Enhancement of light absorption by blood to Nd:YAG laser using PEG-modified gold nanorods

Dual-wavelength long-pulsed 755-nm alexandrite/1,064-nm Nd:YAG laser versus Nd:YAG alone for treatment of palmoplantar verruca

We compared the effectiveness and safety of the long-pulsed neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser alone and combined with a 755-nm alexandrite laser for treating palmoplantar warts. We divided patients into two groups to receive up to four monthly treatments with Nd:YAG alone (single-wavelength) or combined with the alexandrite laser (dual-wavelength). We assessed treatment responses (according to clearance rate), vascular/hyperkeratosis grades, and patient satisfaction and pain ratings. The differences in treatment response (p = .348), patient satisfaction (p = .560), and pain ratings (p = .728) between the groups were not significant. The single- and dual-wavelength treatment options were equally effective in treating recalcitrant palmoplantar warts.

Effect of morphological evolution and aggregation of plasmonic core-shell nanostructures on solar thermal conversion

Achieving high solar energy absorption based on nanofluids (NFs) needs further study in solar photothermal conversion technology. In this work, we performed COMSOL simulations to investigate the solar energy absorption using a core-shell nanostructure composed of the Au core and shell with different materials. The influence of the radius of the Au core, the materials of the shell, and the shell thickness on the solar absorption efficiency factor (SAEF) are systematically studied. The results show that the SAEF of the Au@Li nanoparticle with ratio of 0.5 has the highest SAEF of 1.4779, increasing 1.99 times compared to that of the bare Au nanoparticle of 0.74326 with the same radius. Moreover, the optical properties, electric field distribution, and SAEF of the Au@Li dimer are further evaluated to demonstrate the aggregation effects on SAEF. We find that the SAEF of the Au@Li dimer reaches the maximum of 4.34 with a distance around 1 nm, where the LSPR coupling effect in the nanogap is sharply enhanced 700 times irradiated by light with wavelength of 760 nm. Finally, the direct absorber solar collector performance demonstrates that Au@Li dimer NFs can collect 93% of solar energy compared to 54% for Au@Li NFs and 51% for Au NFs. This work provides the possibility to achieve more efficient solar thermal conversion, and may have potential applications in efficient solar energy harvesting and utilization.

Theoretical and in vivo investigations of morphology and concentration of gold nanoparticles for laser surgery

BACKGROUND AND OBJECTIVE

Precise control of the thermal damage is critical during thermal therapy with the assistance of gold nanoparticles, which depends on the laser parameters and characteristics of gold nanoparticles. However, the current understanding of the relationship between the gold nanoparticles/incident laser light and the efficiency of photothermal therapy is limited, which should be studied systematically.

MATERIALS AND METHODS

In this study, theoretical simulations were conducted to investigate the influence of laser wavelength, the size and shape of gold nanoparticles, and the distance of the particle in complex nanostructures on the optical properties and temperature distribution after laser irradiation, aiming to achieve maximum photothermal conversion efficiency and therapeutic effect during the laser treatment of port wine stains. Thereafter, gold nanoparticles were prepared and in vivo experiments were conducted to evaluate the effect on thermal damage of blood vessels.

RESULTS

For the laser wavelength at 532 nm, gold nanospheres with diameters of 20 nm are ideal in terms of temperature rise. The optimized particle distance is 5 nm and the corresponding concentration is 0.26 mg/ml. For Nd:YAG laser at 1064 nm, gold nanorods with an aspect ratio of 6.3 and an effective radius of 12.7 nm are the most effective photothermal agents. The optimized particle distance is 4 nm, yielding the optimal concentration of 0.017 mg/ml. In vivo results demonstrated that using gold nanoparticles following our simulations as photothermal agents can greatly enhance the thermal damage of diseased blood vessels, reducing the laser energy and laser pulses required for the obvious thermal response of blood vessels.

CONCLUSION

For different laser wavelengths used in clinics in the near future, theoretical models presented in this study can be employed to obtain the morphology of single gold nanoparticle and the concentration of nanoparticles solutions, thereby obtaining the optimal photothermal conversion and enhanced thermal damage assisted by gold nanoparticles.

Gold nanospheres enhanced photothermal therapy in a rat model

BACKGROUND AND OBJECTIVE

Efficient photothermal conversion of gold nanoparticles with strong light absorption suggests their wide use as selective photothermal agents in biomedical fields. The aim of this study is to investigate the use of gold nanospheres (GNPs) as exogenous visible light absorbers to improve laser treatment of port-wine stains.

MATERIALS AND METHODS

Thiol-terminated methoxypolyethylene glycol modified GNPs (PEG-GNPs) with peak extinction matching the visible light wavelength of the laser being used were synthesized. An in vitro capillary experiment was prepared to investigate the thermal response of blood vessels with and without injection of 4.54 mg PEG-GNPs in mice prior to irradiation by a frequency-doubled Nd:YAG laser at a wavelength of 532 nm.

RESULTS

The in vitro results demonstrated that the photocoagulation size in blood vessels after exposed to laser light increased with the increment of concentration of PEG-GNPs in blood within a certain range. However, the unwanted thermal response (i.e., cavitation) occurred when the concentration of PEG-GNPs in blood was larger than 2.5 mg/ml. The in vivo results suggested that more obvious blood thermal response can be induced by laser light after injection of PEG-GNPs. After injection of 4.54 mg PEG-GNPs, laser radiant exposure required for thread-like constriction of blood vessels decreased from 12.5 to 9.8 J/cm2 with the pulse duration of 10 ms, from 15 to 11.85 J/cm2 with the pulse duration of 30 ms, respectively.

CONCLUSION

This in vitro and in vivo experimental results show that PEG-GNPs combined with laser light could be a promising modality to reduce the radiant exposure required for obvious blood thermal response, thereby providing a potential strategy for improving the laser treatment of cutaneous vascular lesions. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

Nd:YAG laser-induced morphology change and photothermal conversion of gold nanorods with potential application in the treatment of port-wine stain

Based on the principle of selective photothermolysis, 1064 nm Nd:YAG laser has great potential for the treatment of deeper and larger PWS. However, the clinical effectiveness is limited because of the weak absorption of blood to Nd:YAG laser. The aim of this study is to obtain the optimal irradiation conditions to effectively destroy vascular lesions with the assistance of PEG-modified gold NRs to enhance blood absorption of Nd:YAG laser. In our study, PEG-modified gold NRs were prepared by the seeded growth method. Gold NRs after exposure to Nd:YAG laser were characterized using absorption spectra and transmission electron microscope images. The tissue-like phantom containing a glass capillary with blood was prepared and exposed to Nd:YAG laser to investigate the laser energy density and pulse number required for blood coagulation before and after the addition of gold NRs in blood. The results show that the millisecond Nd:YAG laser irradiation does not result in the shape change of gold NRs. After injection of gold NRs into the bloodstream (4.60 mg/kg), the absorbance of blood at 1064 nm increased 3.9 times. The threshold energy density for the treatment of PWS decreased by 33% (from 30 to 20 J/cm²). Our findings provide an experimental guide for choosing laser parameters and gold NRs concentration for the treatment of deeper and larger PWS with the assistance of PEG-modified gold NRs in vivo in the future.