Stimuli responsive polymers are now considered as potential vectors for a precise delivery of pharma coactive substances, reducing the global exposure to dangerous compounds. The general strategy is to control the drug encapsulation and bioavailability by a trigger signal chemical such as pH or ions, or physical such as temperature or light. The later one is of interest as it can be delivered on demand temporally and spatially. The most classical architecture is a polymeric micelle in which the hydrophobic sections of amphiphilic polymers are clustered resulting in a “kinetically frozen” nanoparticle. While the outer hydrophilic parts ensure dispersability and stealth, the inner hydrophobic shell offer a suitable medium for hosting a hydrophobic drug. Drug delivery can then be obtained by an appropriate change in the polymer’s hydrophilic hydrophobic balance via a photochemical reaction: the reduction of the hydrophobic section of the polymer induces the disassembly of the nanocargo. Standard uncaging reactions, or the use of photochromic dyes have been used or such a purpose, but this always requires energetic light that can be damaging for the biological material. The recent and development of upconverting nanoparticle, able to convert near infra red light into visible (or UV) light, offers a way to bypass this drawback.<br/>It was shown that a polymer, carrying spiropyran pendant arms, could be a suitable candidate for such a purpose. Indeed the dye’s isomerization from the hydrophobic spiropyran colorless form into the hydrophilic colored merocyanine has been used to drive nanoassembly disaggregation and can be promoted by an upconverting nanoparticle excited in the near IR region. Thus Xing <i>et al</i>. have proposed a drug delivery system based on the entrapment of an hydrophilic drug with a shell of mesoporous silica grown at the surface of an upconverting particle. The drug-filled pores of the silica are then clogged by an amphiphilic polymer whose hydrophobic arms are spiropyran.<br/>The aim of the present proposal is thus to construct a photochromic polymer structurally very close to described one by Xing , and encapsulate an upconverting nanoparticle whose emission matches the absorption of the dye. The polymer will be used to stabilize nanohybrids obtained by coprecipitation of UCNPs and a hydrophobic drug. Upon light irradiation in the NIR region the disassembly of the nanohybrid will expose the hydrophobic drug and increase locally its bioavailability.

Toward photochromic nanohybrids based on upconverting nanoparticle: Nanocargos for drug delivery

253rd National Meeting (2017)

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