After the elastic phase, hair begins the plastic phase when the hair stretches quickly,
approximately 25% to 30% in length, with a moderate increase in load. Maintaining the value of
the constant force applied, the fibers stretch proportionally to the load until rupture occurs [
59
,
60
].
The lower the value of the breaking strength, the more damaged is inflicted on the cortex [12,16].
To evaluate this feature, a device has been used called the Instron Tensile Tester commercially or
Dia-Stron MTT (modified dynamometer) or texturometer. Hair strands are fixed on a support, oriented
from root to tip; the device applies a force or load to disrupt the fibers, which is registered by software,
converting the information into a load graph of elongation [12,14,16,61].
Straightening and bleaching alter the resistance to breakage and tensile properties of human
hair [12,62], while conditioner does not interfere with the test results [14,16].
6. Combing Resistance Analyses
Combing can be defined as the subjective perception of difficulty or ease in which hair can be
combed. This is directly related to the forces that oppose the action of combing hair. This is an
important attribute in the conditioning of hair and in consumer perception; the improvement reflects
the ease of combing hair [63].
Assessing combing requires a modified dynamometer or texturometer with two non-metallic
combs placed on a support [12,64,65].
This method consists of hanging a hair swatch over a force-measuring device (dynamometer or
texturometer), making use of a comb close to the root end of the swatch, setting the comb in a right
combing action directly through the swatch at a standard speed, and recording without interruption
the forces that resist its motion from the point of insertion until it clears the tip end of the swatch [
64
,
65
].
Hair straightening alters the resistance to the combing of human hair, while additionally,
the conditioner agents in hair straightening improve the test results [12].
7. Methodology to Support the Claims of Hair Care Products
Table 1presents a summary of the methodologies applied to test each claim of hair care products.
Cosmetics 2017,4,2 7 of 10
Table 1. A summary table of the methodologies applied to test each claim of hair care products.
Claims Methodologies Applied
Damage hair
reduction
Protein loss [
11
,
12
,
44
–
48
]; Electrophoresis [
13
,
25
]; Scanning Electron Microscopy [
5
,
19
–
22
];
Transmission Electron Microscopy [
6
,
24
,
25
]; Atomic Force Microscopy [
7
,
26
,
28
–
31
]; Optical
Coherence Tomography [8,33]; RAMAN spectroscopy [10,32–34]
Hair Shine-Gloss Diffuse reflectance spectrophotometry [14,33,43,46,50]
Easy to comb Combing resistance [12,64,65]
Strength properties Resistance to breakage [12,14,16,33,61,62]
Photoprotection Photoluminescence spectroscopy [40–43]
Long-lasting color Diffuse reflectance spectrophotometry [14,33]
Heat protection Differential scanning calorimetry and Thermogravimetry [15,54–58]
Moisturizing hair Near Infrared spectroscopy [9,34]; Differential scanning calorimetry and
Thermogravimetry [15,54–58]
8. Conclusions
Hair fiber has many properties and the current methodologies are complementary since, generally,
they are employed to study one single feature. Thus, the use of many procedures enables multiple
variable determinations, i.e., the elucidation of hair fiber properties, allowing wider results considering
the hair attributes tested by adding cosmetic ingredients.
The methodology used for testing hair fiber must be selected according to the property or
characteristic being analyzed, for instance, sensorial analysis; determination of brightness; resistance to
rupture; elasticity; and integrity of hair strain and cortex, among others. If the equipment is appropriate
(availability, initial cost or maintenance cost, for instance) and accurate, reproducibility and ease of
employment of the analytical methodology will be considered.
Usually, the data set must be discussed in order to obtain conclusive answers to the test.
Author Contributions:
Robson Miranda da Gama wrote the paper; André Rolim Baby and Maria Valéria
Robles Velasco reviewed the paper.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Bolduc, C.; Shapiro, J. Hair care products: Waving, straightening, conditioning and coloring. Clin. Dermatol.
