TETRA BLOCK COPOLYMER

Technical Field

The invention is related to biosensors that can measure glucose from sweat.

The invention is particularly related to a biosensor comprising a polyphosphonoundecyl acrylate-co-polyvinylimidazole-co-polyvinylferrocene-co- polyglycidyl methacrylate tetra block copolymer as an electron transmitter between the glucose oxidase and redox centre of the electrode for measuring glucose.

Prior Art

Glucometers that perform electrochemical measurements formed of an electronic circuit and strips that measure glucose from blood are present in the market. Besides these, similar studies that have been published for detecting glucose from sweat are also available. For example in the study of Gao W. et ah, (1) glucose measurement from sweat where chitosan/carbon nanotube/glucose oxidase/ Au/Prussian blue is used, has been examined. In literature, glucose biosensor studies prepared with polymers such as PANI (2), ferrocene, chitosan are available. Nanoparticles such as carbon nanotubes and/or gold, as an electrical transmitter between the redox centre of glucose oxidase and the electrode are also used.

Glucometers that measure glucose from blood, and that are sold commercially perform measurements from high concentrations such as 1-3 mM.

Successful immobilization has been carried out in several sensor studies of enzymes such as glucose oxidase, peroxidase. However, when an electron transfer mediator is absent, the electron transfer effect of the enzyme is very low. The precision of the biosensor can be improved by adding an electron transfer mediator to the system during biosensor construction. The determination of glucose concentration and high precision measurement is crucially important in clinical diagnosis. Glucose oxidase linked ferrocene based modified electrodes (redox-active polymers) have been used from past to present, in order to determine glucose. However, problems such as low precision and rapid breaking down of the stability of the enzyme electrode, are faced in these studies. At the same time, as the enzyme physically binds to the electrode surface, the strips are disposable.

Besides this, various agents are also used such as gold nanoparticles and/or carbon nanotube, in order to increase precision. However, these agents necessitate high potential applications to be carried out on the electrode. The reduction of the applied potential by means of improving the communication between the nanomaterial and the electrode is significantly important for the electrode to be long-lasting.

In the Chinese patent document numbered CN104569116A of the prior art, a method of producing a glucose sensor by using ionic liquid electro coating nanometre material, which does not comprise an enzyme, is disclosed. This method comprises the steps of, grinding a vitreous carbon electrode until the surface is cleaned by using a gamma-aluminium oxide powder.

distributing graphene into perfluorosulfonate-polytetrafluoroethylene copolymer solution and preparing a black suspension liquid,

coating the vitreous carbon electrode with the black suspension liquid and preparing a graphene -perfluorosulfonate-polytetrafluoroethylene copolymer/vitreous carbon electrode,

adding palladium dichloride into 1 -ethyl-3 -methylimidazole tetrafluoroborate in order to prepare a precipitation liquid,

preparing a palladium nano-ion/graphene-chitosan/ vitreous carbon electrode to function as a study electrode by adding graphene-chitosan/ vitreous carbon electrode into the precipitation liquid, - preparing a glucose sensor without an enzyme to be used in order to determine glucose by means of an electrochemical workstation by taking a saturated calomel electrode, and platinum wire as a reference electrode.

In the Russian patent document numbered RU2641966C2 of the prior art, an encapsulation of a glucose sensor, with a glucose oxidase enzyme that is present in a crosslinked hydrophilic copolymer which is in contact with the surface of the electrode, is disclosed. The structure of the hydrophilic copolymer is mentioned in the related document.

In the prior art, the precision of the sensors used to measure the glucose amount in the blood is low. These sensors are generally designed as disposable sensors. Moreover the stability of the enzyme electrode used in these sensors breakdown rapidly.

When the applications in the prior art are taken into consideration, it was realized that a biosensor which comprises polyphosphonoundecyl acrylate-co- polyvinylimidazole-co-polyvinylferrocene-co-polyglycidyl methacrylate tetra block copolymer and which can thereby provide continuous measurement and higher precision was required.

Aims of the Invention

The invention aims to provide a biosensor where polyphosphonoundecyl acrylate- co-polyvinylimidazole-co-polyvinylferrocene-co-polyglycidyl methacrylate tetra block copolymer is used as an electron transfer mediator between the glucose oxidase and redox centre of the electrode. Another aim of the invention is to carry out a biosensor which can provide continuous measurement and higher precision by means of its copolymer content.

