Bioengineering Techniques for the Efficacy Studies of Herbal Cosmetics

 

Sneha Sahu and Swarnlata Saraf*

University Institute of Pharmacy, Pt. Ravishankar Shukla University, Raipur- 492010 CG India

*Corresponding Author E-mail: swarnlata_saraf@rediffmail.com

 

ABSTRACT:

Bioengineering techniques have turned the way of cosmetics evaluation towards the non-invasive direction. The numerical assessment of skin properties improvement sounds interesting to the consumers. Bioengineering techniques have attracted the minds of many researchers and beliefs of consumers towards cosmetic. Instruments developed under these techniques are harmless. These techniques are fruitful not only for the cosmetics evaluation but also for comparative studies and for treatment of diseases. In efficacy studies of cosmetics, of particular importance is the epidermis, its water content, its composition, and its barrier function. It facilitates the quantitative evaluation of moisturizers, fairness creams, sun protection creams, anti-aging products, scrubbers etc.

 

KEYWORDS: bioengineering techniques, instrumentations, skin firmness, skin hydration, skin color, barrier function, wrinkles, sebum level, and microcirculation.

 


INTRODUCTION:

Bioengineering techniques apply engineering principles to address challenges in the fields of biology and medicine. The word bioengineering was coined by British scientist and broadcaster Heinz Wolff in 19541.  Herbal companies all over the world produce a lot of cosmetics for one or the other purpose. The cosmetics are generally used externally like moisturizing lotion, fairness cream, sunscreen lotions, anti-aging creams etc. they show direct effect on the skin after short or long term use.

 

When a herbal cosmetic comes to market it is obvious that it had passed through several evaluation parameters direct from the crude drug to the finished product as per one or the other regulations. There are several guidelines for the efficacy evaluation of cosmetic products e.g. Colipa guidelines 2.  Instrumental tests are part of all the efficacy studies, which are not other than bioengineering techniques. Bioengineering techniques closely relates to the substantiation of cosmetics that have been well developed. Nowadays, the internal structure of human skin and cutaneous cells can be studied non-invasively using these methods. .

 

Such measurement enables us to perform numerical assessment of skin. Skin conditions that have conventionally been categorized as normal can now be classified into various types on the basis of numerical values. Efficacy studies using bioengineering techniques are often being carried out in the companies producing cosmetics.

 

Skin and skin surface properties:

The skin is the largest organ of the body, with a surface area of approximately 1.75 m2 in the average adult3. The skin weighs between 3.5 – 4.5 kg, comprising about 7% of body’s total weight. It is composed of three different layers: the epidermis, dermis, and subcutaneous layers. The epidermis, the outer-most layer. The stratum corneum (SC) is the outer-most layer of the epidermis and is the part of the skin that is in direct contact with the environment. It is composed of approximately 20 layers of dead skin cells. 4-5 Normal skin displays a smooth texture and a rosy, clear surface, with fine pores. There are no visible blemishes, greasy patches or flaky areas; sebum production, moisture content, keratinisation and desquamation are well balanced. Normal skin is often found in young persons. Instruments are available for the assessment of several skin properties like firmness, hydration, barrier function, corneocytes, skin color, sebum level, lines and wrinkles, skin thickness, microcirculation and many other.

 

 

Measurement of firmness

Firmness of skin is measured in terms of collagen content and texture.The total collagen content of the skin decreases, leading to the potential decrease in firmness. The stimulation of collagen production is necessary in aged individuals in order to maintain firm and healthy skin.  Various herbal extracts e.g. extracts of Gottu Cola (Centella Asiatica), have the ability to stimulate dermal fibroblast and increase collagen synthesis. Herbal moisturizers are also available for these purpose of different brands e.g. Himalaya, Ayur, Aroma etc.

 

The way in which skin reacts to the mechanical constraints of pinching, twisting, pulling and creasing vary from one person to another. The methods used will attempt to measure the degree of deformation and the time required for the skin to return to its original state. The skin's firmness and elasticity reflect the elastic properties of the connective tissue in the dermis and the overlapping of collagen and elastin fibres. Over time, this network becomes disorganised, causing this firmness and suppleness to decline. Instruments that measure firmness are:

1.                Torquemeter

2.                Densi-score

3.                Extensometer

4.                Torsional Ballistometer

5.                Gas bearing electrodynamometer

6.                Vesmeter

7.                Cutometer

8.            Reviscometer

 

TORQUEMETER:

Torque meter is a proven method for the evaluation of stratum corneum elasticity, hydration & frictional properties. It is adaptable for either stratum corneum or full skin thickness studies.  Automated analysis of skin is based on Windows™ based applications software.

 

The dermal torque meter provides a tortional force to the skin and measures the response of the skin to this force; the force is then removed and the recovery of the skin is measured.

 

The DTM consist of a sensor head, a control unit and a accompanying computer. The sensor head is constructed of a torque-motor and an angle sensor, with the torque motor being connected to the flat disc at the end of the sensor head. A concentric torque ring around the torque disc defines an annular ring gap, which in turn determines the skin area to be examined. The force is transferred to the skin by securing it to both the torque disc and torque ring using double-sided adhesive tape. The torque disc may then be rotated relative to the torque ring, which supports the surrounding skin. Torque is applied for a pre-determined time and the resulting angular displacement is recorded. When the torque is removed, restoring forces within the skin attempt to return the torque disc to its original position and this is similarly recorded. On initial application of torque an immediate deformation (extensibility) of the skin occurs (Ue). This is followed by a slower deformation, which reflect the visco-elasticity of the skin. After a suitable time period (e.g. 15 secs) the torque is removed and an immediate recovery (Ur) is observed followed by a slower recovery. Ur/Ue Elastic recovery, illustrates the reduction in the ability of the skin to recover from an applied deformation, as the individual becomes older 6.

