Preparation, characterization and in vitro release study of carvacrol-loaded chitosan nanoparticles

Preparation and characterization of carvacrol loaded polyhydroxybutyrate nanoparticles by nanoprecipitation and dialysis methods

In this investigation, preparation of carvacrol loaded polyhydroxybutyrate (PHB) nanoparticles was performed by nanoprecipitation and dialysis methods. PHB particles were obtained by nanoprecipitation method without and with low concentration of Tween 80 or pluronic as surfactant. Nano- and micro-sized particles were formed with trimodal distribution and large aggregates. Size and distribution of nanoparticles were decreased when concentration of Tween 80 was increased to 1% (v/v) in water as polar phase. PHB nanoparticles had narrow size (157 nm) with monomodal distribution. Nanoparticles, which were prepared by dialysis method had 140 nm in diameter with monomodal distribution. Carvacrol was used as a lipophilic drug and entrapped in optimized nanoparticles formulation by nanoprecipitation and dialysis methods. Entrapment efficacy was 21% and 11%, respectively. Morphology of PHB nanoparticles was spherical. The results of kinetic release study showed that carvacrol was released for at least 3 days. Release kinetic parameters showed a simple Fickian diffusion behavior for both formulations. Carvacrol loaded PHB nanoparticles had good dispersion into the agar medium and antimicrobial activity against Escherichia coli. This study describes the 1st work on loading of carvacrol into the PHB nanoparticles by nanoprecipitation and dialysis methods.

Physicochemical, antimicrobial and antioxidant properties of chitosan films incorporated with carvacrol

Chitosan films (CF) with carvacrol (CAR) [0.5%, 1.0% and 1.5% v/v] were prepared by the emulsion method. The retained CAR, water solubility, water vapor permeability (WVP), optical, mechanical properties, antibacterial and antioxidant capacity of films were analyzed. The results indicate that the retention of CAR in the CF was ≈50%. The incorporation of CAR to CF decreased the water solubility, the WVP, the yellowing and transparency and the tensile strength, but increased the stiffness. Microcapsules with diameters of 2 to 7 µm were found on the surface CF-CAR. The CF-CAR with highest CAR concentrations showed antibacterial activity against S. typhimurium and E. coli O157:H7. The CF-CAR had higher antioxidant capacity and an increased protective effect against oxidation of erythrocytes in different grades. These results suggest potential applications of CF-CAR as active packaging to preserve food products.

Application of the central composite design to optimize the preparation of novel micelles of harmine

Lactose–palmitoyl–trimethyl–chitosan (Lac-TPCS), a novel amphipathic self-assembled polymer, was synthesized for administration of insoluble drugs to reduce their adverse effects. The central composite design was used to study the preparation technique of harmine (HM)-loaded self-assembled micelles based on Lac-TPCS (Lac-TPCS/HM). Three preparation methods and single factors were screened, including solvent type, HM amount, hydration volume, and temperature. The optimal preparation technique was identified after investigating the influence of two independent factors, namely, HM amount and hydration volume, on four indexes, ie, encapsulation efficiency (EE), drug-loading amount (LD), particle size, and polydispersity index (PDI). Analysis of variance showed a high coefficient of determination of 0.916 to 0.994, thus ensuring a satisfactory adjustment of the predicted prescription. The maximum predicted values of the optimal prescription were 91.62%, 14.20%, 183.3 nm, and 0.214 for EE, LD, size, and PDI, respectively, when HM amount was 1.8 mg and hydration volume was 9.6 mL. HM-loaded micelles were successfully characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, and a fluorescence-quenching experiment. Sustained release of Lac-TPCS/HM reached 65.3% in 72 hours at pH 7.4, while free HM released about 99.7% under the same conditions.

Is dialysis a reliable method for studying drug release from nanoparticulate systems?-A case study

The kinetics of in vitro drug release from nanoparticulate systems is extensive, though uncritically, being studied by dialysis. Evaluating the actual relevance of dialysis data to drug release was the purpose of this study. Diclofenac- or ofloxacin-loaded chitosan nanoparticles crosslinked with tripolyphosphate were prepared and characterized. With each drug, dynamic dialysis was applied to nanoparticle dispersion, solution containing dissolved chitosan·HCl, and solution of plain drug. Drug kinetics in receiving phase (KRP), nanoparticle matrix (KNM) and nanoparticle dispersion medium (KDM) were determined. Release of each drug from nanoparticles was also assessed by ultracentrifugation. Although KRP data may be interpreted in terms of sustained release from nanoparticles, KNM and KDM data show that, with both drugs, the process was in fact controlled by permeation across dialysis membrane. Analysis of KRP data reveals a reversible interaction of diclofenac with dispersed nanoparticle surface, similar to the interaction of this drug with dissolved chitosan·HCl. No such interactions are noticed with ofloxacin. The results from the ultracentrifugation method agree with the above interpretation of dialysis data. This case study shows that dialysis data from a nanoparticle dispersion is not necessarily descriptive of sustained-release from nanoparticles, hence, if interpreted uncritically, it may be misleading.

Potential antibacterial activity of carvacrol-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles against microbial biofilm

The ability to form biofilms contributes significantly to the pathogenesis of many microbial infections, including a variety of ocular diseases often associated with the biofilm formation on foreign materials. Carvacrol (Car.) is an important component of essential oils and recently has attracted much attention pursuant to its ability to promote microbial biofilm disruption. In the present study Car. has been encapsulated in poly(dl-lactide-co-glycolide (PLGA) nanocapsules in order to obtain a suitable drug delivery system that could represent a starting point for developing new therapeutic strategies against biofilm-associated infections, such as improving the drug effect by associating an antimicrobial agent with a biofilm viscoelasticity modifier.

Optical-scattering method for the determination of the local polymer concentration inside nanoparticles

We have developed a method based on the Mie theory for determining the local polymer concentration inside spherical nanoparticles, thereby obtaining vital information about whether the particles are swelling in the solvent or if they are contracted into a more compact structure. In addition, this method can be used to calculate the number density of the particles, the molecular weight of the particles, and (if M(n) of the polymer is known) the aggregation number. The calculations are based on the relationship between the size of the nanoparticles and the turbidity of the sample.