Gold nanoparticles have been around since ancient times and were historically used as a method to stain glass and were reported to have healing properties. These nanomaterials are now being developed as drug delivery vectors due to their unique properties which allow for targeted cell delivery. The ability of nAu to scatter and absorb visible light is highly dependent on the size and concentrations present. Since algae are reliant on light energy for growth they can be used as a model organism to gain a better understanding of nAu phototoxicity. Currently standard technologies such as spectrometery, which work on absorbance, have limitations for application when it comes to nanomaterials. An AlgaltoxkitF® was used where the protocol was adjusted to use a chlorophyll-a extraction method for 72h at 24 h intervals, using growth inhibition as an end point. A hormetic response was seen where algae showed a decrease in growth at low concentrations and then an increase at the middle range, but still lower than the control, and a complete inhibition at the highest concentration. Visualization of the interaction between the nAu and algae then became a priority.
CytoViva dark field hyperspectral imaging has been specifically designed to allow optical observation and spectral characterization of label free nano-materials interacting with biological matrixes. This technique was used anew to visualize the interactions and adsorption of nAu present in the exposure medium. A medium only slide was made by fixing media with a high concentration of nanomaterials and these were compared to A) control up to D) 50mg/L of nAu. The imaging showed that nAu adhered to the surface of the algae causing light blocking effects which inhibited algal growth.
The image below was taken from:
Tarryn L. Botha, Kailen Boodhia and Victor Wepener (2015). Growth inhibition due to light blocking effects of gold nanoparticles (nAu) on Pseudokirchneriella subcapitata (algae). 7th International Toxicology Symposium in Africa 2015: 85-86. ISBN - 978-0-620-66117-7.