DEVICE AND METHOD FOR STIMULATING SKIN CELLS USING A MICROCURRENT

Abstract

A device for electrically stimulating skin, in particular for stimulating the activity of fibroblasts, including an electronic circuit for generating a sawtooth biphasic or cyclic alternating electric current; at least two electrodes connected to the electronic circuit, which are configured so as to be applied to the skin in order to allow the electric current generated to pass therethrough.

Claims

1. A device for electrically stimulating skin, comprising: an electronic circuit for generating a sawtooth biphasic or cyclic alternating electric current; at least two electrodes connected to the electronic circuit, which are configured so as to be applied to the skin in order to allow the electric current generated to pass therethrough.

2. The device as claimed in claim 1, the electric current having a frequency of between 1 Hz and 1000 Hz and/or the electric current being biphasic and/or the current generated being asymmetric and/or the electric current being biphasic, a cycle of a certain polarity comprising the same number of elementary patterns as a cycle of opposite polarity and/or the electric current being biphasic. a cycle comprising between 3 and 100 elementary patterns.

3-6. (canceled)

7. The device as claimed in claim 1, the device being configured such that a falling edge of an elementary pattern or that a rising edge of an elementary pattern extends over a duration of between 1/2000 and ½ of the duration of the elementary pattern. and/or the device being configured such that a falling edge of an elementary pattern or that a rising edge of an elementary pattern extends over a duration of between ½ and 1999/2000 of the duration of the elementary pattern and/or the device being configured such that a falling edge of an elementary pattern and/or a rising edge of an elementary pattern comprises a decrease, or respectively an increase, in the intensity of the electric current per second, in terms of absolute value. of between 0.001 A and 2.5 A, and/or the device being configured such that a falling edge of an elementary pattern and/or a rising edge of an elementary pattern comprises a decrease. or respectively an increase, in the intensity of the electric current per second, in terms of absolute value, of between 0.05 A and 100 A.

8-10. (canceled)

11. The device as claimed in claim 1, the device being configured such that a rising edgeof an elementary pattern extends over a longer duration than a falling edge of the elementary pattern.

12. The device as claimed in claim 1, the peak intensity being constant.

13. The device as claimed in claim ls, the intensity of the current being such that the electric current density delivered by the electrodes is between 0.1 mA/cm.sup.2 and 2.5 mA/cm.sup.2.

14. The device as claimed in claim 1, the electronic circuit being arranged such that the electric current has elementary patterns that extend over a duration of between 1 ms and 100 ms and/or the electronic circuit being configured such that the voltage between the electrodes without load is between 0.01 V and 45 V.

15. (canceled)

16. The device as claimed in claim 1, the electrodes being borne by a housing accommodating the electronic circuit, and/or the electrodes being borne by a housing accommodating an energy source and/or the electrodes each having an area of contact with the skin that is greater than or equal to 1 cm.sup.2 and/or the electrodes having an area of contact with the skin that is rounded in shape and/or the electrodes being to be attached to the skin.

17. (canceled)

18. The device as claimed in claim 1, comprising a conductive gel to be applied to the skin in the region of application of the electrodes and/or comprising a conductive gel to be applied to the skin in the region of application of the electrodes the gel being without a cosmetic active agent such as for example humectant or moisturizing active agents, anti-aging active agents. for example depiumenting active agents, active agents acting on skin microcirculation or seboregulating active agents, in particular vitamin C and derivatives thereof, hyaluronic acid, or ellagic acid.

19-22. (canceled)

23. The device as claimed in claim 1, being arranged so as to take at least one electrical measurement on the skin via said electrodes, before electrically stimulating the skin.

24. A method for non-therapeutically cosmetically treating a healthy skin, comprising the step of subjecting the skin to a sawtooth biphasic or cyclic alternating electric current, delivered by a device as claimed in claim 1.

