ABSTRACT
Nanomaterials, which exhibit unique optical properties and drug delivery kinetics, have become one of the most promising theranostic platforms. Traditionally, uorophores are conjugated onto therapeutic molecules for theranostic purposes but suer from several potential drawbacks. Firstly, uorophore conjugation may alter the delivery kinetics and therapeutic properties of the molecules. Secondly, problems such as photobleaching and nonuniform labeling hinder the practical quantication of uorophores. Nanomaterials, in contrast, can be made to carry drugs without aecting their delivery kinetics, to target the disease site, and to exhibit high optical signal without photobleaching. To locate malignant tumors, two targeting strategies are commonly employed. While passive targeting exploits the enhanced permeation retention (EPR) eect of the tumor, active targeting acts as a homing beacon, nding its way to the lesion site.16,17 Compared to conventional chemotherapy, an increase in the drug payload to the tumor with reduced systemic side eects has been demonstrated using nanocarriers.18,19 Controlling the drug release mechanism may further enhance the delivery kinetics to the lesion site.20 To date, photonic-active nanomaterials such as quantum dots (QDs), upconverters, dye-doped silica nanoparticles, polymeric particles, plasmonic nanoparticles (silver, gold), and carbon-based nanoparticles (graphene, carbon nanotubes, nanodiamonds) all exhibit distinctive properties favorable for in vivo optical imaging with extended photostability.21 Combining both qualities as drug carrier and imaging contrast agent, theranostic nanomaterials have great potential for image-guided therapy in medicine.
