JPH03127881A - Exciting artificial film for bio-element - Google Patents

Abstract

PURPOSE:To realize the title artificial film capable of self-exciting oscillation for a short time period meeting the requirements for reduced or cancelled external pressure by a method wherein the said film is composed of a porous film on which mixed lipid comprising dioleilphosphate and specific amount of cholesterol is adsorbed. CONSTITUTION:The title artificial film is composed of dioleilphosphate represented by the structural formula I and cholesterol represented by the structural formula II as well as a porous film on which mixed lipid in additive content exceeding 1wt.% and not exceeding 40w.t% is adsorbed. That is, the said film is composed of the porous film on which the mixed lipid comprising dioleilphosphate and cholesterol is adsorbed. Through these procedures, the title exciting artificial film for bio-element capable of notably decreasing the external pressure required for self-exciting oscillation for a short time period compared with that of any conventional films can be formed.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention imitates the information expression and transmission functions of biological nerve cells, etc., and is applicable to biological devices such as sensors for various recognition purposes. This invention relates to an excitable artificial membrane for devices.

(Prior Art) A conventional computer is mainly constructed of inorganic materials such as silicon semiconductors, and its processing function is to execute serial logical operations using the Phono-Neumann method. Although this method is suitable for performing accurate logical operations, it is difficult to simultaneously perform a large number of information processes in parallel, which is necessary for pattern recognition, which is the specialty of the brains of higher organisms, for example.

In recent years, research on the various information recognition functions of living organisms has progressed rapidly. For example, the multiple neurons that make up the brain change their connection relationships with each other as the living body learns and remembers. , it is becoming clear that it has so-called reversibility.

However, it is not always clear what principles the brain's functions such as pattern recognition, learning, and memory are based on, and what components are involved. A large number of researchers are currently working to elucidate these issues.

Living things receive various stimuli from the outside world with their sensory organs,
It is said that information is transmitted to the brain via neurons and synapses that connect multiple neurons, and information is recognized in the brain, which is made up of many neurons.

An example of such a recognition function will be described below.

First, external stimuli (information) are converted into electrical signals, generating nerve impulses. When this nerve impulse reaches the end of the axon that makes up a neuron, chemicals contained in vesicles called neurotransmitters are released. Such neurotransmitters include acetylcholine and, in a broader sense, ions such as calcium (Ca"). Neurotransmitters released outside the cell are transmitted through receptors present in the plasma membrane of adjacent cells, for example. It is taken up into cells and induces new nerve impulses.

Next, neurotransmitters are released from the presynaptic membrane that receives the nerve impulse, as described above, and diffuse to other adjacent postsynaptic membranes, where they are taken up via receptors and triggered by nerve impulses. It will be done. Excitation is a series of information transmission via such nerve impulses, and is thought to reach the brain via multiple synapses.

In order to perform parallel information processing by imitating such biological system functions, there have been attempts to realize functional elements using the lipids that constitute the cell plasma membrane.

For example, in the literature ``Phase transition and self-oscillation phenomena in synthetic lipid membranes'' (Kiyoshi Toko et al., MEMBRANE, 12 (
As disclosed in ILP, 12-21 (1987), an excitable artificial membrane (hereinafter simply referred to as an artificial membrane) in which lipids are adsorbed to a porous membrane is used, and this artificial membrane automatically oscillates. The phenomenon is known.

Here, the above-mentioned automatic oscillation phenomenon will be briefly explained.

First, an artificial membrane is prepared by adsorbing dioleyl phosphate, a synthetic lipid, onto a porous membrane with a pore size of about four sizes. One side of such an artificial membrane is brought into contact with an electrolytic solution with a high salt concentration, and the other side is brought into contact with a low salt concentration. In the artificial membrane placed in such a state, a predetermined potential difference is generated between these electrolytes at a period of several minutes or tens of minutes, and an electrical impulse is generated. Automatic oscillation with such a period is called long-period oscillation.

In addition to the salt concentration difference (ion concentration gradient) mentioned above, by applying a direct current to the artificial membrane and applying a predetermined pressure to the membrane, automatic oscillation with a period of several seconds called short-period oscillation was observed. be done. In this short-period oscillation, the oscillation period of the electrical impulse can be controlled by changing the above-mentioned DC current value.

The above-mentioned automatic oscillation mechanism is presumed to be accompanied by a phase transition of lipids, such as a change from an oil droplet state to a multilayer membrane state, and by using such an excitable artificial membrane, the functions of neurons and synapses can be improved. It is possible to construct a biodevice that mimics the

As a biodevice using the artificial membrane with the above configuration,
The inventors previously filed Japanese Patent Application No. 63-96851 and Patent Application No. 6
No. 3-192116 provides an element that can be applied to, for example, biocomputers and various sensors.

