The development of new materials has brought about a change in the world since the era of bronze and iron. The evolution of stainless steel, concrete, and silicon redefined new boundaries and made modern era possible. It would not be a hyperbole if the present age is termed as the age of nanomaterials. Nanomaterials can be categorized in various types based on their shape and structure such as 0D (quantum dots (QDs)), 1D (nanorods, nanotubes), 2D (nanosheets), and 3D (flower like, cubical etc.).Molybdenum disulfide (MoS 2 ), a typical layered 2D transition metal dichalcogenide, has received colossal interest in the past few years due to its unique structural, physicochemical, optical, and biological properties. While MoS 2 is mostly applied in traditional industries such as dry lubricants, intercalation agents, and negative electrode material in lithium-ion batteries, its 2D and 0D forms have led to diverse applications in sensing, catalysis, therapy, and imaging. Herein, a systematic overview of the progress that is made in the field of MoS 2 research with an emphasis on its different biomedical applications is presented. This article provides a general discussion on the basic structure and property of MoS 2 and gives a detailed description of its different morphologies that are synthesized so far, namely, nanosheets, nanotubes, and quantum dots along with synthesis strategies. The biomedical applications of MoS 2 -based nanocomposites are also described in detail and categorically, such as in varied therapeutic and diagnostic modalities like drug delivery, gene delivery, phototherapy, combined therapy, bioimaging, theranostics, and biosensing. Finally, a brief commentary on the current challenges and limitations being faced is provided, along with a discussion of some future perspectives for the overall improvement of MoS 2 -based nanocomposites as a potential nanomedicine. 2D MoS 2 -Based Nanomaterials www.advancedsciencenews.com

Two-dimensional molybdenum disulfide (MoS2) based nanosheets functionalized or loaded with an antimicrobial agent have recently attracted attention as highly efficient antibacterial agent. MoS2 sheets act as the photothermal transducers in inducing bacterial cell death on impingement of NIR radiation or enabled cell inactivation by wrapping around the cells. However, the intrinsic ability of MoS2 to act as an effective antibacterial agent without the use of any external stimuli or antimicrobial agent is still not well explored. This study provides a detailed mechanism of antibacterial action of chitosan exfoliated MoS2 nanosheets (CS-MoS2) by deciphering the key events happening both at the membrane surface and inside the bacteria as a result of interaction of bacterial cells with the nanosheets. A simple, green, one-step process was employed for synthesizing stable and positively charged MoS2 nanosheets. The prepared nanosheets showed excellent bactericidal activity against both Gram-positive (MIC = 90 μg/mL, MBC = 120 μg/mL) and Gram-negative bacteria (MIC = 30 μg/mL, MBC = 60 μg/mL). Investigations into deciphering the mechanism of action revealed that the CS-MoS2 nanosheets interacted strongly with the bacterial cells through electrostatic interactions and caused rapid depolarization of the membranes through dent formations. On account of strong van der Waals and electrostatic forces occurring between the CS-MoS2 nanosheets and membrane phospholipid molecules, deepening of dents occurred, which resulted in complete membrane disruption and leakage of cytoplasmic contents. This led to inactivation of the bacterial respiratory pathway through inhibition of dehydrogenase enzymes and induced metabolic arrest in the cells. Simultaneously, disruption of the antioxidant defense system of the cells by increased levels of intracellular ROS subjected the cells to oxidative damage and added to the overall bactericidal action. The nanosheets also displayed antibiofilm properties and were found to be compatible with mammalian cells even at high concentrations.

The current pandemic caused by SARS-CoV-2 has seen a widespread use of personal protective equipment, especially face masks. This has created the need to develop better and reusable protective masks with built-in antimicrobial, self-cleaning, and aerosol filtration properties to prevent the transmission of air-borne pathogens such as the coronaviruses. Herein, molybdenum disulfide (MoS 2 ) nanosheets are used to prepare modified polycotton fabrics having excellent antibacterial activity and photothermal properties. Upon sunlight irradiation, the nanosheet-modified fabrics rapidly increased the surface temperature to ∼77 °C, making them ideal for sunlight-mediated self-disinfection. Complete self-disinfection of the nanosheet-modified fabric was achieved within 3 min of irradiation, making the fabrics favorably reusable upon self-disinfection. The nanosheetmodified fabrics maintained the antibacterial efficiency even after 60 washing cycles. Furthermore, the particle filtration efficiency of three-layered surgical masks was found to be significantly improved through incorporation of the MoS 2 -modified fabric as an additional layer of protective clothing, without compromising the breathability of the masks. The repurposed surgical masks could filter out around 97% of 200 nm particles and 96% of 100 nm particles, thus making them potentially useful for preventing the spread of coronaviruses (120 nm) by trapping them along with antibacterial protection against other airborne pathogens.

Gold nanoparticles (AuNPs) have found a wide range of biomedical and environmental monitoring applications (viz. drug delivery, diagnostics, biosensing, bio-imaging, theranostics, and hazardous chemical sensing) due to their excellent optoelectronic and enhanced physico-chemical properties. The modulation of these properties is done by functionalizing them with the synthesized AuNPs with polymers, surfactants, ligands, drugs, proteins, peptides, or oligonucleotides for attaining the target specificity, selectivity and sensitivity for their various applications in diagnostics, prognostics, and therapeutics. This review intends to highlight the contribution of such AuNPs in state-of-the-art ventures of diverse biomedical applications. Therefore, a brief discussion on the synthesis of AuNPs has been summarized prior to comprehensive detailing of their surface modification strategies and the applications. Here in, we have discussed various ways of AuNPs functionalization including thiol, phosphene, amine, polymer and silica mediated passivation strategies. Thereafter, the implications of these passivated AuNPs in sensing, surface-enhanced Raman spectroscopy (SERS), bioimaging, drug delivery, and theranostics have been extensively discussed with the a number of illustrations.

Herein, a stimulus-responsive theranostic nanosystem comprising gold nanorattles (AuNRTs), having a solid octahedron core and thin porous cubic shell, encapsulated within chitosan nanocarriers (CS-AuNRT) has been reported. Due to the plasmonic AuNRTs, CS-AuNRT demonstrated unique features of near infrared (NIR) absorbance and accessible intrinsic electromagnetic “hot spots” arising due to coupling of inner solid core and outer porous shell. These properties enabled CS-AuNRTs to be used for NIR-responsive drug delivery, photothermal therapy, and surface enhanced Raman scattering (SERS) based bioimaging. Following loading of chemotherapeutic drug doxorubicin (DOX) within AuNRTs along with a phase changing material (PCM), application of NIR irradiation resulted in photothermal melting of the PCM and simultaneous payload release in the surrounding medium. Although being nontoxic themselves, CS-AuNRTs with or without loaded DOX could mount significant cell death in breast cancer cell line (MCF-7) in the presence of NIR light as external stimulus. The oxidative stress generated by DOX-loaded and empty CS-AuNRTs upon NIR irradiation were confirmed by flow-cytometric determination of intracellular reactive oxygen species (ROS). Further, the ROS-led induction of apoptosis in treated MCF-7 cells was established from characteristic nuclear fragmentation, morphological changes and membrane blebbing as observed through confocal fluorescence and scanning electron microscopy. Thus, with NIR responsive chemo-photothermal therapy and SERS based bioimaging, the present nanocarrier system holds potential for cancer theranostics.