This study aimed to develop and evaluate hydrogels containing a cyclodextrin complex with clove essential oil and other free volatile oils with antimicrobial properties (tea tree and rosemary essential oils), focusing on their pharmaco-technical and rheological characteristics. The formulations varied in the Carbopol 940 (a hydrophilic polymer) and volatile oils’ concentrations. Rheological analysis indicated that the gels displayed pseudoplastic behavior, with the flow index (n) values below 1, ensuring appropriate consistency and handling. The results showed that increasing the Carbopol concentration significantly enhanced the yield stress, consistency index, and viscosity, with gel B, containing 1% Carbopol, 1.5% tea tree essential oil, and 1.5% rosemary essential oil, demonstrating optimal stability and rheological properties. At the same time, the concentration of volatile oils was found to modulate the gels’ flow parameters, but their effect was less pronounced than that of the gel-forming polymer. Antimicrobial testing revealed that both gel B and gel E (containing 1% Carbopol, 2% tea tree essential oil, and 2% rosemary essential oil) exhibited antimicrobial activity against Gram-positive, Gram-negative bacteria, and Candida spp., with gel E showing superior efficacy against Candida tropicalis. The antimicrobial effects were likely influenced by the higher concentrations of tea tree and rosemary essential oils in gel E. Overall, the study demonstrates that the concentration of Carbopol 940 primarily determines the gel’s rheological behavior, while volatile oil concentration modulates antimicrobial effectiveness.

Clove essential oil (Eugenia caryophyllata essential oil, ECEO) is known for its high eugenol content and notable antimicrobial properties. However, the volatility and instability of its active compounds hinder broader pharmaceutical applications. Methods: This study characterised the chemical composition of ECEO and comparatively evaluated four β-cyclodextrin (β-CD) encapsulation methods: kneading, co-precipitation, lyophilisation, and co-precipitation–lyophilisation for eugenol, eucalyptol, and ECEO. Encapsulation efficiency, physicochemical properties, and antimicrobial potential were assessed. Analytical techniques included Gas Chromatography–Mass Spectrometry (GC-MS), Headspace GC-MS (HS-GC-MS), Differential Scanning Calorimetry (DSC), Job’s method, and Dynamic Light Scattering (DLS). Results: GC-MS identified eugenol (90.67%), eugenyl acetate (4.77%), and (E)–β-caryophyllene (3.98%) as major components of ECEO, while HS-GC-MS indicated a slightly reduced eugenol content (86.46%). The kneading method yielded the highest encapsulation efficiency for eugenol, whereas the co-precipitation–lyophilisation method was optimal for eucalyptol. DSC thermograms confirmed complex formation, and DLS analysis revealed nanostructures averaging 186.4 nm in diameter (PDI = 0.298). Antimicrobial assays showed MIC values ranging from 0.039 mg/mL to 10,000 mg/mL. Notably, ECEO and its β-CD complex displayed enhanced efficacy against Escherichia coli (0.039 mg/mL), surpassing the reference antibiotic gentamicin (0.049 mg/mL). Conclusions: β-Cyclodextrin encapsulation significantly enhances the stability and bioactivity of volatile antimicrobial compounds, thereby supporting their potential integration into advanced essential oil-based pharmaceutical formulations.

This study aimed to develop and characterise novel hydrogels based on natural bioactive compounds for topical antimicrobial applications. Four gel systems were formulated using different polymers, namely polyacrylic acid (Carbopol 940, CBP-G), chitosan with high and medium molecular weights (CTH-G and CTM-G), and sodium alginate (ALG-G), incorporating tinctures of Verbena officinalis and Aloysia triphylla, Laurus nobilis essential oil, and a β-cyclodextrin–clove essential oil complex. All gels displayed a homogeneous macroscopic appearance and maintained stability for over 90 days. Rheological studies demonstrated gel-like behaviour for CBP-G and ALG-G, with well-defined linear viscoelastic regions and distinct yield points, while CTM-G exhibited viscoelastic liquid-like properties. SEM imaging confirmed uniform and continuous matrices, supporting controlled active compound distribution. Thermogravimetric analysis (TG-DTA) revealed a two-step degradation profile for all gels, characterised by high thermal stability up to 230 °C and near-total decomposition by 500 °C. FTIR spectra confirmed the incorporation of bioactive compounds and products and highlighted varying interaction strengths with polymer matrices, which were stronger in CBP-G and CTH-G. Antimicrobial evaluation demonstrated that chitosan-based gels exhibited the most potent inhibitory and antibiofilm effects (MIC = 2.34 mg/mL) and a cytocompatibility assessment on HaCaT keratinocytes showed enhanced cell viability for chitosan gels and dose-dependent cytotoxicity for alginate formulations at high concentrations. Overall, chitosan-based gels displayed the most favourable combination of stability, antimicrobial activity, and biocompatibility, suggesting their potential for topical pharmaceutical use.