2001,19, 431–436. [CrossRef]
2. Gavazzoni-Dias, M.R. Hair cosmetics: An overview. Int. J. Trichol. 2015,7, 2–15. [CrossRef][PubMed]
3.
Lai-Cheong, J.E.; McGrath, J.A. Structure and function of skin, hair and nails. Medicine
2009
,37, 223–226.
[CrossRef]
4.
Guerra-Tapia, A.; Gonzalez-Guerra, E. Hair cosmetics: Dyes. Actas Dermosifiliogr.
2014
,105, 833–839.
[CrossRef][PubMed]
5.
Tomes, C.; Jones, J.T.; Carr, C.M.; Jones, D. Three-dimensional imaging and analysis of the surface of hair
fibers using scanning electron microscopy. Int. J. Cosmet. Sci. 2007,29, 293–299. [CrossRef][PubMed]
6.
Ahn, H.J.; Lee, W. An ultrastructural study of hair fiber damage and restoration following treatment with
permanent hair dye. Int. J. Dermatol. 2002,7, 88–92. [CrossRef]
7.
Dupres, V.; Camesano, T.; Langevin, D.; Checco, A.; Guenoun, P. Atomic force microscopy imaging of hair:
correlations between surface potential and wetting at the nanometer scale. J. Colloid Interface Sci.
2004
,269,
329–335. [CrossRef][PubMed]
8.
Velasco, M.V.R.; Baby, A.R.; Sarruf, F.D.; Kaneko, T.M.; Samad, R.E.; Vieira Junior, N.D.; Freitas, A.Z.
Prospective ultramorphological characterization of human hair by optical coherence tomography.
Skin Res. Technol. 2009,15, 440–443. [CrossRef][PubMed]
9.
Pande, C.M.; Yang, B. Near-infrared spectroscopy: Applications in hair research. Int. J. Cosmet. Sci.
2000
,
51, 183–192.
Cosmetics 2017,4,2 8 of 10
10.
Kuzuhara, A. Analysis of structural changes in bleached keratin fibers (black and white human hair) using
Raman spectroscopy. Biopolymers 2006,81, 506–514. [CrossRef][PubMed]
11.
Faria, P.M.; Camargo, L.N.; Carvalho, R.S.H.; Paludetti, L.A.; Velasco, M.V.R.; Gama, R.M. Protective effect
of argan oil (Argania spinosa Kernel Oil) and cupuassu butter (Theobroma grandiflorum Seed Butter) post
treatment with hair dye. J. Cosmet. Dermatol. Sci. Appl. 2013,3, 40–44.
12.
Sá-Dias, T.C.; Baby, A.R.; Kaneko, T.M.; Velasco, M.V.R. Protective effect of conditioning agents on Afro-ethnic
hair chemically treated with thioglycolate-based straightening emulsion. J. Cosmet. Dermatol.
2008
,7, 120–126.
[CrossRef][PubMed]
13.
Ruetsch, S.B.; Yang, B.; Kamath, Y.K. Chemical and photo-oxidative hair damage studied by dye diffusion
and electrophoresis. J. Cosmet. Sci. 2003,54, 379–394. [PubMed]
14.
Dario, M.F.; Pahl, R.; Castro, J.R.; Lima, F.S.; Kaneko, T.M.; Pinto, C.A.S.O.; Baby, A.R.; Velasco, M.V.R.
Efficacy of Punica granatum L. hydroalcoholic extract on properties of dyed hair exposed to UVA radiation.
J. Photochem. Photobiol. B Biol. 2013,120, 142–147. [CrossRef][PubMed]
15.
Gama, R.M.; Balogh, T.S.; França, S.; Sá-Dias, T.C.; Bedin, V.; Baby, A.R.; Velasco, M.V.R. Thermal analysis of
hair treated with oxidative hair dye under influence of conditioners agents. J. Therm. Anal. Calorim.
2011
,
106, 399–405. [CrossRef]
16.
Velasco, M.V.R.; Balogh, T.S.; Kagiyama, J.W.; Dario, M.F.; Gama, R.M.; Bedin, V.; Baby, A.R. Influence of
Brazilian vegetable oils on mechanical resistance of hair fiber. Biomed. Biopharm. Res. 2015,12, 99–106.
