Virus-mimicking optical nanomaterials: near infrared absorption and fluorescence characteristics and physical stability in biological environments.

The use of viruses as platforms for the development of optical imaging materials has received increasing attention in recent years. We have engineered a hybrid nanomaterial composed of the capsid proteins of genome-depleted plant-infecting Brome mosaic virus that encapsulates the near-infrared (NIR) dye indocyanine green. Herein, we investigate the NIR absorption and fluorescence characteristics of these nanomaterials in biological environments consisting of cell culture media with and without serum proteins. Our results demonstrate that the NIR absorption and fluorescence emission of the constructs are enhanced in the presence of serum proteins. The constructs remain physically stable and maintain their NIR absorption and fluorescence properties for at least 79 days. The presence of serum proteins also reduces the aggregation of the constructs. These findings have relevance for the further development of optical imaging and phototherapeutic methods on the basis of such virus-mimicking nanomaterials as well as the expected optical and physical characteristics of these nanomaterials in vivo.