Associate Professor University of Oklahoma, United States
Introduction: Poly[lactic-co-glycolic acid] nanoparticles (PLGA NPs) are materials for organic nanoparticle drug delivery, currently explored in the treatment of many cancers and diseases. PLGA NPs can be utilized to decrease the severity of symptoms caused by osteoarthritis by delivering drugs to macrophages with the goal of polarizing these macrophages. Increased polarization leads to increased inflammation in the immediate area, which would create additional protection for areas most affected by arthritis. Rosiglitazone is a drug regularly used for the treatment of diabetes, however it also possesses the unique ability to promote the polarization of macrophages towards the M2 phenotype by activating the nuclear receptor PPAR-gamma. Prevailing organic nanoparticle (ONP) synthesis procedures utilized by much of the industry relied upon the use of costly microfluidic setups, which are often cost-prohibitive. Their price often poses a large roadblock for laboratories and researchers wishing to study ONP synthesis. One solution formulated to fix this technological gap included the use of tedious and often unreliable batch methods such as extrusion. A novel microfluidic setup created from a dismantled Ender3 three-dimensional printer was chosen for its low price of ~$300, its portability, and its reliability in the creation of ONPs.
Materials and
Methods: PLGA NPs were synthesized utilizing a modified three-dimensional printer as a custom microfluidic device, allowing for the adjustment of the total flow rate and flow rate ratio of the aqueous and organic phases during the synthesis process. PLGA NPs were synthesized utilizing two separate mixing modules, with each using distinct methods of attachment with the microfluidic tubing. Particles made using these cross mixers were subsequently compared against one another in both polydispersity index (PDI) and hydrodynamic diameter (HDD) by Dynamic Light Scattering (DLS). Two separate DLS instruments were utilized in the characterization of particles. The first was a Malvern DLS system, while the other was a Wyatt plate reader, which used both DLS and static light scattering for characterization. Finally, PLGA NPs were placed in distinct temperature environments designed to simulate specific conditions which the particles may have to endure for great periods of time, with their PDI and HDD tested every other day for twelve days. Particles were placed in 37℃ to simulate presence within the human body after injection into a patient, 4℃ for particles placed in cold storage for long periods of time, and finally room temperature (RT) as a control.
Results, Conclusions, and Discussions: The HDD produced by the Malvern and Wyatt instruments is similar, but the difference in PDI produced by both systems is apparent, with the PDI produced by the Wyatt almost double that of the Malvern. It is important to reiterate that the same particles were characterized by both instruments during this trial, pointing to the differences in how each instrument performs DLS as the reason for this discrepancy. The lower PDI standard deviation for the Malvern system indicates that this instrument produces a more reliable value. The HDD of particles produced by both cross mixers is very close, with the Idex mixer having consistently produced slightly larger particles than the Restek. On the other hand, the PDI of PLGA NPs synthesized using the Idex mixer is noticeably lower than that of particles made by the Restek mixer. The Restek brand cross mixer uses a larger ferrule which could not be taken off the tubing when not in use. The Idex brand mixer’s ferrules were smaller and thus the nut and ferrule could be removed from the tube after completion of particle synthesis, decreasing stress placed on the tube and lengthening each tube’s lifespan. Therefore, this is believed to be the reason why the Idex mixer has been able to make higher quality particles with lower PDI. As for the shelf-life testing, PDI was seen increasing for particles at 37℃, while it decreased over time for particles in the 4℃ and RT environments. HDD slowly increased for particles within the 4℃ environment, while it stayed relatively stagnant for particles at RT and noticeably decreased for particles at 37℃. These trends seem to suggest that the higher heat of 37℃ destabilized particles which had been formed, while the lower temperature of 4℃ attracted free-floating PLGA molecules to join particles which had already formed. This would create a mix of slightly smaller particles and free-floating PLGA strands within the 37℃ solutions, leading to a higher PDI. Additionally, this would create more monodisperse particles within the 4℃ solutions, leading to a lower PDI.
