Plasmonic Particles for Optical Phantoms of Blood Tissue

The biomedical engineering field faces significant challenges in transitioning innovations from proof-of-concept to practical applications. Animal models often contribute to these hurdles due to high costs, ethical concerns, as well as technical limitations. The development of reliable, low-cost, and multipurpose phantoms to reduce or replace animal models, particularly in the context of pure optical imaging techniques and photoacoustic imaging, could have an important impact. In this context, blood plays a crucial role as an endogenous contrast agent. However, creating accurate blood-mimicking materials remains challenging. Here we propose gold nanorods as a solution to mimic the optical properties of blood. By varying their size and aspect ratio, gold nanorods can be precisely tuned, and various batches can be mixed to match the optical absorption of oxy/deoxy-hemoglobin at different ratios, making them suitable for applications like pulse oximetry and multi-spectral photoacoustic measurements of oxygen saturation. We develop three mixtures of particles that reproduce the blood oxygenation levels at 80, 90, and 100% for three wavelengths of interest. This approach may represent a potential alternative to current liquid phantoms and complex oxygenation control systems based on real blood, paving the way for more efficient and ethical research in biomedical optics.