 

Adapted from: Dia-stron limited

 

Fig 2 Torquemeter Supplied by: Dia-stron limited

 

DENSI-SCORE:

Densi-score is a simple instrument that is operated manually. L’Oreal patents this device.

 

This device works on the principle of correlating "skin density" with skin creasing. A baby's skin does not show any creases when pressed between two fingers, whereas that of an older subject will show multiple. This is because a baby's skin has a higher density.

 

 

Fig 3 Densi-score  Supplied by: : Dia-stron limited

Densi-score has two detachable parts which together forms a aperture in the middle. The size of the aperture can be adjusted by the application of force. It consists of applying a reproducible mechanical creasing force of 40% on the forearm. The calibration enables the number of creases to be correlated with the skin's density. This diminishes with age due to the destructuring, which takes place in the dermis and rigidification of the horny layer, resulting in creases becoming more frequent. Scales of creasing are therefore drawn up according to density and age. These are then used to assess the efficiency of an anti-age product designed to improve skin firmness.

Adapted from: Dia-stron limited

 

 

TORSIONAL BALLISTOMETER

A dynamic technique for assessing the intrinsic viscoelastic properties of a material, i.e., determining physical properties of materials which do not depend on the method of measurement.

 

The ballistrometer is based on the "drop impact" of a body onto a stationary surface. A collision in one dimension is provoked by allowing a bard body to drop from a given height onto the skin surface to be tested. After the collision, the impacting body undergoes a variable number of rebounds decreasing in amplitude. By measuring the height of the rebounds, the amount of energy returned by the tissue is calculated in terms of coefficient of restitution e. An increase of e was observed when a high water content was present in the skin 7-8.

 

IDRA®Version 3.0 (Integrated Dynamic Rebound Analyzer) is a PC-based (USB port linked) Ballistometer, which employs a dynamic technique for assessing the intrinsic viscoelastic properties of a material, i.e., determining physical properties of materials which do not depend on the method of measurement. For relatively soft materials, such as skin, the measurement technique generally involves a light-we ight hammer, anchored at one end, which freely falls onto the test surface under gravitational force, recording and analysis of the resulting hammer oscillatory displacement-time data, and the determination of characteristic physical parameters. IDRA® Version 3.0 is installed as an Excel COM Add-in DLL, which greatly extends the functionality of the Instrument. IDRA® hardware/software components and Microsoft's excel synergize to make a powerful diagnostic tool.

Adapted from: Elweco, Inc.

 

 

Supplied by: Elweco, Inc.

GAS BEARING ELECTRODYNOMETER

Gas Bearing Electrodynamometer allows us to measure objectively the viscoelastic properties of the stratum corneum in vivo and to evaluate, in terms of skin softness, the changes of this parameter induced by the application of emollients. The Gas Bearing Electrodynamometer (GBE) has been used for the last 20 years to obtain sensitive measurements of the stratum corneum 9  .

 

It is able to apply a sinusoidal loading stress of less than 5g parallel to the skin surface, with a resulting displacement of less than 1mm in each direction. This is achieved by suspending an armature in a gas bearing to create near friction-free movement. Changes in the magnetic field generated by a surrounding coil cause the armature to oscillate at a known frequency and amplitude. The coil is activated by a sinusoidal signal from a low frequency function generator or from a suitable software trigger. The armature of the instrument is typically attached to the skin surface by a stiff wire probe bent to 90o at its free end. A small plastic stub is usually cemented to the free end of the probe and used to attach the probe to the skin surface using a circular piece of double-sided sticky tape. Displacement of the armature is measured by a sensitive LVDT, mounted coaxially with the coil. Coil and LVDT outputs (force and displacement) are amplified and then supplied for analysis to either a storage oscilloscope or a computer equipped with suitable software.

 

Results of force and displacement measurements of skin are typically displayed as a hysteresis loop. Analysis of the gradient of the loop (force/displacement or displacement/force) yields derivatives of the dynamic spring rate (DSR) usually expressed as g/mm (a measure of the force required to stretch or compress the skin per unit extension), mm/N or µm/g (measures of stretching or compression of the skin in response to a given applied force). Such analysis yields information about the elastic properties of the skin. Analysis of the phase lag between force and displacement responses yields information about the viscous properties of the skin10

 

VESMETER:

It is a novel method using a computer-linked device to simultaneously quantify physical properties of the skin such as hardness, elasticity and viscosity.

 

Skin hardness was calculated by measuring the depth of an indenter pressed onto the skin. The Voigt model was used to calculate skin elasticity, viscosity, visco–elastic ratio and relaxation time by analyzing the waveform of skin surface behaviour.

