TSM biosensor to ex-vivo characterize the viscoelastic properties of skin
The invention concerns a Thickness Shear Mode (TSM) biosensor ( 1 ) which comprises an ex vivo living skin explant ( 2 ), the skin explant ( 2 ) comprising at least one of the skin layers among: hypodermis, dermis ( 2 A), epidermis ( 2 B) and the stratum corneum ( 2 C), a TSM transducer ( 3 ) which comprises: an AT cut quartz resonator 3 C which has two opposite exterior surfaces ( 3 A, 3 B), and two conducting electrodes ( 4 A, 4 B), each conducting electrode being deposited on one of the two exterior surfaces ( 3 A, 3 B), the TSM transducer ( 3 ) allowing to determine micro rheological characteristics of the living skin explant ( 2 ) by piezoelectric transducing using shear waves, the TSM transducer ( 3 ) presenting: measuring means ( 30 ), monitoring and calculating means ( 31 ) which monitor an evolution in time of an electrical response of the living skin explant ( 2 ), and which calculate in time, from the electrical response, micro rheological characteristics of the living skin explant ( 2 ), a bottom surface of the skin explant ( 2 ) being in contact with the TSM transducer ( 3 ), a top surface of the skin explant ( 2 ) being in contact with air.
1. A receptacle comprising:
a Thickness Shear Mode (TSM) biosensor;
a culture medium; and
an ex vivo living skin explant in contact with the culture medium, the skin explant comprising dermis, epidermis and stratum corneum,
wherein the TSM biosensor comprises:
a TSM transducer comprising: an AT cut quartz resonator, wherein the AT cut quartz resonator has two opposite exterior surfaces, and two metal electrodes, each metal electrode being deposited on one of the two exterior surfaces,
the TSM transducer allowing to measure and to convert electrical parameters for determining mechanical characteristics of the living skin explant, and being configured to generate TSM waves into the ex vivo living skin explant,
the dermis being in contact with the TSM transducer, the stratum corneum being in contact with air, and
wherein the TSM biosensor is surrounded by the culture medium, the TSM transducer is immersed in the culture medium so as to maintain the dermis in the culture medium and the stratum corneum in contact with air, allowing the survival of the skin explant during at least several hours.
2. A receptacle according to claim 1 , wherein the culture medium is disposed on one of the two electrodes, and wherein the dermis of the skin explant is in contact with said electrode, in order to guarantee the survival of the skin explant on the TSM transducer at least several hours.
3. A receptacle according to claim 1 , wherein the culture medium is a gel.
4. A receptacle according to claim 2 , wherein the culture medium ( 5 ) provides additional function beyond providing nutrient support for the skin explant.
5. A receptacle according to claim 1 , wherein the electrode in contact with the ex vivo living skin explant has at least one opening which is filled with the culture medium, allowing the survival of the skin explant during at least several hours.
6. A receptacle according to claim 1 , wherein the electrodes cover the entire surface of the AT cut quartz resonator.
7. A receptacle according to claim 1 , wherein the skin explant covers the entire surface of one electrode on which it is deposited.
8. A receptacle according to claim 1 , wherein the electrodes are made of gold.
9. A receptacle comprising:
a culture medium,
a Thickness Shear Mode (TSM) biosensor; and
an ex vivo living skin explant in contact with the culture medium, the skin explant comprising dermis, epidermis and stratum corneum,
wherein the TSM biosensor comprises a TSM transducer which comprises an AT cut quartz resonator, wherein the AT cut quartz resonator has two opposite exterior surfaces and two metal electrodes, each metal electrode being deposited on one of the two exterior surfaces,
the TSM transducer allowing to measure and to convert electrical parameters for determining mechanical characteristics of the living skin explant, and being configured to generate TSM waves into the ex vivo living skin explant,
the dermis being in contact with the TSM transducer, the stratum corneum being in contact with air, and
wherein the TSM transducer comprises a monitoring system with monitoring and calculating means which give access to an additional equivalent electrical impedance of the TSM biosensor loaded by the living skin explant, denoted Z=R+j X, Z being linked with the complex shear modulus G=G′+j G″, representative of skin viscoelasticity from the modified equivalent electrical lumped elements Butterworth-van-Dyke circuit (BVD), using following equations:
R
≅
K
ρ
skin
(
G
(
ω
)
+
G
′
(
ω
)
)
2
ρ
skin
X
≅
K
ρ
skin
(
(
G
(
ω
)
-
G
′
(
ω
)
)
2
ρ
skin
+
ω
h
eff
)
where K is the electromechanical coupling factor ρ skin is the skin density, ω is the resonance pulsation, G′, G″ are respectively the storage modulus and the loss modulus corresponding to the real and imaginary parts of the complex shear modulus G, and h eff is the depth of living skin.
