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APPARATUS FOR IN-VITRO INFLUENCING BIOLOGICAL CELLULAR

MATERIAL, AND USE THEREOF

FIELD OF THE INVENTION

The present invention relates to an apparatus and its use for in-vitro influencing biological cellular material by applying electric and/or electromagnetic emissions to the biological cellular material.

BACKGROUND OF THE INVENTION

In a subject’s body, i.e. a human or animal body, some biological processes are known to be linked to electricity. For example, the functional basis of sensory, nerve and muscle cells is based on the generation, transmission and processing of electrical impulses containing information. By way of example, the beating of the heart is triggered by electrical impulses, the control of muscles occurs through electrical signals, and cognitive activity is related to brain currents, etc. Thereby, e.g. a bloodvessel may act as a transmission line to conduct electricity.

Further, it has been found that different electrical models can be established for tissue, bone, nerve, proteins, etc. For example, proteins may act as a semiconductor, tissues and bones may act as crystalline arrays, and nerves and muscles may act as electrical conductors, which conduct electromagnetic signals. At cell level, due to given permeability and transport properties of a cell membrane, an uneven ion distribution and thus charge distribution between a cell interior and a cell exterior is maintained, resulting in a membrane potential. In this regard, it has been found that the cell membrane may be described by an electrical model, in which the cell membrane model includes various ionic conductance and electromotive forces in parallel with a capacitor.

Since diseases, particularly if they are triggered by pathogens, such as bacteria, parasites, fungi, viruses, etc., in the human or animal body are based at least in part on structures, such as proteins, DNA, cells, etc., which may be electrically and/or electromagnetically influenced or at least stimulated by externally applied electric and/or electromagnetic emissions.

Prior to treating diseases under electric and/or electromagnetic emissions, in particular electrically and/or electromagnetically, text experiments under laboratory conditions must be carried out in a statistically relevant and reliable manner in order to test the efficacy of such treatment,.

SUMMARY OF THE INVENTION

Therefore, a need exists for providing a test apparatus which allows for in-vitro testing of biological cellular material under the influence of electric and/or electromagnetic emissions in a statistically relevant and repeatable manner independent of the experimenter using the test apparatus.

These and possibly other objects of the present invention are solved by the subject matter of the independent claims. Optional or preferred features are subject of the dependent claims.

According to a first aspect of the invention, there is provided an apparatus for in-vitro influencing biological cellular material by applying electric and/or electromagnetic emissions to the biological cellular material. The apparatus comprises a carrier having at least a bottom sized and shaped to receive and carry a biological cellular material, the carrier being made of a biocompatible material; at least two electrical electrodes configured to supply an electric current to the biological cellular material, the at least two electrical electrodes including a first electrical electrode and a second electrical electrode being arranged spaced apart and opposite to one another and being made of an electrically conductive or semiconductive biocompatible material, the first electrical electrode and the second electrical electrode being configured such that, when a current is applied to the first and second electrical electrodes, and when the biological cellular material is located on the bottom of the carrier, an equal electric current flow per cm ² is induced across the bottom of the carrier and through the biological cellular material, and an assembly aid cooperating with the carrier and the at least two electrical electrodes, and being configured such that the at least two electrical electrodes and the carrier can be assembled repeatedly in always the same manner relative to each other.

In an embodiment, the carrier includes a closed sidewall, which is circular, oval, square, rectangular or polygonial, wherein the shape of the at least two electrical electrodes conforms to sections of the sidewall of the carrier.

Preferably, the bottom of the carrier is at least partially transparent or translucent to light visible to the human eye. More preferably, the carrier is made of plastic or glass.

Advantageously, the carrier is the lid or the base of a Petri dish.

According to an embodiment, the at least two electrical electrodes are made at least partially of palladium, titanium, or an alloy thereof.

According to a further embodiment, the at least two electrical electrodes are arranged on the bottom of the carrier such that the at least two electrical electrodes are in physical contact with the biological cellular material.

Preferably, each of the at least two electrical electrodes further comprises a connecting wire which connects the respective electrical electrode with a current driver, and wherein the connecting wire is made of a biocompatible material.

