Design of green magneto-fluorescent γ-Fe2O3-methyldopa conjugate nanocrystal as a targeted probe for monitoring of esterase activity.

One of the most important aspects of the biological systems is the retention of HSA activity. It is known that serum albumin, in addition to ligand binding capabilities, possesses some enzymatic properties such as esterase activity with p-nitrophenyl acetate substrate. The aim of this study was to synthesize and characterize the mono-dispersed magneto-fluorescent methyldopa coated (MNPs-MDP) which provides a unique opportunity to control and monitor the biological interactions by using magnetic force. An Organic fluorophore methyldopa (2-amino-3-(3,4-dihydroxyphenyl)-2-methyl acid, propanoic) (MDP) was introduced into γ-Fe2O3 particles and made the fluorescent and stable colloidal nanocrystals. As a biological host, human serum albumin (HSA) was chosen which is a major constituent of soluble human blood plasma proteins and is therefore considered as a suitable target for nanoparticle-protein interaction studies. MDP-γ-Fe2O3 nanocrystals showed inherent properties including excellent water solubility, and longtime stability against aggregation, biocompatibility and multifunctional surface rich in carboxyl groups. In addition, we tried to assess the influence of PMDP-γ-Fe2O3 binding on the activity of HSA. Such MDP-γ-Fe2O3 showed an increase in esterase activity in comparison with the free HSA. This method therefore provides a unique platform for preserving the protein structure and conformation.