Microspheres of essential oil in polylactic acid and poly(methyl methacrylate) matrices and their blends

Adsorption Properties of Essential Oils on Polylactic Acid Microparticles of Different Sizes

The interaction between the polymer and the materials in contact with it affects its applicability. This can be particularly important in applications such as packaging or controlled drug delivery systems. Because of these interactions, the adsorption and diffusion properties of polylactic acid (PLA) are important. The absorption capacity of different polylactic acid particles for different additives like essential oils (Thymus vulgaris, Melissa officinalis, and Foeniculum vulgare essential oils) was investigated depending on the concentration of the essential oil. The PLA microparticles were prepared by the solvent evaporation emulsification method. The prepared particles had a degree of crystallinity of 0.1% and 16.1%, respectively, according to the granules used. This affects the particles' adsorption properties. The specific essential oil uptake of the more crystalline microparticles was on average 15% higher than that of the amorphous particles. The specific amount of essential oil adsorbed decreases with the decreasing concentration of essential oil in the solutions. We also investigated whether the amount of essential oil taken up was correlated with the solubility parameter of the essential oils. We concluded that the difference between the adsorption of the essential oils on the polymer was related to the essential oils' Hansen solubility parameter.

Intrinsically radiopaque and antimicrobial cellulose based surgical sutures from mechanically powerful Agave sisalana plant leaf fibers

The judicious configuration of a flexible radiopaque suture would be exemplary to facilitate effortless tracking and precise diagnosis of the sutured surgical site by various X-ray assisted imaging modalities and simultaneously serve as a complementary tool for monitoring the fate of the suture material during the post-operative course. A unique radiopaque cellulose based surgical suture (RF) with good mechanical properties was developed by strategically controlled mercerization and bleaching of mechanically strong natural cellulosic fibers extracted from Agave sisalana plant leaves followed by the facile dip-coating of SrO integrated polylactic acid (PLA). RF exhibited admirable straight-pull tensile strength (184 MPa) and commendable contrast enhancement (277.4%) under digital X-ray radiographic imaging which was further validated by micro-CT analysis. Further, RF has a controlled hydrolytic degradation profile favorable for surgical suturing (mass loss ∼22% in 28 days). The microporous surface architecture of RF (pore size < 10 μm) as a result of SrO-PLA coating enabled the loading of antibiotic (ciprofloxacin) deep inside the pores with a cumulative release of 24% at 28 days under physiological conditions substantiating its feasibility to be used as an efficient antimicrobial suture (CRF) that prevents possible bacterial infections at the surgical site. This has been demonstrated by antibacterial disc diffusion assay performed against two Gram-positive and two Gram-negative bacterial strains. Significantly, both RF and CRF are highly biocompatible as confirmed by MTT assay and F-actin staining. Hence, CRF would be a good biocompatible suture candidate holding good tensile properties, exceptional antimicrobial property and intrinsic radiopacity retention for a period >28 days.

Polymeric Carriers Designed for Encapsulation of Essential Oils with Biological Activity

The article reviews the possibilities of encapsulating essential oils EOs, due to their multiple benefits, controlled release, and in order to protect them from environmental conditions. Thus, we present the natural polymers and the synthetic macromolecular chains that are commonly used as networks for embedding EOs, owing to their biodegradability and biocompatibility, interdependent encapsulation methods, and potential applicability of bioactive blend structures. The possibilities of using artificial intelligence to evaluate the bioactivity of EOs—in direct correlation with their chemical constitutions and structures, in order to avoid complex laboratory analyses, to save money and time, and to enhance the final consistency of the products—are also presented.

Preparation and tribological behaviour of poly(methyl methacrylate) (PMMA) microcapsules containing friction modifiers

Aims: Microcapsules comprising of a poly(methyl methacrylate) (PMMA) shell and friction modifier (FM) core were prepared to reduce the friction and extend the service life of engine lubricating oil.Methods: Microcapsules containing both organic FM and molybdenum FM were produced via solvent evaporation technique. The friction coefficient, thermal stability, and chemical composition of microcapsules were investigated.Results: The incorporation of microcapsules in lubricating oil dramatically reduced the friction coefficient to be lower than that of virgin FM. Organic FM and molybdenum FM are compatible during the encapsulation process. The release of the FM inside the microcapsules was controllable by thermal degradation of polymeric shell at 150 °C or mechanical rupture at room temperature.Conclusions: This study provided a novel approach to improve the tribological properties of lubricating oil with long service life, facile fabrication and low cost and will find potential applications in lubrication industry for internal combustion engines.

The effect of initiator encapsulation on methyl methacrylate polymerization by isothermal differential scanning calorimetry

Microcapsules containing initiator of cumene hydroperoxide or tert-butyl peroxy-2-ethylhexanoate as core material and polyurea as shell material were prepared by condensation polymerisation in oil-in-water emulsion at different agitation speeds. And their effects on the polymerisation of methyl methacrylate were investigated by isothermal differential scanning calorimetry. In comparison to unencapsulated initiators, the use of encapsulated initiators significantly delayed the reaction, reduced the maximum heat flow, relatively reduced the maximum reaction rate, and made the conversion smaller. In addition, the encapsulated initiator shortened the time lag, increased the heat flow at the maximum point as the reaction temperature increased, and further delayed the appearance time of the maximum reaction point as the agitation speed decreased. The theoretical values calculated by the modified Kamal model, including the nth-order reaction formula and the autoacceleration reaction, were in good agreement with our experimental data. We observed the more prominent autoacceleration reaction at a higher conversion.

The odour assessment of thyme essential oils in electrospun fibre mat with a virtual sensor array data and its relation to antibacterial activity

Aims: The ability of a single-sensor gas diagnosis device (SSGDD) as a virtual sensor array data to appraise thyme essential oils (TEO) based on its quantitatively release rate from nanofibres was aimed.Methods: To form nylon 6 fragrant electrospun nanofibre, TEO was added as a natural antibacterial substance under homogeniser to make a stable emulsion.Results: The optimised nanofibre inactivated against Escherichia Coli and Staphylococcus Aureus bacteria up to >75% at once and to > 41.9% over 2-weeks period. Moreover, large differences in sensor responses to samples with experimental variables (percent TEO and storage time) and different odour intensity exist which correctly classified by discriminant function analysis.Conclusions: Odour intensity as an accessible incubator evinces the nanofibres efficiency which correlated to the antibacterial activity. With applying SSGDD technique as a quantified subjective solution, carefully odour assessment is possible and prepared mats could be demonstrated as a face-masks' promising candidate.