Riccardo Carzino

Fibrous wound dressings encapsulating essential oils as natural antimicrobial agents

Preventing infections is one of the main focuses of wound care. The colonisation of wounds by microorganisms can in fact have negative consequences on the healing process, delaying it. Here, we propose the use of essential oils as natural antimicrobial agents for cellulose-based fibrous dressings. We demonstrate the production of composite electrospun fibres that effectively encapsulate three different types of essential oils (cinnamon, lemongrass and peppermint). The fibrous scaffolds are able to inhibit the growth of Escherichia coli, even when small amounts of essential oils were used. At the same time, they are not cytotoxic, as proved by biocompatibility assays on skin cell models. The created dressings are promising as advanced biomedical devices for topical treatments.

Very large spot size effect in nanosecond laser drilling efficiency of silicon

The effect of the spot diameter in nanosecond excimer laser percussion drilling of through via in silicon wafer is presented. Experimental results show a ten fold increase of the ablation efficiency when decreasing the spot diameter from 220 μm to 9 μm at constant fluence in the range 7.5 J/cm(2) to 13.2 J/cm(2). Such effect is absent when using 60 ps deep-UV laser pulses. A model is developed that explain the findings in terms of plume shielding effect on the laser pulse. The model is successfully applied also on previously published data on deep-UV laser drilling of Polyamide and Alumina.

All natural cellulose acetate-Lemongrass essential oil antimicrobial nanocapsules.

Nanocapsules and nanoparticles play an essential role in the delivery of pharmaceutical agents in modern era, since they can be delivered in specific tissues and cells. Natural polymers, such as cellulose acetate, are becoming very important due to their availability, biocompatibility, absence of toxicity and biodegradability. In parallel, essential oils are having continuous growth in biomedical applications due to the inherent active compounds that they contain. A characteristic example is lemongrass oil that has exceptional antimicrobial properties. In this work, nanocapsules of cellulose acetate with lemongrass oil were developed with the solvent/anti-solvent method with resulting diameter tailored between 95 and 185nm. Various physico-chemical and surface analysis techniques were employed to investigate the formation of the nanocapsules. These all-natural nanocapsules found to well bioadhere to mucous membranes and to have very good antimicrobial properties at little concentrations against Escherichia coli and Staphylococcus aureus.

Electrospun Fiber Pads of Cellulose Acetate and Essential Oils with Antimicrobial Activity

The method of electrospinning was used to create nanofibers made of cellulose acetate (CA) and essential oils (EOs). CA polymer at 15% w/v was dissolved in acetone and then 1% or 5% v/v of EOs was added to the polymer solution. The utilized essential oils were rosemary and oregano oils. Then, the CA/EOs in acetone solution were electrospun, creating micro/nanofibers, approximately 700–1500 nm in diameter. Raman spectroscopy was used to detect the attachment of the EOs in the CA electrospun fibers (ESFs). Scanning electron microscopy was used to study the morphology, topography and dimensions of the ESFs. The formed CA/EOs ESFs are found to have good antimicrobial properties against three common microbial species, frequently found in difficult to treat infections: Bacteria species Staphylococcus aureus, Escherichia coli and the yeast Candida albicans. ESFs with 5% v/v oregano oil with respect to the initial solution, showed the best antimicrobial and anti-biofilm effects due to the potency of this EO against bacteria and fungi, especially for Escherichia coli and Candida albicans. This work describes an effective and simple method to prepare CA/EOs ESFs and opens up many new applications of micro/nanofibers such as improved antimicrobial wound dressings, anti-biofilm surfaces, sensors and packaging alternatives.

Polylactic Acid—Lemongrass Essential Oil Nanocapsules with Antimicrobial Properties

Polylactic acid was combined with lemongrass essential oil (EO) to produce functional nanocapsules (NCs). The obtained polylactic acid nanoparticles showed antimicrobial activity both with and without the presence of lemongrass oil; however, the presence of EO improved the activity of the NCs. The presence of lemongrass assisted the formation of well-separated NCs and also provided enhanced antimicrobial properties, since lemongrass is known for its antimicrobial character. Fluorescence microscopy was used to optically observe the nanoparticles and NCs and revealed the attachment of lemongrass oil with the polylactic acid NCs. Dynamic light scattering was used to determine their size. UV absorption was used to determine the exact amount of lemongrass oil found in the polylactic acid—lemongrass oil NCs, which was important for understanding the minimum inhibitory concentration for the antimicrobial experiments. A series of clinically important microbial species were used in the study and the obtained NCs proved to have very good antimicrobial properties against all tested strains. Such NCs can be used for the design of ecological strategies, based on natural alternatives, which may be efficient against severe infections, including those that involve resistant pathogens and biofilms or those with difficult to reach localization.

