Influence of alkane chain lengths and head groups on tethering of liposome–gold nanoparticle on gold surface for electrochemical DNA sensing and gene delivery

Abstract

1,2-Dioleoyltrimethylammoniumpropane (DOTAP) liposome–gold nanoparticle (DOTAP–AuNP) is tethered on different thiol monolayers with different chain lengths (carbon number n=3 and 10) and head groups (acid and amine) on gold transducer for applications of DNA sensing, gene transfer and antibacterial activities. Gram −ve (Escherichia coli (E. coli)) and +ve (Staphylococcus aureus (S. aureus)) bacterial cells are used as model systems. The structure of planar and/or spherical liposome–AuNP is ascertained electrochemically in presence of transmembrane protein melittin and electroactive K3[Fe(CN)6]/K4[Fe(CN)6] redox couples. Results from transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), dynamic light scattering (DLS) spectroscopic techniques and electrochemical data confirm the presence of more stable spherical structured DOTAP–AuNPs on the alkane thiols with amine head groups than on the acid terminal alkane thiols irrespective of chain length differences. Label free electrochemical DNA sensing in presence of K3[Fe(CN)6]/K4[Fe(CN)6] indicates large discrimination efficiency at concentrations greater than nano mole for the spherical DOTAP–AuNP on the aminoundecane thiol. DNA transfer into E. coli cells and anti-bacterial studies are made using gram −ve and +ve E. coli cells. The DNA transfer and antibacterial activities are confirmed using differential confocal laser scanning microscopy (CLSM).