On the interaction between up-converting NaYF4:Er3+,Yb3+ nanoparticles and Rose Bengal molecules constrained within the double core of multifunctional nanocarriers

The designed interaction between up-converting nanoparticles and photosensitizers allows for near infrared triggered photodynamic therapy. Depending on their optical properties and spatial arrangement the light energy harvested by the nanoparticles can be transferred to the neighbor photosensitizer molecules via static- or dynamic-type interactions. To study the possibility of photodynamic effect enhancement in such a hybrid system we have engineered polymeric nanocapsules with a structured double compartment core feasible for constraining hydrophobic up-converting NaYF4:Er3+,Yb3+ nanoparticles and hydrophilic Rose Bengal molecules. Due to the chosen encapsulation method there was no necessity for surface functionalization of nanoparticles nor any chemical modification of photosensitizers, thus both of the chromophores exhibited unchanged optical properties. We have obtained a series of nanocarrier samples having a constant amount of up-converting nanoparticles and an increasing amount of Rose Bengal molecules for detailed spectroscopic (up-conversion emission spectra and kinetics) and theoretical (density functional theory based calculations) studies on their mutual interaction. The obtained results show the possibility of both up-conversion emission enhancement in the presence of Rose Bengal molecules, and static-type energy transfer from nanoparticles to photosensitizers. The applicability of the obtained nanocapsules in photodynamic based cancer treatments was further evaluated based on the reactive oxygen species, including singlet oxygen, generation upon near infrared excitation. Additionally, the other surface of the nanocontainers was functionalized with PEG-ylated hyaluronic acid to assure the “stealth” effect and selective accumulation in cancer cells.