Photodegradation Of Deoxynivalenol By Upconversion Material Composite TiO₂ And Its Effect On Wheat Quality

Deoxynivalenol?also known as DON?is a metabolite of Fusarium graminearum,the pathogen of wheat scab.The grain crops such as maize and wheat polluted by DON will decrease the quality and yield,and cause serious agricultural losses.DON has a wide range of pollution and high incidence,which seriously threatens food safety and human health.Therefore,it is of great significance to develop efficient and environmentally friendly DON removal technology for food safety and agricultural economy.As an advanced oxidation technology,photocatalytic technology has been developed and applied in environmental treatment,food sterilization and preservation due to its mild reaction conditions,low cost and no waste disposal problems.Because of its stable chemical properties,low toxicity and low cost,TiO₂ has become the most commonly used photocatalyst,but due to its wide band gap,it can not effectively utilize sunlight to play a photocatalytic role.Upconversion nanomaterials have special optical properties that can convert near-infrared light into ultraviolet-visible light.Core-shell nanomaterials can be prepared by compounding upconversion nanomaterials with TiO₂,which can solve the defect of wide band gap of titanium dioxide and extend the light response range of TiO₂ to near-infrared region,thus improving the degradation and removal efficiency of DON by photocatalytic technology.Firstly,core-shell upconversion nanoparticles coated with titanium dioxide photocatalyst were synthesized by high temperature thermal decomposition method.Photocatalytic experiments were carried out to test the degradation effect of NaYF₄:Yb,Tm@TiO₂ on DON standard,and compared with pure TiO₂.The results show that under UV light?200 nm⁴00 nm?,the composite exhibited similar efficiency to pure TiO₂.The degradation rate of the composite reached 20.9%in 60 min under NIR?800nm²500 nm?,while that of pure TiO₂ was basically 0.Under the full wavelength condition?200 nm²500 nm?,the degradation rate of the composite was 90.7%and that of pure TiO₂was 70.7%in 60 min.Optimizing the photocatalytic reaction conditions at full wavelength,it was concluded that the degradation efficiency of DON could reach 100%in 60 min when the system pH was 8 and 6mg/mL NaYF₄:Yb,Tm@TiO₂.The photodegradation of DON by composite materials conforms to the first-order kinetic model.Meanwhile,the degradation process of DON was monitored by UPLC-Q-TOF MS,and three degradation products were identified,with m/z=329.399?311.243 and 280.913.Secondly,the effect of photodegradation on wheat quality were also evaluated by studying the basic physical and chemical indexes of wheat.The results showed that the removal rate of DON in wheat could reach 72.8%within 90 min when the dosage of photocatalyst UCNP@TiO₂ was 8 mg/mL and the ratio of wheat to liquid was 1:2.The study on wheat nutritional quality showed that photocatalysis had no significant effect on wheat starch,protein,amino acid content and fatty acid value?P>0.05?.But the whiteness of wheat flour decreased and the yellowness increased.Scanning electron microscopy?SEM?analysis of wheat starch showed that the surface of starch granules was damaged to varying degrees with the prolongation of illumination time.At the same time,the wet gluten content and gelatinization characteristics of wheat decreased significantly during photocatalysis?P<0.05?,indicating that photocatalysis technology may affect the processing quality of wheat.Finally,the safety of UCNP@TiO₂ composite was evaluated by morphological observation of HepG2 cells,CCK-8 test,cell apoptosis and ROS level detection.The results showed that the HepG2 cells began to appear irregular morphology,the cell gap became larger,and a few nanocomposites were observed on the surface of the cells with the increase of the concentration of 0?g/mL¹000?g/mL UCNP@TiO₂ for 24 h.The cell survival rate was higher than 80%.The apoptotic fluorescence staining showed that the apoptotic level of early and late stage cells increased significantly when the concentration of nanocomposites was 600?g/mL.When the concentration of UCNP@TiO₂ reaches 1000?g/mL,the ROS level reaches the highest and the fluorescence intensity becomes stronger,which is dose-dependent with the concentration of UCNP@TiO₂.Cell experiments showed that UCNP@TiO₂ concentration ranged from 0?g/mL to 1000?g/mL and had no significant toxic effect on cells.After washing,the composite photocatalyst can be easily separated from the wheat sample completely,thus ensuring the safety of the composite photocatalyst in the process of wheat DON removal.