(Problems to be Solved by the Invention) However, in the conventional excitable artificial membrane for biodevices described above, in addition to the salt concentration difference and direct current, the relatively large external It is also necessary to add specific pressure conditions, which poses a problem in that the degree of freedom in element design commensurate with the setting of the conditions is reduced.

In view of the above-mentioned conventional problems, the present invention has been made to reduce the external pressure required to perform the short-period automatic oscillation under the conditions of the salt concentration difference and DC current application, compared to the conventional artificial pressure. The object of the present invention is to provide an artificial membrane for biodevices that can significantly reduce excitability compared to other membranes.

(Means for Solving the Problems) The present invention consists of dioleyl phosphate and cholesterol (C27H460), and the amount of the cholesterol added is 1 (wtχ
) or more and 40 (wtχ) or less is an excitable artificial membrane for biodevices, which is formed by adsorbing a mixed lipid having a molecular weight of 40 (wtχ) or less on a porous membrane.

(Function) In the excitable artificial membrane for biodevices of the present invention, a mixed lipid consisting of dioleyl phosphate and cholesterol is adsorbed onto a porous membrane. Even if the above-mentioned external pressure is reduced, the lipid phase transition that is thought to occur during the automatic oscillation will be promoted by the mixed lipid.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

First, dioleyl phosphate (hereinafter simply DOPH: Di
Oleyl Phosphate (also referred to as oleyl phosphate) was obtained by reacting oleyl alcohol (manufactured by Kanto Kagaku) with phosphorus oxychloride (manufactured by Kanto Kagaku) and then hydrolyzing the resulting synthetic substance. In addition, cholesterol manufactured by Tokyo Kasei was used.

Next, as a mixed lipid consisting of DOPH and cholesterol as described above, the amount of cholesterol added in this mixed lipid is 20 (wtχ), dissolved in Hensen, and in this solution, 8 (immediate) Cellulose ester porous membrane with pore size (Millipore filter-ξ
(manufactured by Liboa) was immersed. The dry weight of the above mixed lipids is 4
■/ An artificial membrane sample with adsorption amount of c+IT was used. For comparison, a comparative artificial membrane sample with an adsorption amount of 4 .mu./cf+ was prepared by following the same procedure as described above except that only D OPH was adsorbed onto the porous membrane.

FIG. 1 is a schematic explanatory diagram of a conventional automatic oscillation device. The above-mentioned artificial membrane 11 is made of
00mM KCI aqueous solution 15a and second electrolytic cell 13
It is supported in contact with both the 5mM KCf aqueous solution 15b housed in b. These KCI aqueous solutions 15a and 15b contained silver-silver chloride electrodes (Ag-AgC1), respectively.
Standard electrodes 17a and 17b are immersed. The standard electrode 17a of the 100mM MCI aqueous solution 15a on the high concentration side is connected to the anode side of the DC power supply 19, and the standard electrode 17b of the 5mMK (J aqueous solution 15b on the low concentration side) is connected to the same cathode side.Time change in the potential difference applied to the artificial membrane 11 In order to measure and record the
KCI aqueous solutions 15a and 15b corresponding to a and 23b
dipped in each. In the figure, 25 is the first electrolytic cell 13
This is a manometer placed at point a, and is configured to be able to apply external pressure to the artificial membrane 11 as indicated by arrow a.

FIG. 2 shows the results of measuring the relationship between external pressure and oscillation frequency using the above-mentioned apparatus and using the above-mentioned embodiment and comparative height measurement as the artificial membrane 11. In this measurement, while applying a constant current of 0.5 (μA) to the artificial membrane 11, the external pressure a was gradually increased from O (cmHgo).

As is clear from the curves in the example, the artificial membrane sample obtained by adsorbing mixed lipids has a short-period automatic oscillation frequency of about 0.75 (1/sec) even when the external pressure is 0 (cmllzo). Oscillation was observed, and the oscillation frequency showed an increasing tendency as the external pressure was increased.

On the other hand, the comparative artificial membrane requires an external pressure of approximately 18 (cmH□0) as the oscillation starting pressure for short-period automatic oscillation, and the oscillation frequency at that time is approximately 0.57 (1/8 )Met.

