Design and characterization of pectin-starch/organoclay-tea tree essential oil composite hydrogel beads as a...

The therapeutic potential of essential oils in feed and medicine is limited by their volatility, degradation, and poor bioavailability. To overcome these challenges, a novel colon-targeted microsphere was engineered for the controlled delivery of tea tree essential oil (TEO), as illustrated in Scheme 1. A critical component of this system is a pH-responsive coating composed of pectin and starch, which acts as a colon-specific polymeric barrier. This coating demonstrated precise pH-responsive release, with minimal leakage in simulated gastric fluid (SGF) (only 10.87 % release over 4 h) and sustained, colon-specific release in simulated intestinal fluid (SIF) (79.77 % over 14 h). The core of the system, designated TEOCMT, was fabricated through the modification of montmorillonite (MMT) with cetyltrimethylammonium bromide (CTAB), resulting in organo-montmorillonite (CMT). Tea tree essential oil was then encapsulated within the interlayer spaces of CMT, forming an effective sustained-release system (TEOCMT). Compared to raw MMT (5.63 %), the TEO loading capacity of CMT increased 8.3-fold, reaching 46.79 %. Furthermore, the antibacterial activity of PS/TEOCMT microspheres was triggered in alkaline media, where they dissolved and released the TEOCMT core. This resulted in enhanced efficacy, particularly against S. aureus (MIC = 1.25 mg mL^-1), which was superior to that of pure TEO (MIC = 2.5 mg mL^-1). The PS/TEOCMT microspheres also exhibited excellent biocompatibility. This work presents a robust and effective strategy for unlocking the full potential of essential oils in colon-specific applications.