NIR laser pointer for in vivo photothermal therapy of murine LM3 tumor using intratumoral China ink as a photothermal agent

Abstract

The photothermal effect is one of the most promising photonic procedures currently under development to successfully treat several clinical disorders, none the least some kinds of cancer. At present, this field is undergoing a renewed interest due to advances in both photothermal materials and better-suited light sources. However, scientific studies in this area are sometimes hampered by the relative unavailability of state-of-art materials or the complexity of setting up a dedicated optical facility. Here, we present a simple and affordable approach to do research in the photothermal field that relies on a commercial NIR laser pointer and a readily available everyday pigment: China ink. A proof-of-concept study is presented in which mice bearing intradermal LM3 mammary adenocarcinoma tumors were successfully treated in vivo employing China ink and the laser pointer. TUNEL and Ki-67 post-treatment tissue assessment clearly indicates the deleterious action of the photothermal treatment on the tumor. Therefore, the feasibility of this simple approach has been demonstrated, which may inspire other groups to implement simple procedures to further explore the photothermal effect.

Photothermal effect by 808-nm laser irradiation of melanin: a proof-of-concept study of photothermal therapy using B16-F10 melanotic melanoma growing in BALB/c mice

“…The overlying hair on tumors and surrounding skin regions was clipped, and before laser treatment, anesthesia was administrated by intraperitoneal injection of 0.2-0.3 mL of a solution of xylazine (20 mg/kg) and ketamine (50 mg/kg) in saline. Tumors were irradiated for 4, 6 and 10 min with the 808nm laser fixed to a metal frame to keep a constant distance to the target [37]. For an example of the experimental setup, with the position of the NIR laser pointer and a tumor-bearing mouse, readers are referred to Fig.…”

“…For an example of the experimental setup, with the position of the NIR laser pointer and a tumor-bearing mouse, readers are referred to Fig. 3(a) [37].…”

“…In the last few years, carbon-based materials have been used to effectively generate a photothermal action on biological substrates, mainly experimental tumors [36]. We have recently reported that the pigment carbon black (CI: 77266) from China (Indian) ink is an efficient photothermal agent when injected to white mice tumors and irradiated with an 808nm laser [37]. On the premise that melanotic melanoma cells indeed contain melanin as an intrinsic black chromophore, and that the structural and optical features of this biopolymer are similar to carbon black-containing materials with a quasi-graphitic structure [36,[38][39][40], we decided to assess the photothermal effects of this endogenous and readily available intrinsic pigment, mainly in melanoma cells.…”

“…In addition, the present murine model (white skin) is very adequate because if NIR laser irradiation of melanotic melanomas growing in black mice is used, the otherwise normal, but absorbing skin would also be strongly affected. In this work, proof-of-concept demonstrations and an easy-to-implement setup are applied to show the direct photothermal effect on melanotic tumors using NIR irradiation from a commercial laser pointer [37].…”

Localized Free Radicals Burst Triggered by NIR-II Light for Augmented Low-Temperature Photothermal Therapy

“…Herein, low-temperature hyperthermia (<45 °C) was used to generate heat and then trigger the thermal degradation of azo initiator 2,2′-azobis­[2-(2-imidazolin-2-yl)­propane]­dihydrochloride (AIPH) to produce alkyl radicals for tumor therapy (Figure ). In order to achieve efficacious damage to deep-seated tumors, NIR-II laser light with stronger tissue penetration was chosen as an exogenous light stimulation. − At the same time, Hu Kaiwen Ink, a traditional Chinese Ink with good biocompatibility and eminent photothermal conversion efficiency was adopted as the corresponding NIR-II photothermal materials. − Ink was expected to produce local hypothermic stimulation by a 1064 nm laser to trigger the rapid decomposition of AIPH to generate alkyl radicals. The synergistic effect of low-temperature PTT and cytotoxic-free radicals induced apoptosis of tumor cells.…”