Near IR-plasmon enhanced guided fluorescence and thermal imaging of tissue subsurface target using ICG-labeled gold nanourchin and protein contrast agent: implication of stability.

A dual-function nanocomposite agent (NCA) was prepared for deep tissue fluorescence and thermal imaging. The results showed that a combination of some agents such as gold nanourchins (GNU) and indocyanine green (ICG) can have spectral overlapping and hence some peak broadening. Despite 83% and 92% loss of NCA fluorescence after tissue layers L1 and L2, respectively, there was sufficient signal detected for imaging the target buried under the tissue. No fluorescence was detected after L3. A significant contribution was made by GNU for both the fluorescence signal due to the plasmon-enhanced fluorescence (PEF) effect and the thermal heating because of local surface plasmon resonance (LSPR) due to its sharp tips. In the first case, PEF occurred within the first 40 s then followed by a gradual quenching by 23% in 4 min and 72% in the following 6 min. During the second quenching time, the emission signal was blue shifted by 10 nm. Of the three samples, sample 2 (S2) indicated the highest temperature rise ≈ 60 °C in 50 s; sample 3 (S3) produced the lowest temperature of ≈ 33 °C in 250 s after the first layer, thus showing BSA acting as a heat sink. Both the heating and cooling time are determined by the thermal properties of the material such as conductivity and diffusivity. Finally, despite the advantages of PEF, the photostability and quenching rate of a dye molecule must be considered in a dynamic detection monitoring system to account and compensate for the effect of contrast agent quality variation.

Dynamic characterization of indocyanine green-assisted dental caries ablation with continuous diode laser using thermal imaging and fluorescence spectroscopy.

We describe the time-resolved thermal changes in indocyanine green (ICG)-assisted diode laser ablation of dental caries as a potential technique for painless treatment based on the selective photoabsorption and controlled photothermal ablation. Static ablation mode produced a higher temperature rise compared with scanning mode due to localized accumulation of heat. A temperature rise between 45-80 and 70-95 °C was obtained after 20 s that corresponded to 29 and 80 W cm-2, respectively. The temperature of the tooth surface increased by irradiation time, and it behaved linearly up to 70 °C at 29 and 80 W cm-2. A maximum ablation per area of about 0.3 and 0.45 mg cm-2 was achieved after 80 s exposure at 29 and 80 W cm-2, respectively. A statistically significant difference is observed in mean carious teeth weight at various exposure times between low and high irradiances. A thermal penetration depth of 0.8-9 mm is determined for 1-100 s of exposure time. The IR thermal imaging of ICG temperature as a function of exposure time showed a linear increase for 60 s beyond which it deviated. The laser-induced fluorescence spectroscopy indicated that the ICG quality can be altered during the course of irradiation, which in our case, it corresponded to ≈ 78% loss of signal within 23 min of exposure. The caries removal experiment was performed within 100 s corresponding to ≈ 7% loss. We believe that the application of the above-combined technique can be utilized as a monitoring device to control the ablation interaction process.