Influence of Functionalized Gold Nanorods on the Structure of Cytochrome –C: An Effective Bio-nanoconjugate for Biomedical Applications

[Display omitted] •Synthesis of gold nanoparticle (AuNPs) via wet chemical method.•Sphere shape of AuNPs was transformed to Rod shape after the 11-mercaptoundecanoic acid functionalization (11-MUA-AuNRs).•Higher colloidal stability of 11-MUA-AuNRs.•11-MUA-AuNRs interact with Cytochrome C through electrostatic interaction.•Secondary structure of Cytochrome C was preserved in the presence of 11-MUA-AuNRs. Protein interact with functionalized nanoparticle surface (bio-nanoconjugate) has been attracted attention in various biomedical applications such as biosensing, bioimaging, tissue engineering and drug delivery etc. However, the formation of bio-nanoconjugate is inadequately understood in various biomedical applications due to their complex structures. Hence, there is an urgent need to understand the formation of bio-nanoconjugate for safe nanobiomedicine. In this study, we have prepared 11-mercaptoundecanoic acid (11-MUA) functionalized gold nanorods (AuNRs, length 30 nm × width 8 nm) with aspect ratio of 3.75 ± 0.10 through wet chemical method. Optical property, size, morphology, colloidal stability of functionalized gold nanorods (Au-11-MUANRs) were characterized through UV–visible, HR-TEM, DLS, Zeta potential and FT-IR spectral techniques. These functionalized gold nanorods with various concentrations were interacted with Cytochrome C (Cyt-C) under the similar physiological condition (pH 7.4) and its subsequent structural changes were examined through Circular dichroism spectroscopy. The obtained CD result indicated that Au-11-MUANRs were slightly altering the structural conformation of Cyt-C at higher concentration due to the stronger electrostatic interaction between the positively charged Cyt-C with negatively charged Au-11-MUANRs. This study clearly reveals that lower concentration (