Luminescent bio-sensors via co-assembly of hen egg white lysozyme with Eu³⁺/Tb³⁺-complexes

Protein crystals have advantageous properties as framework materials, such as porosity and organized, high-density functional groups with the potential for guest specificity. Thus, protein crystal materials open up vast opportunities for fluorescent species doping and drug sensing. In this work, we explore this frontier by combining two lanthanide complexes with hen egg white lysozyme (HEWL) and directly obtaining co deposited structures in one step using an anti-solvent method different from the previous two-step method. Cross-linking of the protein was achieved using glutaraldehyde, ensuring the stability of the assembly in diverse solvent environments. The use of glutaraldehyde achieved protein cross-linking, ensuring the stability of the components in various solvent environments, including no leakage of fluorescent substances in ultrapure water and anhydrous ethanol. Differential fluorescence quenching effects of amino acids on the two doped luminescent complexes were observed. Introduction of amino acids, varying in concentration and type, resulted in distinct fluorescence enhancement or quenching effects on the protein assembly loaded with the complexes, and the detection results are reflected through different fitting equations and parameters. By exploring the application of this hybrid material for amino acid detection, this work lays the groundwork for broader applications.