Upconversion Nanoparticles: Design, Nanochemistry, and Applications in Theranostics

Theranostics is a concept of integrating imaging and therapy into a single platform for use in the next generation of personalized medicine to meet the challenges in modern health care. The diagnostic role of theranostic agents reports the presence of a disease, its status, and its response to a specific treatment, while the therapeutic role of the agent can be implemented in several forms. Two-photon-excitation or second harmonic generation contrast agents, which utilize longer wavelength light, have been recently developed to overcome these limitations for imaging of cells and small animals. However, they require expensive ultrashort pulsed lasers to perform the excitation as they involve inefficient nonlinear optical processes. For bioimaging, some of the advantages are virtually zero autofluorescence background to improve signal-to-noise ratio, large anti-Stokes shifts allowing us to easily separate the PL from the excitation wavelength, narrow emission bandwidths allowing ease of multiplexed imaging.