Instrument-Free Quantification Of Alkaline Phosphatase Based On The Tyndall Effect

Alkaline phosphatase（ALP）detection plays an important role in physiological activities,and its concentration changes are closely related to liver,prostate,endocrine system,bone tissue and other diseases,so it has important diagnostic significance.We focus on combining the Tyndall effect of nanomaterials to develop three novel simple,rapid,cost-effective methods for highly sensitive and instrument-free quantitative detection of ALP.The details are as follows:（1）In the Chapter 2,a new method was developed for the instrument-free quantitative detection of ALP based on the controlled aggregation of peptide-triggered AuNPs resulting in an enhanced Tyndall effect,by using Au nanoparticles（AuNPs,prepared with sodium citrate as a reducing agent）as colorimetric nanoprobes.We used phosphorylated peptide as the substrate.In the presence of ALP,the phosphorylated peptide was hydrolyzed to generate positively charged products,which induced the aggregation of negatively charged AuNPs by electrostatic adsorption,leading to a significantly-enhanced Tyndall effect signal in the reaction solution.The enhancement level was positively correlated with the concentration of ALP in the sample.The results show that the linear range of ALP detection by the new method is 0.125～7 U/L under optimized experimental conditions.The detection limit estimated according to the 3σrule was 0.00248 U/L.In addition,the new method was applied to the determination of ALP in human serum in a recovery range from 96.16 to 105.10%.（2）In the Chapter 3,since the AuNP probes used in chapter 2 were unstable,a new method was developed for the instrument-free quantitative detection of ALP,by using the target analyte to trigger the in situ generation of Ag NPs to turn on the Tyndall effect.When ALP is present in the sample,the sodium salt of 4-aminophenyl phosphate undergoes dephosphorylation to generate 4-aminophenol,which later reduces Ag⁺ions into Ag NPs,thus achieving the Tyndall effect from scratch.The enhancement degree of the colorimetric signal was positively correlated with the concentration of ALP in the sample.The results show that the linear range of ALP detection by the new method is 0～8 U/L under optimized experimental conditions.The detection limit estimated according to the 3σrule was 0.00197 U/L.In addition,the new method was applied to the determination of ALP in human serum in a recovery range from 94.42 to 96.97%.（3）In the Chapter 4,in order to further improve the detection performance for ALP based on Tyndall effect of nanomaterials in terms of enhanced sensitivity and expanded linear range,manganese dioxide nanosheets（MnO₂ NS）prepared by organic preparation of dimethylimidazole were used as colorimetric probes.A new instrument-free method for quantitative detection via the target-mediated etching of MnO₂ NS to turn off the Tyndall effect.When ALP is present in the sample,the trisodium salt of L-ascorbic acid-2-phosphate（AAP）is hydrolyzed to generate ascorbic acid（AA）with strong reducing property,which further etches MnO₂ NS in the solution to decompose it into Mn²⁺ion,thus achieving the change from the presence to absence of the Tyndall effect.The attenuation of Tyndall signal was positively correlated with the concentration of ALP in the samples.The results show that the linear range of ALP detection by the new method is 0.156～40 U/L under optimized experimental conditions.The detection limit estimated according to the 3σprinciple was 0.00131 U/L.In addition,the new method was applied to the determination of ALP in human serum,and the recoveries were from 96.56 to 104.37%.