Porcine skin damage thresholds and histological damage characteristics from 1319-nm laser radiation

Evaluation of thermodynamic bioeffects of long-pulsed 1064 nm laser in the photothermal lipolysis

OBJECTIVES

To evaluate the lipolysis effect of air cooling assisted long-pulsed 1064 laser for improving local adiposity.

MATERIALS AND METHODS

The second-level (pulse duration of 0.3-60 s) long-pulsed Nd:YAG 1064 nm laser (LP1064 nm) with or without forced-air cooling was used to irradiate ex-vivo subcutaneous adipose tissue (SAT) of pig or human and in-vivo inguinal fat tissue of Sprague Dawley rats. The temperature of skin surface as well as 5 mm deep SAT was monitored by a plug-in probe thermal couple, and the former was confined to 39°C or 42°C during the treatment. Histological analysis of SAT response was evaluated by SAT sections stained with hematoxylin-eosin and oil red O. Ultra-microstructure changes were examined by transmission electron microscopy. A pilot study on human subject utilizing LP1064 nm laser with air cooling was conducted. The changes in gross abdomen circumference and ultrasonic imaging were studied.

RESULTS

Histological examination showed that LP1064 nm laser treatment induced adipocyte injury and hyperthermic lipolysis both in- and ex-vivo. It was also confirmed by clinical practice on patients. By real-time temperature monitoring, we found that in comparison with LP1064 nm laser alone, additional air cooling could increase the temperature difference between epidermis and SAT, promoting heat accumulation deep in fat tissue, as well as providing better protection for epidermis.

CONCLUSION

LP1064 nm laser provided reliable adipose tissue thermolysis when the temperature of skin surface was sustained at 39°C or 42°C for 10 min. Application of air-cooling during the laser treatment achieved better effect and safety of photothermal lipolysis. LP1064 nm laser, as a noninvasive device, has comparable thermal lipolysis effect as other common heat-generating devices.

Laser-induced injury of the skin: validation of a computer model to predict thresholds

The exposure and emission limits of ICNIRP, IEC 60825-1 and ANSI Z136.1 to protect the skin are based on a limited number of in-vivo studies. To broaden the database, a computer model was developed to predict injury thresholds in the wavelength range from 400 nm to 20 µm and was validated by comparison with all applicable experimental threshold data (ED50) in the wavelength range from 488 nm to 10.6 µm and exposure durations between 8 µs and 630 s. The model predictions compare favorably with the in-vivo data with an average ratio of computer prediction to ED50 of 1.01 (standard deviation ± 46%) and a maximum deviation of 2.6. This computer model can be used to improve exposure limits or for a quantitative risk analysis of a given exposure of the skin.

Porcine skin damage threshold from mid-infrared optical parametric oscillator radiation at 3.743 µm

There is increasing use of mid-infrared optical parametric oscillator radiation operating in the wavelength range of 3-5 µm. To expand existing damage data for skin exposure to lasers in this wavelength region, the in-vivo damage threshold at the wavelength of 3.743 µm was determined in a Guizhou miniature pig model for an exposure duration of 1.0 s. The irradiance of the laser spot was nearly Gaussian-distributed and the 1/e² beam diameter on the animal skin surface was fixed at 0.94 and 0.88 cm along horizontal and vertical directions. Damage lesion determinations were performed at 1- and 24-hour post-exposure. The probit analysis was employed to establish the ED₅₀ values. The ED₅₀ expressed in peak radiant exposure for the Gaussian spot was 4.04 J/cm² at the 24-hour post-exposure. Sufficient margin existed between the damage threshold and MPE from the current laser safety standard. The obtained data may contribute to the knowledge base for refinement of laser safety standard in the wavelength range of 2.6-1000 µm.

Gold Nanomaterials for Imaging-Guided Near-Infrared in vivo Cancer Therapy

In recent years, tremendous efforts have been devoted into the fields of valuable diagnosis and anticancer treatment, such as real-time imaging, photothermal, and photodynamic therapy, and drug delivery. As promising nanocarriers, gold nanomaterials have attracted widespread attention during the last two decades for cancer diagnosis and therapy due to their prominent properties. With the development of nanoscience and nanotechnology, the fascinating bio-applications of functionalized gold nanomaterials have been gradually developed from in vitro to in vivo. This mini-review emphasizes some recent advances of photothermal imaging (PTI), surface-enhanced Raman scattering (SERS) imaging, and photoacoustic imaging (PAI)-guided based on gold nanomaterials in vivo therapy in near infrared region (>800 nm). We focus on the fundamental strategies, characteristics of bio-imaging modalities involving the advantages of multiples imaging modalities for cancer treatment, and then highlight a few examples of each techniques. Finally, we discuss the perspectives and challenges in gold nanomaterial-based cancer therapy.