17.
Zhou, W.; Apkarian, R.; Wang, Z.L.; Joy, D. Fundamentals of scanning electron microscopy (SEM). In Scanning
Microscopy for Nanotechnology: Techniques and Applications; Zhou, W., Wang, Z.L., Eds.; Springer: New York,
NY, USA, 2007; pp. 1–39.
18.
Duarte, L.C.; Juchen, P.L.; Pulz, G.M.; Brum, T.M.; Chodur, N.; Liccardo, A.; Fischer, A.C.; Acauan, R.B.
Aplicações de microscopia eletrônica de varredura (MEV) e sistema de energia dispersiva (EDS) no Estudo
de Gemas: Exemplos brasileiros. Pesquisas Geociências 2003,30, 3–15. (In Portuguese)
19.
Ali, N.; Zohra, R.R.; Qader, S.A.; Mumtaz, M. Scanning electron microscopy analysis of hair index on
Karachi’s population for social and professional appearance enhancement. Int. J. Cosmet. Sci.
2015
,37,
312–320. [CrossRef][PubMed]
20.
Monteiro, V.F.; Natal, A.M.D.; Soledade, L.E.B.; Longo, E. Morphological analysis of polymers on hair fibers
by SEM and AFM. Mater. Res. 2003,6, 501–506. [CrossRef]
21.
Camacho-Bragado, G.A.; Balooch, G.; Dixon-Parks, F.; Porter, C.; Bryant, H. Understanding breakage in
curly hair. Br. J. Dermatol. 2015,173, 10–16. [CrossRef][PubMed]
22.
Richena, M.; Rezende, C.A. Effect of photodamage on the outermost cuticle layer of human hair. J. Photochem.
Photobiol. B 2015,153, 296–304. [CrossRef][PubMed]
23.
Sasaki, K.; Murata, H.; Kuroda, K.; Saka, H. Conventional Transmission Electron Microscope observation of
electric and magnetic fields. In The Transmission Electron Microscope; Maaz, K., Ed.; InTech: Rijeka, Croatia,
2012; pp. 1–27.
24.
Thibaut, S.; Barbarat, P.; Leroy, F.; Bernard, B.A. Human hair keratin network and curvature. Int. J. Dermatol.
2007,46, 7–10. [CrossRef][PubMed]
25.
Kim, M. Effect of procyandin oligomers on oxidative hair damage. Skin Res. Technol.
2011
,17, 108–118.
[CrossRef][PubMed]
26.
Longo, V.M.; Monteiro, V.F.; Pinheiro, A.S.; Terci, D.; Vasconcelos, J.S.; Paskocimas, C.A.; Leite, E.R.; Longo, E.;
Varela, J.A. Charge density alterations in human hair fibers: An investigation using electrostatic force
microscopy. Int. J. Cosmet. Sci. 2006,28, 95–101. [CrossRef][PubMed]
27.
Edstrom, R.D.; Meinke, M.H.; Yang, X.; Yang, R.; Evans, D.F. Scanning tunneling microscopy of the enzymes
of muscle glycogenolisis. Ultramicroscopy 1990,33, 99–106. [CrossRef]
28.
Swift, J.A.; Smith, J.R. Atomic force microscopy of human hair. Scanning
2000
,22, 310–318. [CrossRef]
[PubMed]
29.
Gurden, S.P.; Monteiro, V.F.; Longo, E.; Ferreira, M.M. Quantitative analysis and classification of AFM images
of human hair. J. Microsc. 2004,215, 13–23. [CrossRef][PubMed]
30.
Smith, J.; Tsibouklis, J.; Nevell, T.; Breakspear, S. AFM friction and adhesion mapping of the substructures of
human hair cuticles. Appl. Surf. Sci. 2013,285, 638–644. [CrossRef]
31.
Seshad, I.P.; Bhushan, B. Effect of ethnicity and treatments on in situ tensile response and morphological
changes of human hair characterized by atomic force microscopy. Acta Mater.