More preferably, each of the first and the second electrical electrodes includes a first subgroup and a second subgroup of electrical electrodes, and wherein the first subgroup and the second subgroup of electrical electrodes are configured such that, when a current is applied to the first subgroup of electrical electrodes, an electric current flow is induced across the bottom of the carrier and through the biological cellular material along a first direction, and when a current is applied to the second subgroup of electrical electrodes, an electric current flow is induced across the bottom of the carrier and through the biological cellular material along a second direction.

Yet more preferably, the first direction is essentially perpendicular to the second direction.

In an embodiment, the at least two electrical electrodes are fixedly attached to the assembly aid by means of a biocompatible adhesive, a biocompatible mechanical connector or by way of clamping. In yet a further embodiment, the carrier has a circular sidewall, the assembly aid is a retaining ring having a radially outwardly directed outer surface, a radially inwardly directed inner surface, an upper surface and a lower surface, and wherein the radially outwardly directed outer surface of the retaining ring has two recesses arranged radially opposite to one another and each extending along a portion of the circumference of the retaining ring, and wherein the at least two electrical electrodes are accommodated within the two recesses such that the radially outwardly directed outer surface of the retaining ring is flush with a radially outwardly directed outer surface of each of the at least two electrical electrodes.

Preferably, in case the carrier has a circular sidewall, the assembly aid includes two retaining rings, one of the retaining rings being circular and the other one of the retaining rings being elliptical, such that the at least two electrical electrodes are clamped between the two retaining rings upon relative rotation of the two retaining rings.

More preferably, the apparatus further comprises a Helmholtz coil assembly having at least two planar coils for applying a magnetic field to the biological cellular material, wherein each planar coil has an inner coil diameter and an outer coil diameter, and wherein a cylindrical spacer has an outer spacer diameter which corresponds to the inner coil diameter, and wherein the cylindrical spacer supports the carrier and the at least two electrical electrodes.

Yet more preferably, the cylindrical spacer has a centered concavity sized and shaped to receive therein the carrier and the at least two electrical electrodes.

In an embodiment, the apparatus further comprises a protective enclosure which, in use, encloses at least the biological cellular material, the carrier, the at least two electrical electrodes and the assembly aid, wherein the enclosure is made of a non-ferromagnetic material, and wherein the enclosure is configured to protect the biological cellular material from electro-magnetic radiation being present external of the enclosure, and to reduce, preferably eliminate, magnetic flux from an inside to an outside of the enclosure.

Preferably, the enclosure is opaque.

More preferably, a temperature and/or pressure sensor is provided on an outer surface of the enclosure.

Yet more preferably, the shape of the enclosure is such that it only has rounded corners and edges so that all inner and outer surfaces of the enclosure can be wetted, and thus disinfected by using wipe-disinfection.

According to a preferred embodiment, the apparatus further comprises a current driver configured to supply electric current of a predetermined amplitude, frequency and/or waveform to the at least two electrical electrodes.

It is advantageous, if the apparatus is suitable for in-vitro influencing biological cellular material by applying an electric current or a combination of an electric current and a magnetic field to the biological cellular material.

A second aspect of the invention relates to the use of the apparatus according to the first aspect, and which use is directed to in-vitro influencing of biological cellular material by applying electric and/or electromagnetic emissions to the biological cellular material, and in particular to in-vitro testing of the effects of applied electric and/or electromagnetic emissions on pathogens contained in the biological cellular material.

Preferably, the use of the apparatus is directed to in-vitro influencing biological cellular material by applying an electric current or a combination of an electric current and a magnetic field to the biological cellular material.

It is noted that the above embodiments may be combined with each other irrespective of the aspect involved. Accordingly, the use features may be combined with structural features of the apparatus and, likewise, the apparatus features may be combined with the use features.

These and other aspects of the present invention will become apparent from and will be elucidated below with reference to preferred embodiments of the invention described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described by way of example with reference to the drawings.

