During the past few years, nanoparticles have been used for various applications including, but not limited to, protein immobilization, bioseparation, environmental treatment, biomedical and bioengineering usage, and food analysis. Among all types of nanoparticles, superparamagnetic iron oxide nanoparticles, especially Fe₃O₄, have attracted a great deal of attention due to their unique magnetic properties and the ability of being easily chemical modified for improved biocompatibility, dispersibility. This review covers recent advances in the fabrication of functional materials based on Fe₃O₄ nanoparticles together with their possibilities and limitations for application in different fields.

The first luciferase from Antarctic krill (LAK) was cloned and successfully expressed in Escherichia coli BL21(DE3). LAK exhibits the unique ability to emit bright violet fluorescence at an emission wavelength of 350 nm, which represents the lowest reported bioluminescence wavelength for luciferases. However, its low thermal stability poses a limitation to its broader application. In this study, we employed a rational design approach to introduce three pairs of artificial disulfide bonds into LAK. Circular dichroism (CD) analysis revealed that the introduction of artificial disulfide bonds resulted in a significant increase in the secondary structural content of α-helices and β-sheets compared to the wild-type (WT) enzyme. However, these modifications did not influence the emission spectrum. Among the resultant mutant strains, two exhibited markedly enhanced thermal stability. Notably, Mut2 demonstrated a 6.18-fold increase in half-life at 50 °C. Molecular docking studies indicated that D-fluorescein can form additional hydrogen bonds with surrounding amino acid residues (A323, T347, and K534). The docking energies between the enzyme and substrate for WT and Mut2 were −19.5 kcal/mol and −23.4 kcal/mol, respectively, thereby establishing strong interactions within the catalytic pocket region. These interactions likely contribute to a 2.92-fold improvement in substrate affinity, as evidenced by a reduced Michaelis–Menten constant (Km). Our thermal stability and catalytic activity analyses revealed that the linker region between the N- and C-domains plays a crucial role in the overall stability of the enzyme. Furthermore, the C-terminus of LAK does not participate in substrate-binding and catalysis; its local excessive rigidity was found to restrict the release of the AMP product, thereby negatively impacting catalytic activity. These findings offer new insights into the mutagenesis of luciferases and pave the way for the further optimization of LAK for various biotechnological applications.