25. The method as claimed in claim 24, comprising the movement of the electrodes during the treatment.

26. The method as claimed in claim 24, the electric current being applied in the presence of a conductive gel that is without a cosmetic active agent such as humectant or moisturizing active agents, anti-aging active agents, for example depigmenting active agents, active agents acting on skin microcirculation or seboregulating active agents, in particular vitamin C and derivatives thereof, hyaluronic acid, or ellagic acid.

27. The method as claimed in claim 24, the skin region treated exhibiting a lack of firmness, tone or elasticity or comprising a wrinkle.

28. The method as claimed in claim 24, comprising the analysis, by a connected system, of information relating to the skin, originating from electrical measurements taken with the electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] The invention may be understood better from reading the following detailed description of a non-limiting exemplary embodiment thereof and from examining the appended drawing, in which:

[0090] FIG. 1 is a block diagram of an electrical stimulation device according to the invention;

[0091] FIG. 2 schematically shows an exemplary housing;

[0092] FIG. 3 shows different forms of current, some according to the invention and others not;

[0093] FIG. 4 gives the frequency spectra of the different forms of electric current of FIG. 3;

[0094] FIG. 5 shows the power spectra of the different forms of electric current of FIG. 3;

[0095] FIG. 6 is a graph comparing the results obtained when. dermis models are stimulated by electric currents having different waveforms;

[0096] FIG. 7 is a graph comparing the results obtained when dennis models are stimulated by electric currents having different frequencies;

[0097] FIG. 8 is a graph comparing the results obtained when dermis models are stimulated by respectively biphasic and cyclic alternating electric currents;

[0098] FIG. 9 shows an exemplary electric current generated by a device according to the invention; and

[0099] FIG. 10 shows an exemplary elementary pattern.

DETAILED DESCRIPTION

[0100] The device 1 according to the invention shown in FIG. 1 comprises a current generator 20 supplied by an electrical energy source 30. This generator is connected to at least two electrodes 10 to be applied to the skin. The generator is configured to generate a sawtooth biphasic or cyclic alternating electric current.

[0101] The electrical energy source 30 may comprise at least one battery or cell.

[0102] Preferably, the current generator 20 is a low-frequency current generator, operating for example at a frequency of about 100 Hz.

[0103] The current generator 20 may comprise a polarity inverter, operating in particular periodically.

[0104] A current generated according to the invention reproduces a succession of elementary patterns M, each composed of a substantially monotonic variation of the electric current in one direction followed by a substantially monotonic variation of the electric current in the opposite direction. An exemplary elementary pattern M is shown in FIG. 10. In FIG. 10 it is possible to see a variation in the electric current in one direction 43, also called a rising edge, followed by a variation in the opposite direction 44, also called a falling edge. The rising edge exhibits an increase in the intensity in terms of absolute value, whereas the falling edge exhibits a decrease in the intensity in terms of absolute value. At point 45, a discontinuity between the rising edge and the falling edge can be seen. The rising edge extends over a duration tin and the falling edge over a duration td. In this example, the rising edge extends over a longer duration than the falling edge.

[0105] FIGS. 3c, 3f and 9 show exemplary waveforms of electric currents generated by a device according to the invention.

[0106] Cyclic Alternating

[0107] The current generator 20 may be configured to deliver a sawtooth cyclic alternating electric current, as shown in the example of FIG. 3c.

[0108] It can be seen in FIG. 3c that the electric current shown has a constant peak intensity. Preferably, the peak intensity is between 0.1 mA and 2.5 mA, more preferably between 0.3 mA and 1.5 mA, even more preferably about 0.5 mA, as shown in the example of FIG. 3c.

[0109] An elementary pattern M of the electric current of FIG. 3c extends over a duration of 5 ms. Preferably, this duration is between 1 ms and 100 ms, more preferably between 2 ms and 20 ms. A cycle comprising an elementary pattern of a certain polarity followed by an elementary pattern of opposite polarity may extend over a duration of about 10 ms.

