Abietic Acid as a Novel Agent against Ocular Biofilms: An In Vitro and Preliminary In Vivo Investigation

Biofilm-related ocular infections can lead to vision loss and are difficult to treat with antibiotics due to challenges with application and increasing microbial resistance. In turn, the design and testing of new synthetic drugs is a time- and cost-consuming process. Therefore, in this work, for the first time, we assessed the in vitro efficacy of the plant-based abietic acid molecule, both alone and when introduced to a polymeric cellulose carrier, against biofilms formed by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans in standard laboratory settings as well as in a self-designed setting using the topologically challenging surface of the artificial eye. These analyses were performed using the standard microdilution method, the biofilm-oriented antiseptic test (BOAT), a modified disk-diffusion method, and eyeball models. Additionally, we assessed the cytotoxicity of abietic acid against eukaryotic cell lines and its anti-staphylococcal efficacy in an in vivo model using Galleria mellonella larvae. We found that abietic acid was more effective against Staphylococcus than Pseudomonas (from two to four times, depending on the test applied) and that it was generally more effective against the tested bacteria (up to four times) than against the fungus C. albicans at concentrations non-cytotoxic to the eukaryotic cell lines and to G. mellonella (256 and 512 µg/mL, respectively). In the in vivo infection model, abietic acid effectively prevented the spread of staphylococcus throughout the larvae organisms, decreasing their lethality by up to 50%. These initial results obtained indicate promising features of abietic acid, which may potentially be applied to treat ocular infections caused by pathogenic biofilms, with higher efficiency manifested against bacterial than fungal biofilms.

Biological Activity of Poly(1,3-propanediol citrate) Films and Nonwovens: Mechanical, Thermal, Antimicrobial, and Cytotoxicity Studies

Polymers are of great interest for medical and cosmeceutical applications. The current trend is to combine materials of natural and synthetic origin in order to obtain products with appropriate mechanical strength and good biocompatibility, additionally biodegradable and bioresorbable. Citric acid, being an important metabolite, is an interesting substance for the synthesis of materials for biomedical applications. Due to the high functionality of the molecule, it is commonly used in biomaterials chemistry as a crosslinking agent. Among citric acid-based biopolyesters, poly(1,8-octanediol citrate) is the best known. It shows application potential in soft tissue engineering. This work focuses on a much less studied polyester, poly(1,3-propanediol citrate). Porous and non-porous materials based on the synthesized polyesters are prepared and characterized, including mechanical, thermal, and surface properties, morphology, and degradation. The main focus is on assessing the biocompatibility and antimicrobial properties of the materials.

Effect of Camel Peptide on the Biofilm of Staphylococcus epidermidis and Staphylococcus haemolyticus Formed on Orthopedic Implants

The increasing bacterial drug resistance and the associated challenges in the treatment of infections warrant the search for alternative therapeutic methods. Hope is placed in antimicrobial peptides, which have a broad spectrum of action and are effective against strains which are resistant to conventional antibiotics. Antimicrobial peptides are also tested for their efficacy in the treatment of infections associated with the formation of biofilm. The aim of the present study was to examine the effect of Camel peptide on S. epidermidis and S. haemolyticus adhesion to and formation of biofilm on steel cortical bone screws and also on the process of reducing mature biofilm in orthopedic implants. The tests were performed on steel implants for osteosynthesis. The MIC value and MBEC values of the peptide were determined using the microdilution method in microtiter plates. The effect of the peptide on adhesion and biofilm formation, as well as on the activity on the preformed biofilm, was evaluated using quantitative methods and confocal microscopy. The presented research results indicate that the peptide exhibits very good antimicrobial properties against the analyzed strains. Concentrations above MIC reduced biofilm in the range of 90-99%.

