Abstract
Purpose :
Targeted contrast agents can enhance spatial resolution by utilizing optical coherence tomography (OCT) at the micron scale. However, OCT relies on high scattering and absorption, which limits the use of small molecule contrast agents. Thus, there is an urgent need for contrast agents with high scattering, absorption, and backscattering efficiencies. Recent studies show nanomaterials are ideal candidates because of their high scattering rates, and reflectance properties. However, studies on how the physiochemical properties (size, shape, metal core composition) of nanomaterials influence their reflectance are lacking. We hypothesize reflectance of nanomaterials is primarily influenced by the size and metal core composition.
Methods :
In this study, the reflectance of a range of nanomaterials with varying sizes (20 to 100 nm), shapes (spheres, cubes, triangles, and rods), metal core composition (silver, gold, and titanium oxide), and surface coatings in different physiological relevant environments were collected using an Ocean Optics USB-4000 spectrometer equipped with QR400-7-VIS-NIR optical probe with a combined light source and reflectance detector. Sample measurements were collected at 45° to measure diffuse reflectance and referenced to 100 nm Polystyrene latex microsphere under dark conditions to avoid interference from the environment.
Results :
Results show that independent of shape or size, the reflectance is dependent on the concentration of nanoparticles (NPs). Therefore, increasing concentration show enhanced reflectance. When the shape and concentration are kept constant, reflectance is enhanced with increasing size. Similarly, when concentration, size, and metal core composition are constant, we find that the reflectance of silver spheres < triangles < cubes. The metal core composition also has a pronounced effect such that when concentration and size are kept constant, the reflectance of TiO2 > AgNPs > AgNPs. Lastly, the media that the NPs are in also affects reflectance, the reflectance of NPs of the same concentration and size in 0.1 wt % intralipid > DI> 1 wt % Gelatin > 5 wt % Gelatin.
Conclusions :
Our results are consistent with our hypothesis that the reflectance properties of nanomaterials are dominated by the size and metal core composition of nanoparticles. Here we have identified key features of nanomaterials that can be used as OCT contrast agents.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.