 

When the probe is placed at a right angle on the skin, the indenter is depressed onto the skin at a constant speed by means of electromagnetic power, and the position sensor constantly traces the path of the indenter. The hardness of an object can then be expressed as the area of the depression divided by the pressure of the indenter. The stress relaxation behavior of viscoelastic materials can be analysed by using the Voigt model that consists of two components, a purely viscous dashpot and a purely elastic spring connected in parallel. Elasticity (G), viscosity ({eta}), visco–elastic ratio (VER) and the relaxation time ({tau})  can be calculated by analysing the waveform of the stress relaxation behaviours of the skin with a computer. VER is related to the superiority of the viscous element over the elastic element. The relaxation time is related to the time taken by the deformed material to return to its original state. Before this device is used for the human skin, accuracy of the measurements is examined by using test samples made with polyurethane or silicon gel of a known hardness, elasticity and viscosity. The measurements thus obtained are compared with those of the standards of the American Society for Testing and Materials (ASTM) for hardness and of the International Organization for Standardization (ISO) for elasticity and viscosity. The range of the samples measured fully covered the range of human skin from normal to extremely hard11.

 

FIG. 6. Photograph (A) and configuration (B) of the probe.

 

 

The results of the measurements are displayed on the computer screen connected to the probe. The numbers in (B) indicate the following components: 1, recognition mark; 2, position sensor; 3, indenter; 4, measurement head; 5, electromagnetic coil; 6, permanent magnet; 7, power switch.

Adapted from: Dia-stron limited”:

 

CUTOMETER:

It is well-established Elasticity Measurement tool. The Cutometer® MPA 580, controlled by a Windows® based software, is a frequently used model.

The measuring principle is based on the suction method.

 

Negative pressure is created in the device and the skin is drawn into the aperture of the probe. Inside the probe, the penetration depth is deter- mined by a non-contact optical measuring system. This optical measuring system consists of a light source and a light receptor, as well as two prisms facing each other, which project the light from transmitter to receptor. The light intensity varies due to the penetration depth of the skin. The resistance of the skin to be sucked up by the negative pressure (firmness) and its ability to return into its original position (elasticity) are displayed as curves at the end of each measurement. From these curves interesting measurement parameters can be calculated.

 

The small, convenient size of the probe allows successful measurement of skin areas that are difficult to reach. The probe contains an elastic spring that provides constant pressure of the probe on the skin. In addition, the probe can be fixed to the measured skin area by double-sided adhesive rings. The specific calibration values of each probe are stored in its plug, thus allowing simple and quick exchange for servicing purpose.

 

Adapted from: Courage + Khazaka electronic GmbH

Fig 7 Supplied by: Courage + Khazaka electronic GmbH

 

 

REVISCOMETER :

The reviscometer® is used to diagnose the condition of the collagen and elastin fibers with reference to the respective age of the individuals. The special measurement method of the Reviscometer® RV 600 allows investigation of new interesting fields as orientation of incision during cutaneous surgery, relation between body mass index and elasticity, photoageing and many more.

 

The new aspect of the measurement - based on Resonance Running Time of the Reviscometer® RV 600 - in addition to finding elastic and viscoelastic features is to determine the direction of the collagen and elastine fibres.

 

The probe head contains two sensors which are placed on the skin. One is emitting acoustical shockwaves, the other serves as receiver. Shockwaves propagate differently through the skin according to the state of the elastic fibres and the moisture content of the skin. The time As the time depends to a high amount on the fact whether the measurement is executed with the direction of the fibres or against it, and the measurement can be performed in different directions on the same skin site, the direction of the fibres is measured. the wave needs to travel from emitter to receiver is the measured parameter.  A positioning top with marks for the direction in 0- 180°, 45-225°, 90-270°, and 135-315°-axis, fixed with a double sided adhesive ring, enables the user to easily measure in all directions on one skin site. The modern, high quality electronics of the probe allow a very quick, easy and precise measurement. Its low weight assists in ease of handling. All calibration data are inside the probe. Thus the probe is completely self contained and can be connected to different device types. The accuracy of the device can easily be checked at any time on a special silicone material.

sourced by:  Courage + Khazaka electronic GmbH

 

Fig 8: Supplied by: Courage + Khazaka electronic GmbH.

 

Measurement of hydration

Skin properties are highly dependant of its water content. It is easy to observe that a tanned or older skin is dryer and rougher than the skin of a child. The polysaccharide content of the dermis is responsible for the hydration of the skin. As we age, we experience a reduction of these structures in the skin. A reduction of the water binding capacity of the skin leads to the appearance of lines and wrinkles. Many herbals can increase the skin hydration. E.g.  Fractions of Echinacea angustifolia.

 

CORNEOMETER:

Corneometer® provides a well-established method to determine reproducibly and accurately the hydration level of the skin surface. It is the world’s best  skin hydration measurement device. This is well documented in dermatology and cosmetology literature in which the terms “corneometry” and skin hydration measurements are inseparable.

 

The corneometer or Dermodiag operates according to the principle of electrolysis, with electrodes being applied to the skin in which the water and associated ions circulate. Current measurements indicate the amount of water present and therefore the degree of skin moisturisation.

 

It consists of a console housing and a humidity sensing probe. The probe consists of an inter-digital grid of electrodes covered by low dielectric vitrified material that prevents direct contact between the electrode and the skin 12.  Tile value appears as a maximum 3-digit figure on 40 x 18 mm display. The method is based on the fact that the dielectric constant of water varies considerably and a suitably-shaped measuring capacitor reacts, according to the water-content, with the various changes of capacity to samples brought about into its measuring volume. The variations of the probe capacitor are automatically recorded by the device. The display records a value between 0-10 when the sensing probe is in contact with dry air and 150-160 with a completely moist palm 13.

