title: A facile low-cost enzymatic paper-based assay for the determination of urine creatinine.
abstract: Creatinine is one of many markers used to investigate kidney function. This paper describes a low-cost enzymatic paper-based analytical device (enz-PAD) for determining urine creatinine. The disposable dead volumes of creatinine enzyme reagents from an automatic analyser cassette were utilised. Whatman No. 3 paper was cut into long rectangular shapes (4×40 mm(2)) on which the enzyme reagents, R1 and R2, were adsorbed in two consecutive regions. The assay was performed by immersing test strips into urine samples contained in microwells to allow creatinine in the sample to react with immobilised active ingredients and, then, traverse via capillary action to the detection area where chromogen products accumulated. The method is based on hydrogen peroxide (H2O2) formation via creatinine conversion using creatininase, creatinase, and sarcosine oxidase. The liberated H2O2 reacts with 4-aminophenazone and 2,4,6-triiodo-3-hydroxybenzoic acid to form quinoneimine with a pink-red colour at the detection zone. The linear range of the creatinine assay was 2.5-25 mg dL(-1) (r(2)=0.983), and the detection limit was 2.0 mg dL(-1). The colorimetric enz-PAD for the creatinine assay was highly correlated with a conventional alkaline picrate method when real urine samples were evaluated (r(2)=0.977; n=40). This simple and nearly zero-cost paper-based device provides a novel alternative method for screening urinary creatinine and will be highly beneficial for developing countries.
authors.affiliation: Clinical Biochemistry and Molecular Medicine, Faculty of Allied Health Sciences, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
authors.forename: Kwanrutai
authors.initials: K
authors.lastname: Talalak
authors.affiliation: Clinical Biochemistry and Molecular Medicine, Faculty of Allied Health Sciences, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
authors.forename: Julaluk
authors.initials: J
authors.lastname: Noiphung
authors.affiliation: Department of Clinical Chemistry, Faculty of Allied Health Sciences, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
authors.forename: Temsiri
authors.initials: T
authors.lastname: Songjaroen
authors.affiliation: Electrochemistry and Optical Spectroscopy Research Unit (EOSRU), Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand; Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
authors.forename: Orawon
authors.initials: O
authors.lastname: Chailapakul
authors.affiliation: Department of Clinical Chemistry, Faculty of Allied Health Sciences, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand. Electronic address: Wanida.L@chula.ac.th.
authors.forename: Wanida
authors.initials: W
authors.lastname: Laiwattanapaisal
mesh_terms: D001204:Ascorbate Oxidase / Q000737:chemistry; D002374:Catalase / Q000737:chemistry; D003124:Colorimetry / Q000379:methods; D003365:Costs and Cost Analysis; D003404:Creatinine / Q000737:chemistry / Q000652:urine*; D057075:Enzyme Assays / Q000191:economics / Q000379:methods*; D006801:Humans; D010209:Paper; D009195:Peroxidase / Q000737:chemistry; D050879:Sarcosine Oxidase / Q000737:chemistry; D014512:Ureohydrolases / Q000737:chemistry
chemical_list: D003404:Creatinine; D001204:Ascorbate Oxidase; D002374:Catalase; D009195:Peroxidase; D050879:Sarcosine Oxidase; D014512:Ureohydrolases; C019944:creatinase
keywords: Dead-volume reagent; Enzymatic assay; Lab-on-paper; Low-cost diagnostic; Paper-based analytical devices; Urinary creatinine