Construction Of A Modified Paper-based Microfluidic Chip And Its Application In The Determination Of Urinary Calculus-related Substances

Micro fluidic paper-based analytical devices are also known as μPAD.It has attracted great attention from researchers around the world since Whitesides group first proposed the paper-based chip model,especially in the field of "instant testing"(POCT).The μPAD has many advantages such as low cost,no pollution,fast analysis and simple technical operation.And it is considered to have great potential as a good substitute for POCT compared with traditional μTAS devices that use glass and polymer as supporting materials.By combining colorimetric analysis method with microfluidic paper chip to prepare colorimetric paper chip,the visual semi-quantitative or quantitative determination of the target object can be realized through the color change before and after reaction on the paper chip.Colorimetric microfluidic paper chips have a wide development prospect in clinical detection applications due to its unique advantages.Nano-sized zinc oxide materials have large specific surface area and strong capability of immobilizing enzymes.By loading zinc oxide nanorods on paper-based microfluidic chips,the analysis ability of paper chips will be effectively improved.This paper focuses on the preparation and application of colorimetric paper chips and nanomaterials modified paper chips.Kidney-stone disease can lead to abnormal levels of several indicators in urine,such as calcium ions,inorganic phosphorus,oxalate ions and urate ions,etc.,for which a paper based detection method was developed.The complexation method was used for the clinical determination of calcium ions,and the detection range was 0-10 mmol L-1.It is known that the normal content of calcium in urine of healthy people is 2.5-7.5 mmol L-1.The detection range of inorganic phosphorus can reach 5-30 mmol L-1 by displacement method.In clinical practice,if urine inorganic phosphorus reaches 28 mmol L-1,the patients are regarded as high phosphorus patients.This method can be successfully used in clinical detection of inorganic phosphorus.By improving the oxalic acid kit and applying it on a paper chip,the detection of oxalic acid in urine can be reached.The presence of ascorbic acid will affect the detection of oxalic acid,and we use Reagent A in the kit to eliminate the interference of ascorbic acid for detection.The detection range can reach 0-1.0 mmol L-1.The detection of uric acid can be achieved using the enzymatic reaction method,and the range can reach 0.1-3 mmol L-1.We further designed a new type of 3D μPAD that can be used for the simultaneous determination of multiple small biochemical molecules.Zinc oxide nanorods were loaded on the surface of the 3D μPAD,and the material ZNR-3/WFP had the best detection performance and was selected for the following determination of uric acid and glucose.For glucose,the linear range is 0.01-10 mmol L-1,whereas for uric acid the linear range is 0.01-5 mmol L-1.The detection limit of glucose and uric acid can be as low as 3 μmol L-1 and 4 μmol L-1(3 σ/K,n=7),respectively.