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

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).