How Liquid-Filled Capsules Are Made—and Why Sealing Technology Matters

1. Capsule Shell Selection

Manufacturing begins with selecting an appropriate capsule shell material—most commonly gelatin or plant-based polymers such as HPMC or pullulan. Shell choice influences:

• Moisture and oxygen barrier properties
• Compatibility with lipid-based or hygroscopic fills
• Thermal behavior during sealing
• Regulatory and patient acceptance considerations

Plant-based shells are increasingly used in both industrial and pharmacy settings due to their compatibility with lipid systems and predictable sealing behavior (Uttreja et al., 2025; Podczeck & Jones, 2004).

2. Filling Accuracy and Environmental Control

Liquid or semi-solid formulations are dosed using volumetric or gravimetric systems designed for high reproducibility. For oxidation-sensitive formulations, controlled environments and nitrogen purging are frequently applied to minimize oxygen exposure during filling (Waterman & Adami, 2005; ICH, 2003).

However, precise filling alone does not guarantee product performance. Without effective sealing, filled capsules remain vulnerable to leakage, oxidation, and contamination.

3. Why Sealing Is Critical

Sealing transforms a filled capsule into a finished dosage form capable of withstanding handling, transport, and storage. Poor sealing can result in:

• Leakage or evaporation
• Oxygen and moisture ingress
• Reduced shelf life and dose variability
• Compromised tamper evidence

As such, sealing is a core quality determinant in LFHC manufacturing.

4. Sealing Technologies: Fusion Sealing, LEMS® technology vs. Banding

Three main approaches are used in pharmaceutical manufacturing:

 Fusion Sealing

Fusion sealing applies a hydroalcoholic or aqueous solution to the capsule seam, followed by controlled heat and pressure to fuse the cap and body into a continuous structure.

Advantages include:

• Integrated, tamper-resistant seals
• No additional materials or components
• High reproducibility and throughput
• Enhanced resistance to environmental stress

Fusion-sealed capsules demonstrate low oxygen permeability and strong mechanical integrity, particularly when combined with nitrogen purging (Woo et al., 2023; Szweda et al., 2024).

 LEMS® Technology (Liquid Encapsulation Microspray Sealing)

LEMS® technology is an enhanced sealing method in which a fine microspray of sealing fluid is applied to the capsule seam, followed by gentle heating to fuse the cap and body into a continuous closure.

Reported advantages include:

• Larger sealed area compared with traditional banding, which can improve structural integrity and reduce leakage risk (NutraIngredients, 2007)
• Elimination of external banding, resulting in a continuous cap–body interface (Pharmaceutical Online, 2007a)
• Demonstrated integrity in stability testing, with capsules remaining leak-free under extended storage conditions (Pharmaceutical Online, 2007b)

LEMS® technology is particularly beneficial for lipid-based, oxidation-sensitive, or otherwise formulation-challenging fills, providing reproducible sealing while maintaining product stability.

 Banding

Banding involves applying a polymer solution or band around the capsule seam after filling. Common banding materials include gelatin or polysaccharide-based polymers. Banding has been shown to improve leakage resistance and tamper evidence; however, published studies highlight potential limitations:

• Additional processing steps and drying time
• Variability in band thickness and appearance
• Compatibility constraints with certain shell polymers

Comparative evaluations indicate that while banding improves leakage resistance and tamper evidence, fusion sealing and LEMS® technology generally provides superior seam integrity and process efficiency for liquid-filled applications (Jones & Podczeck, 2001; Podczeck & Jones, 2004).

5. Impact on Stability, Safety, and Compliance

Sealing performance directly affects stability outcomes. Fusion-sealed LFHCs have demonstrated strong performance in accelerated stability studies for hygroscopic and oxidation-sensitive formulations (Woo et al., 2023; Waterman & Adami, 2005; ICH, 2003). From a regulatory and patient-safety perspective, tamper-evident sealing improves confidence in dose integrity and reduces manipulation risk.

Conclusion

In liquid-filled capsule manufacturing, sealing is not a secondary step—it is foundational to quality, stability, and patient safety. Understanding sealing technologies, including LEMS® technology, enables formulators to select appropriate manufacturing strategies aligned with formulation sensitivity and lifecycle requirements.

In the next article, we explore why formulators and pharmacies alike are increasingly adopting in-house liquid capsule filling solutions: Why Compouding Pharmacies Are Turning to In-House Capsule Filling Solutions

References:

• Capsugel. (n.d.). Licaps® Fusion Technology Overview.
• Capsugel. (n.d.). CFS 1200® Capsule Filling and Sealing Machine Specifications.
• Holm, R., Kuentz, M., Ilie-Spiridon, A.-R., & Griffin, B. T. (2023). Lipid-based formulations as supersaturating oral delivery systems: From current to future industrial applications. European Journal of Pharmaceutical Sciences, 189, 106556.
• Woo, S.-w., Hwang, S.-J., & Cho, C.-W. (2023). Liquid-filled hard capsule formulation of choline alfoscerate: In vitro/in vivo evaluation and bioequivalence to softgels. Journal of Pharmaceutical Investigation, 53(4), 517–526.
• Szweda, N. M., Rapin, M. N., Evans, P., Braun, S., & Hacker, M. C. (2024). Carrageenan-based solutions for the sealing of liquid-filled pullulan hard capsules. PBP World Meeting.
• Podczeck, F., & Jones, B. E. (2004). The sealing of hard gelatin capsules. International Journal of Pharmaceutics, 274(1–2), 1–12.
• Jones, B. E., & Podczeck, F. (2001). Evaluation of the sealing performance of banded hard gelatin capsules. Pharmaceutical Development and Technology, 6(3), 359–371
• Rowe, R. C., Sheskey, P. J., & Quinn, M. E. (Eds.). (2012). Handbook of pharmaceutical excipients (7th ed.). Pharmaceutical Press.
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• ICH. (2003). Q1A(R2): Stability testing of new drug substances and products. International Council for Harmonisation.
• Uttreja, P., Karnik, I., Youssef, A. A. A., et al. (2025). Self-emulsifying drug delivery systems (SEDDS): Transition from liquid to solid—A comprehensive review. Pharmaceutics, 17(1), 63.
• Industry best practices for nitrogen purging in pharmaceutical manufacturing. (n.d.). Retrieved December 23, 2025.
• NutraIngredients. (2007, June 25). Capsugel says new Licap suited to supplements. NutraIngredients. https://www.nutraingredients.com/Article/2007/06/25/capsugel-says-new-licap-suited-to-supplements
• Pharmaceutical Online. (2007a). Licaps capsules. Pharmaceutical Online. https://www.pharmaceuticalonline.com/doc/licaps-capsules-0001
• Pharmaceutical Online. (2007b). Allows rapid in-house manufacture of capsules. Pharmaceutical Online. https://www.pharmaceuticalonline.com/doc/allows-rapid-in-house-manufacture-of-capsules-0001