Detection Of Indole Acetic Acid And Abscisic Acid By SPR Biosensors

3 – indole acetic acid(IAA)and abscisic acid(ABA)are plant hormones,which can effect plants' growth.The basic function of IAA can not only promote and regulate plant growth,but also inhibit growth and organ formation and so on.The basic function of ABA is to promote and inhibit the growth of plants,promote the shedding of leaves and fruit,affect the bloom stage.The research methods for these two plant hormones had complex sample pretreatment,high cost,poor reproducibility,selectivity,time-consuming and so on.Therefore we use surface plasmon resonance(SPR)biosensor which advantages are real-time online monitoring,sample without pretreatment,sensitive and rapid detection to detect IAA and ABA plant hormones.In order to improve the SPR biosensors' sensitivity,we adopt two kinds of methods to improve sensitivity: The one is based Au/Ag alloy nanoparticles to improve SPR biosensor's sensitization,the other is to lengthen detection chain to improve sensitivity.In this paper,including two parts:(1)Established two SPR biosensors and detected IAA: The one was the traditional model SPR biosensor(sensor 1)and the other was introducing Au/Ag alloy nanoparticles as sensitization materials to SPR biosensor(sensor 2).The SPR biosensor chip was modified by using molecular self-assembly technique.For the sensor 1: firstly,using MPA as basement membrane,then modified protein A,protein A's amino can combine the activated carboxyl of MPA.After being inactivated by ethanolamine,the sensor chip immobilized IAA antibody through the combination with protein A.Finally detected IAA by sensor 1.For the sensor 2: firstly,using HDT as basement membrane,then Au/Ag alloy nanoparticles can be modified onto chip by combining with Ag-S and Au-S bonds.Next the method of biosensor modification of various reagents and detection of IAA was as same as the sensor 1.As a result,both of the two SPR biosensors could detect the IAA successfully.The wavenumber shifts of sensor 1 was linearly proportional to the IAA concentration in a range from 175 to 350 ?g/L,the detection limit was 25 ?g/L(S/N=3),linear equation was y =-6.58 + 0.103 x,R2 = 0.994.The wavenumber shifts of sensor 2 was linearly proportional to the IAA concentration in a range from 17.5 to 250 ?g/L,the detection limit was 2.2 ?g/L(S/N=3),linear equation was y = 4.27 + 0.104 x,R2 = 0.999.The result demonstrated that introducing Au/Ag alloy nanoparticles to SPR biosensor is effectively improve the sensitivity of biosensor.Moreover,the fabricated SPR biosensor had good stability,repeatability and specificity.(2)SPR biosensors were fabricated for ABA detection: Sensor 1 was based on MPA,sensor 2 was based on thiol caproic acid.The SPR biosensor chip was modified by using molecular self-assembly technique.For the sensor 1,the chip was modified orderly by HDT,Au/Ag alloy nanoparticles,MPA,protein A and ABA antibody.The difference between sensor 1 and sensor 2 was replaced sensor 1 MPA with thiol caproic acid,lengthen three carbon chain.Improving the sensitivity of SPR biosensor by lengthen detection chain.As a result,both of the two SPR biosensors could detect the ABA successfully.The wavenumber shifts of sensor 1 was linearly proportional to the ABA concentration in a range from 13.1 to 23.8 ?g/L with a detection limit of 2.3 ?g/L(S/N=3),and linear equation was y = 1.29 + 0.074 x,R2 = 0.995;The wavenumber shifts of sensor 2 was linearly proportional to the ABA concentration in a range from 3.3 to 40 ?g/L,the detection limit was 0.56 ?g/L(S/N=3),and linear equation was y = 1.12 + 0.044 x,R2 = 0.992.The result demonstrated that lengthen detection chain could effectively improve the sensitivity of biosensor.Moreover,the fabricated SPR biosensor had good precision,stability,repeatability and specificity.