Characterization of crosslinked hard gelatin capsules for a structural assembly of elementary osmotic pump delivery system

  • Chaowalit Monton
  • Poj KulvanichEmail author
Original Article


The objective of this study was to characterize the crosslinked hard gelatin capsules (HGCs) for use as a structural assembly of elementary osmotic pumps (EOP). HGCs were crosslinked in formaldehyde vapor for 6, 12, and 24 h. Weight loss after immersing in various mediums, water soluble protein fraction, loss on drying, and formaldehyde residue were investigated. Fourier transform infrared (FTIR) spectra were used to detect the crosslinking formation. The EOP capsules were prepared for delivery of diltiazem hydrochloride (DIL HCl) and ambroxol hydrochloride (AMB HCl), which are freely and sparingly water soluble drugs, respectively. Physicochemical stability of storage crosslinked HGC shells was investigated. All crosslinked HGC shells were water insoluble. FTIR spectra exhibited intermediate lysine methylol and arginine methylol peaks. Storage time increased, moisture content increased and formaldehyde residue decreased. The developing EOP capsules were more appropriate for delivery of high water soluble rather than low water soluble drug. EOP capsule contained 100 mg DIL HCl using HGCs crosslinked for 12 h provided release profiles for 12 h with a lag time of 2.6–3.1 h. It was also found that DIL HCl EOP capsules prepared using crosslinked HGC shells stored for 90 days maintained the similar drug release profiles. AMB HCl EOP capsules exhibited low drug release. In summary, the crosslinked HGCs were applicable as a structural assembly of the osmotic controlled drug delivery system.


Crosslinked hard gelatin capsules Structural assembly Elementary osmotic pumps 



The authors greatly appreciate Graduate School and College of Pharmacy, Rangsit University for financial support. We would like to acknowledge Biolab Co., Ltd., Thailand, Siam Pharmaceutical Co., Ltd., Thailand, Capsules Products Co., Ltd., Thailand, Onimax Co., Ltd., Thailand, Sun Herb Thai Chinese Manufacturing, Thailand, and Colorcon Inc., USA for contribution of some drugs, chemicals, and materials in this study. The authors are grateful to Professor J. E. Moreton, School of Pharmacy, University of Maryland at Baltimore, for his comments, assistance in reading and editing the manuscript.

Compliance with ethical standards

Conflict of interest

All authors (C. Monton and P. Kulvanich) declare that they have no conflict of interest.

Human and animal rights

This article does not contain any studies with human or animal subjects performed by any of the authors.


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Copyright information

© The Korean Society of Pharmaceutical Sciences and Technology 2019

Authors and Affiliations

  1. 1.College of PharmacyRangsit UniversityPathum ThaniThailand

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