 

Fig 9: supplied by: Courage + Khazaka electronic GmbH

: Dia-stron limited

sourced by: Courage + Khazaka electronic GmbH : Dia-stron limited

 

 

SKICON 200 SKIN CONDUCTANCE METER

This is the 2nd most widely used device for the assessment of skin hydration.

 It measures high frequency conductance of the upper layer of the stratum corneum of which conductance is increased when the upper layer is well hydrated.

The probe of skicon contains concentric electrodes of 2 and 4mm external diameters connected to a tuning circuit. When the probe contacts the skin, conductance between the electrodes is detected as a change of the resonance voltage in the tuning circuit and displayed in micro-siemens on the digital screen.

 

 

Fig 10: Supplied by: I.B.S. Co ltd. Japan

Sourced  by: I.B.S. Co ltd. Japan

 

HYDROSENSOR:

The worldwide unique hydration measurement device, that considers room temperature and humidity in the measurement, thus allowing its usage in all different climates. The result is shown quickly on a diode chain.

It works on capacitance principle. The device is light, battery operated and portable, thus ideal to be used either on the counter, in a beauty or hairdressers salon or at the dermatologist or pharmacy to attract customers and to increase the sales of cosmetic products.

 

Fig 11: supplied by: Courage + Khazaka electronic GmbH sourced by: Courage + Khazaka electronic GmbH

DERMLAB-NOVA

The DPM 9003 is a portable, multifunctional electronic laboratory instrument that measures skin impedance. It is designed to provide a non-invasive, objective, reproducible method of measurement to quantify biophysical characteristics and relative hydration of the skin.

 

It works on electrical impedance measurement principle.

It is used on larger surface areas like the volar surface of the arm, face, back, etc. The new XPRT software, for Windows 98/2000/XP makes collecting data with the DPM 9003 more efficient than ever. A user-friendly interface combined with real-time data collection makes it easy to compile databases of information about products. Use the data to create charts and graphs making information easily presentable.

Supplied by: nova

 

Fig: 12

 

 

MOISTURE CHECKER

The Scalar Moisture Checker is a unique and powerful point of purchase selling tool that instantly shows the effectiveness of moisturizing and conditioning products, and lets you evaluate the progression of the skin care regimen.

 

It uses a conductance measurement principle to measure the water binding capacity of the stratum corneum.

 

Just press it onto the area to be measured during an examination, wait for the beep, then read the display. Measurements are given as % of moisture in the skin and can be evaluated with a simple chart. If skin has poor moisture content you would recommend your products and treatments to correct the condition. If moisture content is normal, the skin can look even better by using your product or treatment and even if the moisture content is high you would recommend continuing the use of moisturizing products, differentiating your product.

Sourced by: Scalar Corporation

 

Fig 13: Supplied by: Scalar Corporation

CONFOCAL RAMAN SPECTROSCOPY

Introduction: Confocal Raman microspectroscopy is the first commercially available technique that provides a non-invasive, in vivo method to determine depth profiles of water concentration in the skin [14]. Compared with conventional optical microscopy, confocality can deliver a representative image of the volume to be explored at a pre-selected depth. With spatial resolution of 1 µm in three directions, we are able to penetrate the skin outermost, horny layer, µm by µm. Confocal microscopy gives a clear view - with unprecedented accuracy - of keratinocytes in each epidermis layer, or it can track red blood cells in a microcapillary. This technique is the most recent of the major non-invasive observation methods, used in vivo. Resolution is so high, that in addition to measuring tissue thickness (horny layer, epidermis), cells can be counted, and melanosome appearance and distribution in the epidermis monitored after sun exposure.



CONFOCAL RAMAN SPECTROSCOPY

Confocal Raman microspectroscopy is the first commercially available technique that provides a non-invasive, in vivo method to determine depth profiles of water concentration in the skin 14. skin is illuminated with specific wavelength of light. Light inelastically scattered by the skin contains information of its composition. Using a variably focused laser light source and appropriate detection, this technique can be combined with confocal microscopy .

 

Compared with conventional optical microscopy, confocality can deliver a representative image of the volume to be explored at a pre-selected depth. With spatial resolution of 1 µm in three directions, we are able to penetrate the skin outermost, horny layer, µm by µm. Confocal microscopy gives a clear view - with unprecedented accuracy - of keratinocytes in each epidermis layer, or it can track red blood cells in a microcapillary.

 

This technique is the most recent of the major non-invasive observation methods, used in vivo. Resolution is so high, that in addition to measuring tissue thickness (horny layer, epidermis), cells can be counted, and melanosome appearance and distribution in the epidermis monitored after sun exposure.



Confocal microscopy is the method of imagery best suited to examining the horny layer and the epidermis. It therefore complements ultrasound echography and MRI, which are better suited to studying the dermis and hypodermis. The technique presented has great potential for fundamental skin research, pharmacology (percutaneous transport), clinical dermatology, and cosmetic research, as well as for noninvasive analysis of blood analytes, including glucose 15.

