Poster J3 - PLGA Average Molecular Weight Effects on Protein Release

Friday, October 25, 2024

3:30 PM - 4:30 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Tarini Ravikumar

Student
University of Pittsburgh, United States

Co-Author(s)

Matthew Borrelli

PhD Candidate
University of Pittsburgh, United States

Primary Investigator(s)

SL

Steven Little, PhD

Distinguished Professor and Department Chair
University of Pittsburgh, United States

Introduction: One of the major limiting factors in the development of therapeutic peptides and proteins has been their short half-lives due to rapid enzymatic degradation. One approach to increasing therapeutic bioavailability is to encapsulate a therapeutic in biodegradable synthetic polymers, which can shield its cargo from circulating enzymes in the interstitium. The FDA approved polyester poly (lactic-co-glycolic acid) (PLGA) is commonly used to encapsulate peptides and proteins due to its proven biocompatibility and adjustable degradation rate. Commonly supplied PLGA polymers can have a ranging distribution of molecular weights, but it is unknown how shifts in these distributions may affect the release of peptides and proteins. The aim of this study was to explore how changes in the molecular weight distribution of PLGA polymers affect biomolecule release from PLGA microparticles.

Materials and

Methods: Microparticles (MP) were fabricated through emulsification. Different molecular weight combinations of (2 kDa, 5 kDa, 10 kDa, 20 kDa and 40 kDa) PLGA were used. The total average molecular weight for the various formulations, made with 5, 4, 3 or 2 components of PLGA, were maintained at 15 kDa and 10 kDa. The planned studies to characterize MP release kinetics and to quantify loading of peptides in MP were done in triplicates (N = 3) for each batch of MP, plus no peptide controls. To characterize release, 10 mg of MP was incubated in release media at 37°C and sampled at specific time points (2 hours, day 1, day 3, etc. until day 25). TAMRA labeled peptides of Positive and Neutral charge were encapsulated within the MP. Measurement of loaded and released peptide was performed using fluorescence (552/578 nm, ex/em).

Results, Conclusions, and Discussions: In general, the release kinetics of positive charged peptides was much slower than the neutral charged peptides. In both groups, the 5-component (equal mass fraction) among the 15 kDa formulations was the fastest releasing and exhibited the highest burst. However, this difference was not statistically significant in the positive charged peptide, indicating that there may be a greater tolerance for variability in the polymer molecular weight. The worst performing 15 kDa formulations were those that lacked the 2 kDa component and had more than 50% of a particular PLGA component. Formulations that contained greater than 50% of a single polymer exhibited the lowest release rate. The 10 kDa formulations for both positive and neutral peptides showed increased release compared to the 15 kDa formulations. The best performing 10 kDa formulations were the 3a and 2 component ones which had higher proportions of the 2 kDa PLGA component. The 10 kDa 3a component formulation seemed to have a linear release pattern.

There is evidence that a heterogeneous molecular weight distribution of PLGA polymers influences peptide release. The 5-component 15 kDa formulation has higher release of both positive and neutral peptides, but it was also the only formulation to include the 2 kDa PLGA and a similar trend was seen among the 10 kDa formulations. Thus, this study suggests inclusion of lower molecular weight PLGA can significantly affect the release rate of PLGA microparticles. In future work, the influence of molecular weight distributions with a bias toward lower molecular weight can be further studied. The data we have generated suggests that quantifying and controlling the full molecular weight distribution of PLGA polymer is necessary to produce reproducible release profiles, which is a critical hurdle for cGMP manufacturing.

Acknowledgements (Optional):