Low cost electrochemical disposable sensor for measuring glycated hemoglobin
Design of a disposable screen printed electrode (SPE) for sensing percentage glycated hemoglobin using electrochemistry is disclosed. SPE has four electrodes, one working electrode for the detection of glycated hemoglobin, one working electrode for the detection of hemoglobin and the other two electrodes are counter and reference electrodes that are common for both detection schemes. It also has a cellulose acetate membrane with lysis agents and surfactant embedded in it. Lysis agents lyse erythrocytes and release hemoglobin. Surfactants modify hemoglobin structure and enhance the rate the electron transfer and thereby the output signal during the electrochemical analysis. The SPE is low cost and user friendly. The only input from the user is a drop of blood.
1. A sensor for measuring percentage glycated hemoglobin (GHb) and total hemoglobin (Hb), said sensor comprising:
a salts-and-surfactant-embedded membrane to receive a blood sample, and for lysing erythrocytes in said blood cell sample to release hemoglobin molecules,
said salts-and-surfactant-embedded membrane to allow said hemoglobin molecules and plasma to pass through as a filtrate, wherein said blood sample contains erythrocytes, white blood cells (WBCs), and platelets;
a first working electrode to measure concentration of glycated hemoglobin (GHb) contained in said filtrate;
a second working electrode to measure concentration of total hemoglobin (Hb) contained in said filtrate;
a reference electrode to operate as a reference with respect to which measurements from said first working electrode and said second working electrodes are made; and
a counter electrode for providing charge balance,
wherein said salts-and-surfactant-embedded membrane has pores of small enough magnitude to retain any unlysed erythrocytes, said WBCs and said platelets, such that said filtrate passed through contains only said hemoglobin molecules and plasma.
2. The sensor of claim 1 , wherein said electrodes are screen printed electrodes.
3. The sensor of claim 1 , wherein said membrane is a porous asymmetric cellulose acetate membrane.
4. The sensor of claim 1 , wherein said salts-and-surfactant-embedded membrane comprises a cellulose acetate membrane.
5. The sensor of claim 1 , wherein said reference electrode and said counter electrodes have shapes selected from circles, squares, hexagons and pentagons around said working electrodes.
6. The sensor of claim 1 , wherein said sensor is a bufferless sensor.
7. The sensor of claim 1 , wherein said first working electrode is coated with GO-APBA (Graphene oxide-Aminophenyl Boronic Acid), said second working electrode is coated with GO (Graphene Oxide),
wherein said GO is enabled to facilitate transfer of electron from heme of said Hb to said second working electrode, as a basis for said measurement of concentration of total Hb in said filtrate.
8. The sensor of claim 7 , wherein said GO-APBA is obtained by the chemical modification of graphene oxide with amino phenyl boronic acid, wherein said chemical modification includes reacting GO (graphene oxide) with ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) in the presence of deionised water.
9. The sensor of claim 1 , wherein said porous membrane comprises a dense layer and an open porous sub layer, wherein the pores of said dense layer have an average diameter of less than or equal to 1.5 μm and greater than 5.5 nm to be able to retain cells remaining in said blood sample after said lysing.
10. The sensor of claim 9 , wherein pores in the dense top layer allow hemoglobin and plasma to pass through.
11. The sensor of claim 9 , wherein said membrane is attached on top of the electrodes such that the porous sub layer faces the air and the dense porous layer faces the electrodes.
12. The sensor of claim 9 , wherein said salts-and-surfactant-embedded membrane is a porous polymeric membrane.