Nanoparticle hybrids as efficient theranostic nanoagents with enhanced near-infrared optical absorption and scattering

The design of high-efficiency theranostic nanoagents that can be utilized in tumor diagnosis and treatment has been investigated extensively in recent years. However, most of the existing nanoagents consist of uncommon materials and complex shell structures. Despite the efforts that have been made, the development of a simple and easily synthesized theranostic nanoplatform that can be applied in optical-based imaging-guided photothermal therapy still remains a challenge. In this paper, we investigated the optical characteristics of nanoparticle aggregates as potential theranostic nanoplatforms. The mechanism of spectrum shifting and the optical properties of contacting and non-contacting short nanochains were investigated. It was found that the near-field interaction of the gold nanosphere will not shift the localized surface plasmon resonance peak to the near-infrared region. However, when the nanospheres are connected to each other, a low energy resonance peak will be excited. On this basis, a simple hybrid theranostic nanoagent consisting of different nanosphere clusters was proposed. The nanohybrid exhibits high absorption and low scattering in the first near-infrared window (NIR-I) and high scattering and near-zero absorption in the second NIR (NIR-II). This characteristic can be beneficial to tumor diagnosis and treatment, i.e., NIR-I for photothermal therapy and NIR-II for optical imaging. Numerical results show that the performance of the proposed hybrid theranostic nanoagent remains excellent even with the existence of potential impuritie