Professor Sangyong Jon of the Department of Biological Sciences has synthesized a nanoparticle capable of optical imaging and photothermal therapy. The team managed to produce the nanoparticles without using carbon but instead with the abundant pigments found within the human body.

Many near-infrared (NIR) light-responsive nanomaterials have emerged in the field of biomedical industry with possible applications in imaging and sensing. However, due to their slow degradation time, the nanoparticles end up accumulating in the body of the subject. The potential toxicity from the accumulation has prevented biomedical engineers and scientists from using the nanoparticles to their full potential.

In the search for a non-toxic, biologically degradable particle, Professor Jon’s research team synthesized a cisplatin-chelated bilirubin-based nanoparticle (BRNP). Bilirubin is a major pigment in gallstones formed in the gallbladders. The advantage of using bilirubin as an ingredient for the nanoparticle was that bilirubin is a pigment from a human body unlike the other artificially synthesized materials, therefore making BNRP less likely to be harmful, even though it accumulates within the body.

Bilirubin has antioxidant and anti-inflammatory properties that can protect cells from reactive oxygen species-mediated damage on DNA and RNA. Previously, its hydrophobic property made it difficult to use in medical applications as it also accumulated in the body and was not water-dispersible. However, by synthesizing bilirubin with hydrophilic polyethylene glycol (PEG), the nanoparticle becomes hydrophilic and biodegradable, while still preserving its antioxidant and anti-inflammatory properties.

The BNRP also resembles NIR light-responsive nanomaterials in its NIR-absorption properties. The BNRP can now be safely used for potential use in improving photoacoustic imaging technology over NIR light-responsive nanomaterials.

The efficacy of BNRP in tumor regression was demonstrated in an experiment with tumor-carrying mice. BNRP’s efficacy in photothermal therapy was demonstrated through a comparison of hematoxylin and eosin staining on the mice with that of previously developed photothermal therapies. The analysis was able to demonstrate that the toxicity of the treatment was minimal, unlike the previously developed treatments that damaged the tumor.

Professor Jon shared his optimism on a possible future for treating cancer through the new materials, “Currently developed materials are based on artificial materials with low biocompatibility and potential toxicity. We hope the BNRP acts as a new platform for preclinical research and applications in photoacoustic imaging and photothermal therapy.”

The research was published in Angewandte Chemie International Edition, a German scientific journal in the field of applied chemistry.