[0110] Additionally, in this example, the elementary patterns M of a certain polarity are not symmetrical with respect to the elementary patterns of opposite polarity. The rising edge 43 of positive polarity does not have the same slope as the rising edge 43′ of negative polarity. The rising edge 43 of positive polarity has a slope that is less steep than the slope of the rising edge 43′ of negative polarity. Similarly, the falling edge 44 of positive polarity does not have the same slope as the falling edge 44′ of negative polarity, the slope of the falling edge 44 of positive polarity being steeper than the slope of the falling edge 44′ of negative polarity.

[0111] Biphasic

[0112] The current generator 20 may be configured to deliver a sawtooth biphasic electric current, as shown in the examples of FIGS. 3f and 9.

[0113] The exemplary electric currents according to the invention shown in FIG. 3f and FIG. 9 have a constant peak intensity. Preferably, the peak intensity is between 0.1 mA and 2.5 mA, more preferably between 0.3 mA and 1.5 mA, even more preferably about 0.5 mA, as shown in the examples of FIGS. 3c, 3f and 9.

[0114] In the examples of FIGS. 3f and 9, each elementary pattern M extends over a duration of 10 ms. Additionally, in these examples, each cycle 41; 41′ of positive and negative polarity comprises ten elementary patterns M.

[0115] In the examples of FIGS. 3f and 9, the elementary patterns M of a certain polarity are not symmetrical with respect to the elementary patterns of opposite polarity. Specifically, the rising edge 43 of positive polarity does not have the same slope as the rising edge 43′ of negative polarity. Similarly, the falling edge 44 of positive polarity does not have the same slope as the falling edge 44′ of negative polarity. In these particular examples, the rising edge 43 of positive polarity has a slope that is substantially equal to the slope of the falling edge 44′ of negative polarity and the rising edge 43′ of negative polarity has a slope that is substantially equal to the slope of the falling edge 44 of positive polarity.

[0116] In the examples shown in FIGS. 3f and 9, it can be seen that each cycle 41 or 41′ comprises the same number of elementary patterns M. The rising edge 43 of an elementary pattern M of positive polarity has a slope, |dI/dt|, that is less than the slope of the falling edge 44 of the elementary pattern M of positive polarity. Conversely, the rising edge 43′ of an elementary pattern M of negative polarity has a slope, |dI/dt|, that is greater than the slope of the falling edge 44′ of the elementary pattern M of negative polarity.

[0117] Equivalently, the rising edge 43 of an elementary pattern of positive polarity may have a slope that is greater than the slope of the falling edge 44 of the elementary pattern of positive polarity and the rising edge 43′ of an elementary pattern of negative polarity may have a slope that is less than the slope of the falling edge 44′ of the elementary pattern of negative polarity.

[0118] In the example of FIG. 3f, the rising edge 43 of positive polarity has a slope, |dI/dt|, that is approximately equal to 0.05 A/s, and the rising edge 43′ of negative polarity has a slope, |dI/dt|, that is approximately equal to 2.1 A/s. Conversely, the falling edge 44 of positive polarity has a slope, |dI/dt|, that is approximately equal to 2.1 A/s, and the falling edge 44′ of negative polarity has a slope, |dI/dt|, that is approximately equal to 0.05 A/s.

[0119] Gel

[0120] A conductive gel is preferably applied to the region of skin to be treated, allowing the resistance of the interface with respect to that of the skin to be minimized. Thus, the electric current can flow between the electrodes substantially without modification of its amplitude due to a variation in the quality of th.e interface. Th.e voltage of the alternating current generator 20 is preferably adjusted in real time in order to maintain the intensity at the desired value. Thus, the voltage may vary in order to adapt to the presence or otherwise of the conductive gel on the skin, the moisture level of the skin and/or the skin region treated. This advantageously makes it possible to take into account the sensitivity of the skin region treated and to avoid any painful sensations when using the device, for example sensations of tingling and/or irritation,

[0121] Housing

[0122] The device may comprise a user interface allowing adjustments to be made, in particular to adjust the voltage of the alternating current generator 20, and/or define and/or view a duration of application of the cosmetic or dermatological treatment,

[0123] The device may make it possible to select predefined voltages according to the presence of a gel, or the skin region treated.

