Patrycja Szymczyk

Efficacy of antiseptics containing povidone‐iodine, octenidine dihydrochloride and ethacridine lactate against biofilm formed by Pseudomonas aeruginosa and Staphylococcus aureus measured with the novel biofilm‐oriented antiseptics test

Increasing data suggesting that microorganisms in the biofilm form are among the leading agents of persistent infections of chronic wounds require the development of new approaches to treatment. The aim of this article was to compare the efficacy of three commonly used antiseptics using a biofilm‐oriented approach. Biofilm‐oriented antiseptics test (BOAT), the innovative method, allows to estimate, in a quick and reliable manner, the in vitro activity of working solutions of antiseptics in real contact times against bacteria in the biofilm form and to use the results in the selection of an appropriate antiseptic to treat local infections in the clinical practice.

Modification of bacterial cellulose through exposure to the rotating magnetic field

The aim of the study was to assess the influence of rotating magnetic field (RMF) on production rate and quality parameters of bacterial cellulose synthetized by Glucanacetobacter xylinus. Bacterial cultures were exposed to RMF (frequency f=50Hz, magnetic induction B=34mT) for 72h at 28°C. The study revealed that cellulose obtained under RMF influence displayed higher water absorption, lower density and less interassociated microfibrils comparing to unexposed control. The application of RMF significantly increased the amount of obtained wet cellulose pellicles but decreased the weight and thickness of dry cellulose. Summarizing, the exposure of cellulose-synthesizing G. xylinus to RMF alters cellulose biogenesis and may offer a new biotechnological tool to control this process. As RMF-modified cellulose displays better absorbing properties comparing to non-modified cellulose, our finding, if developed, may find application in the production of dressings for highly exudative wounds.

Bisphosphonates enhance bacterial adhesion and biofilm formation on bone hydroxyapatite.

BACKGROUND Because of the suspicion that bisphosphonates enhance bacterial colonization, this study evaluated adhesion and biofilm formation by Streptococcus mutans 25175, Staphylococcus aureus 6538, and Pseudomonas aeruginosa 14454 reference strains on hydroxyapatite coated with clodronate, pamidronate, or zoledronate. MATERIAL AND METHODS Bacterial strains were cultured on bisphosphonate-coated and noncoated hydroxyapatite discs. After incubation, nonadhered bacteria were removed by centrifugation. Biofilm formation was confirmed by scanning electron microscopy. Bacterial colonization was estimated using quantitative cultures compared by means with Kruskal-Wallis and post-hoc Student-Newman-Keuls tests. Modeling of the interactions between bisphosphonates and hydroxyapatite was performed using the Density Functional Theory method. RESULTS Bacterial colonization of the hydroxyapatite discs was significantly higher for all tested strains in the presence of bisphosphonates vs. CONTROLS Adherence in the presence of pamidronate was higher than with other bisphosphonates. Density Functional Theory analysis showed that the protonated amine group of pamidronate, which are not present in clodronate or zoledronate, forms two additional hydrogen bonds with hydroxyapatite. Moreover, the reactive cationic amino group of pamidronate may attract bacteria by direct electrostatic interaction. CONCLUSION Increased bacterial adhesion and biofilm formation can promote osteomyelitis, cause failure of dental implants or bisphosphonate-coated joint prostheses, and complicate bone surgery in patients on bisphosphonates.

Microbial biofilms are able to destroy hydroxyapatite in the absence of host immunity in vitro.

PURPOSE It is widely thought that inflammation and osteoclastogenesis result in hydroxyapatite (HA) resorption and sequestrum formation during osseous infections, and microbial biofilm pathogens induce the inflammatory destruction of HA. We hypothesized that biofilms associated with infectious bone disease can directly resorb HA in the absence of host inflammation or osteoclastogenesis. Therefore we developed an in vitro model to test this hypothesis. MATERIALS AND METHODS Customized HA discs were manufactured as a substrate for growing clinically relevant biofilm pathogens. Single-species biofilms of Streptococcus mutans, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans and mixed-species biofilms of C albicans plus S mutans were incubated on HA discs for 72 hours to grow mature biofilms. Three different non-biofilm control groups also were established for testing. HA discs were then evaluated by means of scanning electron microscopy, micro-computed tomography metrotomography, x-ray spectroscopy, and confocal microscopy with planimetric analysis. In addition, quantitative cultures and pH assessment were performed. Analysis of variance was used to test for significance between treatment and control groups. RESULTS All investigated biofilms were able to cause significant (P < .05) and morphologically characteristic alterations in HA structure as compared with controls. The highest number of alterations observed was caused by mixed biofilms of C albicans plus S mutans. S mutans biofilm incubated in medium with additional sucrose content was the most detrimental to HA surfaces among single-species biofilms. CONCLUSIONS Our findings suggest that direct microbial resorption of bone is possible in addition to immune-mediated destruction, which has important translational implications for the pathogenesis of chronic bone infections and for targeted antimicrobial therapeutics.

Preparation and Properties of Polymer Composites Filled with Low Melting Metal Alloys

Composites of polymers and low melting point metal alloys are little known classes of materials. In this work thermoplastic composites filled with differing contents of Woods metal or Cerromatrix alloys have been studied in respect to their microstructure, mechanical, thermal, and electrical properties. It was found that the type of filler employed had significant influence only on the mechanical and thermal properties of composites. The results of volume resistivity show that all composites conduct electrical current well, even when metal loading is below 10vol.%. Low percolation threshold is caused by a unique interpenetrating network structure created by polymer and metal co-continuous phases.