Fig. 1 A shows an electrode assembly and a carrier for the biological cellular material according to an embodiment;

Fig. IB shows the electrodes of the electrode assembly according to an embodiment;

Fig. 2A shows an electrode assembly according to an embodiment;

Fig. 2B shows an exploded view of an electrode assembly according to an embodiment;

Fig. 3 shows an electrode assembly and a carrier placed inside a Helmholtz coil;

Fig. 4 shows the electrode assembly and the carrier of Fig. 3 disposed inside an protective enclosure;

Fig. 5 shows in a schematic block diagram an electric current generator useful for the electrode assembly of Fig. 1.;

Fig. 6 shows in a schematic block diagram the electric current generator of Fig. 5 in more detail.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention generally relates to an apparatus, and its use, for in-vitro influencing biological cellular material by applying specifically selected and finely controlled electric and/or electromagnetic emissions to the biological cellular material. Preferably, the electric and/or electromagnetic emissions are applied to the biological cellular material in the form of an electric current or a combination of an electric current and a magnetic field. The application of a combination of an electric current and a magnetic field may be applied to the biological cellular material either at the same time or at different times. The electric current may be a direct current or an alternating current with a timely constant frequency and/or amplitude. The magnetic field may also be a constant magnetic field or an alternating magnetic field. Specifically, the amplitude, the frequency and/or the waveform of the electric current and/or the magnetic field may timely vary or may be timely constant.

Biological cellular material, in particular those containing pathogens, may exihibit a detectable reaction under the influence of an electric current or a combination of an electric current and a magnetic field. The present invention aims to help investigating the physiological effects of an electric current or a combination of an electric current and a magnetic field on the biological cellular material, in particular on pathogens contained therein.

For this purpose, the biological cellular material is located on a carrier which, in its simplest form, may be a two-dimensional plate of any desired shape. However, the carrier may also be any sort of three-dimensional container, vessel or dish that is suitable in terms of size and shape for accommodating the biological cellular material. Because the sample to be investigated is a biological sample, any two- or three-dimensional carrier must be made from a biocompatible and non- genotoxic material, and must be suitable for investigating the effects of an electric current, alternatively a combination of an electric current and a magnetic field, on the biological cellular material. Examples of suitable materials are glass, plastic, wood, stone, ceramics, etc.

The size and shape of the carrier must be such that it is suitable for use in a laboratory environment. Preferably, the carrier is designed for placement under a microscope, after the biological cellular material has been placed on the carrier and exposed to an electric current or a combination of an electric current and a magnetic field.

With reference to Fig. 1 A, the carrier may simply be a Petri-dish 20. A Petri-dish 20 is normally made of a biocompatible, non-genotoxic plastic material or glass. Fig. 1 A shows a circular Petri-dish. However, the present invention is not limited to circular geometries. The Petri-dish 20 generally has a planar bottom 24 with an upwardly protruding, closed sidewall 22 extending around the bottom 24.

In general, the bottom of any carrier may at least partially be transparent or translucent to light visible to the human eye. The carrier may include a sidewall that is closed along the circumference of the carrier. The circumference of the carrier may be circular, oval, square, rectangular or polygonal.

The Petri-dish 20 of Fig. 1 A may include an agar plate which contains a growth medium solidified with agar, and which is used to culture the biological cellular material. The diameter of the Petri-dish 20 of Fig. 1A may vary from 30 to 200 mm. However, any two- or three-dimensional carrier that can be used in the context of the present invention may well have a dimension of up to 500 mm.

A pair of electrodes 12a, 12b is arranged inside the Petri-dish 20. The arc-shape of the electrodes 12a, 12b conforms to at least sections of the circular sidewall 22 of the Petri-dish 20. The electrodes 12a, 12b are arranged such that one electrode 12a is diametrically opposite the other electrode 12b. In case of a cylindrical (circular) Petri-dish 20, the arc length of each electrode 12a, 12b is such that electrical interference between the electrodes 12a, 12b is reduced to a minimum, preferably reduced to zero. For example, for a Petri dish with an inner diameter of minimal 83 mm and nominal of 85 mm, each electrode 12a, 12b has a radius of curvature of approximately 37 mm, a length of approximately 56 mm, a height of approximately 12 mm and a thickness of approximately 1 mm.

