JPS5928357Y2 - Medical FET sensor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a medical FET center using an insulated gate field effect transistor (hereinafter referred to as FET) having a selectively sensitive film in the gate portion.

In recent years, in the fields of physiology and medicine, substances in body fluids such as blood, such as ions such as hydrogen, sodium, and potassium, oxygen, gases such as carbon dioxide, their derivatives, glucose, lactose, hormones, enzymes, antibodies, etc. Concentration measurements have become more frequent.

Various methods for measuring the above-mentioned substances have been studied, and among them, a sensitive membrane that selectively adsorbs, coordinates, or permeates a specific substance at a gate portion is disclosed in JP-A No. 51-139289. Gate insulated FETs are easy to miniaturize, the measurement circuit is simple and the equipment is inexpensive, and various substances can be measured by changing the selectively sensitive film in the gate area. , which is very promising as a medical sensor.

However, for continuous measurement of biological components, especially components in blood, it is common to insert a sensor directly into a blood vessel.

In order to use the FET sensor for the above purpose, the inventors of the present invention proposed a hollow member with excellent blood compatibility, such as a catheter at the tip of a hollow member such as a catheter disclosed a medical sensor in which an electrode part other than the gate part of an FET is inserted, and a water-resistant electrical insulating adhesive is liquid-tightly filled in the gap between the electrode part and the inner wall of a hollow member.

The inventors coated the outside of the above-mentioned sensor with an anticoagulant polymer, and then inserted it into the femoral artery and vein of a dog to continuously monitor blood components. Within a few hours, the sensitivity of the sensor becomes very low.
It was not possible to obtain stable measurement values.

Such unstable sensors have poor reliability and are difficult to put into practical use as biological monitoring sensors.

As a result of a thorough study of the structure of the sensor, the inventors of the present application found that because the gate part of the sensor protrudes from the end of the hollow member, blood pools around the gate part and foreign body reaction is accelerated. We assumed that blood clots would occur at the gate in a short period of time, and as a result of intensive research, we arrived at the present invention in order to provide a sensor with a structure that does not allow blood to accumulate.

That is, in the present invention, a gate insulated field effect transistor is inserted into a hollow member having at least one opening on the side surface with the gate portion located near the opening,
A medical FET characterized in that the transistor other than the gate part is buried in a water-resistant adhesive sealed inside a hollow member, and the gate part is covered with a hydrophilic polymer material.
It's a sensor.

This structure prevents blood from coagulating at the gate of the FET, making it possible to perform stable measurements over a long period of time.

Next, an example of the structure of the medical FET sensor of the present invention will be explained with reference to the drawings.

In FIG. 1, a hollow member having an opening 8 on its side surface, for example, a blood vessel catheter 2, is inserted into the inside of the catheter 2 so that the gate portion 3 of the FET 1 is positioned near the opening.

It is preferable that the electrode part 4 and the lead wire 5 of the FET be separated from the opening, and the opening 8 should not reach the electrode part.

The FET and the inner wall of the catheter near the aperture are sealed with a water-resistant adhesive 6, and it is particularly preferable that the tip of the catheter and the vicinity of the aperture be rounded without edges to prevent blood clotting.

As the adhesive, epoxy-based, urethane-based, polyester-based, acrylic resin-based, silicone rubber-based resins, etc. can be used, but silicone rubber-based resins are preferred in terms of ease of use.

The gate portion 3 is protected by a hydrophilic pommer 7, and it is preferable for the protective surface to be approximately the same as the external shape of the catheter in order to prevent blood clots.

The wood-philic polymer coated on the gate portion is a very general polymer that does not have the function of reacting with or adsorbing a specific substance, and these polymers have a water content of 10% or more.

If the water content is too low, the response time of the sensor becomes longer and drift tends to occur, which is not preferable.

More preferably, the water content is 30-90%.

Here, the moisture content refers to the polymer film created under the same conditions as the coating layer on the sensitive film of the FET gate.
This is the amount defined by immersing it in pure water at 7° C. for 24 hours, wiping off the water on the surface, and weighing it, where Wl is the weight, and W2 is the weight when completely dry.

That is, the water content is a property of the film itself that coats the FET, and is not the water content of the film that actually coats the FET.

However, since the FET sensor is immersed in water during use, the water content is almost the same as this.

Such hydrophilic polymers include various polymers such as polyether, acrylic acid, methacrylic acid polymers, cellulose, gelatin, and maleic acid polymers, but preferably poly-β-hydroxyethyl methacrylate (p.

Hydrophilic polymethacrylic typified by HEMA), polydimethylaminoethyl methacrylate, polyacrylamide, polyvinylpyridine, polyvinylpyrrolidone, polyvinyl alcohol, and the like.

These polymers may be not only homopolymers but also copolymers with other copolymerizable monomers.

Among these polymers, polyhydroxyethyl methacrylate-based polymers or polyvinyl alcohol-based polymers are preferred from the viewpoint of preventing blood clotting, especially when blood is to be measured.

These polymers may also be heparinized to further enhance anticoagulant properties.

Since the hydrophilic polymer coated on the gate portion is immersed in water during the measurement, it is in the state of a hydrogel containing 10 to 90% water.

FIG. 2 shows a structure in which the FET sensor 1 is protected by a support 9.

Use of such a support facilitates insertion of the FET into the catheter.

Such a support preferably has a smooth tip, for example, a conical shape, and may be made of a material that is not harmful to living organisms, such as methacrylate resin, polyester resin, or vinyl chloride resin.

In addition to this embodiment, there are a plurality of FET sensors 1 inside the hollow member 2.
It goes without saying that it can also be used in the composite sensor shown in FIGS. 3 and 4 in which 0.11 is inserted.

The medical FET sensor having the above-described structure has become practical for the first time as a medical sensor in which the FET is inserted into a blood vessel and used for a long period of time.

[Brief explanation of drawings]

The drawings are an example of the medical FET sensor of the present invention, FIG. 1 is an example in which the FET sensor is inserted into a hollow member, and FIG. 2 is an example in which the FET sensor is protected by a support. FIGS. 3 and 4 are examples of a composite sensor in which a plurality of sensors are inserted into a hollow member. 1...FET sensor, 2...Hollow member, 3...FET gate part, 6...Water resistant adhesive, 7... Hydrophilic polymer, 8...
...Open hole.

Claims (1)

[Scope of utility model registration request] A gate insulated field effect transistor is inserted into a hollow member having at least one opening on a side surface with a gate portion located near the opening, and the transistor other than the gate portion is sealed inside the hollow member. A medical FET sensor characterized by being embedded in a water-resistant adhesive and having a gate portion covered with a hydrophilic polymer.