Figure 4
Enhanced cavitation effect and efficiency of AuNRs release.
(a) Differential ICD–time curve showing the change in the cavitation effect induced by the indicated contrast-agent-assisted energy application methods. Upon exposure to ultrasound and laser radiation simultaneously for 5 minutes, the dICD value was enhanced by 3.3 fold for AuNDs compared to AuMBs with the same treatment and it was enhanced by 3.4 fold compared to AuNDs exposed to ultrasound only. The time zero (t = 0) labeled at the X axis is the starting time to transmit the ultrasound signal from the 1 MHz transmitting transducer and the amount of cavitation signals are collected by the 10 MHz receiving transducer with a 13-seconds delayed. (b,c) The destruction ratio and the rate of AuNRs release were measured after AuNDs or AuMBs were exposed to the indicated energy modalities. The initial OD values of the same number of the intact AuNDs or AuMBs before exposed to the indicated energy modalities were 0.084 ± 0.006 or 0.068 ± 0.009 (mean ± SD), respectively. Statistically significant differences between two independent groups were determined using the statistical methods described in the Methods. Data are mean and SD values. *p < 0.05. (d) The plot showing the OD values function to the different concentrations of free AuNRs. Temperatures labeled near the black circles indicate the final temperatures after indicated concentration of free AuNRs was exposed to laser radiation for 5 minutes. The initial temperature before the treatment is 18.2 °C. The R-squared is 0.99211 and the equation for the best fit regression line is y = 0.2089x-0.002.
