Detection Of Acrylamide And Different Isoelectric Point Proteins By Gold Nanoparticle Colorimetry

In recent years,the frequent occurrence of food safety has attracted people's attention.In order to solve the problem of food safety,many new strategies have been developed for the detection of food hazards.Among them,the biosensor based on nanomaterials is a fast,sensitive,efficient and portable detection method,which can overcome the limitations of traditional methods?such as liquid chromatography,gas chromatography?,including complex sample pretreatment,long detection time,expensive instruments,and the need for professional technicians to operate the instrument.Acrylamide?AA?is a potentially carcinogenic substance with neurotoxicity produced in hot food processing.Allergenic proteins seriously affect the quality of life of the intakes.In this study,acrylamide mediated functionalized gold nanoparticles were polymerized for colorimetric detection of acrylamide,and aptamer/AuNPs probes were used for colorimetric sensing of allergic proteins with different isoelectric points.The main results are as follows:?1?Colorimetric and visual determination of acrylamide via acrylamide-mediated polymerization of acrylamide-functionalized gold nanoparticlesIt is based on color changes induced by an increase in the distance between gold nanoparticles?AuNPs?that is caused by AA copolymerization and a sensing method for colorimetric detection AA is developed.First,the gold nanoparticles were modified with a thioacrylamide polyethylene glycol?AA-PEG-SH?containing AA structure,and the carbon-carbon double bonds on the modified AuNPs can be polymerized under the catalysis of a photoinitiator and under UV irradiation.This results in the aggregation of the AuNPs and in a color change from red to gray.In the presence of AA,the distance between the AuNPs increases due to copolymerization with AA,and the solution of AuNPs preserves its original red color.Under the optimized conditions,the absorption ratio(A₅₂₅/A₇₄₀)of the solution increases linearly in the 1 nM to 10?M free AA concentration range,with a 0.2 nM limit of detection.Hence,the method meets the need for rapid monitoring of trace AA in food.?2?Detection of proteins with different isoelectric points based on unmodified gold nanoparticlesIt has been reported that proteins can form protein corona on the surface of gold nanoparticles,which has a negative effect on the development of colorimetric detection proteins based on unmodified gold nanoparticles.In this paper,the color change of gold nanoparticle was taken as the signal to systematically investigate the pH value range which hinders the formation of protein corona by different isoelectric point proteins.A colorimetric method was developed for the detection of allergic proteins?beta-lactoglobulin and lactoferrin?.Specific pH ranges that hinder the production of protein corona from acidic,neutral and alkaline proteins were studied,represented by beta-lactoglobulin?pI=5.3?,lactoferrin?pI=8.7?and lysozyme?pI=11.1?.The results showed that the optimum pH values of?-lactoglobulin,lactoferrin and lysozyme were 5.3⁶.5,8.7⁹ and 11¹1.5,respectively.An unmodified colorimetric sensing method based on aptamer/AuNPs probe was developed with allergens?beta-lactoglobulin,lactoferrin?as the implementation object.When the pH value was 5.3 and the concentration of beta-lactoglobulin was 0.04²0 ng/mL,the A₇₀₀/A₅₂₂22 in the system presented a linear relationship with the change of beta-lactoglobulin concentration,and the detection limit was 36 pg/mL.When the pH value was 9 and the concentration of beta-lactoglobulin was 0.8⁸00 ng/mL,in the LF/AuNPs system,the A₇₀₀/A₅₂₂22 presented a linear relationship with the change of lactoferrin concentration,and the detection limit was 292.8 pg/mL,which meets the need for rapid monitoring of trace allergic proteins in dairy products.