  The development of multi-drug-resistant bacterial infections seriously
threatens public health, so efforts are needed to develop a new class of safe
and effective antibacterial agents. Here, we report a bio-inspired synthesis of
surface-modified MoS$_2$ Nanoflowers with L-cysteine (MoS$_2$-cys NFs) that
show good colloidal stability in an aqueous medium. The FE-SEM and TEM data
confirm the flower-like morphology and determine the size of NFs (537+-12 nm);
the XRD data predicts the hexagonal crystal structure of the NFs. The XPS peaks
confirm the formation of MoS$_2$ NFs with surface modification by L-cysteine.
FTIR measurements also confirm the presence of L-cysteine in the NFs. The
antibacterial activity of as-prepared MoS$_2$-cys NFs examined over
gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria
shows inhibition of nearly 97% and 90%, respectively, at concentrations 250
$\mu$g/mL each after incubation of 6 hrs. The antibacterial mechanism is mainly
attributed to the generation of oxidative stress, which can occur through both
ROS-dependent and ROS-independent pathways. The ROS-dependent and
ROS-independent oxidative stresses were measured using flow cytometry and
fluorescence imaging using DCFH-DA staining, and Ellman's assay, respectively.
Moreover, the toxicity studies of the MoS$_2$-cys NFs towards HFF cell lines
suggested the high biocompatibility of the nanomaterial with a cell viability
of nearly 90%. We report the intrinsic antibacterial efficiency of MoS$_2$-cys
NFs without any external stimulus (light, H2O2, etc.), doping, or drug loading.
Our study indicates that the proper surface modification can enhance the
colloidal stability and antibacterial potency of MoS$_2$-based nanomaterials
for further applications such as antibacterial coatings, water disinfection,
and wound healing.
