Calcium Carbonate Nanoparticles Stimulate Cancer Cell Reprogramming to Suppress Tumor Growth and Invasion in an Organ-on-a-chip System

Abstract

The acidic microenvironment of solid tumors induces the propagation of highly invasive and metastatic phenotypes. However, simulating these conditions in animal models present challenges that confound the effects of pH modulators on tumor progression. To recapitulate the tumor microenvironment and isolate the effect of pH on tumor viability, we developed a bifurcated microfluidic device that supports two different cell environments for direct comparison. RFP-expressing breast cancer cells (MDA-MB-231) were cultured in treatment and control chambers surrounded by fibrin, which received acid-neutralizing CaCO3 nanoparticles (nanoCaCO3) and cell culture media, respectively. Data analysis revealed that nanoCaCO3 buffered the pH within the normal physiological range and inhibited tumor cell proliferation compared to the untreated control (p < 0.05). Co-incubation of cancer cells and fibroblasts, followed by nanoCaCO3 treatment showed that the nanoparticles selectively inhibited the growth of the MDA-MB-231 cells and reduced cellular migration of these cells with no impact on the fibroblasts. Sustainable decrease in the intracellular pH of cancer cells treated with nanoCaCO3 indicates that the extracellular pH induced cellular metabolic reprogramming. These results suggest that the nanoCaCO3 can restrict the aggressiveness of tumor cells without affecting the growth and behavior of the surrounding stromal cells.

Eco-friendly processes for the synthesis of amorphous calcium carbonate nanoparticles in ethanol and their stabilisation in aqueous media

“…The synthesis in ethanol limits the presence of water, preventing the spontaneous aggregation and crystallisation of CaCO 3 NPs without the need for synthetic additives. 6,11,20,21,23,26,45–50 This method leads to the obtention of pure ACC nanoparticles with a size under 150 nm.…”

“…The synthesis in ethanol limits the presence of water, preventing the spontaneous aggregation and crystallisation of CaCO 3 NPs without the need for synthetic additives. 6,11,20,21,23,26,[45][46][47][48][49][50] This method leads to the obtention of pure ACC nanoparticles with a size under 150 nm. This method is increasingly employed in the biomedical field to produce highly regular pure ACC NPs in terms of size and shape.…”

“…This method is increasingly employed in the biomedical field to produce highly regular pure ACC NPs in terms of size and shape. 6,11,20,23,26,[46][47][48][49][50] However, the investigation of ACC NPs formation mechanisms in absolute ethanol using ADM is at its beginning. 21,49 Therefore, several variations in the process parameters are present in the literature.…”

“…21,49 Therefore, several variations in the process parameters are present in the literature. 6,11,20,21,23,26,[45][46][47][48][49][50] The following work intends to bring new data and understanding on the ethanol ADM formation of ACC NPs, as a base for process efficiency optimisation. As ethanol is used as only solvent, improving the process efficiency reduces the amount of ethanol needed to synthesise a specific mass of particles, decreasing the ecological impact of the process.…”

“…[41][42][43][44] Pure ACC NPs with a size under 150 nm can be easily obtained without synthetic additives via a low cost and facile vacuum-assisted process in absolute ethanol developed over the last ten years. 6,11,20,21,23,26,[45][46][47][48][49][50] This process is the ammonia diffusion method (ADM), usually known for the synthesis of CaCO 3 NPs in water or in a mix water/ethanol. 32,33,51 In this variation, absolute ethanol is used as unique solvent to limit the amount of water and prevent the crystallisation of ACC NPs into vaterite or calcite without the need for synthetic additives.…”