In any event, the position of the electrodes 12a, 12b relative to each other inside the Petri-dish 20 as well as the size and shape of the electrodes 12a, 12b is such that when an electric current is supplied to both electrodes 12a, 12b, an equal electric current flow per cm ² is induced across the bottom of the Petri-dish 20 and through the biological cellular material located on the bottom 24 of the Petri-dish 20. In other words, the electric current density is equal throughout the bottom 24 of the Petri-dish 20, possibly except regions in the vicinity of the circular sidewall 22 of the Petri-dish 20 and the small side edges 12a-2, 12b-2 of the electrodes 12a, 12b.

The electrodes 12a, 12b may generally be made from an electrically conductive or semiconductive material. Examples of conductive materials may include titanium, titanium alloys, for example Ti6A14V, stainless steel, gold, platinum, cobalt-chromium alloys, and poly(trimethylene carbonate) (PTMC). Examples of semi-conductive materials may include silicon carbide, graphene-based nanomaterials, and nanocrystals.

A connecting wire 15 is used to connect each of the electrodes 12a, 12b to an electric current generator. The connecting wire 154 may preferably be made from the same electrically conductive or semiconductive material as the electrodes 12a, 12b.

In general, the pair of electrodes 12a, 12b may be arranged on the carrier 20 such that they are in physical contact with the biological cellular material. However, arrangements are conceivable in which there is no direct physical contact between the electrodes 12a, 12b and the biological cellular material. As indicated in Fig. IB by the use of dashed lines, each of the pair of electrodes 12a, 12b may include a first subgroup 12a*, 12b* and a second subgroup 12b*, 12b**of electrical electrodes. When an electric current is supplied to the electrodes of the first subgroup 12a*, 12b*, and an electric current is supplied to the electrodes of the second subgroup 12b*, 12b**, an electric current is induced between the electrodes of the first subgroup 12a*, 12b* and along a first direction, and an electric current flow is induced between the electrodes of the second subgroup 12a**, 12b** along a second direction. Preferably, the first direction is essentially perpendicular to the second direction.

Referring again to Fig. 1 A, a ring 14 is used to fix the pair of electrodes 12a, 12b at a certain distance and orientation relative to each other and within the Petri-dish 20. The ring 14 serves the purpose of an assembly aid which allows mounting and assembling the pair of electrodes 12a, 12b within the Petri-dish 20 repeatedly in the same manner. This is of paramount importance in that an experimental evaluation of the influence of an electric current (or a combination of an electric current and a magnetic field) on one or various biological cellular materials must have statistical relevance, i.e., they must repeatedly be carried out in a large number in always the same way and must be independent of the person who carries out the experiments. The ring 14 and the electrodes 12a, 12b which may be seen as an electrode assembly 10 are preferably sized and shaped such that the eletrode assembly 10 is snugly received inside the Petri-dish 20.

The ring 14 may be fixed to the pair of electrodes 12a, 12b in a number of ways. One way is to use a mechanical fastener 16, such as screws, to mount the electrodes 12a, 12b to the ring 14, as can be seen in Fig. 2A. However, means for adhesively adhering the electrodes 12a, 12b to the ring 14 may also be used, such as a potting compound normally used by dentists, or an epoxy or silicon glue. Alternatively, a pair of rings 14a, 14b may be used as is shown only schematically in Fig. 2B. The electrodes 12a, 12b are placed onto, for example, a circular lower ring 14a and within the upwardly extending shoulder 14a-l and on top of the crossbar 14a-2. An upper non-symmetrical or eccentric ring 14b may be placed on top of the lower ring 14a, whereby through a rotation of the upper ring 14b, for example by 90°, the electrodes 12a 12b are clamped between the shoulder 14a-l of the lower ring 14a and the upper ring 14b. Other clamping mechanisms are conceivable to clampingly engage the electrodes 12a, 12b with an assembly aid 14.

The ring 14 shown in Fig. 1 A has two diametrically opposite recesses 14-2 into which the electrodes 12a, 12b are inserted such that an outer surface 12a-l of each electrode 12a, 12b is flush with a radially outwardly directed outer surface 14-1 of the ring 14. In other words, the electrode assembly 10 including the ring 14 has preferably a continuous, radially outwardly directed outer surface, i.e., the radially outwardly directed outer surface of the electrode assembly 10 has no bumps.

