The synthesis, characterization, DNA/BSA/HSA interactions, molecular modeling, antibacterial properties, and<i>in vitro</i>cytotoxic activities of novel parent and niosome nano-encapsulated Ho(<scp>iii</scp>) complexes

Based on the importance of metal-centered complexes that can interact with DNA, this research focused on the synthesis of a new Ho(iii) complex. This complex was isolated and characterized <i>via</i> elemental analysis, and FT-IR, fluorescence, and UV-vis spectroscopy. Additional confirmation of the Ho(iii) complex structure was obtained <i>via</i> single-crystal X-ray diffraction. DNA interaction studies were carried out <i>via</i> circular dichroism (CD) spectroscopy, UV-vis absorption spectroscopy, viscosity measurements and emission spectroscopy; it was proposed that the metal complex acts as an effective DNA binder based on studies in the presence of fish DNA (FS-DNA), showing high binding affinity to DNA in the presence of hydrophobic and electron donating substituents. Also, the interactions of this complex with human (HSA) and bovine serum albumin (BSA) proteins were studied <i>via</i> fluorescence spectroscopy techniques and the obtained results reveal an excellent propensity for binding in both cases. Furthermore, the interactions of the Ho(iii) complex with DNA, BSA and HSA were confirmed <i>via</i> molecular docking analysis. The antimicrobial activities of the Ho(iii) complex were tested against Gram-negative bacteria and Gram-positive bacteria. In addition, a niosome nano-encapsulated Ho(iii) complex was synthesized, and the parent and encapsulated complexes were evaluated as potential antitumor candidates. The main structure of the Ho(iii) complex is maintained after encapsulation using niosome nanoparticles. The MTT method was used to assess the anticancer properties of the Ho(iii) complex and its encapsulated form toward human lung carcinoma and breast cancer cell lines. The anticancer activity in the encapsulated form was more than that of the parent Ho(iii) complex. In conclusion, these compounds could be considered as new antitumor candidates.