(J-372) Development of a novel dual stimuli-responsive nanocarrier

Nanoformulations have the advantage compared to conventional drug delivery due to application-specific tunable design. The goal of this study is to develop a novel nanoformulation with dual stimuli-responsive properties to deliver drugs with high efficiency. The formulation has been tuned to have ultrasound and temperature-responsive properties. The nanoparticle is composed of three components. Poly(lactide-co-glycolic acid) (PLGA), was chosen as the base polymer due to its biocompatibility and biodegradability. Peflouropentane (PFP) was chosen due to its liquid properties at room temperature, which changes to the gas phase at physiological condition, and render ultrasound-responsive burst release. The third component is Pluronic F127, a thermoresponsive polymer, which has a lower critical solution temperature at physiological conditions. The particles were formed by nanoprecipitation and were characterized by dynamic light scattering (DLS) and spectroscopy methods. When subjected to ultrasound and or temperature stimuli, the particles exhibited significant release of coumarin-6, a model hydrophobic dye. The results show the feasibility of the formulation for enhanced drug release when subjected to ultrasound or temperature change. Currently, we are testing therapeutic drugs and peptide aggregates released from the formulation. The dual stimuli-responsive nanoformulation could be used to deliver drugs with high therapeutic efficacy for various biomedical applications. 

All chemicals used were purchased from Sigma Aldrich or Fisher Scientific. Nanoparticles were formed using nanoprecipitation method. Our two formulations were 10mg PLGA polymer and  5μl of prepared coumarin-6 alone or with 100μl PFP and 25mg of F127. The formulations were dissolved in  1000 and 900μl of DMF(Dimethylformamide) respectively. The solutions were then dripped into DI water and stirred overnight. Next, the nanoparticles were purified by centrifugation at 10,000 G for 30 minutes. Size measurements were characterized by DLS. Ultrasound responsiveness of the particle was tested using an ultrasonicator 740 from Mettler Electronic Corp (intensity 1.6 W/cm2, 1 cm2 applicator) in the laboratory. The sonication was applied for 3 minutes, in one-minute intervals. The release of the coumarin-6 dye was measured by spectroscopy at 454/511 excitation/emission. Temperature-responsive drug release was measured by incubating the particles at 42℃ for 30 minutes. By using data from the three scenarios, no stimuli, ultrasound, and 42℃ we were able to develop an understanding of their effects on the drug release. The t-test was used to determine statistical significance, between the formulations with and without stimuli as * p < 0.05, or ** p < 0.01, or *** p < 0.001.

Results 

First, our no-treatment nanoparticles size and fluorescence data were characterized. The average size of the PLGA particles was found to be 106 d.nm, and PLGA/F127/PFP was 151 d.nm (Figure 1A). The particles' response to stimuli was then studied. The release of coumarin-6 before and after ultrasound was found to be significantly higher in the PLGA/F127/PFP nanoformulation 1.72 times greater, compared to the control which only exhibited a 1.17 times greater change based on fluorescence data (Figure 1B). As for the temperature responsiveness, particles were incubated, and the release was measured immediately following completion. Based on data from our fluorescence data from Figure 1C, PLGA/F127/PFP exhibited significant release when subjected to temperature, 1.87 times greater compared to 1.22 times greater for the control formulation. These results demonstrate the effectiveness of the formulation to create a more effective drug release. 

Conclusions

We have produced PLGA/F127/PFP-based dual stimuli-responsive nanoparticles. Our current studies revealed PLGA nanoformulations with ultrasound-sensitive and temperature-responsive properties showed significant release profiles. The promising initial results indicate the potential of PLGA/F127/PFP nanoparticles ultrasound and temperature-responsive targeted drug delivery. Further optimization of the formulation to have a range of physiologically relevant stimuli responsiveness and disease-specific therapeutics release will be performed.  The nanoformulation could be used for treating diseases that could benefit from ultrasound and temperature stimuli-mediated delivery.

Discussions 

The main objective of the study is to develop a novel drug delivery system with ultrasound and temperature-responsive properties. In this pilot study, hydrophobic dye release was tested and can be extended to other disease-relevant drugs/agents. In addition, surface modification of the nanoformulation could further improve the targeting capabilities. The multi-stimuli phase shift nanoparticles could provide novel drug depot systems.