Antimicrobial Lemongrass Essential Oil—Copper Ferrite Cellulose Acetate Nanocapsules

Cellulose acetate (CA) nanoparticles were combined with two antimicrobial agents, namely lemongrass (LG) essential oil and Cu-ferrite nanoparticles. The preparation method of CA nanocapsules (NCs), with the two antimicrobial agents, was based on the nanoprecipitation method using the solvent/anti-solvent technique. Several physical and chemical analyses were performed to characterize the resulting NCs and to study their formation mechanism. The size of the combined antimicrobial NCs was found to be ca. 220 nm. The presence of Cu-ferrites enhanced the attachment of LG essential oil into the CA matrix. The magnetic properties of the combined construct were weak, due to the shielding of Cu-ferrites from the polymeric matrix, making them available for drug delivery applications where spontaneous magnetization effects should be avoided. The antimicrobial properties of the NCs were significantly enhanced with respect to CA/LG only. This work opens novel routes for the development of organic/inorganic nanoparticles with exceptional antimicrobial activities.

New perspectives for the Silicon-On-Diamond material

A recent laser bonding technique has been developed to prepa re silicon-on-diamond material. This method allows the independent choice of the quality of t he silicon and diamond plates to be processed. This opens a wide field of applications for silico n-on-diamond devices. We present and discuss the laser technique and the experimental result s achieved. Two new projects involving relevant issues both in high energy physics and in biologica l applications are also presented.

Laser-induced disaggregation of TiO2 nanofillers for uniform nanocomposites

Exploiting the intrinsic photosensitivity of TiO₂ nanoparticles, we demonstrated how ultraviolet (UV) pulsed laser irradiation of acrylate polymer nanocomposite solutions can separate the initial clusters of these colloidal semiconductor nanorods into clearly distinct units. From the irradiated solutions, optically clear nanocomposite films are obtained which exhibit enhanced optical properties with respect to the nanocomposites obtained without previous UV treatment.

Cellulose acetate - essential oil nanocapsules with antimicrobial activity for biomedical applications

This study aimed to obtain bioactive nanosystems by combining cellulose acetate with three selected essential oils (EOs) to create spherical nanocapsules (NCs) using the solvent/anti-solvent technique. The biological activity of the obtained NCs was promoted by the use of some antimicrobial EOs: Peppermint, Cinnamon and lemongrass which were grafted on the cellulose acetate molecules. Due to their chemistry, such as long hydrocarbon tails and heads with functional groups these EOs were playing also the role of surfactant-like substance facilitating the formation of NCs. A dispersion of NCs was obtained in water and various spectroscopy techniques used to examine their size, morphology and chemistry. Dynamic light scattering calculate the size of the NCs whereas scanning electron microscopy showed their morphology. Fluorescent microscopy and Raman spectroscopy proved the attachment of the EOs in the cellulose acetate molecules. The antimicrobial activity of the obtained nanomaterials was tested against four microbial strains (bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and a yeast strain of Candida albicans). The obtained results demonstrated that such NCs can be used in a variety of applications including medical, pharmaceutical recipients and in household products for treating or preventing microbial colonization and biofilm development.

Investigation of the electro-spinnability of alginate solutions containing gold precursor HAuCl4.

Alginate nanofibers with an average diameter of 75nm have been prepared by the electrospinning process. In addition, the spinnability of the solutions in the presence of the gold precursor HAuCl4 was investigated. At low concentrations of HAuCl4 well-formed nanofibers were produced, whereas as its concentration increases the nanofibrous mats present an increased number of bead-like defects. Herein, the in situ preparation of gold nanoparticles (Au NPs) is discussed since sodium alginate (SA) acts as the reducing agent and a mechanism is proposed in order to explain the bead-effect as well as the surface morphology of the alginate fibers decorated with Au NPs.