The apparatus of the present invention may preferably be used for experiments that not only induce an electric current through the biological cellular material, but at the same time or with a predetermined time lag apply a magnetic field thereto. To this end, and as shown in Fig. 3, a Helmholtz coil 30 is used that produces in its center a nearly uniform magnetic field. As is known, a Helmholtz coil 30 consists of two circular coils (electromagnets) 32a, 32b that are arranged on the same axis. The distance between the two circular coils 32a, 32b equals the radius of each coil 32a, 32b. The coils 32a, 32b are attached to mounting bars 33 which help maintaining the correct axial distance between the coils 32a, 32b and give stability to the Helmholtz coil 30.

A cylindrical spacer 40 is shown in Fig. 3 which has an outer diameter that more or less corresponds to the inner diameter of each planar circular coil 32a, 32b of the Helmholtz coil 30. The spacer 40 includes a concavity 42 in its center and at the upper surface 41 thereof. The concavity 42 is sized and/or shaped such that the Petri-dish 20 and the electrode assembly 10 located inside the Petri-dish 20 can be received inside the concavity 42. Preferably, the Petri-dish 20 is snugly received inside the concavity 42 of the spacer 40 in order to ensure that the Petri-dish 20 is always positioned within the concavity 42 of the spacer 40 in a number of experiments in the same manner. When the Petri-dish 20 and the electrode assembly 10 are received within the concavity 42 of the spacer 40, the biological material, i.e. the bottom of the Petri-dish 20, is advantageously positioned in the center of the Helmholtz coil 30.

With reference to Fig. 4, an protective enclosure 50 is shown into which the electrode assembly 10, the Petri-dish 20, the Helmholtz coil 30 and the spacer 40 can be accomodated. The enclosure 50 is made from a non-ferromagnetic material in order to prevent that any electromagnetic radiation which is present outside of the enclosure 50 may penetrate through the walls 52 and into the enclosure 50 and causes unwanted disturbances of the magnetic field generated by the Helmholtz coil 30. The enclosure 50 also prevents that the magnetic field generated by the Helmholtz coil 30 penetrates through the enclosure 50.

The enclosure 50 is closed, andmay preferably be sealed, preferably in an air-tight manner in order to avoid contamination of the biological sample. Although not shown, the enclosure 50 may have a vacuum port to reduce the atmospheric pressure inside the enclosure 50. The same or another port may be used in connection with a pump to increase the pressure inside the enclosure 50 above atmospheric pressure so that any airborne particles be kept outside the enclosure 50. Depending on the nature and type of the biological sample, a gas, such as CO2, may be supplied to the inside of the enclosure 50.

The protective enclosure 50 includes a feedthrough 54 through which electrical leads may extend to establish an electrical connection of the pair of electrodes 12a, 12b with an electric current generator 100 described in more detail with reference to Fig. 5 and Fig. 6 and to connect the Helmholtz coil 30 with a magnetic field generator. The protective enclosure 50 may have a lid 55 and a base 51. The base may have a pair of handles 53, and the lid 55 may have a pair of handles 56. The lid 55 may at least be partially transparent for visible light. A metal wire mesh 57 helps electro-magnetically shielding the transparent portion of the lid 55, and thus the inside of the enclosure 50. Alternatively, the lid 55 may include a massive metal plate that, together with a base 51 made of a metal, acts as a Faraday cage.

As schematically indicated in Fig. 4, a temperature sensor 60 and a pressure sensor 70 are located on the outer surface of the enclosure 50. The sensors 60, 70 are used to monitor the ambient temperature and atmospheric pressure that prevail on the outside of the enclosure 50.

A camera 80a, which is only schematically indicated in Fig. 4, may be mounted on the interior surface of the lid 55. The position of the camera 80a may be such that the Petri-dish 20 is in the field of view of the camera 80a. A preferred position of the camera 80a is the center on the interior surface of the lid 55. A camera 80a is particularly useful for measurements, preferably in real-time, in the course of which the biological sample has to be protected from ambient light penetrating through the lid 55 and/or the base 51, and hence experiments for which the enclosure 50 is advantegeously not permeable for UV, visible or IR light, preferably for visible light.

