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Drug Delivery

Drug Delivery - Poster Session D

Poster X16 - Characterizing Diclofenac Encapsulation of Polycaprolactone-based Nanoparticles

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Introduction
Nanoparticles (NPs) are defined as small particles of less than 1000nm in diameter. Polymeric NPs are promising tools for the treatment and study of traumatic brain injury (TBI). After TBI, the blood-brain barrier (BBB) becomes semipermeable for an extended period post-injury. This BBB disruption allows the extravasation of macromolecules into the brain that would otherwise be unable to diffuse or be actively transported through the BBB – including NPs. For TBI and other acute trauma scenarios, sustained release of anti-inflammatory small molecules may diminish the magnitude of acute inflammation that may perpetuate pro-inflammatory signaling milieu. A previous study demonstrated successful encapsulation efficiency and loading capacity of an anti-inflammatory drug, diclofenac (DCF), within polymeric NPs fabricated with poly lactic-co-glycolic acid. Here, this study aims to analyze the encapsulation of DCF in polycaprolactone (PCL) NPs; we assessed the diameter, polydispersity index (PDI), zeta potential (Z-pot), encapsulation efficiency (EE), and loading capacity (LC) of PCL-based NPs.

Materials and

Methods:  Materials and Methods
The NPs were fabricated via nanoprecipitation with a low-cost 3D printed nanoprecipitation rig. The organic solution was prepared by dissolving PCL(10k)-PEG(2k) in a 45:45:10 blend of acetone:dichloromethane:ethanol at a concentration of 9mg/mL and mixed overnight. DCF was added at 30% and 50% relative to the weight of the polymer in the formulation. The aqueous solution was 0.3% poly vinyl alcohol and a 45:1 ratio of aqueous to organic was used. The organic solution was loaded into a gas-tight glass syringe fitted with a fused silica tubing (100 µm internal diameter). The organic solution was then injected at a rate of 3mL/min into the aqueous solution stirring at 400rpm. The solvent in the newly produced NP suspension was allowed to evaporate for one hour. This step was followed by a washing centrifugation process where the sample was centrifuged, and the supernatant was replaced by deionized water thrice. After the final centrifugation, the NP suspension was loaded in a syringe and passed through a 0.22µm filter. The NP diameter, PDI, and Z-pot were measured using dynamic light scattering (DLS). The NP suspension was stored in the -80°C and lyophilized. All the lyophilized samples were redissolved in ethanol to analyze via Ultraviolet-Visible (UV-Vis) spectroscopy to evaluate the EE and LC. The remaining NP suspension was dried via desiccation on top of a 6x6mm glass square and coated twice via gold sputtering for scanning electron microscopy (SEM).

Results, Conclusions, and Discussions: Results
Four replicates were measured via DLS to calculate the average diameter length, Z-pot, and PDI for each of the formulations. The average diameter for 0%, 30%, and 50% DCF formulations were 90.8±14.5, 100.3±11.5, and 104±12nm respectively (mean ± standard deviation). The average Z-pot for 0%, 30%, and 50% DCF formulations were -17±5, -19.4±6.4, and -8.4±3.2mV respectively. The average PDI for 0%, 30%, and 50% DCF formulations were 0.170±0.047, 0.209±0.029, and 0.197±0.02 respectively. A single-factor one-way ANOVA showed no significant differences for diameter length, Z-pot, and PDI among the three different DCF formulation groups (p>0.05). The UV-Vis results of 30% and 50% DCF formulations indicated an extremely low EE of about 0.15% and 0.2% and LC of about 0.5% and 1.5% respectively. For the SEM images, 30% and 50% DCF formulations confirmed the DLS results illustrating that spherical-shaped particles roughly 100nm in size were fabricated with this protocol.

Discussion
The DLS results indicate promising outcomes for PCL-based NPs, consistently producing particles near-100nm in diameter. This size is attractive for intravenous delivery where a balance of size is necessary to maximize circulation time. Additionally, the average Z-pot, ranging from -10 to -20mV, aligns well with the objective of enhancing BBB viability. The low PDI further demonstrates the consistency and uniformity of these NPs. Notably, changing the diclofenac loading concentration had no significant effect on the dependent variables of the NPs, which could allow for more flexibility in drug loading options. We acknowledge the very low EE and LC of the NPs, indicating that further optimization is necessary to encapsulate diclofenac within PCL NPs.

Conclusion
The DLS and SEM results indicate that the fabrication protocol consistently produces near 100nm PCL NPs with physical characteristics that are ideal for drug delivery applications to the brain. However, there was low EE and LC in the PCL NPs. Further testing will be conducted with changes in protocol focusing on improving encapsulation using methods such as double emulsion, longer stirring times, different surfactant concentrations, and potentially looking at complete different NP base materials for new formulations.

Acknowledgements (Optional):