In vitro efficacy of paclitaxel-loaded dual-responsive shell cross-linked polymer nanoparticles having orthogonally degradable disulfide cross-linked corona and polyester core domains.

Paclitaxel-loaded shell cross-linked polymeric nanoparticles having an enzymatically and hydrolytically degradable poly(lactic acid) core and a glutathione-responsive disulfide cross-linked poly(oligoethylene glycol)-containing corona were constructed in aqueous solution and investigated for their stimuli-responsive release of the embedded therapeutics and in vitro cytotoxicity. Paclitaxel release from the nanoparticles in PBS buffer was accelerated in the presence of glutathione at both pH 5.5 and pH 7.4, reaching ca. 65% cumulative drug release after 8 d, whereas only ca. 50% and 35% extents of release were observed in the absence of glutathione at pH 5.5 and pH 7.4, respectively. Enzyme-catalyzed hydrolysis of the nanoparticle core resulted in the degradation of ca. 30% of the poly(lactic acid) core to lactic acid within 12 h, with coincidently triggered paclitaxel release of ca. 37%, as opposed to only ca. 17% release from the uncatalyzed nanoparticles at pH 7.4. While empty nanoparticles did not show any inherent cytotoxicity at the highest tested concentrations, paclitaxel-loaded nanoparticles showed IC50 values that were similar to those of free paclitaxel at 72 h incubation with KB cells and were more efficacious at ca. 3-fold lower IC50 value (0.031 µM vs 0.085 µM) at 2 h of incubation. Against human ovarian adenocarcinoma cells, the paclitaxel-loaded nanoparticles exhibited a remarkable ca. 11-fold lower IC50 than a Taxol-mimicking formulation (0.0007 µM vs 0.008 µM) at 72 h of incubation. These tunable dual-responsive degradable nanoparticles show great promise for delivery of paclitaxel to tumor tissues, given their superior in vitro efficacies compared to that of free paclitaxel and Taxol-mimicking formulations.

Paclitaxel-loaded SCK nanoparticles: an investigation of loading capacity and cell killing abilities in vitro.

Block copolymer nanoparticles having two different hydrodynamic diameters (120 nm vs 50 nm) and core diameters (60 nm vs 20 nm) with variable paclitaxel loading (5 to 20 wt % with respect to polymer weight, 4.4 µg/mL to 21.7 µg/mL paclitaxel concentrations in ultrapure water) were prepared for their in vitro cytotoxicity evaluation. Empty nanoparticles did not show any inherent cytotoxicity even at their highest concentration, whereas paclitaxel-loaded nanoparticles resulted in IC50 values that were better than free paclitaxel at 2 h (0.021 µM vs 0.046 µM) incubation periods, and approximately equal to free paclitaxel at 72 h (0.004 µM vs 0.003 µM) continuous incubation. Confocal fluorescence microscopy images demonstrated that the drug-loaded nanoparticles internalized into KB cells within 2 h and released their payload, resulting in cytotoxicity as evident from the fragmented nuclei present. Functionalization of the nanoparticle surfaces with poly(ethylene oxide) (2 kDa PEO, 5 PEO per block copolymer chain) did not affect the loading of paclitaxel or cell kill ability. No free paclitaxel was found in these nanoparticle formulations indicated by analytical assays.

Spectroscopic analysis of highly concentrated suspensions of bovine somatotropin in sesame oil.

Spectroscopy was employed to analyze the structural and thermal stability of highly concentrated oil suspensions of bovine somatotropin (bST). These methods were then compared with more dilute aqueous solutions (1 and 10 mg/mL). All oil suspensions were opaque, viscous, and highly concentrated in bST (>300 mg/mL) and thus provided unique analytical challenges. Using front surface fluorescence and ATR-FTIR spectroscopy, protein structure and stability could be directly monitored in this environment. Differences were detected in structure between concentrated oil and dilute aqueous formulations. Fluorescence spectroscopy found that bST was highly thermally stabile within oil suspensions, since minimal changes in emission peak maxima and emission intensity were observed with increasing temperature when compared to dilute solutions. It was also observed that the amount of aggregate in a sample had some effect on the fluorescence spectra. As the amount of aggregated protein increased, the emission peak maximum and emission intensity changed. Employing ATR-FTIR, the secondary structure was examined with increasing temperature. The secondary structure of bST was also found to be very thermally stabile since no change in relative amount of helix/random structure is observed up to 70 degrees C while significant losses are observed in aqueous solution. This study demonstrates that conformational stability can be directly analyzed within highly concentrated, opaque environments using slight modifications of conventional methods.