Designing a nanoparticle for real-world cellular imaging and therapy requires the expertise of many collaborators: in the case of a recent paper by a collaboration from Texas the number was 18 (ACS Nano doi: 10.1021/nn900440e; 2009). How did such a large collaboration come together? In short, one person at a time. Thomas Milner, an expert in biomedical optics, had been working with Marc Feldman, a cardiologist, for several years on imaging atherosclerosis with nanoparticles and optical coherence tomography. In 2006, they contacted Keith Johnston to design advanced nanoparticles to improve imaging and therapy. Kostia Sokolov added expertise on cellular studies, and Stanislav Emelianov on photoacoustic and ultrasonic imaging.

The team fabricated and characterized a nanoparticle that ticks many boxes. It is small enough (30 nm) to demonstrate uptake by macrophages, aided by a biomimetic coating. It is stable in deionized water over a period of 8 months. It absorbs light in the near infrared, where soft tissue, haemoglobin and water absorb only weakly, and shines brightly as a result. Finally, the particle is magnetically active, allowing MRI contrast imaging. It can also be used for therapy: a single laser pulse will heat a nanoparticle-laden macrophage enough to destroy it.

Such a large collaboration required a well-defined flow of ideas — what Johnston calls an event sequence: “For medical applications of nanoparticles, the clinical and biomedical constraints drive the optical and magnetic interrogation that drives the chemical engineering.” The biggest challenge was “keeping the scope from growing too large, as various groups favoured certain aspects, each of which could be a full study in itself”. The students, as well as the principal investigators, helped set the tone: “Most of the students need to be extroverted and educated in researching in teams, as their interactions drive the collaboration as much as those of the faculty.”