Next, regarding the example artificial membrane, when the external pressure is 0 (cmHz
Under the condition O), the direct current applied to the artificial membrane 11 was varied, and the relationship between each current value and the oscillation frequency string was determined, and the results are shown in FIG. According to the figure, when the DC current is 0.25 (μA), the artificial membrane of the example is about 0.55 (1/
automatic oscillation occurred at the oscillation frequency of see ). It was also confirmed that as the DC current increased, the oscillation frequency also increased, and that the DC current and the oscillation frequency were approximately proportional.

From the above results, it was found that the oscillation frequency of the artificial membrane according to the embodiment of the present invention can be controlled by adjusting only the direct current without applying external pressure, as in the case of conventional artificial membranes.

Next, the Example artificial membrane was heated to zero without applying external pressure.
．． When self-oscillating with a direct current of 5 (μA),
Figure 4 shows the results of examining the oscillation waveform of a 1.5mM KC/aqueous solution with reference to the b side. What is clear from this figure is that the example artificial membrane is an excitable artificial membrane in which the potential difference rises rapidly even when it is automatically oscillated without external pressure, and its fall is trailing. It had a unique oscillation waveform.

Next, in Figure 5, the amount of cholesterol added is changed to 0.5.
FIG. 3 is a characteristic curve diagram showing the results of measuring the oscillation start pressure when a direct current of (μA) is applied. The mixed lipid adsorption amount is 4 mg.
/c+fl. It is clear from the figure that the oscillation onset pressure of the conventional artificial membrane without addition of cholesterol is approximately 18 (CIIll + 20), whereas
In the artificial membrane obtained by adding cholesterol 1 (wtZ), the oscillation onset pressure was rapidly reduced to about 10 (cmHz). And the added amount of cholesterol is 5
(6 (cmH, o) for a wt artificial membrane, 1
In the artificial membrane set to 0 (wtZ), the oscillation starting pressure was 3 (cmll□0). Especially cholesterol added 4jt15
In the range of htχ) to 40(wtZ), the oscillation start pressure was 0 (cmH, o) in all cases. Although not shown, the amount of cholesterol added exceeds the preferred range of the present invention, and is 42.5 (wt) at least 50 (
Even when external pressure of C[1H20) was applied, no automatic oscillation was observed.

According to the results of the above examples, the external pressure necessary for the automatic oscillation can be reduced when the cholesterol content in the mixed lipid is in the range of 1 to 40 (wtZ). In particular, it has been found that short-period automatic oscillation is possible at 15 to 40 (wtZ) without substantially applying external pressure.

This invention is not limited to the above-described embodiments.

For example, the effects of the excitable artificial membrane for biodevices of the present invention are not necessarily achieved only by the specific implementation device described above. Furthermore, the porous membrane for the artificial membrane is not limited to a specific material or pore size.

Furthermore, the amount of adsorption of mixed lipids on the porous membrane is as follows:
Various changes can be made depending on the material and pore diameter of these porous membranes. Actually, the above mixed lipid adsorption amount is 3 to 6 (■/
The same effect as in the above-mentioned example was obtained at a value of about 1.afl).

(Effects of the Invention) According to the excitable artificial membrane for biodevices of the present invention, by adsorbing a mixed lipid of dioleyl phosphate and cholesterol on a porous membrane, the excitable artificial membrane for biodevices has a higher It becomes possible to realize an artificial membrane capable of short-period automatic oscillation under one of the conditions, which is a reduction or zero external pressure.

Therefore, the degree of freedom in element design that matches the setting of the pressure conditions is significantly improved, and as a result, the field of application to various sensors and biocomputers can be expected to expand.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an automatic oscillation device, FIGS. 2 and 3 are membrane characteristic diagrams of the artificial membrane of the present invention, FIG. 4 is a characteristic waveform diagram, and FIG. 5 is a membrane characteristic diagram. 11... Excitable artificial membrane, 13a... First electrolytic cell, 1
3 b...Second electrolytic cell, 15 a-100mM M
CI aqueous solution, 15 b -5mM MCI aqueous solution, 17
a, 17b -- Standard electrode, 19 -- DC power supply, 21
... Measuring device, 23a. 23b... Standard electrode, 25... Manometer a.
...external pressure.

Claims (1)

[Claims] Dioleyl phosphate▲There are mathematical formulas, chemical formulas, tables, etc.▼ and cholesterol (C_2_7H_4_6O)▲There are mathematical formulas, chemical formulas, tables, etc.▼, and the added amount of the cholesterol is 1 (wt%)
An excitable artificial membrane for biodevices, comprising a porous membrane adsorbing a mixed lipid of at most 40 (wt%) or less.