2008
,56, 3585–3597. [CrossRef]
Cosmetics 2017,4,2 9 of 10
32.
Freitas, A.Z.; Amaral, M.M.; Raele, M.P. Optical coherence tomography: Development and applications.
In Laser Pulse Phenomena and Applications; Duarte, F.J., Ed.; InTech: Rijeka, Croatia, 2010; pp. 409–432.
33.
Velasco, M.V.R.; Abreu, S.R.P.; Freitas, A.Z.; Bedin, V.; Baby, A.R.; Gama, R.M. Optical coherence tomography
to evaluate the effects of oxidative hair dye on the fiber. Skin Res. Technol.
2016
,22, 430–436. [CrossRef]
[PubMed]
34.
Rodrigues, A.G.; Galzerani, J.C. Espectroscopias de infravermelho, Raman e de fotoluminescência:
Potencialidades e complementaridades. Rev. Bras. Ensino Fis. 2012,34, 1–9. (In Portuguese) [CrossRef]
35.
Miyamae, Y.; Yamakawa, Y.; Ozaki, Y. Evaluation of physical properties of human hair by diffuse reflectance
near-infrared spectroscopy. Appl. Spectrosc. 2007,61, 212–217. [CrossRef][PubMed]
36.
Kuzuhara, A. Analysis of structural changes in permanent waved human hair using Raman spectroscopy.
Biopolymers 2007,85, 274–283. [CrossRef][PubMed]
37.
Kuzuhara, A.; Fujiwara, N.; Hori, T. Analysis of internal structure changes in black human hair keratin fibers
with aging using Raman spectroscopy. Biopolymers 2007,87, 134–140. [CrossRef][PubMed]
38.
Kuzuhara, A. Internal structural changes in keratin fibres resulting from combined hair waving and stress
relaxation treatments: A Raman spectroscopic investigation. Int. J. Cosmet. Sci.
2016
,38, 201–209. [CrossRef]
[PubMed]
39. Dyer, J.M.; Bringans, S.D.; Bryson, W.G. Determination of photo-oxidation products within photoyellowed
bleached wool proteins. Photochem. Photobiol. 2006,82, 551–557. [CrossRef][PubMed]
40.
Longo, V.M.; Silva-Pinheiro, A.; Sambrano, J.R.; Agnelli, J.A.M.; Longo, E.; Varela, J.A. Towards an insight on
photodamage in hair fibre by UV-light: An experimental and theoretical study. Int. J. Cosmet. Sci.
2013
,35,
539–545. [CrossRef][PubMed]
41.
Signori, V. Review of the current understanding of the effect of ultraviolet and visible radiation on hair
structure and options for photoprotection. J. Cosmet. Sci. 2004,55, 95–113. [CrossRef][PubMed]
42.
Dario, M.F.; Baby, A.R.; Velasco, M.V. Effects of solar radiation on hair and photoprotection. J. Photochem.
Photobiol. B 2015,153, 240–246. [CrossRef][PubMed]
43.
Fernández, E.; Martínez-Teipel, B.; Armengol, R.; Barba, C.; Coderch, L. Efficacy of antioxidants in human
hair. J. Photochem. Photobiol. B 2012,117, 146–156. [CrossRef][PubMed]
44.
Sandhu, S.S.; Ramachandran, R.; Robbins, C.R. A simple and sensitive method using protein loss
measurements to evaluate damage to human hair during combing. J. Soc. Cosmet. Chem. 1995,46, 39–52.
45.
Sandhu, S.S.; Robbins, C.R. A simple and sensitive technique, based on protein loss measurements, to assess
surface damage to human hair. J. Soc. Cosmet. Chem. 1993,44, 163–175.
46.
Nogueira, A.C.S.; Joekes, I. Hair color changes and protein damage caused by ultraviolet radiation.
J. Photochem. Photobiol. B 2004,74, 109–117. [CrossRef][PubMed]
47.
