Analysis of Polylactic-co-Glycolic Acid (PLGA) by Gel Permeation Chromatography (GPC) using the Arc™ HPLC System with a Refractive Index (RI) Detector

Significance of the Topic

PLGA is a biodegradable copolymer extensively employed in medical and pharmaceutical applications to regulate drug release kinetics. Its molecular weight and distribution critically influence degradation rate and release profiles of active pharmaceutical ingredients.

Aims and Overview of the Study

This study aimed to determine the molecular weight distribution and polydispersity of PLGA polymers with various lactide:glycolide ratios using gel permeation chromatography (GPC). It also assessed polymer degradation in aqueous media over a 14-day period.

Methodology

GPC analysis was performed isocratically using tetrahydrofuran as the mobile phase. A three-column series with varying pore sizes covered molecular weight ranges from 100 to 600,000 Da. Polystyrene standards (Mp: 0.266–130 kDa) established a relative calibration curve. PLGA samples (50:50, 65:35, 75:25, 85:15) were dissolved in THF, filtered, and injected (50 µL). Degradation samples were incubated in 0.5% PVA at 37 °C and sampled at multiple intervals. Data were processed with Empower 3 software GPC option.

Used Instrumentation

• Arc HPLC System with quaternary solvent manager, flow-through needle sample manager, and strong solvent compatibility kit
• 2414 Refractive Index Detector
• Styragel HR columns (HR 4: 5,000–600,000 Da; HR 2: 500–20,000 Da; HR 1: 100–5,000 Da), 7.8×300 mm, 5 µm
• Column heater/cooler set to 35 °C
• Empower 3 Chromatography Data System (GPC option)

Main Results and Discussion

A third-order polynomial calibration curve (R^2 > 0.9998) enabled accurate determination of PLGA molecular weights (Mw: ~39.7–74.7 kDa, PDI: 1.6–1.7). The degradation study revealed a progressive decrease in Mw over 14 days for 50:50 and 75:25 PLGA samples. Day-14 50:50 samples exhibited increased PDI (up to 2.4), indicating broader molecular weight distributions due to hydrolytic chain scission. Chromatograms confirmed later elution of lower-mass fragments over time.

Benefits and Practical Applications

• Reliable determination of PLGA molecular weight distribution using a robust HPLC setup
• Rapid data processing and reporting via Empower software
• Capability to monitor polymer degradation in aqueous environments, aiding formulation stability studies

Future Trends and Potential Applications

Advancements may include:

• Integration of multi-detector GPC systems for improved polymer characterization
• Real-time monitoring of polymer degradation kinetics in complex matrices
• Application to novel biodegradable polymers and copolymer blends for tailored drug delivery profiles
• Enhanced software algorithms for automated interpretation of high-throughput GPC data

Conclusion

The Arc HPLC System equipped with a strong solvent compatibility kit and RI detection offers an effective platform for GPC analysis of PLGA polymers, delivering precise molecular weight and polydispersity assessments. The study confirmed water-mediated degradation trends, supporting quality control and formulation optimization in drug delivery research.

Reference

1. Lu Y, Cheng D, Niu B, Wang X, Wu X, Wang A. Properties of Poly(Lactic-co-Glycolic Acid) and Progress of Poly(Lactic-co-Glycolic Acid)-Based Biodegradable Materials in Biomedical Research. Pharmaceutical. 2023;16:454.
2. Makadia HK, Siegel SJ. Poly Lactic-co-Glycolic Acid (PLGA) as a Biodegradable Controlled Drug Delivery Carrier. Polymers. 2011;3:1377–1397.
3. D’Souza S, Dorati R, DeLuca PP. Effect of Hydration on Physicochemical Properties of End-Capped PLGA. Advances in Biomaterials. 2014;Article ID 834942.
4. Waters Corporation. Arc HPLC Strong Solvent Compatibility Guide. User Guide 715009279.
5. Maziarz M. Accurate Molecular Weight Determination of Polystyrene-Tetrahydrofuran Solutions using the Arc HPLC. Waters Application Note 720008301. 2024.
6. Waters Corporation. Empower GPC Software Getting Started Guide. User Guide 71500031303.
7. Waters Knowledge Base. Get Empowered: Review Window and the Processing Method - Working with GPC/SEC data in Empower - Tip125.