The effects of rotating magnetic field and antiseptic on in vitro pathogenic biofilm and its milieu

The application of various magnetic fields for boosting the efficacy of different antimicrobial molecules or in the character of a self-reliant antimicrobial agent is considered a promising approach to eradicating bacterial biofilm-related infections. The purpose of this study was to analyze the phenomenon of increased activity of octenidine dihydrochloride-based antiseptic (OCT) against Staphylococcus aureus and Pseudomonas aeruginosa biofilms in the presence of the rotating magnetic field (RMF) of two frequencies, 5 and 50 Hz, in the in vitro model consisting of stacked agar discs, placed in increasing distance from the source of the antiseptic solution. The biofilm-forming cells' viability and morphology as well as biofilm matrix structure and composition were analyzed. Also, octenidine dihydrochloride permeability through biofilm and porous agar obstacles was determined for the RMF-exposed versus unexposed settings. The exposure to RMF or OCT apart did not lead to biofilm destruction, contrary to the setting in which these two agents were used together. The performed analyses revealed the effect of RMF not only on biofilms (weakening of cell wall/membranes, disturbed morphology of cells, altered biofilm matrix porosity, and composition) but also on its milieu (altered penetrability of octenidine dihydrochloride through biofilm/agar obstacles). Our results suggest that the combination of RMF and OCT can be particularly promising in eradicating biofilms located in such areas as wound pockets, where physical obstacles limit antiseptic activity.

'Cookies on a tray': Superselective hierarchical microstructured poly(l-lactide) surface as a decoy for cells

In this research we developed a micro-sized hierarchical structures on a poly(l-lactide) (PLLA) surface. The obtained structures consist of round-shaped protrusions with a diameter of ~20 μm, a height of ~3 μm, and the distance between them ~30 μm. We explored the effect of structuring PLLA to design a non-cytotoxic material with increased roughness to encourage cells to settle on the surface. The PLLA films were prepared using the casting melt extrusion technique and were modified using ultra-short pulse irradiation - a femtosecond laser operating at λ = 1030 nm. A hierarchical microstructure was obtained resembling 'cookies on a tray'. The cellular response of fibro- and osteoblasts cell lines was investigated. The conducted research has shown that the laser-modified surface is more conducive to cell adhesion and growth (compared to unmodified surface) to such an extent that allows the formation of highly-selectively patterns consisting of living cells. In contrast to eukaryotic cells, the pathogenic bacteria Staphylococcus aureus covered modified and unmodified structures in an even, non-preferential manner. In turn, adhesion pattern of eukaryotic fungus Saccharomyces boulardii resembled that of fibro- and osteoblast cells rather than that of Staphylococcus. The discovered effect can be used for fabrication of personalized and smart implants in regenerative medicine.

Rotating Magnetic Field Increases β-Lactam Antibiotic Susceptibility of Methicillin-Resistant Staphylococcus aureus Strains

Methicillin-resistant strains of Staphylococcus aureus (MRSA) have developed resistance to most β-lactam antibiotics and have become a global health issue. In this work, we analyzed the impact of a rotating magnetic field (RMF) of well-defined and strictly controlled characteristics coupled with β-lactam antibiotics against a total of 28 methicillin-resistant and sensitive S. aureus strains. The results indicate that the application of RMF combined with β-lactam antibiotics correlated with favorable changes in growth inhibition zones or in minimal inhibitory concentrations of the antibiotics compared to controls unexposed to RMF. Fluorescence microscopy indicated a drop in the relative number of cells with intact cell walls after exposure to RMF. These findings were additionally supported by the use of SEM and TEM microscopy, which revealed morphological alterations of RMF-exposed cells manifested by change of shape, drop in cell wall density and cytoplasm condensation. The obtained results indicate that the originally limited impact of β-lactam antibiotics in MRSA is boosted by the disturbances caused by RMF in the bacterial cell walls. Taking into account the high clinical need for new therapeutic options, effective against MRSA, the data presented in this study have high developmental potential and could serve as a basis for new treatment options for MRSA infections.