Detailed Description of the Invention

In the invention polyphosphonoundecyl acrylate-co-polyvinylimidazole-co- polyvinylferrocene-co-polyglycidyl methacrylate tetra block copolymer was synthesized using 11-phosphonoundecyl acrylate, 1-vinylimidazole, vinylferrocene, glycidyl methacrylate monomers. The application of the polymer obtained by using 4 different monomer units as a glucose biosensor provides several advantages such as, improving the measurement of each monomer respectively (enabling measurement at very low detection limits (10 mM)), being able to measure several times with the same electrode, providing non-invasive glucose measurement and carrying out glucose measurement from sweat.

The synthesis scheme of the polymer is given below. (Scheme 1)

Scheme 1. Polymer synthesis scheme

A

(Formula I)

In the invention, the glucose oxidase enzyme polymeric electron transfer receiver for measuring glucose has been covalently bonded to epoxy groups in the polyphosphonoundecyl acrylate-co-polyvinylferrocene-co-polyglycidyl methacrylate copolymer. An azobisisobutyronitrile (AIBN) polymer starter and the polymer subject to the invention have been prepared at different ratios at a temperature of 70°C by means of the free radical copolymerization method. Tetra block copolymer acts as an electron transfer mediator between glucose oxidase and the redox centre of the electrode. It has been enabled for epoxy groups to easily bind to copolymers by means of this method. Thereby the polymer that can be prepared in a single step, enables to obtain of a biosensor that can carry out rapid, practical and high precision glucose measurement. In the copolymer of the invention, the (A) group is a polyphosphonoundecyl group and it comprises a phosphono group (PO3H2) and functional groups whose alkyl chain numbers can vary between 11-15 C. The (B) group is a polyvinylimidazole group, and it can comprise methyl groups at the imidazole 2, 3, 5 positions. The (C) group, comprises the ferrocene group. The (D) group may comprise the derivatives of the glycidyl group.

By means of the polyphosphonoundecyl acrylate-co-polyvinylimidazole-co- polyvinylferrocene-co-polyglycidyl methacrylate tetra block copolymer used during biosensor construction, glucose measurement has been enabled at concentrations up to 10 mM. For example, Koh A. et al. (3) have mentioned that they can go as below as 200 mM concentration for measuring glucose concentration in sweat.

At least 55 measurements can be taken with a single electrode of the biosensor designed with the polymer subject to the invention and it costs 50% less than other glucose measurement devices. By means of the polymer subject to the invention, a non-invasive glucose measurement has been carried out from a sweat sample without requiring to take a blood sample with a needle or lancet.

By means of the synthesized polymer of the invention, the enzyme chemically bonds to the surface of the electrode and the same electrode can be used at least 55 times for measuring, as opposed to the disposable options provided by competitors.

Thanks to the polymer structure of the invention, the level of detection (LOD) has been reduced to 10mM and thereby precision has been increased.

The polymer claimed as the invention can perform glucose measurement from sweat in a very short period of time (10 seconds). It can be used in the health sector particularly for diabetes patients, in order to produce a glucose biosensor which gives fast results which is practical and provides high precision. Moreover, by means of the high stability of the polymer subject to the invention, several measurements (e.g. 55) can be taken with a single electrode, and therefore the cost of the product shall be reduced. The disposable glucose measurement strips available in the market can be used only once. As the enzymes used in these sensors can physically bind to the surface of the electrode, they allow a single measurement only. By means of the polymer, we have developed the enzyme is chemically bonded to the surface of the electrode and it provides continuous glucose measurement (55 measurements). Moreover, the sensor we have developed is high precision, thereby it performs glucose measurement for concentrations as low as IOmM.

By means of the polymer we have developed, our product provides continuous, painless, measurement from sweat samples, and thereby reduces costs up to at least 66% .

REFERENCES

1. Gao, W. ei al,“Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis.’’Nature, 1529, 509-514, (2016)

2. Garjonyte, R., Malinauskas, A.,“Amperometric glucose biosensors based on Prussian Blue- and polyaniline-glucose oxidase modified electrodes.” Biosensors & Bioelectronics, 15, 445-451, (2000)

3. Koh, A.,“A soft, wearable microfluidic device for the capture, storage, and colorimetric sensing of sweat.” Science Translational Medicine , 8(366): 366ral65, (2016)