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ORIGINAL RESEARCH

Catechin encapsulation and controlled release through pH-sensitive multi-branched copolymers for optimized antimicrobial activity

Mohammed Belkadi1* ,  Ridouan El Yousfi2* ,  Oumayma Sayah3 ,  Mohammed Dalli4 ,  Aziza Hami1 ,  Adil Maleb5
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1 Laboratory of Bioresources, Biotechnology, Ethnopharmacology, and Health, Faculty of Sciences, University Mohammed First, Oujda, Oriental Region, Morocco
2 Laboratory of Applied Chemistry and Environment, Faculty of Sciences, Mohamed First University, Oujda, Oriental Region, Morocco
3 Department of Chemistry, Faculty of Sciences, Mohammed First University, Oujda, Oriental Region, Morocco
4 Department of Human Physiology and Ethnopharmacology, Higher Institute of Nursing Professions and Health Techniques, Mohammed First University, Oujda, Oriental Region, Morocco
5 Laboratory of Microbiology, Faculty of Medicine and Pharmacy, University Mohammed the First, Oujda, Oriental Region, Morocco
BMT, 61 https://doi.org/10.12336/bmt.25.00061
Submitted: 10 June 2025 | Revised: 25 August 2025 | Accepted: 28 August 2025 | Published: 14 November 2025
© 2025 by the Author(s). Licensee Biomaterials Translational, USA. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 (CC BY-NC-SA 4.0) (https://creativecommons.org/licenses/by-nc-sa/4.0/deed.en)
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Abstract

Conventional delivery systems, such as liposomes or non-responsive micelles, often fail to adequately protect catechin from premature degradation or to achieve effective bioavailability. To address these limitations, we developed an advanced delivery architecture that safeguards catechin and ensures targeted activity within acidic infection microenvironments, offering a promising strategy for antimicrobial therapy amid rising bacterial resistance. In this study, a multi-branched copolymer poly(4-vinylpyridine) (P4VP)-(poly[ε-caprolactone]20)5 (PCL) with an AB5 architecture was designed, where P4VP constitutes the hydrophilic segment and PCL forms the hydrophobic segment. This copolymer was engineered to encapsulate catechin and ensure its controlled release. Upon self-assembly in aqueous solution, it formed vesicles with well-defined morphologies, as confirmed by dynamic light scattering and transmission electron microscopy. At physiological conditions (pH 7.0), the vesicles were stable (~90 nm, ζ-potential <3 mV). At acidic conditions (pH 5.5), they underwent structural disorganization accompanied by an increase in size (~130 nm) and surface charge (+42 mV), which triggered catechin release (>90% within 24 h). Antibacterial assays demonstrated a marked enhancement in efficacy after encapsulation. Compared to free catechin, which exhibited limited inhibition zones (7–8 mm), catechin-loaded vesicles achieved zones of 22 mm against Staphylococcus aureus and 23 mm against Escherichia coli. Minimum inhibitory concentration values also decreased by an order of magnitude, highlighting the superior potency of the encapsulated formulation. Our findings highlight the P4VP-(PCL20)5 copolymer as a unique nanocarrier that unifies stability, pH-responsiveness, and drug protection within a single platform.

Keywords
Nanoencapsulation
Catechin
Controlled release
Self-assembly
Antibacterial activity
Funding
None.
Conflict of interest
The researchers declare that they do not have any conflicts of interest concerning this publication.
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