Additional sensors 80b, 80c, 80d and 80e, which are only schematically indicated in Fig. 4, may be mounted inside the enclosure 50, preferably on an interior surface of a sidewall 52 of the enclosure 50. These sensors may include a Hall sensor 80b for measuring and monitoring the magnetic field generated by the Helmholtz coil 30. Alternatively, a magnetoresistive sensor or a magnetometer may be used. Reference numerals 80c and 80d may be a pressure sensor and a temperature sensor. A light sensor 80e may used to measure and monitor the light intensity present in the inside of the air-tight enclosure 50. The inside of the enclosure 50 preferably has no sharp comers or sharp edges. Any corner and edges are preferably rounded in order to facilitate cleaning and sterilization of the enclosure 50. The enclosure 50 may be an incubator. Both the inner surfaces and the outer surfaces of the enclosure 50 are such that they can be disinfected by using wipe-disinfection, i.e., they can easily be wetted with no regions that remain unwetted.

Experiments in the course of which an electric current, alternatively a combination of an electric current and a magnetic field are applied to the biological cellular material, are carried out inside the enclosure. Once the experiments are finished, the Petri-dish is taken out from the enclosure and is closed, preferably using the so far unused lid of the Petri-dish. After a certain time period, the biological sample inside the Petri-dish is examined for any physiological alterations caused by the exposure to the electric current, alternatively to the combination of the electric current and the magnetic field. Preferably, a microscope is used to examine the biological sample.

The assembly aid 14 and the cylindrical spacer 40 may be made from an electrically non-conductive material. Examples of electrically insulating materials include medical-grade silicone, polyvinylchloride (PVC), Teflon, Nylon 680, Nylon 12, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTE), polymethylmethacrylate (PMMA), polyurethane (PU), polyethylenterephthalate (PET), polyethersulfone (PES), polyetherimide (PEI), polycarbonates (PC), polyetheretherketone (PEEK), trimethylcarbonate, TMC NAD-lactide, zirconia, alumina, hydroxyapatite, bioglass, and tricalcium phosphate.

For supplying an electric current to the electrodes 12a, 12b, and thus to the biological material, an electric current generator 100 is used. An example of an an electric current generator 100 is briefly described below and with reference to Fig. 5 and Fig. 6. The electric current generator 100 is described in more detail in a PCT application PCT/EP2021/059300 filed on 9 April, 2021, the content of which is hereby incorporated in its entirety by reference.

Fig. 5 shows in a schematic block diagram an exemplary electric current generator 100, which is configured to provide an electric current signal to a subject S, which, for the sake of subject application, is the biological cellular material disposed on the carrier 20. The electric current signal preferably serves for providing specific electric current signals to the subject S. For example, the electric current signal may be selected and/or specified to stimulate a pathogen, such as a bacteria, fungus, virus etc., present at the subject in a frequency domain harmful to the pathogen.

The electric current generator 100 further comprises a controller 110, which may be divided into one or more sub-units or functional units. In the following, the nomenclature 110-xx may indicate that the correspondingly designated unit can, optionally, be structurally and/or functionally associated with the controller 110. However, it is also conceivable that the sub-units or functional units designated by the above nomenclature at least in part are separated from the controller 110.

The controller 110 comprises at least a signal source 110-10 configured to generate an analog signal Sx, and particularly a first analog signal output with a first phase and, simultaneously, a second analog signal with a second phase phase-shifted to the first phase. The first and second analog signal, which may be designated as Sxl and Sx2, may be equal to each other (and may therefore be summarized under designation Sx, i.e. it may be a common signal that is picked up phase-shifted), but may be generated or provided with a phase-shift to each other. For example, the first and second analog signal Sxl, Sx2 may be composite to each other, i.e. having a 180° phase-shift to each other. For example, the analog signal Sx, Sxl, Sx2 may be generated based on a control program, which is described below in more detail.

The electric current generator 100 further comprises a first voltage- controlled current source 120, connected to the signal source 110-10 to receive the first analog signal Sxl and to generate, based on the received first analog signal Sxl, an electric current signal, and configured to provide a first output impedance. Thereby, by varying the first analog signal Sxl, the electric current signal at the output side of the first current source 120 may be controlled.

