HYDROGEL, PREPARATION METHOD THEREOF, AND pH SENSOR COMPRISING THE SAME

Abstract

The present invention relates to a hydrogel, a preparation method thereof, and a pH sensor comprising the same, and more particularly, to a hydrogel, which can substitute for conventional pH paper, is continuously usable, can be used in various applications, and reversibly changes color depending on the pH of a sample, and to a pH sensor comprising the same. The hydrogel comprises: a polymer complex wherein a first organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto is joined to a carboxyl group-containing polysaccharide by a peptide bond; and an organic dye comprising a second organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto.

What is claimed is: 
     
         1 . A hydrogel that reversibly changes color depending on pH, the hydrogel comprising:
 a polymer complex wherein a first organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto is joined to a carboxyl group-containing polysaccharide by a peptide bond; and   an organic dye comprising a second organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto.   
     
     
         2 . The hydrogel of  claim 1 , wherein the polysaccharide is alginate. 
     
     
         3 . The hydrogel of  claim 2 , wherein the aromatic functional group contained in each of the polymer complex and the organic dye is a catechol group. 
     
     
         4 . The hydrogel of  claim 3 , wherein the first organic compound is dopamine, and the polymer complex is a compound represented by the following formula 1: 
       
         
           
           
               
               
           
         
       
       wherein m and n are positive real numbers; 0<m; n<1; and m+n=1. 
     
     
         5 . The hydrogel of  claim 3 , wherein the second organic compound is pyrocatechol violet. 
     
     
         6 . The hydrogel of  claim 5 , wherein the polymer complex and the organic dye are mixed at a ratio of 10:1 to 1000:1 (weight (mg):volume (ml)). 
     
     
         7 . The hydrogel of  claim 3 , wherein the polymer complex has a degree of catechol substitution of 1.3-2.0%. 
     
     
         8 . A pH sensor having a sample sensing region coated with the hydrogel of  claim 1 . 
     
     
         9 . A method for preparing a hydrogel that reversibly changes color depending on pH, the method comprising the sequential steps:
 (S 10 ) dissolving a carboxyl group-containing polysaccharide in buffer to obtain a polysaccharide solution;   (S 20 ) adding a cross-linker solution composed of a mixture of an organic solvent and a cross-linker to the polysaccharide solution;   (S 30 ) adding, to the cross-linker-containing polysaccharide solution resulting from step (S 20 ), an organic solution composed of a mixture of an organic solvent and a first organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto, to form a mixture solution, and allowing the mixture solution to react;   (S 40 ) obtaining a polymer complex from the reaction mixture resulting from step (S 30 ); and   (S 50 ) mixing the polymer complex from step (S 40 ) with an organic dye comprising a second organic compound containing an aromatic functional group having at least one hydroxyl group bonded thereto.   
     
     
         10 . The method of  claim 9 , wherein the polysaccharide is alginate, and the aromatic functional group contained in each of the polymer complex and the organic dye is a catechol group. 
     
     
         11 . The method of  claim 10 , wherein the first organic compound is dopamine, and the polymer complex is a compound represented by the following formula 1: 
       
         
           
           
               
               
           
         
       
       wherein m and n are positive real numbers; 0<m; n<1; and m+n=1. 
     
     
         12 . The method of  claim 11 , wherein the second organic compound is pyrocatechol violet. 
     
     
         13 . The method of  claim 12 , wherein the fifth step (S 50 ) comprises mixing the polymer complex and the organic dye are mixed at a ratio of 10:1 to 1000:1 (weight (mg):volume (ml)). 
     
     
         14 . The method of  claim 9 , wherein the cross-linker is a carboimide-based compound. 
     
     
         15 . The method of  claim 9 , wherein the cross-linker is a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) coupling agent. 
     
     
         16 . The method of  claim 9 , wherein the buffer is phosphate buffered saline (PBS). 
     
     
         17 . The method of  claim 9 , wherein step (S 20 ) of adding the cross-linker solution and step (S 30 ) of adding the organic solution are performed with methanol as the organic solvent. 
     
     
         18 . The method of  claim 17 , wherein step (S 40 ) of obtaining the polymer complex comprises the steps of (S 41 ) removing the methanol by fractional distillation; and (S 42 ) dissolving a material remaining after removal of the methanol in deionized water, followed by dialysis and freeze drying.