Electrospun upconversion composite fibers as dual drugs delivery system with individual release properties

Novel multifunctional poly(ε-caprolactone)-gelatin encapsulating upconversion core/shell silica nanoparticles (NPs) composite fibers as dual drugs delivery system (DDDS), with indomethacin (IMC) and doxorubicin (DOX) releasing in individual release properties, have been designed and fabricated via electrospinning process. Uniform and monodisperse upconversion (UC) luminescent NaYF₄:Yb³⁺, Er³⁺ nanocrystals (UCNCs) were encapsulated with mesoporous silica shells, resulting in the formation of core/shell structured NaYF₄:Yb³⁺, Er ³⁺@mSiO₂ (UCNCs@mSiO₂) NPs, which can be performed as DOX delivery carriers. These UCNCs@mSiO₂ NPs loading DOX then were dispersed into the mixture of poly(ε-caprolactone) (PCL) and gelatin-based electrospinning solution containing IMC, followed by the preparation of dual drug-loaded composite fibers (DDDS) via electrospinning method. The drugs release profiles of the DDDS were measured, and the results indicated that the IMC and DOX released from the electrospun composite fibers showed distinct properties. The IMC in the composite fibers presented a fast release manner, while DOX showed a sustained release behavior. Moreover, the UC luminescent intensity ratios of ²H_11/2/⁴S _3/2-⁴I_15/2 to ⁴F_9/2- ⁴I_15/2 from Er³⁺ vary with the amounts of DOX in the system, and thus drug release can be tracked and monitored by the luminescence resonance energy transfer (LRET) mechanism.