Adjustable Intermolecular Interactions Allowing 2D Transition Metal Dichalcogenides with Prolonged Scavenging Activity for Reactive Oxygen Species.

There is an increasing demand for control over the dimensions and functions of transition metal dichalcogenides (TMDs) in aqueous solution toward biological and medical applications. Herein, an approach for the exfoliation and functionalization of TMDs in water via modulation of the hydrophobic interaction between poly(ε-caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) and the basal planes of TMDs is reported. Decreasing the hydrophobic PCL length of PCL-b-PEG from 5000 g mol-1 (PCL5000 ) to 460 g mol-1 (PCL460 ) significantly increases the exfoliation efficiency of TMD nanosheets because the polymer-TMD hydrophobic interaction becomes dominant over the polymer-polymer interaction. The TMD nanosheets exfoliated by PCL460 -b-PEG5000 (460-WS2 , 460-WSe2 , 460-MoS2 , and 460-MoSe2 ) show excellent and prolonged scavenging activity for reactive oxygen species (ROS), but each type of TMD displays a different scavenging tendency against hydroxyl, superoxide, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals. A mechanistic study based on electron paramagnetic resonance spectroscopy and density functional theory simulations suggests that radical-mediated oxidation of TMDs and hydrogen transfer from the oxidized TMDs to radicals are crucial steps for ROS scavenging by TMD nanosheets. As-prepared 460-TMDs are able to effectively scavenge ROS in HaCaT human keratinocytes, and also exhibit excellent biocompatibility.

Silica-Based Platform Decorated with Conjugated Polymer Dots and Prussian Blue for Improved Photodynamic Cancer Therapy.

To advance cancer treatment, we have developed a novel composite material consisting of conjugated polymer dots (CPDs) and Prussian blue (PB) particles, which were immobilized on, and encapsulated within, silica particles, respectively. The CPDs functioned as both a photosensitizer and a photodynamic agent, and the PB acted as a photothermal agent. The silica platform provided a biocompatible matrix that brought the two components into close proximity. Under laser irradiation, the fluorescence from the CPDs in the composite material enabled cell imaging and was subsequently converted to thermal energy by PB. This efficient energy transfer was accomplished because of the spectral overlap between the emission of donor CPDs and the absorbance of acceptor PB. The increase in local temperature in the cells resulted in a significant increase in the amount of reactive oxygen species (ROS) generated by CPDs, in which their independent use did not produce sufficient ROS for cancer cell treatment. To assess the impact of the enhanced ROS generation by the composite material, we conducted experiments using cancer cells under 532 nm laser irradiation. The results showed that with the increase in local temperature, the generated ROS increased by 30% compared with the control, which did not contain PB. When the silica-based composite material was positioned at the periphery of the tumor for 120 h, it led to a much slower tumor growth than other materials tested. By using a CPD-based photodynamic therapy platform, a new simplified approach to designing and preparing cancer treatments could be achieved, which included photothermal PB-assisted enhanced ROS generation using a single laser. This advancement opens up an exciting new opportunity for effective cancer treatment.

Target-specific near-IR induced drug release and photothermal therapy with accumulated Au/Ag hollow nanoshells on pulmonary cancer cell membranes.

Au/Ag hollow nanoshells (AuHNSs) were developed as multifunctional therapeutic agents for effective, targeted, photothermally induced drug delivery under near-infrared (NIR) light. AuHNSs were synthesized by galvanic replacement reaction. We further conjugated antibodies against the epidermal growth factor receptor (EGFR) to the PEGylated AuHNS, followed by loading with the antitumor drug doxorubicin (AuHNS-EGFR-DOX) for lung cancer treatment. AuHNSs showed similar photothermal efficiency to gold nanorods under optimized NIR laser power. The targeting of AuHNS-EGFR-DOX was confirmed by light-scattering images of A549 cells, and doxorubicin release from the AuHNSs was evaluated under low pH and NIR-irradiated conditions. Multifunctional AuHNS-EGFR-DOX induced photothermal ablation of the targeted lung cancer cells and rapid doxorubicin release following irradiation with NIR laser. Furthermore, we evaluated the effectiveness of AuHNS-EGFR-DOX drug delivery by comparing two drug delivery methods: receptor-mediated endocytosis and cell-surface targeting. Accumulation of the AuHNS-EGFR-DOX on the cell surfaces by targeting EGFR turned out to be more effective for lung cancer treatments than uptake of AuHNS-EGFR-DOX. Taken together, our data suggest a new and optimal method of NIR-induced drug release via the accumulation of targeted AuHNS-EGFR-DOX on cancer cell membranes.

Polymer-mediated formation and assembly of silver nanoparticles on silica nanospheres for sensitive surface-enhanced Raman scattering detection.

To impart a desired optical property to metal nanoparticles (NPs) suitable for surface-enhanced Raman scattering (SERS) applications, it is crucial to assemble them in two or three dimensions in addition to controlling their size and shape. Herein, we report a new strategy for the synthesis and direct assembly of Ag NPs on silica nanospheres (AgNPs-SiNS) in the presence of poly(ethylene glycol) (PEG) derivatives such as PEG-OH, bis(amino)-PEGs (DA-PEGs), and O,O'-bis(2-aminopropyl)PEG (DAP-PEG). They exhibited different effects on the formation of Ag NPs with variable sizes (10-40 nm) and density on the silica surface. As the molecular weight (MW) of DA-PEGs increased, the number of Ag NPs on the silica surface increased. In addition, DAP-PEG (MW of 2000), which has a 2-aminopropyl moiety at both ends, promoted the most effective formation and assembly of uniform-sized Ag NPs on a silica surface, as compared to the other PEG derivatives with the same molecular weight. Finally, we demonstrated that AgNPs-SiNS bearing 4-fluorobenzenethiol on its surface induced the strong SERS signal at the single-particle level, indicating that each hybrid particle has internal hot spots. This shows the potential of AgNPs-SiNS for SERS-based sensitive detection of target molecules.