Nanodiamond–Gold Nanocomposites with the Peroxidase-Like Oxidative Catalytic Activity

Novel nanodiamond–gold nanocomposites (NDAus) are prepared, and their oxidative catalytic activity is examined. Gold nanoparticles are deposited on carboxylated nanodiamonds (NDs) by in situ chemical reduction of gold precursor ions to produce NDAus, which exhibit catalytic activity for the oxidation of <i>o</i>-phenylenediamine in the presence of hydrogen peroxide similarly to a peroxidase. This remarkable catalytic activity is exhibited only by the gold nanoparticle-decorated NDs and is not observed for either Au nanoparticles or NDs separately. Kinetic oxidative catalysis studies show that NDAus exhibit a ping-pong mechanism with an activation energy of 93.3 kJ mol^–1, with the oxidation reaction rate being proportional to the substrate concentration. NDAus retain considerable activity even after several instances of reuse and are compatible with a natural enzyme, allowing the detection of xanthine using cascade catalysis. Association with gold nanoparticles makes NDs a good carbonic catalyst due to charge transfer at the metal–carbon interface and facilitated substrate adsorption. The results of this study suggest that diverse carbonic catalysts can be obtained by interfacial incorporation of various metal/inorganic substances

Paclitaxel–Nanodiamond Nanocomplexes Enhance Aqueous Dispersibility and Drug Retention in Cells

Nanodiamonds (NDs) with 5 nm crystalline structures have been recognized as emerging carbon delivery vehicles due to their biocompatible inertness, high surface-to-volume ratio, and energy absorbance properties. In this study, carboxylated nanodiamond (ND–COOH) was reduced to hydroxylated nanodiamond (ND–OH) for stable and pH-independent colloidal dispersity. The poorly water-soluble paclitaxel (PTX) was physically loaded into ND–OH clusters, forming amorphous PTX nanostructure on the interparticle nanocage of the ND substrate. Stable physical PTX loading onto the ND substrate with stable colloidal stability showed enhanced PTX release. ND–OH/PTX complexes retained the sustained release of PTX by up to 97.32% at 70 h, compared with the 47.33% release of bare crystalline PTX. Enhanced PTX release from ND substrate showed low cell viability in Hela, MCF-9, and A549 cancer cells due to sustained release and stable dispersity in a biological aqueous environment. Especially, the IC₅₀ values of ND–OH/PTX complexes and PTX in Hela cells were 0.037 μg/mL and 0.137 μg/mL, respectively. Well-dispersed cellular uptake of suprastructure ND–OH/PTX nanocomplexes was directly observed from the TEM images. ND–OH/PTX nanocomplexes assimilated into cells might provide convective diffusion with high PTX concentration, inducing initial necrosis. This study suggests that poorly water-soluble drugs can be formulated into a suprastructure with ND and acts as a highly concentrated drug reservoir directly within a cell

Durable Urushiol-Based Nanofilm with Water Repellency for Clear Overlay Appliances in Dentistry

With increased esthetic needs, orthodontics is an indispensable medical treatment in dentistry, and transparent clear overlay appliances (COAs) are in general use to fix teeth. However, COAs are easily worn out because of the lack of durability. Here, we applied a nanofilm onto COAs using urushiol (U), a durable coating material from plant via a layer-by-layer assembly technique. In particular, polymerized urushiol (PU) provided COAs with higher mechanical strength in the large-scale assessment, lower cytotoxicity, and intrinsic hydrophobicity for antimicrobial use. In this report, we inceptively attempted to functionalize COAs with nanofilm for advanced biomedical use

Energy-Absorbing and Local Plasmonic Nanodiamond/Gold Nanocomposites for Sustained and Enhanced Photoacoustic Imaging

