Enhanced photocatalytic and photodynamic activity of chitosan and garlic loaded CdO-TiO2 hybrid bionanomaterials

Herein, the work addresses the synthesis of biomaterials (chitosan and garlic) loaded CdO-TiO₂ hybrid nanocomposites for photocatalytic water treatment and photodynamic cancer therapeutic applications that were reported the first time. CdO-TiO₂ (CT) nanocomposites were synthesized and loaded with the biomaterials such as chitosan and garlic by simple sol-gel method. The nanomaterials were characterized and the photodegradation of three model pollutants, Methylene blue (MB), Methyl orange (MO) and Rhodamine B (Rh-B) was opted to investigate the efficiency of the synthesized photocatalyst under the solar light. From the results, the garlic-loaded CdO-TiO₂ (AS-CT) hybrid nanocomposites exhibit a superior photocatalytic activity than the chitosan-loaded CdO-TiO₂ (CS-CT) and CdO-TiO₂ (CT) nanocomposites under the irradiation of solar light. Additionally, the cell viability of the synthesized nanocomposites was carried out in HeLa cell lines under different concentrations, light doses and incubation periods using an LED light source. Compared to the CS-CT and CT nanocomposites, an efficient photodynamic activity was achieved in the case of AS-CT hybrid nanocomposites. Actually, the end-use properties required for both processes in AS-CT nanocomposites appear similar due to the presence of organo sulphurus compounds.

Mn3O4 nanoparticles bearing 5-amino-2-mercapto benzimidazole moiety as antibacterial and antifungal agents

The antibacterial and antifungal effects of non-functionalized and surface-functionalized Mn₃O₄ nanoparticles were comparatively analyzed to reason out the potential changes in antimicrobial activities due to functionalization with 5-amino-2-mercapto benzimidazole (AMB) molecule. The surface functionalization of Mn₃O₄ nanoparticles with AMB molecule was confirmed by the XRD result, which shows the shift in 2θ values with noticeable peaks. The surface morphology and functionalization of Mn₃O₄ nanoparticles were additionally confirmed by HR-SEM and EDAX studies. Antimicrobial activities were investigated by an agar-well-diffusion method using the bacteria Staphylococcus aureus and Pseudomonas aeruginosa and fungi Aspergillus niger. The functionalized Mn₃O₄ nanoparticles possess remarkable antibacterial and antifungal effect than the non-functionalized Mn₃O₄ nanoparticles and AMB molecule. The coating of low energy surface layer over metal oxide nanoparticles such as Mn₃O₄ offers an active surface toward both transfer of electron and the adsorption or desorption of water, inorganic ions, and other molecules, which leads to the increased antimicrobial activity of f-Mn₃O₄ nanoparticles.Communicated by Ramaswamy H. Sarma.

Photodynamic cancer therapy: role of Ag- and Au-based hybrid nano-photosensitizers

The utilization of photodynamic therapy (PDT) has been rapidly increasing due to its advantage as an effective treatment modality for cancer. The organic photosensitizers employed for PDT have some disadvantages, including high toxicity, non-selectivity toward tumors and poor absorption of light. The low light penetration into the tumor sites resulting from low wavelength of absorption and long-term skin photosensitivity. Hence, the attention toward non-toxic inorganic photosensitizers like noble metal nanoparticles (NPs) has been increasing nowadays. In bioscience, NPs are replacing organic dyes since they have photostability and non-toxicity. Generally, nanomaterials can easily form compounds with other substances as well as organic materials and the modified NPs surface enhances the chemical activity. Among the metal NPs, noble metals, especially gold and silver are attractive because of their size and shape-dependent unique optoelectronic properties. The coating of inorganic/organic materials on top of the noble metal makes the NPs bio-compatible and less toxic. Furthermore, Ag- and Au-based inorganic/organic complex NPs could offer a new possibility because of their unique structures. Meanwhile, the coating of inorganic/organic complex NPs protects the noble metals and stabilizes them against chemical corrosion and enhances the production of reactive oxygen species. Thus, in this review, we have highlighted the role of Ag- and Au-based inorganic/organic hybrid nano-photosensitizers in photodynamic therapy.Communicated by Ramaswamy H. Sarma.

Preparation and characterization of core-shell type Ag@SiO2 nanoparticles for photodynamic cancer therapy

With recent scientific developments, Photodynamic therapy (PDT) offers the promisie to become incorporated into the mainstream of cancer therapy. Noble metal based nano-PDT is increasing due to its advantages in the field of biomedicine. In this study, noble metal based Ag@SiO₂ core-shell nanoparticles were synthesized and to confirm the core-shell structure they were characterized by UV-vis, XRD, FTIR, TEM, and EDX. Our data confirm that core-shell type Ag@SiO₂ nanoparticles maintain its ability to kill cancer cells upon light irradiation. This shows that SiO₂ shell may not only prevent aggregation but it also may enhance the photodynamic activity of Ag nanoparticles.

Photodynamic activity and DNA binding studies of Pd@SiO2 core-shell nanoparticles in vitro

Metal-semiconductor core-shell type Pd@SiO₂ nanoparticles (NPs) were successfully synthesized by Stober's method and the product was characterized by UV-vis, XRD, FT-IR, SEM, HR-TEM and EDX techniques. In vitro Photodynamic activity and DNA binding studies of Pd@SiO₂ core shell nanoparticles were studied. Cell viability of the core-shell nanoparticles against HeLa cell line was screened by MTT assay after exposing at different light doses. The outcome of the present study indicates that the core-shell Pd@SiO₂ NPs are highly stable and exhibited strong photodynamic efficiency under LED light illumination in HeLa cells. The results indicated that SiO₂ supported on the surface of Pd NPs not only prevented the aggregation in addition exhibited remarkable photodynamic activity.

Study of photodynamic activity of Au@SiO2 core-shell nanoparticles in vitro

Metal-semiconductor core-shell type Au@SiO2 nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, HR-TEM and EDAX techniques. The resulting modified core-shell nanoparticles shows that the formation of singlet oxygen, which was confirmed by ESR technique. The photohemolysis studies were carried out under two different experimental conditions. It is observed that the photohemolysis increases with concentration as well as light dose. Cell viability of the core-shell nanoparticles against HeLa cell lines were studied by MTT assay method. The outcomes of the present study indicate that, the Au@SiO2 core-shell nanoparticles are extremely stable with a very high photodynamic efficiency under visible light illumination.

Comparison of antibacterial activities of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles

Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity.