Fluorescent Nanoparticles in Coca-Cola and Pepsi

I always get a sketchy feeling when I think about Coca Cola. According to a recent post by @selfi, the soft-drink giant has now introduced an alcoholic version of its product to Japan, targeting young girls.


Image: Maxwell Rushton (Maxwellrushton.com)

Foodborne nanoparticles (NPs) have been linked to human health concerns and have thus created a stir in the research community. A study performed by Li and colleagues (2018) detected the presence of fluorescent NPs, approx. 5 nm, in you guessed it, Coca-Cola and Pepsi-Cola.

These Coca-Cola NPs contain Hydrogen, Carbon and Oxygen, three elements with a quantum yield of 3.3% (Coke) and 4.3% (Pepsi) and a tunable emission. This study confirmed the presence of sp3-hybridized carbon atoms of alcohol and ether bonds via nuclear magnetic resonance (NMR) spectroscopy analysis. NMR spectroscopy is a spectroscopic technique used to observe local magnetic fields around atomic nuclei. CH4 is when a carbon has s and p valence orbitals, enabling 4 sigma (single) bonds.




The main point here is that NPs can be “eaten up” by living cells, and once this happens they just accumulate within the cell membrane and/or cytoplasm. This particular study used BALB/c mice (albino, laboratory-bred strain of the House Mouse) to evaluate potential acute toxicity of the NPs; they found that the mice appeared healthy after administration of a single dose of 2 g kg-1 body weight.

Glutamate Pyruvate Transaminase (GPT): plays a key role in the intermediary metabolism of glucose and amino acids.

Glutamic Oxaloacetic Transaminase (GOT): catalyzes the reversible transfer of an amino group from aspartate to α-ketoglutarate, forming glutamate andoxaloacetate. It requires the coenzyme pyridoxal phosphate; it is typically observed in serum and in various body tissues, especially in the heart and liver.

Urea: serves an important role in metabolizing nitrogen rich compounds. It is the main supply of nitrogenous substances in mammalian urine.

Creatine: a nitrogenous organic acid that occurs naturally in vertebrates and acts as a pH buffer in tissues. Facilitates recycling of adenosine triphosphate (the energy currency of the cell) primarily in muscle and brain tissue. This process occurs via the recycling of adenosine diphosphate to ATP via donation of phosphate groups.

Analysis of these components showed statistically significant differences in these biochemical parameters between the test and control groups. There was no observable organ damage or unusual histopathology seen in the BALB/c mice.

The big finding here in my opinion was that these NPs had no trouble accumulating in the digestive tract, which may interfere with our microbiome. Additionally, NPs were capable of crossing the blood-brain barrier, and are thus able to disperse and remain in brain tissue.

Furthermore, in vitro (outside) digestion of the NPs showed a significant fluorescence quenching of the NPs. This study is important because it represents the first report of foodborne fluorescent NPs present in Coke and Pepsi. Coke and Pepsi are the most consumed soft-drinks on this earth. Additionally, this study seeks to uncover the mechanistic physiochemical properties of these NPs and their toxicity characteristics both in vitro (“within the glass”) and in vivo (“within the living”).

Li, S., Jiang, C., Wang, H., Cong, S., & Tan, M. (2018). Fluorescent nanoparticles present in Coca-Cola and Pepsi-Cola: physiochemical properties, cytotoxicity, biodistribution and digestion studies. Nanotoxicology, 12(1), 49-62.