Cytotoxicity Study of UV-Laser-Irradiated PLLA Surfaces Subjected to Bio-Ceramisation: A New Way towards Implant Surface Modification

In this research we subjected samples of poly(L-lactide) (PLLA) extruded film to ultraviolet (193 nm ArF excimer laser) radiation below the ablation threshold. The modified film was immersed in Simulated Body Fluid (SBF) at 37 °C for 1 day or 7 days to obtain a layer of apatite ceramic (CaP) coating on the modified PLLA surface. The samples were characterized by means of optical profilometry, which indicated an increase in average roughness (Ra) from 25 nm for the unmodified PLLA to over 580 nm for irradiated PLLA incubated in SBF for 1 day. At the same time, the water contact angle decreased from 78° for neat PLLA to 35° for irradiated PLLA incubated in SBF, which suggests its higher hydrophilicity. The obtained materials were investigated by means of cell response fibroblasts (3T3) and macrophage-like cells (RAW 264.7). Properties of the obtained composites were compared to the unmodified PLLA film as well as to the UV-laser irradiated PLLA. The activation of the PLLA surface by laser irradiation led to a distinct increase in cytotoxicity, while the treatment with SBF and the deposition of apatite ceramic had only a limited preventive effect on this harmful impact and depended on the cell type. Fibroblasts were found to have good tolerance for the irradiated and ceramic-covered PLLA, but macrophages seem to interact with the substrate leading to the release of cytotoxic products.

The Effect of Pore Size Distribution and l-Lysine Modified Apatite Whiskers (HAP) on Osteoblasts Response in PLLA/HAP Foam Scaffolds Obtained in the Thermally Induced Phase Separation Process

In this research, we prepared foam scaffolds based on poly(l-lactide) (PLLA) and apatite whiskers (HAP) using thermally induced phase separation technique supported by the salt leaching process (TIPS-SL). Using sodium chloride having a size of (a) 150-315 μm, (b) 315-400 μm, and (c) 500-600 μm, three types of foams with different pore sizes have been obtained. Internal structure of the obtained materials has been investigated using SEM as well as μCT. The materials have been studied by means of porosity, density, and compression tests. As the most promising, the composite prepared with salt size of 500-600 μm was prepared also with the l-lysine modified apatite. The osteoblast hFOB 1.19 cell response for the scaffolds was also investigated by means of cell viability, proliferation, adhesion/penetration, and biomineralization. Direct contact cytotoxicity assay showed the cytocompatibility of the scaffolds. All types of foam scaffolds containing HAP whiskers, regardless the pore size or l-lysine modification induced significant stimulatory effect on the cal-cium deposits formation in osteoblasts. The PLLA/HAP scaffolds modified with l-lysine stimulated hFOB 1.19 osteoblasts proliferation. Compared to the scaffolds with smaller pores (150-315 µm and 315-400 µm), the PLLA/HAP foams with large pores (500-600 µm) promoted more effective ad-hesion of osteoblasts to the surface of the biomaterial.

Biological evaluation of selective laser melted magnesium alloy powder

Purpose: The current study examined magnesium alloy AZ31B specimens manufactured with Additive Manufacturing method (selective laser melting – SLM) to investigate the applicability of this technology for the production of medical devices. Methods: Osteoblast cells and bacterial biofilm growth ability on specimen was examined and the effect of surface state on corrosion resistance was evaluated by electrochemical and immersion methods. Results: High survival of hFOB cells, as well as a strong tendency for Pseudomonas aeruginosa and Staphylococcus aureus biofilm proliferation on the surface of the tested specimens were shown. SLM-processed AZ31B alloy has a higher corrosion resistance in 0.9% NaCl solution and in a multi-electrolyte saline solution than the material in a conventional form of a rolled sheet. Conclusions: It has been demonstrated that the strong development of the surface of as-built processed specimens results in a significantly increased corrosion rate, which hinders the production of complex structures in tissue engineering products that support cell ingrowth.