Curcumin is a natural pigment that generates singlet oxygen upon light excitation, hence it can be used as a photosensitizer in photodynamic therapy. The extremely low water solubility and poor systemic bioavailability make curcumin a challenging molecule to be used clinically. In this study, two nanocarrier systems for curcumin were prepared and characterized; nanoliposomes and polyvinyl pyrrolidone-capped gold nanoparticles. The dark and photocytotoxicity were investigated as a function of light fluence rate (100 and 200 mW/cm) on HepG2 cancer cells. In vivo Erlich tumor model was developed and comparison of the tumor volume, survival rate, and histopathological alterations was made for the two nanocarriers. Results showed that both curcumin nanocarriers were successfully prepared and characterized. Light irradiation was able to augment the cytotoxicity of both curcumin liposomes and gold nanoparticles, with the former being superior in cytotoxicity compared to the latter. The tumor size was almost diminished 1 month post-photodynamic treatment for both systems with regression in the number of tumor cells upon histopathological evaluation, with curcumin liposomes producing better tumor regression than gold nanoparticles with comparable survival rate. Liposomes were confirmed to be superior to gold nanoparticles as a photodynamic treatment modality for cancer.

Background Sepia melanin (SM) is a natural photothermal biopolymer. Its biomedical applications are limited due to its poor solubility and bioavailability. This study aims to prepare a soluble formulation of sepia melanin to enhance its solubility, in turn, its bioavailability, and its use in photothermal therapy of cancer. SM was extracted from a sepia ink sac and prepared as insoluble powdered (SM) which is identified by FTIR, 1H-NMR, thermogravimetric analysis (TGA), and scanning electron microscope. SM was self-assembled using tween 80 into dispersed nanoparticles (SM-NP-Tw). The prepared SM-NP-Tw were fully characterized. The photothermal performance of SM-NP-Tw was assessed. Dark and photocytotoxicity of SM-NP-Tw was studied on HepG2 cells using two wavelengths (660 nm and 820 nm). Results The insoluble powdered (SM) exhibited a spherical nanoparticle-like shape as revealed by scanning electron microscope and was soluble only in an alkaline aqueous solution. TGA of SM showed high resistance to thermal degradation indicating good thermal stability. The prepared SM-NP-Tw exhibited a spherical shape with mean sizes of 308 ± 86 nm and a zeta potential of − 25 mv. The cell viability decreased significantly upon increasing the concentration and upon radiation at 820 nm. The results of UV–Vis spectroscopy and the photothermal performance revealed that melanin can absorb light in a wide range of wavelengths including near the IR region; thus, it can emit sufficient heat to kill cells through the photoheat conversion effects. Conclusion Sepia melanin nanoparticles self-assembled into tween-based nanostructures could be a promising natural platform for photothermal cancer therapy.