Silva, A.L.; Nunes, A.S.; Gesztesi, J.L. Protein loss quantification of abraded virgin and abraded bleached
hair according to Bradford assay. J. Cosmet. Sci. 2004,55 (Suppl. 2), S175–S179. [CrossRef][PubMed]
48.
França-Stefoni, S.A.; Dario, M.F.; Sá-Dias, T.C.; Bedin, V.; Almeida, A.J.; Baby, A.R.; Velasco, M.V. Protein
loss in human hair from combination straightening and coloring treatments. J. Cosmet. Dermatol.
2015
,14,
204–208. [CrossRef][PubMed]
49. Westermeier, R. Electrophoresis in Practice; Wiley-VCH: Weinheim, Germany, 2005; p. 427.
50.
Scanavez, C.; Zoega, M.; Barbosa, A.; Joekes, I. Measurement of hair luster by diffuse reflectance
spectrophotometry. J. Cosmet. Sci. 2000,55, 289–302.
51.
Gulrajani, M.L. Colour Measurement: Principles, Advances and Industrial Applications; Woodhead Publishing:
London, UK, 2010; p. 310.
52.
Silva, E.C.; Velasco-de-Paola, M.V.R.; Matos, J.R. Análise térmica aplicada à cosmetologia. Rev. Bras.
Cienc. Farm. 2007,43, 347–357. (In Portuguese) [CrossRef]
53. Wendlandt, W.W. Thermal Analysis, 3rd ed.; Wiley: New York, NY, USA, 1986; p. 1.
54.
Lima, C.R.R.; Almeida, M.M.; Velasco, M.V.R.; Matos, J.R. Thermoanalytical characterization study of hair
from different ethnicities. J. Therm. Anal. Calorim. 2016,123, 2321–2328. [CrossRef]
55.
Éhén, Z.; Novák, C.; Sztatisz, J.; Bene, O. Thermal characterization of hair using TG-MS combined
thermoanalytical technique. J. Therm. Anal. Calorim. 2004,78, 427–440. [CrossRef]
56.
Wortmann, F.J.; Stapels, M.; Elliott, R.; Chandra, L. The effect of water on the glass transition of human hair.
Biopolymers 2006,81, 371–375. [CrossRef][PubMed]
Cosmetics 2017,4,2 10 of 10
57.
Wortmann, F.J.; Springob, C.; Sendelbach, G. Investigations of cosmetically treatedhuman hair by differential
scanning calorimetry in water. J. Cosmet. Sci. 2002,53, 219–228. [PubMed]
58.
Belleti, K.M.S.; Fererman, I.H.; Mendes, T.R.O.; Piacekeski, A.D.; Monteiro, V.F.; Carreño, N.V.; Valentini, A.;
Leite, E.R.; Longo, E. Evaluation of hair fiber hydration by differential scanning calorimetry, gas
chromatography and sensory analysis. J. Cosmet. Sci. 2003,54, 527–535.
59. Woodruff, J. Improving hair strength. Cosmet. Toilet. 2002,117, 33–36.
60.
Jachowicz, J.; Smewing, J. Using texture analysis to substantiate hair care claims. Cosmet. Toilet.
2006
,121,
69–76.
61.
Ruetsch, S.B.; Weigmann, H.D. Mechanism of tensile stress release in the keratin fiber cuticle: I.
J. Soc. Cosmet. Chem. 1996,47, 13–26.
62.
Robbins, C.R.; Crawford, R.J. Cuticle damage and the tensile properties of human hair. J. Soc. Cosmet. Chem.
1991,42, 49–58.
63.
Wortmann, F.J.; Schwan-Joncyk, A. Investigating hair properties relevant for hair ‘handle’. Part I: Hair
diameter, bending and frictional properties. Int. J. Cosmet. Sci. 2006,28, 61–68. [CrossRef][PubMed]
64. Garcia, M.L.; Diaz, J. Combability measurements on hair. J. Soc. Cosmet. Chem. 1976,27, 379–398.
65. Evans, T. Evaluating hair conditioning with instrumental combing. Cosmet. Toilet. 2011,126, 558–563.
©
2017 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