Photoacoustic (PA) imaging is a laser-mediated optical ultrasound-based visualization that allows imaging of optical energy absorbers in deep tissue, offering higher spatial resolution, compared with that of NIR fluorescence. To enhance a gold nanoparticles-based PA agent, carbon crystalline nanodiamonds and gold nanocomposites (NDAuNPs) were synthesized by chemical reduction of a carboxylate nanodiamond and gold precursor. Reduced hydroxyl-terminated nanodiamonds have stable colloidal dispersion and provide a platform where AuNPs are localized on the ND surface with high density. NDAuNP agglutinates were 100 nm in size, and AuNPs with a size distribution of 5–20 nm were chemically conjugated on the ND surface. The surface-enhanced Raman scattering spectra showed enhanced intensity of NDAuNPs in a concentration-dependent manner. Energy-absorbing nanodiamonds facilitated energy transfer into AuNPs, inducing a local plasmonic effect. The PA signal of NDAuNPs was stronger than that of the AuNPs, as well as the signal maintenance during a prolonged period of laser irradiation. Tissue images of TEM showed that after 2 h irradiation NDAuNPs were maintained without gold degradation, while AuNPs were degraded. The local plasmonic and the energy-absorbing properties of NDAuNPs amplified the PA signal and impeded the degradation of gold without PA signal decay. The NDAuNP nanocomposites may serve as an imaging probe, providing high PA amplitudes

Nanocomposites of Molybdenum Disulfide/Methoxy Polyethylene Glycol-<i>co</i>-Polypyrrole for Amplified Photoacoustic Signal

Photoacoustic activity is the generation of an ultrasonic signal via thermal expansion or bubble formation, stimulated by laser irradiation. Photoacoustic nanoplatforms have recently gained focus for application in bioelectric interfaces. Various photoacoustic material types have been evaluated, including gold nanoparticles, semiconductive π-conjugating polymers (SP), etc. In this study, surfactant-free methoxy-polyethylene glycol-<i>co</i>-polypyrrole copolymer (mPEG-<i>co</i>-PPyr) nanoparticles (NPs) and mPEG-<i>co</i>-PPyr NP/molybdenum disulfide (mPEG-<i>co</i>-PPyr/MoS₂) nanocomposites (NCs) were prepared and their photoacoustic activity was demonstrated. The mPEG-<i>co</i>-PPyr NPs and mPEG-<i>co</i>-PPyr/MoS₂ NCs both showed photoacoustic signal activity. The mPEG-<i>co</i>-PPyr/MoS₂ NCs presented a higher photoacoustic signal amplitude at 700 nm than the mPEG-<i>co</i>-PPyr NPs. The enhanced photoacoustic activity of the mPEG-<i>co</i>-PPyr/MoS₂ NCs might be attributed to heterogeneous interfacial contact between mPEG-<i>co</i>-PPyr and the MoS₂ nanosheets due to complex formation. Laser ablation of MoS₂ might elevate the local temperature and facilitate the thermal conductive transfer in the mPEG-<i>co</i>-PPyr/MoS₂ NCs, amplifying PA signal. Our study, for the first time, demonstrates enhanced PA activity in SP/transition metal disulfide (TMD) composites as photoacoustic nanoplatforms

Polyamidoamine-Decorated Nanodiamonds as a Hybrid Gene Delivery Vector and siRNA Structural Characterization at the Charged Interfaces

Nanodiamonds have been discovered as a new exogenous material source in biomedical applications. As a new potent form of nanodiamond (ND), polyamidoamine-decorated nanodiamonds (PAMAM-NDs) were prepared for E7 or E6 oncoprotein-suppressing siRNA gene delivery for high risk human papillomavirus-induced cervical cancer, such as types 16 and 18. It is critical to understand the physicochemical properties of siRNA complexes immobilized on cationic solid ND surfaces in the aspect of biomolecular structural and conformational changes, as the new inert carbon material can be extended into the application of a gene delivery vector. A spectral study of siRNA/PAMAM-ND complexes using differential scanning calorimetry and circular dichroism spectroscopy proved that the hydrogen bonding and electrostatic interactions between siRNA and PAMAM-NDs decreased endothermic heat capacity. Moreover, siRNA/PAMAM-ND complexes showed low cell cytotoxicity and significant suppressing effects for forward target E6 and E7 oncogenic genes, proving functional and therapeutic efficacy. The cellular uptake of siRNA/PAMAM-ND complexes at 8 h was visualized by macropinocytes and direct endosomal escape of the siRNA/PAMAM-ND complexes. It is presumed that PAMAM-NDs provided a buffering cushion to adjust the pH and hard mechanical stress to escape endosomes. siRNA/PAMAM-ND complexes provide a potential organic/inorganic hybrid material source for gene delivery carriers