Hello! My name is Thomas Gilman. I am working on the gold nanoparticle coating lab under Dr. Andresen and Dr. Thompson’s collaborative project. In this project we are aiming to wrap DNA around gold nanoparticles and be able to characterize them to see the treatment potential they have on diseases in the human body, such as cancer. In wrapping DNA, the nanoparticles must first be wrapped in a positive charged polymer, PAH (polycyclic aromatic hydrocarbon). Once this has successfully been completed, the DNA is then coated onto these nanoparticles with PAH already wrapped onto the gold nanoparticles. These particles are characterized through UV-Visibility spectra, which measures the absorbance of the sample; DLS (Dynamic Light Scattering), which measures the size of the particles in the sample; and Zeta, which measures the Zeta potential of the sample. Through characterization, we will be able to see the success of the coating and determine the possible further uses of such particles.
In the first week, we completed trial runs of the first step of the coating process which was the initial coating of PAH on the gold nanoparticles. Our initial runs were conducted including a 10:2:1 ratio of the nanoparticles, PAH, and NaCl, respectively. With these samples, we allowed for a coating time of 30 minutes. After the 30 minutes concluded, the samples were run through the centrifuge in order to create a pellet of the coated particles. The samples were then run through a cleaning process to remove excess non-coated particles and solution components, and then the remaining pellet was resuspended in water. These resuspended samples were then run through the characterization tests described before. Our data, shows that there is slight aggregation with the 30 minute coating sample having the 10:2:1 ratio (Figure 1) seen in the separation of the data line and the normalized line between 575 and 700 nm. With this, I then conducted the same test again, as well as comparable 24 hour coating time samples (Figure 2). After concluding these tests then, it was found that the longer the coating time, the less the aggregation present among the nanoparticles. This lesser aggregation can be seen in the normalization graphs presented as well, with the curves being more matched together for the 24 hour sample, compared to the 30 minute sample.
With this data, and the overall success of the initial coating with PAH, the next steps are to look into coating these wrapped nanoparticles once more, now with DNA. In order to do so, the DNA must be sheared and prepared first to be added to the existing solution in order for a more successful wrapping. For week two, this was our focus, and being able to do the first test coating on a smaller sample on Thursday, and letting it coat for 16 hours overnight into Friday. In the meantime I made larger sample sizes to be ready, in the best case scenario where the DNA successfully wrapped around the nanoparticles. This will be measured through the same tests as mentioned before, where the success will be measured by a higher absorbance (meaning a high concentration), a larger size (meaning there is the extra layer onto the particles), and a negative Zeta potential (meaning that the DNA successfully wrapped and charged the charge of the particle). Stay tuned to know if these tests were successful next week!
Figure 1: UV-Vis Graph for sample TG 5.28.21 30 min 200 µL Citrate Au Nanoparticles with significant aggregation present between 575 and 700 nm present
Figure 2: UV-Vis Graph for sample TG 5.27.21 24 hour 200 µL Citrate Au Nanoparticles with minimal aggregation present in the region of comparison from the 30 min coating sample
