The excessive production of endogenous hydrogen sulfide (H₂S) in cancer cells leads to enhanced tumor growth and metastasis. On the other hand, decreased endogenous H₂S suppresses tumor growth. The reported approaches for inhibiting tumor growth are selective silencing of the tumor-promoting genes and pharmacological inhibition of these proteins. To enhance the antitumor efficacy of frontline chemotherapeutic agents, herein, we synthesized a highly sensitive endogenous H₂S responsive fluorescent probe, i.e., a hydrogen sulfide-sensing naphthalimide-based peptide conjugate (HSNPc), which showed selective inhibition of proliferation of cancer cells due to apoptosis induction. Furthermore, HSNPc suppressed the glycolytic reserve, a critical energy source for the proliferation of cancer cells. HSNPc also decreased the Young's modulus of HeLa cells compared to the control cells, which demonstrated a direct relation between cell apoptosis and cell stiffness. Taken together, we demonstrated the dual function of detection and killing of cancer cells by HSNPc that can be likened to a theranostic role.

Diatoms are nature's nanobot because they can be described as cells in a glass house. Three-dimensional nanobio-engineered frustules of diatoms have vast applications in nanomaterials and bio-photonics. The amorphous silica of diatom frustules is not a good semiconductor, but when coated with titanium dioxide (TiO₂), the semiconducting efficiency of the frustules becomes adequate for use in numerous device applications, including solar cells. The metabolic incorporation of titanium dioxide nanoparticles in the diatom frustules is primarily used for the construction of titanium nanotubes. In the present study, TiO₂ was metabolically inserted by a two-stage cultivation process and its incorporation in the diatom frustules was studied by spectroscopic and atomic force microscopic methods. It was found that diatom frustules metabolically inserted with nanostructured TiO₂ by a two-stage cultivation in f/2 medium could replace nanostructured surface doping with titanium in dye-sensitized solar cells for heat and electricity production. The DSSC made from the titanium-doped diatom frustule has a power efficiency almost double (9.45%) that of the simple DSSC (4.20%) without any diatom frustule metabolically inserted with TiO₂. Alternatively, these nanoarray diatom containing tubes may also be used for the construction of novel dye-sensitized solar cells, which may help in oozing lipids from living diatom cells, such as in algal cells, for the generation of an electric current.