Preparation Of Mn²⁺-doped Luminescence Enhancement Upconversion Nanomaterials And Their Application In Bioassay

In recent years,rare earth upconversion luminescent nano material has attracted for people.The photochemical properties ofthe upconversionmaterials is stable to photolysis,the general biological toxicity is low,the biological tissue has good penetration and have no greater damage to the organism.Using near infrared laser as the excitation source,only upconversionmaterials can emit light while the labeled biomolecules and the detected biological system as it has no upconversion luminescence properties to emit light.It greatly reduce the detection background which improves the detection sensitivity so that it has a wide application prospects in biological analysis.Combined with the above advantages,the Mn²⁺-doped NaYF₄:Yb,Er upconversion nanorods in red regionand the Mn²⁺-doped NaYF₄:Yb,Tm upconversion nanoparticles in the near-infrared?NIR?region was synthesizedthen luminescence energy transfer?LET?system was successfully established for the detection of human prostate antigen?PSA?and alpha fetoprotein?AFP?.The oxidation and reduction luminescent switch system was established.Specific contents are as follows:?1?The Mn²⁺-doped NaYF₄:Yb,Er upconversion luminescence nanorods with an emission peak located in the red region were synthesized.The presence of Mn²⁺ markedly increased the luminescence intensity.The surfaces of Mn²⁺-doped NaYF₄:Yb,Er upconversion nanorods were modified with poly?acrylic acid?.Then the PSA antibody was covalently coupled to the surface of carboxyl-functionalized Mn²⁺-NaYF₄:Yb,Er nanorods,which acted as the energy donor,gold nanorods acted as the energy acceptor in this LET system.When the PSA antigen was added into the system,the energy donors and the energy acceptors were separated due to the binding affinity between PSA and anti-PSA was greater than the electrostatic interactions thereby the luminescence was recovered.The linear range of detecting PSA was from 0.1172 to 18.75 ng/mL,with a limit of detection for PSA as low as 0.1129 ng/mL.?2?The as-prepared Mn²⁺-doped NaYF₄:Yb,Tm UCNPs exhibited a emission in the NIR region and were modified with poly-acrylic acid.Then the AFP antibody was covalently coupled to the carboxyl-functionalized Mn²⁺-NaYF₄:Yb,Tm nanoparticles,which acted as the energy donor.When energy acceptor-gold nanorods was added,their distance was in close proximity due to electrostaticinteractions,which quenched the luminescence emission of the Mn²⁺-dopedNaYF₄:Yb,Tm UCNPs.When AFP was added,the binding affinity between AFP and anti-AFP is stronger than the electrostatic interactions.Thus,the donor separated fromthe acceptor and the luminescence was restored.Under optimal conditions,the restored luminescence exhibited a linear relationship with AFP concentrations ranging from 0.3574 to 19.50 ng/mL and a limit of detection as low as 0.2544 ng/mL.?3?Utilize the Mn²⁺-NaYF₄:Yb,Tm upconversion luminescence in the near-infrared?NIR?region,an upconversion luminescenceswitching system was designed based on the reversible reaction of redox reaction.When oxidizing substance such as Ce⁴⁺or MnO₄^-was added in Mn²⁺-NaYF₄:Yb,Tmupconversion nanoparticles solution.Mn²⁺ can be oxidized to MnO₂ so that MnO₂ covers the surface of the material,luminescence quenching.When reducing substance such as cysteine,glutathione or ascorbic acid was added into the system,the MnO₂ was reduced to Mn²⁺ then the luminescence was recovered.Based on this,an upconversion luminescence switching system was designed.