Understanding the Photothermal and Photocatalytic Mechanism of Polydopamine Coated Gold Nanorods

Localized surface plasmon resonance (LSPRs) shown by gold nanorods (AuNRs) has several applications in photocatalysis, sensing, and biomedicine. The combination of AuNRs with Polydopamine (PDA) shells results in a strong photo-thermal effect, making them appealing nanomaterials for biomedical applications. However, the precise roles and relative contributions of plasmonic effects in gold, and light-to-heat conversion in PDA are still debated. Herein, a hybrid nanoplatform made by an AuNR core surrounded by a polydopamine (PDA) shell is synthesized, and its photocatalytic behavior is studied. Synthesis is based on a seed-mediated growth followed by the further self-polymerization of dopamine hydrochloride (DA) on the surface of the AuNRs, and the effect of the thickness of the PDA shell on the plasmon response of the composite is the main examined parameter. Photocatalytic performance is tested toward Rhodamine 6G (Rh6G), with the nanocomposites achieving better performance than bare AuNRs and bare PDA nanoparticles. The degradation of 54% of Rh6G initial concentration is achieved within 60 min of irradiation with a catalyst concentration of 7.4 µg mL⁻¹. Photodegradation kinetics, time-resolved spectroscopy, and finite-element-method simulations of plasmons show that AuNRs plasmons, coupled with the low thermal conductivity of PDA, provide slow thermalization, while enhancing the charge carrier transfer.     

Acridine/Acridone–Carborane Conjugates as Strong DNA-Binding Agents with Anticancer Potential

Synthesis of acridine derivatives that act as DNA-targeting anticancer agents is an evolving field and has resulted in the introduction of several drugs into clinical trials. Carboranes can be of importance in designing biologically active compounds due to their specific properties. Therefore, a series of novel acridine analogs modified with carborane clusters were synthesized. The DNA-binding ability of these analogs was evaluated on calf thymus DNA (ct-DNA). Results of these analyses showed that 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propylamino]acridine ( 30 ) interacted strongly with ct-DNA, indicating its ability to intercalate into DNA, whereas 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propanamido]acridine ( 29 ) changed the B-form of ct-DNA to the Z form. Compound 30 demonstrated cytotoxicity, was able to inhibit cell proliferation, arrest the cell cycle in the S phase in the HeLa cancer cell line, and induced the production of reactive oxygen species (ROS). In addition, it was specifically localized in lysosomes and was a weak inhibitor of Topo IIα.