Self-assembly of an europium-containing polyoxometalate and the arginine/lysine-rich peptides from human papillomavirus capsid protein L1 in forming luminescence-enhanced hybrid nanoparticles

Through a self-assembly of arginine/lysine-rich peptide from human papillomavirus (HPV) capsid protein and an Eu-containing polyoxometalate (POM), Na₉[EuW₁₀O₃₆]·32H₂O (EuW10), the formation of well-defined hybrid nanospheres in aqueous solution is presented, showing large luminescence enhancement of POM and use as a potential "turn-on" fluorescence probe in biology. The binding mechanisms between them have been explored at the molecular level by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), fluorescence spectra, isothermal titration calorimetry (ITC), ζ-potential, and nuclear magnetic resonance (¹H NMR) titration spectra. ITC study confirmed the assembly was completely enthalpy driven, and ζ-potential proved that the driving force was governed mainly by the electrostatic interaction. ¹H NMR spectroscopy indicated changes in hydrogen bond of EuW10 and the peptide segment, and the binding model was clarified. Our design constructed the self-assembly fabrication of well-defined nanoparticles by using inorganic POM and bioapplicable peptide combined with strong fluorescence characterization together. The enhanced luminescence and specific targeted-HPV peptide ability would be important and useful in the detection of HPV capsid protein and/or HPV genotypes, and such a protocol could be extended to another virus once using the corresponding peptides. Therefore, the present report will be helpful to promote the development of antivirus agents in the future.