The aim of this work was to load an anticancer drug, paclitaxel (PTX), on Silk Fibroin Nanoparticles (SFNs) by using an exogenous approach. SFNs were produced, freeze-dried and then loaded with PTX. An exogenous method allowed us to reduce both drug loss and environmental impact. In order to quantify PTX loaded in SFNs, a simple and reliable method using reversed phase liquid chromatography coupled to tandem mass spectrometry (rp-UHPLC-MS/MS) was developed. This methodology was validated by the determination of spiked QC samples in three consecutive days. Good accuracy and precision of the method were obtained, while the intra-day and inter-day precisions were less than 10.3%. For PTX, the limit of quantitation (LOQ) was 5.0 ng/mL. Recovery from the matrix (SFNs-PTX pellets) was calculated (81.2% at LOQ value) as PTX was entrapped in a new matrix like the polymer silk fibroin-based. This method was successfully applied to determine the encapsulation efficiency (1.00 ± 0.19%) and the nanoparticle loading (0.12 ± 0.02% w/w). The in vitro anticancer activity of SFNs-PTX was tested against CFPAC-1 cancer cells; results demonstrated a very high cytotoxic activity of SFNs-PTX, with a dose dependent inhibition of CFPAC-1 proliferation, confirmed by the IC50 value of 3450 ± 750 ng/mL.
Keywords: UHPLC-MS/MS; method validation; nanoparticles; paclitaxel; silk fibroin.