 

Fig 14: INFRARED SPECTROSCOPY

 

INFRARED SPECTROSCOPY

This is a rapid, non-contact and non-invasive technique to provide information on skin hydration of use to medical and cosmetic research and clinical practice.  A digital imaging system has been developed to collect skin hydration data. The system combines a near-infrared camera with a liquid-crystal tunable filter (LCTF) to acquire spectral images at multiple narrow wavelength bands between 960 and 1700 nm. Software has been developed to control the instrument and to process the data. Reflectance images were collected of subjects whose forearms had been treated to increase and decrease skin moisture. The infrared absorption band between 1400 and 1500 nm was used to calculate relative skin moisture, and the intensity of this band was plotted as a function of position in the form of a grayscale image

 

OPTO THERMAL TRANSIENT EMISSION RADIOMETRY

Novel infra-red remote sensing technology. Excitation spectroscopy with Opto-Thermal Transient Emission Radiometry (OTTER) was used to measure waterkeratin interaction energies in excised stratum corneum (SC) under controlled ambient relative humidity (RH) conditions. Such interactions lead to small but measurable wavelength shifts in the peaks of the absorption spectra of the interacting molecules 16.

 

Measurement of skin barrier function (TEWL)

The barrier function of stratum corneum can be examined using a non invasive method called  transepidermal water loss which measures amount of water being lost slowly from thebody through stratum corneum. As the skin becomes dry the lipid domains in between the corneocytes in the stratum corneum is disrupted and the TEWL increases. Occlusives are employed to prevent transepidermal water loss by sealing the stratum corneum.e.g.petrolatum, beeswax. A critical function of the skin is to protect the body from the environmental damage and moisture loss. This protection is provided by the skin barrier that resides in the stratum corneum. It is now well established that the barrier function is enabled by skin lipids produced by the epidermal cells 17-18. Therefore, an adequate and continuous production of lipids is essential for skin barrier functionality. As one ages, the ability to produce skin lipids diminishes 19, 20. Certain skin diseases also diminish the production of skin lipids 21, 22. These decreases in lipid production have deleterious consequences on the barrier function of the skin. Thus, there is a need of a technology that can enhance the production of skin lipids.

 

EVAPORIMETER

Measuring transepidermal water loss (TEWL) is a good indication of the skin barrier function efficiency. This is carried out using an evaporimeter, consisting of a sensor placed 3 or 6 mm above the surface of the skin. This apparatus measure the amount of water lost by evaporation. This shows that a irritant product will increase the water loss, while a moisterizer will reduce it.

Supplied by: Servo Med, Stockholm, Sweden

 

TEWAMETER TEWAMETER

Since 1990 CK has been manufacturing one of the most accepted and best selling TEWL measurement devices, the Tewameter® TM 210. Many international scientific studies demonstrate its importance in dermatological and cosmetological fields.

 

The measurement of the water evaporation is based on the diffusion principle in an open chamber dm/dt=-D x A x dp/dx

where: A = surface in m˛, m = water transported (in g), t = time (h), D = diffusion constant (=0.0877 g/m(h(mm Hg), p = vapour pressure of the atmosphere (mm Hg), x = distance from skin surface to point of measurement (m).

 

The density gradient is measured indirectly by the two pairs of sensors (temperature and relative humidity) inside the hollow cylinder and is analysed by a microprocessor. The small size of the probe head minimizes the influence of air turbulences inside the probe. Also the low weight of the probe has no influence on the skin surface structure and allows easy handling. All calibration data are inside the probe. Thus the probe is completely self contained and can be connected to different device types.

 

Open and closed chamber measurements are possible. For quickly stable measurements the Probe Heater PR 100 is available, which keeps the probe head to a certain temperature of 28-32 şC (corresponding to skin temperature). The accuracy of the probe can be checked at any time by a small electronic unit. Separate display of the values for the upper and lower relative humidity and temperature sensors in the probe is present.

 

The information about temperature and humidity during the TEWL-measurement is of great importance for the evaluation of the accuracy of the TEWL results. A room condition sensor to measure the rel. humidity and temperature of the environment can be connected to the system and stable TEWL-measurements.
sourced by: Courage + Khazaka electronic GmbH

 

Fig 15: supplied by: Courage + Khazaka electronic GmbH

 

Corneocytes diagnosis

To maintain a constant thickness of the stratum corneum the desquamation rate and the de novo production of corneocytes is delicately balanced. There is a continuous production of new stratum corneum. In order to maintain a constant stratum corneum thickness at a given body site super®cial parts of the stratum corneum must be continuously shed in the process of desquamation at a rate which balances de novo production of corneocytes. Desquamation normally occurs invisibly with shedding of individual cells or small aggregates of cells. Disturbances in this process results in the accumulation on the skin surface of only partially detached cells with or without a concomitant thickening of the stratum corneum. The severity of the disturbance may vary from modest to very pronounced, from a barely visible scaling combined with a feeling of roughness and dryness of the skin surface, to the accumulation of thick brittle scales such as in psoriasis or in the various forms of ichthyosis 23. The cosmetic product used for the removal of dead cells contains exfoliants like lactic acid. A well-regulated desquamation is a prerequisite for the barrier function of the stratum corneum and for a normal skin appearance.

 

MONOCHROMATIC LIGHT:

Monochromatic light is focused at the proximal end of a coherent bundle of optical fibres. Fluorescence of skin, stained with fluorescein, is then captured by the same fibre bundle and displayed, through a dichroic mirror, by a CCD camera. Fluorescence images are analysed using dedicated software to measure the projected area of cells. The new device allows the mean projected area of corneocytes to be routinely studied and quantified on most of the skin areas of the human body.

 

CORNEOFIX® F 20

Desquamation Collector: A special transparent adhesive tape which collects corneocytes from the top layer of the skin. This method allows the visualisation of the level of dryness or damaged skin accurately. The desquamation collector foils are a very good addition to the Visioscan® VC 98 skin camera. With software the number, size and area covered with flakes can be evaluated as well as a desquamation index. The foils are absolutely harmless to the skin.

