Bifunctional conducting polymer matrices with antibacterial and neuroprotective effects.

Current trends in the field of neural tissue engineering include the design of advanced biomaterials combining excellent electrochemical performance with versatile biological characteristics. The purpose of this work was to develop an antibacterial and neuroprotective coating based on a conducting polymer - poly(3,4-ethylenedioxypyrrole) (PEDOP), loaded with an antibiotic agent - tetracycline (Tc). Employing an electrochemical technique to immobilize Tc within a growing polymer matrix allowed to fabricate robust PEDOP/Tc coatings with a high charge storage capacity (63.65 ± 6.05 mC/cm2), drug release efficiency (629.4 µg/cm2 ± 62.7 µg/cm2), and low charge transfer resistance (2.4 ± 0.1 kΩ), able to deliver a stable electrical signal. PEDOP/Tc were found to exhibit strong antimicrobial effects against Gram-negative bacteria Escherichia coli, expressed through negligible adhesion, reduction in viability, and a characteristic elongation of bacterial cells. Cytocompatibility and neuroprotective effects were evaluated using a rat neuroblastoma B35 cell line, and were analyzed using MTT, cell cycle, and Annexin-V apoptosis assays. The presence of Tc was found to enhance neural cell viability and neurite outgrowth. The results confirmed that PEDOP/Tc can serve as an efficient neural electrode coating able to enhance charge transfer, as well as to exhibit bifunctional biological characteristics, different for eukaryotic and prokaryotic cells.

Electrically-responsive antimicrobial coatings based on a tetracycline-loaded poly(3,4-ethylenedioxythiophene) matrix.

The growth of bacteria and the formation of complex bacterial structures on biomedical devices is a major challenge in modern medicine. The aim of this study was to develop a biocompatible, conducting and antibacterial polymer coating applicable in biomedical engineering. Since conjugated polymers have recently aroused strong interest as controlled delivery systems for biologically active compounds, we decided to employ a poly(3,4-ethylenedioxythiophene) (PEDOT) matrix to immobilize a powerful, first-line antibiotic: tetracycline (Tc). Drug immobilization was carried out simultaneously with the electrochemical polymerization process, allowing to obtain a polymer coating with good electrochemical behaviour (charge storage capacity of 19.15 ± 6.09 mC/cm2) and high drug loading capacity (194.7 ± 56.2 µg/cm2). Biological activity of PEDOT/Tc matrix was compared with PEDOT matrix and a bare Pt surface against a model Gram-negative bacteria strain of Escherichia coli with the use of LIVE/DEAD assay and SEM microscopy. Finally, PEDOT/Tc was shown to serve as a robust electroactive coating exhibiting antibacterial activity.

Bacterial Surface Colonization of Sputter-Coated Platinum Films.

Due to its biocompatibility and advantageous electrochemical properties, platinum is commonly used in the design of biomedical devices, e.g., surgical instruments, as well as electro-medical or orthopedic implants. This article verifies the hypothesis that a thin layer of sputter-coated platinum may possess antibacterial effects. The purpose of this research was to investigate the adhesion and growth ability of a model strain of Gram-negative bacteria, Escherichia coli, on a surface of a platinum-coated glass slide. Although some previous literature reports suggests that a thin layer of platinum would inhibit the formation of bacterial biofilm, the results of this study suggest otherwise. The decrease in the number of bacterial cells attached to the platinum-coated glass, which was observed within first three hours of culturing, was found to be a short-time effect, vanishing after 24 h. Consequently, it was shown that a thin layer of sputter-coated platinum did not exhibit any antibacterial effect. For this reason, this study indicates an urgent need for the development of new methods of surface modification that could reduce bacterial surface colonization of platinum-based biomedical devices.

Initial stage of the biofilm formation on the NiTi and Ti6Al4V surface by the sulphur-oxidizing bacteria and sulphate-reducing bacteria.

The susceptibility to the fouling of the NiTi and Ti6Al4V alloys due to the adhesion of microorganisms and the biofilm formation is very significant, especially in the context of an inflammatory state induced by implants contaminated by bacteria, and the implants corrosion stimulated by bacteria. The aim of this work was to examine the differences between the sulphur-oxidizing bacteria (SOB) and sulphate-reducing bacteria (SRB) strains in their affinity for NiTi and Ti6Al4V alloys. The biofilms formed on alloy surfaces by the cells of five bacterial strains (aerobic SOB Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans, and anaerobic SRB Desulfovibrio desulfuricans-3 strains) were studied using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The protein concentrations in liquid media have also been analyzed. The results indicate that both alloys tested may be colonized by SOB and SRB strains. In the initial stage of the biofilm formation, the higher affinity of SRB to both the alloys has been documented. However, the SOB strains have indicated the higher (although differentiated) adaptability to changing environment as compared with SRB. Stimulation of the SRB growth on the alloys surface was observed during incubation in the liquid culture media supplemented with artificial saliva, especially of lower pH (imitated conditions under the inflammatory state, for example in the periodontitis course). The results point to the possible threat to the human health resulting from the contamination of the titanium implant alloys surface by the SOB (A. thiooxidans and A. ferrooxidans) and SRB (D. desulfuricans).

Supramolecular structure of human aortic valve and pericardial xenograft material: atomic force microscopy study.

