Concentration dependence of gold nanoshells on the enhancement of optical coherence tomography images: a quantitative study

摘要

The effective use of gold nanoshells as a contrast agent for optical coherence tomography (OCT) may be hampered by the delivery of a wrong dose to tissue that results in unwanted signal attenuation. In this study we examine how changes in (mu)_(s) due to concentration variations affect the OCT image and then define a dosing range that would result in appropriate scattering coefficient, (mu)_(s), to maintain an acceptable signal attenuation level. Our results show that an increase in sample (mu)_(s) not only enhances the OCT signal near the surface but also attenuates the signal deeper into the sample. We synthesized gold nano-shells with an 81 nm radius silica core and 23 nm shell thickness and found that a concentration range of 5.6 X 10~(9) < c < 2.3 X 10~(10) particles/ml provided adequate signal enhancement near the surface without severely compromising the imaging depth due to signal attenuation. We also demonstrate the extraction of (mu)_(s) from the OCT signal to estimate the gold nanoshells' concentration in vivo and verified that the estimated concentration of 6.2 X 10~(9) particles/ml in a mouse tumor after intravenous delivery lies within this concentration range to effectively enhance the tumor image.