Nanoparticles of varying composition, size, shape, and architecture have been explored for use as photothermal agents in the field of cancer nanomedicine. Among them, gold nanoparticles provide a simple platform for thermal ablation owing to its biocompatibility in vivo. However, the synthesis of such gold nanoparticles exhibiting suitable properties for photothermal activity involves cumbersome routes using toxic chemicals as capping agents, which can cause concerns in vivo. Herein, gold nanoparticles, synthesized using green chemistry routes possessing near-infrared (NIR) absorbance facilitating photothermal therapy, would be a viable alternative. In this study, anisotropic gold nanoparticles were synthesized using an aqueous route with cocoa extract which served both as a reducing and stabilizing agent. The as-prepared gold nanoparticles were subjected to density gradient centrifugation to maximize its NIR absorption in the wavelength range of 800-1000 nm. The particles also showed good biocompatibility when tested in vitro using A431, MDA-MB231, L929, and NIH-3T3 cell lines up to concentrations of 200 μg/mL. Cell death induced in epidermoid carcinoma A431 cells upon irradiation with a femtosecond laser at 800 nm at a low power density of 6 W/cm(2) proved the suitability of green synthesized NIR absorbing anisotropic gold nanoparticles for photothermal ablation of cancer cells. These gold nanoparticles also showed good X-ray contrast when tested using computed tomography (CT), proving their feasibility for use as a contrast agent as well. This is the first report on green synthesized anisotropic and cytocompatible gold nanoparticles without any capping agents and their suitability for photothermal therapy.

Anisotropic noble metal nanoparticles especially branched gold nanoparticles with a large absorption cross-section and high molar extinction coefficient have promising applications in biomedical field. However, sophisticated and cumbersome methodologies of synthesis along with toxic precursors pose serious concern for its use. Herein, we report the synthesis of branched gold nanostructures from protein (albumin) nanoparticles by a simple reduction method. Albumin nanoparticles were synthesized by a modified desolvation technique with poly-l-arginine (cationic poly amino acid) substituting the conventional toxic cross-linker, glutaraldehyde. In silico molecular docking was carried out to study the interaction of poly-l-arginine with albumin which revealed its binding to Pocket 1B of the A-chain of albumin. The poly-l-arginine-albumin core-shell nanoparticles of ∼100 nm in size served as a base for attachment of gold ions and its reduction to form 140 nm sized branched gold nanostructures conjugated with glutathione. These gold nanostructures exhibited near-infrared absorption λmax at 800 nm with extreme compatibility toward non cancerous (NIH 3T3), oral epithelial carcinoma (KB) cell lines, and human blood (red blood cells, platelets, and coagulation mechanisms) even up to a high concentration of 250 μg/mL. These structures demonstrated superior computed tomographic (CT) contrast ability and marked photothermal cytotoxicity on KB cells. This study reports for the first time a method to develop blood and cell compatible branched gold nanostructures from protein nanoparticles as a dual CT diagnostic and photothermal therapeutic agent.

No abstract

Targeted biological contrast agents are emerging as promising candidates in the field of cancer theragnostics. Herein, we report an ambient temperature synthesis of a nanosized, antibody functionalized lanthanide doped CaF 2 biolabel and demonstrate in vitro its potential for cancer cell targeting efficacy and specificity. Monodispersed citrate stabilized lanthanide (Eu 3+ ) doped CaF 2 nanoparticles with size ∼25 nm, exhibiting strong fluorescent emission at 612 nm, were prepared using an aqueous wet chemical route at room temperature. Biofunctionalization of the fluorescent nanoparticles using an anti-EGFR antibody through EDC-NHS coupling chemistry enabled targeting of EGFR over-expressing cells. The nanobioconjugates showed preferential binding to EGFR +ve oral epithelial carcinoma cells (KB) and human epidermoid carcinoma cells (A431) with no accumulation onto EGFR −ve non-cancerous NIH 3T3 cells. The fluorescence was maintained after the bioconjugation as well as after attachment to the cancer cells, demonstrating their potential as targeted biolabels. Cytotoxicity evaluation with several cancerous (A431, KB) and non-cancerous (NIH 3T3, L929) cell lines revealed no toxicity at concentrations up to 1 mM. Thus, the fluorescence characteristics and biocompatibility, coupled with the molecular receptor targeting capability, suggest the potential use of CaF 2 in the field of bioimaging.

Albumin stabilization of gold nanostars, which demonstrate high stability, biocompatibility, superior CT contrast, SERS and photothermal cytotoxicity towards cancer cells.