Further, the electric current generator 100 comprises a second voltage- controlled current source 130, connected to the signal source 110-10 to receive the second analog signal Sx2 and to generate, based on the received second analog signal, an electric current, and configured to provide a second output impedance different to the first output impedance. Thereby, by varying the second analog signal Sx2, the electric current signal at the output side of the second current source 130 may be controlled. Further, for example, the second output impedance may be lower than the first output impedance. This may result in the electric current generator 100 obtaining control of the output potential at the second current source 130. Thereby, the second output impedance of the second current source 130 may be variable or adjustable within the second current source 130.

As can be seen in Fig. 5 (and also in Fig. 6), the first current source 120 and the second current source 130 are connected in series with the subject S (biological sample). This may result in the output voltage capability of the electric current generator 100 to be increased, and particularly in case of at least two current sources to be at least doubled.

Fig. 6 shows in a schematic block diagram the electric current generator 100 in more detail. In principle, Fig. 6 shows the electric current generator 100 from Fig. 5, but for better understanding shows more details of the components, units and/or circuits used.

According to Fig. 6, the first current source 120 and the second current source 130 each comprise an operational amplifier 120-1, 130-1, OP AMP 120-1, 130-1, connected to the signal source 111 and a resistor bridge 120-2 connected to the corresponding OP AMP 120-1, 130-1. An input side of the OP AMP 120-1 of the first current source 120 is connected to the signal source 111 to receive the analog signal Sx with the first phase (Sxl as shown in Fig. 5), and an input side of the OP AMP 130-1 of the second current source 130 is connected to the signal source 111 to receive the analog differential signal Sx with the second phase (Sx2 as shown in Fig. 5). As the analog signal Sx, Sxl, Sx2 may be a differential signal, it, and particularly the first and second analog signal Sxl, Sx2 may also be designated as +Sxl and -Sx2, as indicated in Fig. 6 . The resistor bridge 120-2, 130-2 of the first current source 120 and second current source 130 each comprise resistors Rl, R2, R4 and R5, connected as shown in Fig. 6 as an example. It is noted that at least one of the resistors Rl, R2, R4 and R5 of the resistor bridge 120-2 of the second current source 130 is configured to be adjustable in terms of its resistance value. Further, the controller 110 is configured to vary and/or adjust the resistance value of the resistor bridge 130-2 of the second current source 130, thereby causing the resistor bridge 120-2 to be unbalanced. It is noted that the resistor bridge 130-2 is unbalanced in terms of a corresponding resistor matching condition that may be expressed by n [(R, _t + AR) + R-] * R ₂ R ₃ , wherein the variable and/or adjustable resistance value is indicated by AR. In contrast thereto, the resistance bridge 122 of the first current source 120 is unbalanced, which may be expressed by (R ₁ (R ₄ + R _s • 1.1 r deriveable from

Further, the electric current generator 100 comprises, e.g. as part of the controller 110, a signal generator 110-20, connected, with its output side, to the signal source 111 and configured to provide at least a source signal of the first and/or second analog signal Sx (Sxl and Sx2 as shown in Fig. 5) based on one or more signal parameters, included in the control program, describing the corresponding analog signal to be output by the signal source 110-10. For the latter, the signal generator 110-20 may be connected, with its input side, to e.g. a computer 200, as indicated in Fig. 6 by an arrow. The one or more signal parameters may be part of or may form the control program for the electric current generator 100 in accordance to which the signal source 110-10 is controlled to provide the analog Signal Sx, Sxl, Sx2 based on the control program in order to cause the first and/or second current source 120, 130 to provide a corresponding electric current signal. The one or more parameters may comprise one or more of a signal shape or waveform, amplitude, frequency, and signal duration. These parameters may define a specific signal shape or waveform, which may also comprise one or more sequences of specific signal shapes or waveforms and/or one or more combinations of signal shapes or waveforms. For example, the specific signal shape or waveform may be sine, half sine, saw-tooth, triangle, line, DC, square, pulse, sinesegment, trapezoidal segment, Gaussian distribution, ECG, an arbitrary waveform, or the like. Optionally, the medical device may be configured to vary one or more parameters of the specific signal shape or waveform, such as duration, frequency, phase, duty cycle, pulse and/or amplitude.