Double Inner Standard Plot Model Of An Electrophoresis Titration Chip For A Portable And Green Assay Of Protein Content In Milk

Protein content assay is of great significance in the field of food safety control,proteomics and clinical diagnosis.Therefore,many detection methods have been developed for the assay,such as the classical Kjeldahl method,coommas bright blue method,Folin phenol method,BCA method,biuret method and near-infrared spectroscopy,etc.However,there are still some issues in these methods,such as interference of non-protein nitrogen(NPN)reagents,expensive instrumentation,large size of equipment,additional fluorescence detection equipment required,tedious procedures and long assay time consumed,etc.Recently,the moving reaction boundary of electrophoresis titration has been successfully developed for total protein detection without the interference of NPN reagents.However,these MRBET based devices have many disadvantages such as low sensitivity,long time consumption,large volume,high energy consumption,large sample demand and the need for high-power pump drive,which greatly limit the application.To solve these problems,this study takes double inner standard plot(DISP)method as the core and the DISP-ET chip as the platform.We developed a fast qualitative and quantitative protein analysis method based on DISP and a portable analytical device.The device has the advantages of portable,visualized,green,cheap,rapid integration and high degree of automation,and has been successfully applied for the field test in a dairy farm.The model and the device of DISP-ET provide a lot of inspiration and reference for the application of visual analysis and portable design in the field of food safety control and POC diagnosis.The main research contents of this work are as follows:1.Brief theory of DISP-ET model and the portable device design.Herein a facile double inner standard plot(DISP)model of electrophoresis titration(ET)was proposed for portable and visual protein assay of test milk sample without use of pump,power supply and detector based on moving reaction boundary(MRB)chip.The DISP-ET model predicted that(i)by setting the upper and lower limits(UL,LL)of double inner standard milk protein contents,Point U and L were respectively achieved in the relation of D =-a C + b(D: MRB motion distance,C: protein content);and(ii)the two points divided both C-axis and D-axis into poor,eligible and superior rulers scaled for quantitative assay of test sample.To demonstrate the model of DISP-ET,an original portable device(120 mm ×78 mm × 30 mm,341g)was designed,which had a chip(25 mm × 25 mm × 4 mm)of three channels(15 mm × 200 m × 80 m),platinum electrodes,lithium cell and touch screen.A series of experiments were performed based on the developed portable device.The relevant experiments systemically demonstrated the validity of DISP-ET model,theory and method.2.Validation of DISP-ET modelTo verify the validity of the DISP-ET model,this study used three kinds of model protein in a series of experiments to demonstrate the DISP-ET model.The experiment results show that the in crease of protein content,the shorter MRB migration distance will be.It has a good linear relationship,and we can detect protein content via the MRB distance.The novel DISP-ET model can realize qualitative by naked eye and rapid quantitative analysis,and the model has good selectivity,high sensitivity and high accuracy as well as short time consumption(no more than 15 minutes in total).3.Application of DISP-ET modelWe used the portable device into on-spot detection,to evaluate its application in food safety control and in-situ test.We compared with the traditional MRBET methods,the results showed that there was no significant difference between two methods,but the detection time significantly shortened.It realized truly portable testing and has the ability from sample-in to answer out.In conclusion,we developed and verified the feasibility and effectiveness of DISP-ET model,designed a novel portable device,and successfully applied to on-spot milk sample assay.This model and portable device provide new ideas and methods for the real visualization and portability of food safety control,and have important enlightening significance.