10. A receptacle according to claim 9 , wherein the monitoring and calculating means integrate an electrical model of the biosensor by an electrical circuit,
the biosensor being modeled by an electrical circuit which comprises:
a static branch modeling the electrical behavior of quartz, and
a dynamic branch parallel to the static branch and modeling the mechanical behavior of quartz and the mechanical behavior of skin,
the static branch comprising a resistor and a capacitor connected in parallel,
the dynamic branch comprising in series:
a capacitor, a self-inductance and a resistor modeling the mechanical behavior of quartz, and
the additional equivalent electrical impedance Z modeling the mechanical behavior of the skin.
11. Method for determining mechanical characteristics of ex vivo living skin explant being in contact with a culture medium, the living skin explant comprising dermis, epidermis, and stratum corneum, using a TSM transducer which comprises: an AT cut quartz resonator which has two opposite exterior surfaces, and two metal electrodes, each metal electrode being deposited on one of the two exterior surfaces, the method comprising:
(a) putting the dermis in contact with the TSM transducer,
(b) generating, by the TSM transducer, TSM waves into the ex vivo living skin explant,
(c) measuring and converting, by the TSM transducer, electrical parameters for determining mechanical characteristics of the living skin explant,
wherein the TSM transducer is immersed in and surrounded by the culture medium so as to maintain the dermis in the culture medium and the stratum corneum in contact with air, allowing the survival of the skin explant during at least several hours.
12. A method according to claim 11 , wherein the living skin explant is hydrated or delipidated.
13. A method according to claim 11 , wherein, the living skin explant is treated with at least one product, prior to or after its deposition on the TSM transducer, for monitoring products-to-skin effects.
14. A method according to claim 11 comprising testing ex vivo mechanical behavior of living skin explant and determining viscoelastic characteristics of the living skin explant.
15. A method according to claim 11 , comprising detecting and/or following skin diseases to analyse the effect of a product on the skin explant.
16. Method for determining mechanical characteristics of ex vivo living skin explant being in contact with a culture medium, the living skin explant ( 2 ) comprising dermis, epidermis, and stratum corneum, using a TSM transducer which comprises: an AT cut quartz resonator which has two opposite exterior surfaces, and two metal electrodes, each metal electrode being deposited on one of the two exterior surfaces, the method comprising:
(a) putting the dermis in contact with the TSM transducer,
(b) generating, by the TSM transducer, TSM waves into the ex vivo living skin explant,
(c) measuring and converting, by the TSM transducer, electrical parameters for determining mechanical characteristics of the living skin explant, wherein the TSM transducer comprises a monitoring system with monitoring and calculating means which give access to an additional equivalent electrical impedance of the TSM biosensor loaded by the living skin explant, denoted Z=R+j X, Z being linked with the complex shear modulus G=G′+j G″, representative of skin viscoelasticity from the modified equivalent electrical lumped elements Butterworth-van-Dyke circuit (BVD), using following equations:
R
≅
K
ρ
skin
(
G
(
ω
)
+
G
′
(
ω
)
)
2
ρ
skin
X
≅
K
ρ
skin
(
(
G
(
ω
)
-
G
′
(
ω
)
)
2
ρ
skin
+
ω
h
eff
)
Where K is the electromechanical coupling factor, ρ skin is the skin density, ω is the resonance pulsation, G′, G″ are respectively the storage modulus and the loss modulus corresponding to the real and imaginary parts of the complex shear modulus G, and h e ff is the depth of living skin,
the biosensor ( 1 ) being modeled by an electrical circuit which comprises:
a static branch modeling the electrical behavior of quartz, and
a dynamic branch parallel to the static branch and modeling the mechanical behavior of quartz and the mechanical behavior of skin,
the static branch comprising a resistor and a capacitor connected in parallel,
the dynamic branch comprising in series:
a capacitor, a self inductance and a resistor modeling the mechanical behavior of quartz, and
the additional equivalent electrical impedance Z modeling the mechanical behavior of the skin.