[0124] FIG. 2 shows an exemplary housing according to the invention. The electrodes 10 are borne by the housing accommodating the electrical energy source 30, and the current generator 20.

[0125] The electrodes have an area of contact with the skin that is rounded in shape, and may be free to rotate, the area of contact with the skin being greater than or equal to 1 cm.sup.2. The electrodes are each, for example, in the form of a ball.

[0126] Comparison of the Effects of Stimulation for Different Electric Currents

[0127] FIG. 3 shows different forms of electric current. FIGS. 3a and 3b show cyclic alternating electric currents, outside the scope of the invention, respectively of sinusoidal and square waveform. FIG. 3c shows a cyclic alternating electric current, according to the invention, of sawtooth waveform. FIGS. 3d and 3e show biphasic electric currents, outside the scope of the invention, comprising 10 elementary patterns per cycle, respectively of sinusoidal and square waveform. FIG. 3f shows a biphasic electric current, according to the invention, comprising 10 elementary patterns per cycle, of sawtooth waveform.

[0128] In Vitro Stimulation Protocol

[0129] Dermis models are distributed. in wells of a culture plate. Each well contains a dermis model, made from 3.5 ml of a solution containing 1 to 1.5 mg/ml bovine collagen and 500 000 human fibroblasts, cultured in MEM (minimal essential medium) with 10% FCS, L-glutamine, non-essential amino acids. Na-pyruvate and antibiotics.

[0130] The wells are covered with a cover provided with electrodes made of carbon, such that the electrodes penetrate into the dermis solution, allowing the electric current to flow through the dermis models.

[0131] The electric current is generated by a current generator, for example the Keysight B2911A current generator, allowing different. waveforms, in particular sawtooth, square, and sinusoidal, different frequencies, and different cycles to be set.

[0132] Each dermis model is then subjected to an electric current of peak intensity equal to 0.5 mA for 4 h. Other dermis models are set up in the same way, with the electrodes in contact, but are not subjected to an electric current, thereby making it possible to compare the results of the electrical stimulations on the dermis models with respect. to a situation without electrical stimulation. These dermis models which are not electrically stimulated are hereinafter referred to as the “reference dermis model”.

[0133] Comparison of Cyclic Alternating/Biphasic

[0134] FIG. 8 shows a graph illustrating the effect of electrical stimulation of a dermis model using a sawtooth biphasic electric current comprising cycles of ten elementary patterns and the effect of electrical stimulation of a dermis model using a sawtooth cyclic alternating electric current.

[0135] The frequency of the biphasic and cyclic alternating electric currents is 100 Hz.

[0136] The electrical stimulation of a dermis model using a biphasic electric current simultaneously promotes an increase in the quantity of the proteins IL6, TIMP1 and of MMP1. Specifically, more IL6, TIMP1 and MMP1 is observed in the dermis model stimulated by the biphasic current than in a reference dermis model (see FIG. 8).

[0137] IL6 is a cytokine released by fibroblasts. TIMP1 is a natural inhibitor of MMPs such as MMP1, MMPs allowing in particular the remodeling of dermal tissues by breaking down components of the extracellular matrix. In particular, IL6 and TIMP1 allow the regulation of MMP1. Fibronectins are proteins present in the extracellular matrix, promoting in particular the adhesion of cells to the extracellular matrix and the assembly of fibrillar collagen fibrils formed of type 1 collagen.

[0138] The increase in IL6, TIMP1, MMP1 and fibronectins is an indicator thvorable to the remodeling of the skin.

[0139] In contrast to the stimulation using a biphasic electric current, a decrease in the quantity of TIMP1, MMP1 and IL6 is observed in the dermis model stimulated using a cyclic alternating electric current with respect to the amount of TIMP1, MMP1 and IL6 present in a reference dermis model.

