Enhancing photothermal therapy via blood clot induced by needle-type sodium hydroxide-loaded starch implant

Abstract

Photothermal therapy (PTT) is an innovative and minimally invasive approach to cancer treatment, which uses photothermal agents to absorb light energy and convert it to heat, causing irreversible cellular damage and tumor cell death. Although current photothermal agents like indocyanine green (ICG), gold nanoparticles, and carbon-based materials have been used, they present challenges in terms of photostability, rapid elimination, and potential toxicity.

Hemoglobin, a protein found in red blood cells with light absorption and heat conversion properties, has emerged as a potential alternative. In particular, the high concentration of hemoglobin in fixed blood clots, unlike the hemoglobin in fluid blood, can induce an effective photothermal effect. NaOH can be injected into tumors to induce necrosis and promote blood coagulation via strong alkalinization. However, NaOH, being a highly alkaline substance, is rapidly absorbed when administered systemically and can increase systemic pH, leading to toxicity.

To address this, a needle-type sodium hydroxide (NaOH)-loaded starch (NST) implants was developed for the targeted delivery of NaOH directly to the tumor site. The NST implant, prepared by loading NaOH into a starch implant and drying, promotes localized tissue necrosis and subsequent blood clotting at the injection site, while ensuring controlled release of NaOH to reduce toxicity. In contrast to NaOH solution, the NST implant did not exhibit systemic toxicity upon administration and effectively induced thrombosis at the injection site.

Upon laser irradiation of the induced blood clot, the NST implant demonstrated a significant photothermal effect, exceeding 60 °C, and exhibited potent anticancer properties. Consequently, this novel method leverages the photothermal properties of endogenous hemoglobin within induced blood clots for effective tumor treatment. The NST implant approach shows potential as a biodegradable, efficient, and safe PTT method, offering a promising alternative to traditional photothermal agents.