Pericardial tissue (bovine or porcine), chemically stabilized with glutaraldehyde (GA), is widely used in cardiovascular surgery in the form of bioprosthetic valves. GA reacts with tissue proteins and creates inter- and intra-molecular cross-links, resulting in improved durability. However, tissue calcification and mechanical damage are still unresolved problems. The purpose of this study was to examine the surface topography of normal human aortic valve and GA-stabilized porcine pericardium tissue in order to gain comparative insight into supramolecular structure of both tissues. The analysis was focused on morphologic evaluation of collagen constituents of the tissues. Atomic force microscopy working in the contact mode in air was employed in the study. Considerable diversity in the spatial orientation of collagen fibrils for the human aortic valve and pericardial tissue were observed. It was found that different forms of collagen fibril packing, i.e. dense and "in phase" or loose, could have an impact on the collagen D-banding pattern. Stabilization with GA introduced significant changes in the surface topography of collagen fibrils and in their spatial organization on the tissue surface. Strong disturbance in the fibril's D-spacing was observed. It was also suggested, that the observed structural changes at the supramolecular level might make an important contribution to the progressive damage and calcification of the tissue. The presented results demonstrate that the AFM method can be useful for non-destructive structural characterization of heart valves and bioprosthetic heart valve material.

Susceptibility of Desulfovibrio desulfuricans intestinal strains to sulfasalazine and its biotransformation products.

BACKGROUND: Desulfovibrio desulfuricans intestinal bacteria may contribute to toxic hydrogen sulfide production in the human gut. Our objective was to examine whether the D. desulfuricans strains isolated from the human body are susceptible to sulfasalazine (SAS) and the products of its biotransformation, i.e. 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), in order to determine the relationship between the strains' susceptibility to SAS and their ability to reduce the azo bond within this drug. MATERIAL/METHODS: Six wild strains of D. desulfuricans (isolated from feces and biopsy specimens from patients with colitis ulcerosa, Crohn's disease, irritable bowel syndrome, colonic diverticula, primary biliary cirrhosis, or tubular adenomas of the colon) were cultured in the presence of SAS, 5-ASA, and SP. Growth inhibition coefficients were compared with coefficients of inhibition of the azo-bond reduction in SAS. RESULTS: The D. desulfuricans strains present in the human digestive tract were susceptible to a small degree to SAS and to 5-ASA and SP. CONCLUSIONS: The intestinal D. desulfuricans strains differed in their susceptibility to SAS and its biotransformation products. The strains showing higher susceptibility to SAS lost the ability to reduce the azo bond in this drug, which may be attributed to the lower metabolic activity of the bacteria. The presence of D. desulfuricans in the large intestines of patients with ulcerative colitis and the confirmed diversity of the biological activity of the isolated strains demonstrate the need for clinical examination of the role of these bacteria in the development of some inflammatory disorders.

Raman spectroscopic study of glutaraldehyde-stabilized collagen and pericardium tissue.

For the first time, Raman spectroscopy has been employed to investigate formation of cross-links in collagen and porcine pericardium tissue upon glutaraldehyde (GA) treatment. GA treatment causes a very high fluorescence background, which overlaps Raman bands. It has been found that short fixation time, i.e. 2 h, reduces background radiation significantly, providing new possibilities for studying changes in molecular structure of collagen upon GA modification. The observed changes in position and intensity of Raman bands allowed us to recognize different types of GA-collagen interactions. Strong spectral evidence has been found for the peptide contribution to the formation of the GA-collagen cross-links and for the formation of secondary amines via Schiff base intermediates, and pyridinium-type cross-links. The results also revealed that different hydration levels and a more complex structure of intact tissue in comparison to collagen preparation strongly influence the formation of a GA cross-linking network, e.g. ether-type bond is preferred to form in a less hydrated collagen preparation. Our results have shown that GA treatment causes an increase in water content of pericardium tissue and collagen.

Alteration of growth and metabolic activity of cells in the presence of propranolol and metoprolol.

Mechanisms of action at the cellular level of a variety of drugs and xenobiotics may be assessed using Chlorella vulgaris cells. Synchronous culture, which consists of cells at the same phase of development, provides the most convenient model for studying processes at the cellular level. Stability of metabolic activity of synchronously growing cells is achieved by conducting cell culturing under strictly controlled conditions. The aim of the present study was to determine to what extent propranolol and metoprolol alter the Chlorella vulgaris metabolic activity, expressed by the number of progeny cells, the culture absorbance at lambda = 680 nm and the amount of selected photosynthetic pigments (chlorophyll a, chlorophyll b, antheraxanthin, lutein, violaxanthin and beta-carotene). Three different concentrations (10(-4), 10(-5) and 10(-6) M) of propranolol and metoprolol were administered to the Chlorella vulgaris cultures. It has been demonstrated that the higher the propranolol and metoprolol concentrations (from 10(-6) M to 10(-4) M) the lower the number of progeny cells in the cultures, expressed by the lower values of division coefficient. Both the propranolol and metoprolol caused a decrease in the photosynthetic pigments production in the mother cells. This effect was more important in the propranolol-treated cultures. The higher values of photosynthetic pigments concentrations in the progeny cells grown under the presence of a drug indicate that both the drugs tested influence mainly the cell growth and in a lower manner--their metabolic activity, expressed by the production of photosynthetic pigments.