 

Sourced  by: Courage + Khazaka electronic GmbH

 

Fig 16: Supplied by: Courage + Khazaka electronic GmbH


3S-BIOKIT® The application of the 3S-Biokit is restricted to qualified persons under medical surveillance for obtaining skin surface strippings. These are used for skin surface diagnosis in dermatology. The system consists of: adhesive: cyanoacrylic acid ethyl ester 5g; sample carrier : polyester (PET) foil 100 pcs.

Supplied by: Courage + Khazaka electronic GmbH

 

Measurement of skin colour

Human skin color can range from almost black (due to very high concentrations of the dark brown pigment melanin) to nearly colorless (appearing pinkish white due to the blood vessels under the skin) in different people. Skin color is determined primarily by the amount and type of melanin, the pigment in the skin. Variation in skin color is largely due to genetics. The human eye is very sensitive to the distinction of colours viewed side by side. But, as soon as they meet the eye separately, differences can often not be detected. Furthermore, the impression the eye receives from colours depends on the ambient lighting. To check Fairness creams efficiecy, therefore numerical assessment is required.

 

MEXAMETER® MX 18

The Mexameter® MX 18 is a very easy, quick and economical tool to measure the two components, mainly responsible for the colour of the skin: melanin and haemoglobin (erythema). Many international scientific studies demonstrate its benefits in all important dermatological and cosmetological application fields.

 

The measurement is based on absorption/reflexion. The probe of the Mexameter® MX 18 emits 3 specific light wavelengths. A receiver measures the light reflected by the skin. The positions of emitter and receiver guarantee that only diffuse and scattered light is measured. As the quantity of emitted light is defined, the quantity of light absorbed by the skin can be calculated. The melanin is measured by specific wavelengths chosen to correspond to different absorption rates by the pigments. For the erythema measurement also specific wavelengths are used, corresponding to the spectral absorption peak of haemoglobin and to avoid other colour influences (e. g. bilirubin). The results for both parameters are immediately shown as index numbers.

 

The modern, high quality electronics of the probe allow a very quick measurement. A spring in the measuring head provides constant pressure on the skin. Its low weight ensures easy handling. All calibration data are inside the probe. Thus the probe is completely self contained and can be connected to different device types. It is also a significant advantage for quick and easy servicing of the probe. The resolution of the measuring results is higher than in the previous model the Mexameter® MX 16. The Mexameter® MX 18 shows the melanin and erythema values in a range from 0-999. The accuracy of the probe can be checked any time with a special tube.

 

sourced by: Courage + Khazaka electronic GmbH

 

Fig 17: supplied by: Courage + Khazaka electronic GmbH

MINOLTA CHROMAMETER: supplied by Konica minolta.

 

Measurement of sebum level

A lipidic film resulting from the sebum secreted by the sebaceous glands, covers a normal skin. Between 1 and 5 grams a day are usually produced, anything in excess of that amount tending to make the skin shiny and oily. Sebum removal or reduction is often a mojor performance claim for cosmetic products. Many different methods have been developed to sample sebum from the skin surface. These include absorption into bentonite clay, transfer to ground glass, gravimetric paper absorption, and absorption to various tape substrates 24.

 

SEBUMETER® SM 815

The Sebumeter® is the most widely acknowledged and successful sebum measurement device for skin, hair and scalp. Various in vitro and in vivo tests and comparisons with other measurement techniques are documented in literature and demonstrate its importance in dermatological and cosmetological fields. The measurement with the Sebumeter® SM 815 allows determination of even slightest changes in the skin surface sebum content.

The measurement is based on grease-spot photometry. A special tape becomes transparent in contact with the sebum on the skin surface. For the determination of the sebum, the measuring head of the cassette is inserted into the aperture of the device, where the transparency is measured by a light source sending light through the tape which is reflected by a little mirror behind the tape. A photocell measures the transparency. The light transmission represents the sebum content on the surface of the measuring area. A microprocessor calculates the result, which is shown on the display in µg sebum/cm˛ of the skin.

 

The measuring head of the cassette exposes a 64 mm2 measuring section of the tape. For a measurement the tape is transported forward by a trigger at the side of the cassette to expose a new section of the tape. The used tape is rewound inside the cassette. One cassette can be used for approx. 450 measurements. The scale from 1-0 on the trigger shows how much of the tape is still unused. For hygienic reasons when exhausted, the cassette is simply replaced. The modern, high quality electronics allow a very quick measurement. A spring in the measuring head provides constant pressure on the skin. Its low weight makes handling easy.

 

Fig 18: SEBUFIX® F 16

 

SEBUFIX® F 16

Sebum Collecting Tape: A special tape that collects sebum in a very short time. It shows spots for the activity of the sebacious glands. Using the Sebufix® together with the Visioscope® allows the sebum production to be watched live. A microporous film is applyied to a previously cleansed area of the skin for one hour. Sebum secretions are absoded, staining the film. The number and extent of spots have then to be quantified in order to measure sebaceous gland activity. Sebutape can characterise a oily skin and check the efficiency of a boosting lipid synthesis product for dry skin or one designed to reduce excessive secretions of sebum.

 

Measurement of lines and wrinkles

Wrinkles are fine lines or deep furrows, where the skin has become thinned and damaged. As we age, our skin undergoes changes that make it more difficult for the skin to repair itself, and these changes lead to wrinkles. causes of wrinkles and Changes that occur in  skin as age advances.