[0140] The electric current generated according to the invention is therefore preferably biphasic.

[0141] Comparison of the Effect of the Waveform

[0142] FIG. 6 shows a graph illustrating the effect of electrical stimulation of a dermis model using a biphasic electric current having a sawtooth waveform, according to the invention, the effect of electrical stimulation of a dermis model using an electric current having a square waveform, and the effect of electrical stimulation of a dermis model using an electric current having a sinusoidal waveform.

[0143] The frequency of the electric currents generated is 100 Hz.

[0144] The peak intensity of the electric currents generated is 0.5 mA.

[0145] In general, an increase in the quantity of MMPI secreted by the fibroblasts is observed during electrical stimulation of a dermis model using an electric current with. respect to the quantity of MMPI present in a reference dermis model.

[0146] However, stimulation of a dermis model using an electric current having a sawtooth waveform allows a greater increase in the quantity of MMPI with respect to the electric currents having a square and/or sinusoidal waveform. A sawtooth waveform is significantly more effective.

[0147] Effect of Frequency

[0148] FIG. 7 shows a graph illustrating the effect of electrical stimulation of a dermis model using an electric current having a frequency of 1 Hz, of 10 Hz and of 100 Hz.

[0149] The electric currents generated have a biphasic sawtooth waveform.

[0150] The stimulation of a dermis model using a 1 Hz electric current has no effect on the quantity of IL6 and TIMP1 with respect to a reference dermis model.

[0151] The stimulation of a dermis model using a 10 Hz electric current promotes an increase in the quantity of fibronectin with respect to a reference dermis model.

[0152] The stimulation of a dermis model using a 100 Hz electric current promotes an increase in the quantity of IL6, TIMP1 and fibronectin with respect to a reference dermis model.

[0153] Additionally, it is advantageous that the level of modulation of TIMP1 is similar to that of MMP1.

[0154] Thus, a device according to the invention, generating an electric current with a frequency of about 100 Hz, promotes the stimulation of the skin, allowing the remodeling thereof.

[0155] Additionally, electrical stimulation of the skin using an electric current having a sawtooth waveform, a frequency of about 100 Hz and being biphasic also allows an increase α-SMA, a protein of the cytoskeleton. present in the fibroblasts which actively remodel the extracellular matrix such as in the phases of wound healing. When the expression of α-SMA is transient and controlled in the fibroblasts, it is beneficial to the renewal of the matrix. For example, levels of a-SMA are high in the ventral skin of females post-partum (in the weeks following the birth of their babies).

[0156] Electrical stimulation of the skin using an electric current having a sawtooth waveform, a frequency of about 100 Hz and being biphasic surprisingly makes it possible to obtain biological responses that are more advantageous than electrical stimulation of the skin. using an electric current having a square or sinusoidal waveform and/or a frequency of 1 Hz or 10 Hz and/or being cyclic alternating.

[0157] The differences between the electric currents studied and shown in FIG. 3 are more explicit when these electric currents are observed in the frequency domain.

[0158] FIG. 4 shows the frequency spectra of the electric currents shown in FIG. 3.

[0159] It can be seen that the distribution of the harmonics is highly distinct when the three, square, sinusoidal and sawtooth, waveforms are compared for each of the two, cyclic alternating and biphasic, modes.

[0160] The harmonics of the cyclic alternating electric currents are spaced further apart than those of the biphasic electric currents.

[0161] More low-frequency harmonics are also observed to be present in the frequency representation of the biphasic electric currents than in the frequency representation of the cyclic alternating electric currents.

[0162] FIG. 5 shows the power spectra of the electric currents of FIG. 3. The difference between these different electric currents is even more explicit when the power spectra are observed.

[0163] The invention is not limited to the embodiments described and shown above. Thus, the current may be applied using a plurality of electrodes. The frequency may vary within a cycle, as may the amplitude, and the slope of the rising and falling edges. The rising and falling edges may be non-linear.