Self-Inclusion and Dissociation of a Bridging β-Cyclodextrin Triplet

A biocompatible β-cyclodextrin inclusion complex containing natural extracts: a promising antibiofilm agent

Biofilms formed by several bacterial strains still pose a significant challenge to healthcare due to their resistance to conventional treatment approaches, including antibiotics. This study explores the potential of loading natural extracts with antimicrobial activities into β-cyclodextrin (βCD) nanoparticles, which are FDA-approved and have superior biocompatibility owing to their cyclic sugar structures, for biofilm eradication. An inclusion complex of βCD carrying Boswellia sacra essential oils (BOS) was prepared and characterized with regard to its physicochemical properties, antimicrobial efficacy, and antibiofilm activities. Encapsulation of BOS into βCD significantly enhanced the antimicrobial activity of BOS by 4-fold against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and by 8-fold against Gram-negative (Escherichia coli and Pseudomonas putida) bacteria, with minimum inhibitory concentrations ranging from 2.5 to 5 mg mL-1. Furthermore, the BOS-βCD complex demonstrated a dual-action against bacterial biofilms where it prevented biofilm formation and disrupted established biofilms. This resulted in a significant reduction in biofilm biomass, with prevention and disruption rates reaching up to 93.78% and 82.17%, respectively. Additionally, the formula revealed an excellent biocompatibility profile with no induction of oxidative stress in human skin fibroblast cells. Our findings suggest that βCD nanoparticles loaded with BOS essential oils hold promise as an effective formula for preventing the formation of bacterial biofilms and combating preformed ones for use in relevant medical applications.

Antimicrobial Activities of Pistacia lentiscus Essential Oils Nanoencapsulated into Hydroxypropyl-beta-cyclodextrins

The rising risks of food microbial contamination and foodborne pathogens resistance have prompted an increasing interest in natural antimicrobials as promising alternatives to synthetic antimicrobials. Essential oils (EOs) obtained from natural sources have shown promising anticancer, antimicrobial, and antioxidant activities. EOs extracted from the resins of Pistacia lentiscus var. Chia are widely utilized for the treatment of skin inflammations, gastrointestinal disorders, respiratory infections, wound healing, and cancers. The therapeutic benefits of P. lentiscusessential oils (PO) are limited by their low solubility, poor bioavailability, and high volatility. Nanoencapsulation of PO can improve their physicochemical properties and consequently their therapeutic efficacy while overcoming their undesirable side effects. Hence, PO was extracted from the resins of P. lentiscusvia hydrodistillation. Then, PO was encapsulated into (2-hydroxypropyl)-beta-cyclodextrin (HPβCD) via freeze-drying. The obtained inclusion complexes (PO-ICs) appeared as round vesicles (22.62 to 63.19 nm) forming several agglomerations (180 to 350 nm), as detected by UHR-TEM, with remarkable entrapment efficiency (89.59 ± 1.47%) and a PDI of 0.1475 ± 0.0005. Furthermore, the encapsulation and stability of PO-ICs were confirmed via FE-SEM, 1H NMR, 2D HNMR (NOESY), FT-IR, UHR-TEM, and DSC. DSC revealed a higher thermal stability of the PO-ICs, reaching 351.0 °C. PO-ICs exerted substantial antibacterial activity against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli as compared to free PO. PO-ICs showed significant enhancement in the antibacterial activity of the encapsulated PO against S. aureus with an MIC90 of 2.84 mg/mL and against P. aeruginosa with MIC90 of 3.62 mg/mL and MIC50 of 0.56 mg/mL. In addition, PO-ICs showed greater antimicrobial activity against E. coli by 6-fold with an MIC90 of 0.89 mg/mL, compared to free PO, which showed an MIC90 of 5.38 mg/mL. In conclusion, the encapsulation of PO into HPβCD enhanced its aqueous solubility, stability, and penetration ability, resulting in a significantly higher antibacterial activity.

Asymmetric Cyclodextrin-Dimer-Involved Nanoassemblies by Selective Host-Guest Interactions: Concentration-Dependent Morphology Evolution and Light-Regulated Biomedical Applications

Supramolecular assembly has attracted significant attention and has been applied to various applications. Herein, a β-γ-CD dimer was synthesized to complex different guest molecules, including single-strand polyethylene glycol (PEG)-modified C60 (PEG-C60), photothermal conversion reagent (IR780), and dexamethasone (Dexa), according to the complexation constant-dependent specific selectivity. Spherical or cylindrical nanoparticles, monolayer or bilayer vesicles, and bilayer fusion vesicles were discovered in succession if the concentration of PEG-C60 was varied. Moreover, if near-infrared light was employed to irradiate these nanoassemblies, the thermo-induced morphological evolution, subsequent cargo release, photothermal effect, and singlet oxygen (1O2) generation were successfully achieved. The in vitro cell experiments confirmed that these nanoparticles possessed excellent biocompatibility in a normal environment and achieved superior cytotoxicity by light regulation. Such proposed strategies for the construction of multilevel structures with different morphologies can open a new window to obtain various host-guest functional materials and achieve further use for disease treatment.

Improved antimicrobial activities of Boswellia sacra essential oils nanoencapsulated into hydroxypropyl-beta-cyclodextrins

Natural antimicrobials have recently gained increasing interest over synthetic antimicrobials to overcome foodborne pathogens and food microbial contamination. Essential oils (EOs) obtained from Boswellia sacra resins (BO) were utilized for respiratory disorders, rheumatoid arthritis, malignant tumors, and viral infections. Like other EOs, the therapeutic potential of BO is hindered by its low solubility and bioavailability, poor stability, and high volatility. Several studies have shown excellent physicochemical properties and outstanding therapeutic capabilities of EOs encapsulated into various nanocarriers. This study extracted BO from B. sacra resins via hydrodistillation and encapsulated it into hydroxypropyl-beta-cyclodextrins (HPβCD) using the freeze-drying method. The developed inclusion complexes of BO (BO-ICs) had high encapsulation efficiency (96.79 ± 1.17%) and a polydispersity index of 0.1045 ± 0.0006. BO-ICs showed presumably spherical vesicles (38.5 to 59.9 nm) forming multiple agglomerations (136.9 to 336.8 nm), as determined by UHR-TEM. Also, the formation and stability of BO-ICs were investigated using DSC, FTIR, FE-SEM, UHR-TEM, 1H NMR, and 2D HNMR (NOESY). BO-ICs showed greater thermal stability (362.7 °C). Moreover, compared to free BO, a remarkable enhancement in the antimicrobial activities of BO-ICs was shown against three different bacteria: Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. BO-ICs displayed significant antibacterial activity against Pseudomonas aeruginosa with an MIC90 of 3.93 mg mL-1 and an MIC50 of 0.57 mg mL-1. Also, BO-ICs showed an increase in BO activity against Escherichia coli with an MIC95 of 3.97 mg mL-1, compared to free BO, which failed to show an MIC95. Additionally, BO-ICs showed a more significant activity against Staphylococcus aureus with an MIC95 of 3.92 mg mL-1. BO encapsulation showed significantly improved antimicrobial activities owing to the better stability, bioavailability, and penetration ability imparted by encapsulation into HPβCD.