Increased water content in bacterial cellulose synthesized under rotating magnetic fields

ABSTRACT The current study describes properties of bacterial cellulose (BC) obtained from Komagataeibacter xylinus cultures exposed to the rotating magnetic field (RMF) of 50 Hz frequency and magnetic induction of 34 mT for controlled time during 6 days of cultivation. The experiments were carried out in the customized RMF exposure system adapted for biological studies. The obtained BC displayed an altered micro-structure, degree of porosity, and water-related parameters in comparison to the non-treated, control BC samples. The observed effects were correlated to the duration and the time of magnetic exposure during K. xylinus cultivation. The most preferred properties in terms of water-related properties were found for BC obtained in the setting, where RMF generator was switched off for the first 72 h of cultivation and switched on for the next 72 h. The described method of BC synthesis may be of special interest for the production of absorbent, antimicrobial-soaked dressings and carrier supports for the immobilization of microorganisms and proteins.

Increased yield and selected properties of bacterial cellulose exposed to different modes of a rotating magnetic field

Rotating magnetic field (RMF) is an interesting alternative to conventional bacterial cellulose (BC) production methods. The BC synthesis processes may be affected by RMF, which facilitates the transfer of oxygen and nutrients from the media to the microbial cells. RMF may also directly influence the various physical and chemical properties of BC. The main aim of the present study was to evaluate the impact of the RMF on the BC in regard to its yield and material properties. The correlation between the efficiency of polymer production and the different time of exposure to the RMF was also analyzed to determine the conditions of lower energy consumption during the cellulose formation process. It was found that the Gluconacetobacter xylinus cultures exposed to the RMF for a half of the time of the entire cellulose production process (72 h), considering the results obtained in controls, synthesized BC more effectively than bacteria continuously exposed to the RMF for 144 h. Furthermore, the application of the RMF, regardless of the exposure mode, did not negatively affect the polymer material properties. It was concluded that the use of the RMF may provide a novel technique for altering cellulose biogenesis and may be used in multiple biotechnological applications.

Composite Laser-Clad Coating on Titanium Substrate Using Pure Hydroxyapatite Powder

Biocomposite (or bioceramic) materials have become very popular, especially for replacing some human bone parts, such as hip joints, knee joints, and producing implants for dentistry and others. It is supposed that cladding coatings with hydroxyapatite (HA) on a metallic substrate could be a good solution for implants. Production of laser cladding coatings using pure HA powder and titanium substrate is investigated.

Application of Ti6Al7Nb Alloy for the Manufacture of Biomechanical Functional Structures (BFS) for Custom-Made Bone Implants

Unlike conventional manufacturing techniques, additive manufacturing (AM) can form objects of complex shape and geometry in an almost unrestricted manner. AM’s advantages include higher control of local process parameters and a possibility to use two or more various materials during manufacture. In this work, we applied one of AM technologies, selective laser melting, using Ti6Al7Nb alloy to produce biomedical functional structures (BFS) in the form of bone implants. Five types of BFS structures (A1, A2, A3, B, C) were manufactured for the research. The aim of this study was to investigate such technological aspects as architecture, manufacturing methods, process parameters, surface modification, and to compare them with such functional properties such as accuracy, mechanical, and biological in manufactured implants. Initial in vitro studies were performed using osteoblast cell line hFOB 1.19 (ATCC CRL-11372) (American Type Culture Collection). The results of the presented study confirm high applicative potential of AM to produce bone implants of high accuracy and geometric complexity, displaying desired mechanical properties. The experimental tests, as well as geometrical accuracy analysis, showed that the square shaped (A3) BFS structures were characterized by the lowest deviation range and smallestanisotropy of mechanical properties. Moreover, cell culture experiments performed in this study proved that the designed and obtained implant’s internal porosity (A3) enhances the growth of bone cells (osteoblasts) and can obtain predesigned biomechanical characteristics comparable to those of the bone tissue.

Bad to the Bone: On In Vitro and Ex Vivo Microbial Biofilm Ability to Directly Destroy Colonized Bone Surfaces without Participation of Host Immunity or Osteoclastogenesis.

Bone infections are a significant public health burden associated with morbidity and mortality in patients. Microbial biofilm pathogens are the causative agents in chronic osteomyelitis. Research on the pathogenesis of osteomyelitis has focused on indirect bone destruction by host immune cells and cytokines secondary to microbial insult. Direct bone resorption by biofilm pathogens has not yet been seriously considered. In this study, common osteomyelitis pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Streptococcus mutans) were grown as biofilms in multiple in vitro and ex vivo experiments to analyze quantitative and qualitative aspects of bone destruction during infection. Pathogens were grown as single or mixed species biofilms on the following substrates: hydroxyapatite, rat jawbone, or polystyrene wells, and in various media. Biofilm growth was evaluated by scanning electron microscopy and pH levels were monitored over time. Histomorphologic and quantitative effects of biofilms on tested substrates were analyzed by microcomputed tomography and quantitative cultures. All tested biofilms demonstrated significant damage to bone. Scanning electron microscopy indicated that all strains formed mature biofilms within 7 days on all substrate surfaces regardless of media. Experimental conditions impacted pH levels, although this had no impact on biofilm growth or bone destruction. Presence of biofilm led to bone dissolution with a decrease of total volume by 20.17±2.93% upon microcomputed tomography analysis, which was statistically significant as compared to controls (p <0.05, ANOVA). Quantitative cultures indicated that media and substrate did not impact biofilm formation (Kruskall-Wallis test, post-hoc Dunne’s test; p <0.05). Overall, these results indicate that biofilms associated with osteomyelitis have the ability to directly resorb bone. These findings should lead to a more complete understanding of the etiopathogenesis of osteomyelitis, where direct bone resorption by biofilm is considered in addition to the well-known osteoclastic and host cell destruction of bone.