Smartphone Based Differential Molecularly Imprinted Sensors

Molecularly imprinted polymers(MIPs),also known as plastic antibody,have complementary recognition cavities to the templates in shape,size,and functional groups.Various MIPs have been widely applied in industrial and environmental fields,sample pretreatment,host-guest chemistry,antibody mimics,and biological sensors,etc.Compared with biological receptors,MIPs offer the advantages in low cost and durability to environmental conditions,but there is still an obvious gap in their recognition selectivity.To improve the recognition selectivity of MIPs,many methods are developed to prepare better MIPs,enhancing the anti-interference ability of MIPs sensor.The slow progress in enhancing the recognition selectivity of MIPs is due to the nonspecific adsorption of interferents on the surface of MIPs,limiting the further improvement of the selectivity of MIPs sensors.From the selectivity experimental data reported in the literatures,we found that the adsorption amount of interferents on MIPs and non-imprinted polymers(NIPs)is very similar.By using the difference of the amounts of adsorbed between MIPs and NIPs,the amounts of the interferents adsorbed are expected to offset while most of the amounts of the template molecules adsorbed are still retained.Thus,interference caused by the adsorption of interferents on MIPs can be eliminated effectively,which improves significantly the selectivity of MIPs sensors.According to this idea,differential MIPs analytical methods are developed in thesis.In addition,smartphone based smart phone detection platform is home-made to perform photometric analysis on field if needed.The main contents are outlined below.1.Differential MIPs ratiometric fluorometry for glutathione determinationBy using ethylene glycol dimethacrylate(EDGMA)as the functional monomer.azodiisobutyronitrile(AIBN)as the crosslinking agent,and glutathione(GSH)as the template,magnetic(MIPs)was prepared on the surface of Fe3O4@SiO2 for selective adsorption of GSH.Under the same conditions,magnetic NIPs was prepared to measure the adsorption amount of interferents and used as a reference for differential detection.In the fluorometry,BCNO/MnO2 complex is used as the signal probe.In the presence of MnO2,the fluorescence intensity of BCNO is weak.After adding GSH,part of MnO2 is consumed and the fluorescence of BCNO is enhanced,which can be used to determine GSH.Because many reducing substances can also react with MnO2 to enhance the fluorescence of BCNO/MnO2 complex,causing interfere for the determination of GSH.But the amounts these reducing substances adsorbed on NIPs is linearly correlated with those on MIPs.Because the specific surface area of NIPs is slightly smaller than that of MIPs,a correction factor 1.21 is used to balance the adsorption amounts of the interferents between NIPs and MIPs,making difference in adsorption amounts of the interferents between NIPs and MIPs to be close to 0.Thus,the anti-interference ability of MIPs sensor is significantly improved in the differential model.With CdTe QDs@SiO2 as the reference signal,the ratiometric fluorometry was established for the determination of GSH.The linear range of the proposed differential MIPs sensor is 0.02～1μM and the detection limit is 8 nM.The proposed method is used to determine GSH in human serum samples.In addition,a smartphone based fluorescent detection device is also designed to perform the ratiometric fluorometry in the differential MIPs sensor.2.Adsorption behavior of MIPs recognition cavities and determination of malachite green by differential colormetryBy using methacrylic acid and EGDMA as functional monomers,AIBN as crosslinking agent,and malachite green(MG)as template,magnetic(MIPs)was prepared on the surface Fe3O4@SiO2 for selective adsorption of MG.Magnetic NIPs was prepared under the same conditions to measure the adsorption amount of interferents and used as a reference for differential detection.In the absorbance measurement,a smartphone based absorbance measurement device with long absorption path(maximum 10 cm)is designed.The adsorption amounts of MG in MIPs and NIPs are measured in real time.According to the adsorption amount difference between MIPs and NIPs,the pure adsorption amount of MIPs recognition cavities can be obtained.Under the experimental conditions,the adsorption isotherm of MG in MIPs recognition cavities follows to the Langmuir isotherm model.The adsorption equilibrium constant is 0.573 L/mg and the maximum adsorption capacity is 25.3 mg/g.The adsorption kinetics is well described by a quasi second-order adsorption kinetic model.MG in the sample solution is enriched by MIPs and determined in the eluent.The interference level of other substances in the sample in the determination of MG is eliminated by using the eluent from NIPs as the reference solution in absorbance measurement.Hence,the differential MIPs method has excellent anti-interference ability.The proposed analytical method is used to determine MG in fish and water samples,with the recovery in the range of 91～106%.The portability of the device can be used to detect MG in water samples on field is needed.