Novel Biosensor Method Based On Upconversion Nanomaterials

With the continuous development of nanotechnology and the emerging of new nanomaterials, which have injected new vitality and provided new ideas for the design of efficient biosensors. In recent years, a growing number of new nanomaterials have been regarded as the research focus due to their unique optical properties, especially for upconversion luminescent nanomaterials, which can convert near infrared light?typically ca. 980 nm? into strong visible light through a multi-photon mechanism, with low energy light, low background, improved quantum yield, minimal photobleaching, high and stable luminous intensity, emission wavelength can be adjusted by controlling the composition and so on, this advantages make it has been widely used in biology detection, its low toxicity, good biocompatibility and high tissue penetration ability allowed it to get a strong development in cells, tumor imaging diagnosis and therapy. Based on this, the three parts of paper about upconversion nanoparticles are as follows:1. Oil-soluble NaYF₄:Yb,Tm/NaYF₄ nanoparticles were obtained by solvothermal method. Based on the optical properties of UCNPs and the special electronic properties of graphene oxide, we developed a simple and ultrasensitive method for S1 nuclease detection. The principle of the upconversion FRET-based biosensor was as follows: The hydrophobic OA-coated UCNPs were first converted into water-dispersible DNA-functionalized UCNPs by using the 5'-end phosphate-modified DNA oligonucleotides through the interaction between the negatively cha rged phosphates of the DNA with surface lanthanide ions. When adding GO, DNA-functionalizable UCNPs could adsorb on the surface of GO via ?-? stacking interactions and hydrophobic interactions. The upconversion fluorescence could be completely quenched through energy-transfer or electron-transfer processes. In contrast, if S1 nuclease is introduced into the system, DNA was cleaved into mono- or shortoligonucleotides fragments. Therefore the ?-? stacking and hydrophobic interactions would be weakened, which kept the UCNPs far away from the GO surface, resulting in the decrease in quenching efficiency and the recovery of upconversion fluorescence. The proposed method shows relatively good selectivity for S1 nuclease, a high sensitivity exhibited with a detectabl e minimum concentration of 1 × 10^-4 units m L^-1 S1 nuclease, which was more sensitive than the developed approaches, and its inhibitors assay was verified. This innovative approach provides a successful paradigm in exploring fascinating properties of upconv ersion FRET complexes and a new opportunity for extending their applications in a wide range of fields, such as biology, biomedicine, and more bio/chemo sensing.2. Oil-soluble NaYF₄:Yb,Er nanoparticles were obtained by solvothermal method. Based on the optical properties of UCNPs and the special electronic properties of graphene oxide, we developed a simple and highly sensitive method for sensitive amplified determination of Breast Cancer Gene?BRCA1?. The principle of the upconversion FRET-based biosensor was as follows: The hydrophobic OA-coated UCNPs were first converted into water-dispersible DNA-functionalized UCNPs by ligand exchange. When adding GO and Exo ?, DNA-functionalizable UCNPs could adsorb on the surface of GO via ?-? stacking interactions and hydrophobic interactions. The upconversion fluorescence could be completely quenched through energy-transfer or electron-transfer processes. In contrast, if target DNA is introduced into the system, the capture DNAs prefer to bind to the target DNA, resulting in the specific recognition of the targets. The binding of the target DNA to the functionalized UCNPs leaded to the exonuclease stimulated recycling of the target DNA, and therefore, the UCNPs were far away from the GO surface in the ampli fied sensing process, resulting in the decrease in quenching efficiency and the recovery of upconversion fluorescence. The proposed method shows high sensitivity and facile fabrication, the linear range of this relationship varied from 0.02 nM to 0.9 nM?R = 0.997?3. Oil-soluble NaYF₄:Yb,Tm/NaYF₄ nanoparticles were obtained by solvothermal method. Based on the optical properties of UCNPs and the special electronic properties of Hg²⁺, we developed a simple and highly sensitive method for Hg²⁺ detection. The principle of the upconversion biosensor was as follows: The hydrophobic OA-coated UCNPs were first converted into water-dispersible DNA-functionalized UCNPs by ligand exchange. In the presence of Hg²⁺, the DNA-UCNPs fluorescence could be effectively quenched due to facilitating non-radiative electron/hole recombination annihilation through an effective electron transfer process. The results showed that the sensor can be used for Hg²⁺ sensing both in an aqueous and in local tap water with comparable performances, under the optimal conditions, and the fluorescence quenching efficiency was linearly correlated to the Hg²⁺ ions concentration?correlation coefficient R2 = 0.993? in the range from 10 nM to 10 u M. The detection limit of Hg²⁺ ions was calculated to be 5 nM according according to the 3? rule. In addition, the recoveries of the biological samples are acceptable for quantitative assays.