Using zeta potential to study the ionisation behaviour of polymers employed in modified-release dosage forms and estimating their pKa

Joao Cunha Barbosa, Malaz Abdelsadig, Barbara Conway, Hamid Merchant

Research output: Contribution to journalArticle

Abstract

A range of enteric polymers is used in pharmaceutical industry for developing gastro-resistant formulations. It is generally implied that these coatings are interchangeable due to similar dissolution pH thresholds reported by suppliers. Despite rapid dissolution in compendial phosphate buffers, these products can take up to 2 h to disintegrate in-vivo in the human small intestine. The factors primarily responsible for such variability in dissolution of these polymeric coatings are the differences in ionisation of acidic functional groups on polymer chains and their interplay with ions and buffer species present in gastrointestinal fluids. In this study, we aim to develop a novel, simple and inexpensive technique that can be used under various in-vitro conditions to study the ionisation behaviour of commonly used polymers (EUDRAGIT-E100, L100, S100, HPMC AS-LF, AS-HF, HP-50, HP-55) and to estimate their pKa. Moreover, this method was successfully applied to study the ionisation behaviour of a range of natural polymers (Guar, Tara, locust bean, Konjac gums, gum Arabic, citrus pectin, chitosan and alginate) and their pKa was also estimated. The proposed method would allow a better understanding of the dissolution behaviour of these polymers within gastrointestinal tract and will aid rational design of modified release dosage forms.
LanguageEnglish
Article number100024
Pages1-11
Number of pages11
JournalInternational Journal of Pharmaceutics: X
Volume1
Early online date19 Jul 2019
DOIs
Publication statusE-pub ahead of print - 19 Jul 2019

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Dosage Forms
Polymers
Buffers
Amorphophallus
Gum Arabic
Cyamopsis
Chitosan
Drug Industry
Small Intestine
Gastrointestinal Tract
Phosphates
Ions

Cite this

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title = "Using zeta potential to study the ionisation behaviour of polymers employed in modified-release dosage forms and estimating their pKa",
abstract = "A range of enteric polymers is used in pharmaceutical industry for developing gastro-resistant formulations. It is generally implied that these coatings are interchangeable due to similar dissolution pH thresholds reported by suppliers. Despite rapid dissolution in compendial phosphate buffers, these products can take up to 2 h to disintegrate in-vivo in the human small intestine. The factors primarily responsible for such variability in dissolution of these polymeric coatings are the differences in ionisation of acidic functional groups on polymer chains and their interplay with ions and buffer species present in gastrointestinal fluids. In this study, we aim to develop a novel, simple and inexpensive technique that can be used under various in-vitro conditions to study the ionisation behaviour of commonly used polymers (EUDRAGIT-E100, L100, S100, HPMC AS-LF, AS-HF, HP-50, HP-55) and to estimate their pKa. Moreover, this method was successfully applied to study the ionisation behaviour of a range of natural polymers (Guar, Tara, locust bean, Konjac gums, gum Arabic, citrus pectin, chitosan and alginate) and their pKa was also estimated. The proposed method would allow a better understanding of the dissolution behaviour of these polymers within gastrointestinal tract and will aid rational design of modified release dosage forms.",
keywords = "pKa, Ionisation, Enteric, Gastro-resistant, Modified-release, Zeta-potential, Charge, Dissolution, pK",
author = "{Cunha Barbosa}, Joao and Malaz Abdelsadig and Barbara Conway and Hamid Merchant",
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AU - Merchant, Hamid

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