Ř  Changes in epidermis: The epidermal cells become thinner as age advances .They also lose their stickiness.

This change in epidermal cells allows the moisture to escape instead of retaining it back causing dryness of the skin. As we get old the epidermal cells start dividing slowly and the rate of repairing process also retards.Thus thinning of skin leads to wrinkles

Ř  Changes in dermis:

·        The collagen fiber production reduces.

·        The elastin fibers wear out.

·        The production of sebum from sebaceous glands decreases.

·        There will be a decrease in number of sweat glands.

·        The supply of nutrients also decreases. All the above mentioned changes lead to formation of wrinkles.

Ř  Changes in subcutaneous tissues: The fat cells get smaller with age. All these changes in three layers of skin lead to wrinkles and sagging.

Ř  The factors that cause early aging and formation of wrinkles

1. Sun: Constant exposure to U-V radiations from sun cause premature aging of skin. Due to constant exposure to sun the epidermis becomes thin and many harm full lesions like basal cell carcinoma and squamous cell carcinomas occur. Sun light also damages collagen fibers of dermis causing early aging.

2. Hormones: The hormonal changes  due to menopause or decreased estrogen        production may lead to changes in skin.

 

MAPPING WRINKLE TOPOGRAPHY BY SKIN REPLICA:

Close observation of the surface of human skin, over the whole body, reveals a relief featuring a great many forms of considerably different shapes and sizes. This microrelief is a marker of ageing and methods of topographical mapping have proved invaluable for assessing the skin and the efficiency of cosmetic products

 

The principle is to scan the replica or skin surface, using one or two light beams, or a grazing incidence light and to measure both the cast shadows and the deformation of a beam of fringes

 

A preliminary and essential step, to any study of the relief, is the preparation of a mould or a print. Easy and rapid to obtain, polysilicone or araldite replica must be extremely accurate, since it will be studied by profilometry or a scanning microscope. Wrinkle orientation, density and depth can be plotted, and of course efficiency of cosmetics designed to attenuate wrinkles and fine lines, measured.

 

FRICTIOMETER ® FR 770

The frictional resistance is influenced by skin roughness, wrinkles and the skin care products on the skin surface. Consequently there is also a variety of different readings. It is possible to classify normal and dry skin, wrinkly and less wrinkled skin and appropriate changes of the skin condition after applying cosmetic products. This is an important aspect for the product development. It allows for instance to determine that a W/O emulsion offers better smoothing characteristics than an O/W emulsion. surfaceIn addition, the penetrating capacity of a formulation can time-dependently be measured; if it stays on the skin for a long time there will be only a very insignificant change in the frictional values.

 

The probe contains a motor, a steering unit and the friction head. A constant rotational speed (adjustible to different speeds) is applied onto the skin by the friction head. The torque is measured and the result is displayed as Frictiometer® units in the MPA software. The probe contains a rotating teflon disc which is applied on the skin. A selection of different teflon discs is available.

 

sourced by: Courage + Khazaka electronic GmbH

 

Fig 19: supplied by:  : Courage + Khazaka electronic GmbH

 

VISIO FACE

The camera takes pictures of the entire face. It provides color images and allows UV diagnoses with image analysis. Photos taken before and after the cosmetic or dermatological treatment or pictures taken over a longer period can be superimposed on the other which allows to completely document the progress of a treatment. An advantage here is that imaging conditions are reproducible and costly locations can be avoided.

 

source by: Courage + Khazaka electronic GmbH

 

Fig 20: supplied by: Courage + Khazaka electronic GmbH

 

SKIN-VISIOMETER® SV 600

The device features a parallel light source and a b/w CMOS-camera with 640 * 480 pixels. The replica is placed between these. The light absorption of the blue color is known. When the light penetrates the replica, it is absorbed according to the thickness of the silicone material. The replica reproduces the heights and depths of the skin as a negative, i.e. wrinkles are higher in the replica as the silicone is thicker in this place.

 

The amount of absorbed light is calculated by Lambert and Beer’s Law. The outgoing light is proportional to the incoming light, the thickness of the material and the material constant k.

sourced by: Courage + Khazaka electronic GmbH

 

Fig 21: supplied by: Courage + Khazaka electronic GmbH

 

Microcirculation

The blood supply to the skin is provided by a network of arterioles, capillaries and venules organized into a superficial and a deep plexus. The assessment of skin microcirculation is of valuable interest in cosmetology in the quantification of the sun protection factor, skin irritation and efficacy of antiredness treatments. Skin microcirculation can be measured by means of different techniques, based mainly on the quantification of optical and thermal properties of the skin which are modified by the amount of blood perfusion. Relevant and reproducible data can be obtained only through the understanding of the biophysical background of the technique(s) utilized. Standardization of measuring conditions and procedures is particularly required for blood flow assessment.

