Biocompatible quaternary pullulan functionalized 2D MoS2 glycosheet-based non-leaching and infection-resistant coatings for indwelling medical implants.

Medical implants are frequently used in medicine and reconstructive surgery to treat various pathological and anatomical conditions. However, over time, biofilm formation on the surface of these implants can cause recurrent infections and subsequent inflammatory responses in the host, resulting in tissue damage, necrosis, and re-hospitalization. To address these implant-associated infections, the best approach is to create antimicrobial coatings. Here, we report the fabrication of a biocompatible, non-leaching, and contact-based antibacterial coating for implants using quaternary pullulan functionalized MoS2 (MCP) glycosheets. The cationic MCP glycosheets were coated on the surfaces of polydopamine-modified stainless steel and polyvinyl fluoride substrates through a simple process of electrostatic interaction. The developed coating showed excellent antibacterial activity (>99.5%) against E. coli and S. aureus that remained stable over 30 days without leaching out of the substrates and retained its antibacterial activity. MCP-coated implants did not induce any acute or sub-chronic toxicity to mammalian cells, both in vitro and in vivo. Furthermore, MCP coating prevented S. aureus colonization on stainless steel implants in a mouse model of implant-associated infection. The MCP coating developed in this study represents a simple, safe, and effective antibacterial coating for preventing implant-associated infections.

Palladium Nanocapsules for Photothermal Therapy in the Near-Infrared II Biological Window.

Recent developments in nanomaterials with programmable optical responses and their capacity to modulate the photothermal effect induced by an extrinsic source of light have elevated plasmonic photothermal therapy (PPTT) to the status of a favored treatment for a variety of malignancies. However, the low penetration depth of near-infrared-I (NIR-I) lights and the need to expose the human body to a high laser power density in PPTT have restricted its clinical translation for cancer therapy. Most nanostructures reported to date exhibit limited performance due to (i) activity only in the NIR-I region, (ii) the use of intense laser, (iii) need of large concentration of nanomaterials, or (iv) prolonged exposure times to achieve the optimal hyperthermia state for cancer phototherapy. To overcome these shortcomings in plasmonic nanomaterials, we report a bimetallic palladium nanocapsule (Pd Ncap)─with a solid gold bead as its core and a thin, perforated palladium shell─with extinction both in the NIR-I as well as the NIR-II region for PPTT applications toward cancer therapy. The Pd Ncap demonstrated exceptional photothermal stability with a photothermal conversion efficiency of ∼49% at the NIR-II (1064 nm) wavelength region at a very low laser power density of 0.5 W/cm2. The nanocapsules were further surface-functionalized with Herceptin (Pd Ncap-Her) to target the breast cancer cell line SK-BR-3 and exploited for in vitro PPTT applications using NIR-II light. Pd Ncap-Her caused more than 98% cell death at a concentration of just 50 µg/mL and a laser power density of 0.5 W/cm2 with an output power of only 100 mW. Flow cytometric and microscopic analyses revealed that Pd Ncap-Her-induced apoptosis in the treated cancer cells during PPTT. Additionally, Pd Ncaps were found to have reactive oxygen species (ROS) scavenging ability, which can potentially reduce the damage to cells or tissues from ROS produced during PPTT. Also, Pd Ncap demonstrated excellent in vivo biocompatibility and was highly efficient in photothermally ablating tumors in mice. With a high photothermal conversion and killing efficiency at very low nanoparticle concentrations and laser power densities, the current nanostructure can operate as an effective phototherapeutic agent for the treatment of different cancers with ROS-protecting ability.