Diatoms, the most common type of algae, are one of the most prevalent organisms in the world. They live in wet ambient environments such as oceans, lakes and rivers and are easily recognizable because of their unique structure. Diatoms are surrounded by a silica cell wall called a frustule. The mineralization of the frustule is initiated and controlled by a small protein (R5). The overall goal of this project is to mimic this frustule self-assembly process and apply it to the formation of SiO₂, GeO₂, and TiO₂ nanoparticles. Nanoparticles have several practical applications, among which are surface coating for biological applications and drug delivery. Here we explore whether the bio-mineralization process used by diatoms is also an efficient generator of nanoparticles.
Specifically the project focused on replicating the diatoms’ production of silica nanoparticles via two proteins R5 and poly-l-lysine and to explore if comparable nanoparticles could be made using germanium and titanium precursors. This would be highly advantageous, because this method involves a benign environment and is relatively low-cost
The primary goal was to develop and implement reliable techniques to form nanoparticles using the two different precursors. Previously silica nanoparticles have been created mimicking diatoms under well characterized ambient conditions. We chose to utilize the same formula in our initial experiments, except substituting of germanium (IV) ethoxide for the silica precursor. This experiment used a concentration of 5 mg/mL of the R5 in phosphate citrate buffer, with 91.9 µL of germanium precursor. It was found that using the previously published procedure was not effective within this context. In particular, it was noted that in the previous efforts the concentration of the precursor in buffer solution was to low. Thus realizing that in order to make an effective solution for the generation of nanoparticles we must use a higher concentration of germanium precursor. The methods found were first tested using the germanium precursor and the R5 peptide (concentration of 5 mg/mL) but this time with 10 µL of germanium precursor and 200 µL of phosphate citrate buffer. The methods were then tested using the germanium precursor and poly-l-lysine; this also resulted in a high yield of particles.
The success of the first two experiments led us to investigate our secondary goal, which was to see if titanium (IV) ethoxide would create particles when combined with either the peptide R5 or the macromolecule poly-l-lysine. A positive result was achieved by using the titanium precursor in R5 and poly-l-lysine. Future tests using the methods we created include combining the germanium and titanium precursors in solution and the silicon and germanium precursors in solution.
Overall the methods developed were proved successful. The size and shape of particles created will be characterized by scanning electron microscopy, which we hope will demonstrate that well defined spherical particles were formed.
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