 

LASER DOPPLER VELOCIMETRY

With this method light is transmitted from a helium –neon laser source in the instrument to the skin via an optical fibre.the laser provides light of single frequency 632.9 nm and allows the Doppler effect to be exploited. The incident radiation enters the skin tissue and is multiplied scattered and reflected by non moving components and by the mobile red blood cells that are encountered as the radiation penetrates to the depth of 1-1.5mm. a portion of scattered/reflected incident radiation exits the skin and is collected by 2nd or 3rd optical fibre that carry the light back to the instrument. He returning radiation falls on the photodetector and is converted to the electrical signal

 

SKIN-THERMOMETER

The measurement is based on contact free infrared reading of the reflection of the skin surface and read with a specific sensor within the probe. The temperature of the skin indirectly informs on the blood circulation. Well supplied skin parts are warmer than less circulated areas.

sourced by: Courage + Khazaka electronic GmbH

 

Fig 22: supplied by: Courage + Khazaka electronic GmbH

Miscellaneous

SPECTRONIC 20 SPECTROPHOTOMETER 320-400 NM

Effectiveness of several sunscreens using a Spectronic 20 spectrophotometer in the 320 to 400 nm range can be evaluated and the SPF rating of the laboratory prepared sunscreen lotion can be determined. Although this UV radiation is in the UVA range, general trends in UV absorption can be observed allowing the sunscreen lotions to be quantitatively compared.

 

SKIN-PH-METER ® PH 905

An adequate pH value is essential for a healthy skin. It can be measured with the Skin-pH-Meter. Recommended measuring areas are the back of the hand, the forearm, the front and the cheeks, however readings are also possible on any other body part. The measurement of the pH-level on the skin surface is an important parameter for evaluating the quality of the hydrolipidic film on the skin especially in developing soaps, cleanser or detergents

sourced by: Courage + Khazaka electronic GmbH 

 

Fig 23: supplied by: Courage + Khazaka electronic GmbH

 

VISIOSCOPE

This unique video camera delivers very impressive images of skin, hair and scalp. The camera shows a skin area of 6 x 8 mm and monitors: skin texture (smoothness, wrinkles), desquamation (scaliness), skin impurities (reddening, pigmentation spots, acne, comedones etc.), hair structure, dandruff and condition of the scalp. The camera must be connected to a video monitor.

Sourced by: Courage + Khazaka electronic GmbH

 

fig 24: Visioscope® Color 32

 

CONCLUSION:

Subjective observation that can be recognized only by the observer himself lacks reproducibility and reliability. The instrumental measurement of the living skin has been developed based on the idea of analytical science to understand skin conditions through analyzing instrumental measurement data. The effect of cosmetics can be numerically assessed and also one product can be compared to other very conveniently.

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6.       N I Chanoller, SP Chahal, and R T Jones, “ evaluation of the use of proteinsas moisturizing and skin tightening active ingredients within skin care formulations”,1996.

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11.     Y. Kuwahara, Y. Shima, D. Shirayama, M. Kawai, K. Hagihara, T. Hirano, J. Arimitsu, A. Ogata, T. Tanaka and I. Kawase, “Quantification of hardness, elasticity and viscosity of the skin of patients with systemic sclerosis using a novel sensing device (Vesmeter): a proposal for a new outcome measurement procedure”,2008.

12.     Gregor B. E. JemeC and Renhua na acta Derm Venereol, 82:   322–324 “Hydration and Plasticity Following Long-term Use of a Moisturizer: A Single-blind Study” Division of Dermatology, Department of Medicine, Roskilde Hospital, and Department of Dermatology, Bispebjerg Hospital, Copenhagen University, Denmark,2002.

13.     AB Gupta, Manisha Bhattacharya, B Haldar Year : 1990  |  Volume : 56  |  Issue :     1  |  Page : 15-17 State of hydration and electrical conductance of ichthyotic skin.

14.     J. Wu and T. G. Polefka, “Confocal Raman microspectroscopy of stratum corneum: a pre-clinical validation study,” Colgate Palmolive Company, 909 River Road, Piscataway, NJ 08854, USA,2007.

15.     P. J. Caspers,* G. W. Lucassen, and G. J. Puppels, “Combined In Vivo Confocal Raman Spectroscopy and Confocal Microscopy of Human Skin” Biophysical Society,2003.

16.     Xinxin Guo*, Robert E. Imhof†* and Jean de Rigal‡ “Spectroscopic Study of        Water-Keratin Interactions in Stratum Corneum” analytical sciences april 2001, VOL.17 Special Issue The Japan Society for Analytical Chemistry.

17.     Wertz, P.W. Acta Derm Venereol (Stockh).Sippl. 208: 7-11, 2000.

18.     Denda, M. Cosmetic Lipids and Skin Barrier, 97-120, 2002.

19.     Rawlings, A.V., Rogers, J, Mayo, A.M. Biocosmet Skin Aging 1: 31-45, 1993.

20.     Ghadially, R., Brown, B.E., Sequeira-Martin, S.M., Feingold, K.R., Elias, P.M. J. Clin. Invest. 95: 2281-2290, 1995.

21.     Imokawa, G., Abe, A, Jin, K., Higaki, Y., Kawashima, M., Hidano, A. J. Invest.  Dermatol. 96:523-526, 1991.

22.     Di Nardo, A., Wertz, P., Giannetti, A., Seidenari, S. Acta Derm Venereol (Stockh) 78: 27-30, 1998.

23.     Torbjoč RN Egelrud Desquamation in the Stratum Corneum Acta Derm Venereol 2000; Supp 208: 44±45.

24.    James D. Ayres methods for evaluating sebum removal”, Anway corporation, ada,    Michigan.                         

 

 

 

 

Received on 24.12.2009                    Accepted on 20.02.2010        

©A&V Publications all right reserved

Res. J. Topical and Cosmetic Sci. 1(1): Jan. – June 2010 page 1-12