Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces.

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70-77% and 52-75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74-88% for Pseudomonas aeruginosa and up to 86-100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40-100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80-100% for Pseudomonas aeruginosa and by about 79-100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91-100% for Pseudomonas aeruginosa and up to 95-100% for Staphylococcus aureus.

Chitosan-based films enriched by caffeic acid with poly(ethylene glycol) - A physicochemical and antibacterial properties evaluation.

In this work, chitosan/caffeic acid mixtures in the weight ratios of 80/20 and 50/50 were used to obtain thin films enriched with poly(ethylene glycol). It was hypothesized that the presence of caffeic acid indicates the antibacterial properties of the materials (i) and that poly(ethylene glycol) acts as a films modifier (ii). The results showed that by poly(ethylene glycol) addition, the surface free energy as well as mechanical and thermal properties were improved. Moreover, water vapor permeability was observed. All the tested materials showed antioxidant properties in the range of approximately 90%. They also showed antibacterial effectiveness against both Gram-positive and Gram-negative bacteria. The most appropriate material for the application as packaging was composed of chitosan and caffeic acid mixed in a 50/50 weight ratio with 20% PEG addition.

The Preparation and Characterization of Chitosan-Based Hydrogels Cross-Linked by Glyoxal.

In this study, hydrogels based on chitosan cross-linked by glyoxal have been investigated for potential medical applications. Hydrogels were loaded with tannic acid at different concentrations. The thermal stability and the polyphenol-releasing rate were determined. For a preliminary assessment of the clinical usefulness of the hydrogels, they were examined for blood compatibility and in the culture of human dental pulp cells (hDPC). The results showed that after immersion in a polyphenol solution, chitosan/glyoxal hydrogels remain nonhemolytic for erythrocytes, and we also did not observe the cytotoxic effect of hydrogels immersed in tannic acid (TA) solutions with different concentration. Tannic acid was successfully released from hydrogels, and its addition improved material thermal stability. Thus, the current findings open the possibility to consider such hydrogels in clinics.

Preparation and characterization of collagen/hyaluronic acid/chitosan film crosslinked with dialdehyde starch.

In this work thin film made from the mixture of collagen, hyaluronic acid and chitosan were obtained during solvent evaporation method. The mixtures of biopolymers were modified by dialdehyde starch, which was used as a crosslinking agent. The influence of crosslinking agent on the physico-chemical properties of polymeric matrices was evaluated. The interactions between functional groups of polymers were evaluated by Fourier transform infrared spectroscopy for both unmodified and modified samples. Mechanical properties of film were tested in dry condition using a mechanical testing machine. Morphology of the surface was studied by Atomic Force Microscopy and the roughness parameters were analyzed. Moreover, surface free energy and its polar and dispersive components were evaluated by contact angle measurements. It was found that the addition of dialdehyde starch modified all tested parameters of the studied films. Samples became less elastic and more resist for rupture. Moreover, samples became less rough after crosslinking process and surface free energy increased. Thin film made from the mixture of collagen, hyaluronic acid and chitosan crosslinked with dialdehyde starch can be applied in medicine and in cosmetics.