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Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA. [ABSTRACT FROM AUTHOR]

Research has been conducted on Enterococcus faecalis ATCC 29212. The role of serum in physicochemical surface properties and adhesion of this bacterium to silicon and glass has been investigated, and the results are reported.

High temperatures cause greater adhesion of Candida parapsilosis to polystyrene, according to researchers who tested adhesion at 22 degrees C. and 37 degrees C. This organism causes infections in hospital patients because it adheres to the plastic tubes and catheters used in most hospitals.

Surface electrical characterization of metals and semiconductors with extensive geometry continues to be of interest. This work explores the electrical information that can be extracted from the electrokinetic (zeta) potential of metallic surfaces, and proposes an analytical model based on streaming potential/current data. In particular, our study focuses on the alloy Ti6Al4V, which is capable of modifying its surface electrical properties after excitation with ultraviolet irradiation due to the semiconductor properties of its TiO2 passivation layer. Evidence is presented for the first time of electronic activity inside the passivation layer following UV excitation. Charge displaced through sample (Q), electrons density (evol), surface charge density (s) and current density (J) are extracted from the proposed model. The amount of displaced charge through Ti6Al4V disks not exposed to UV irradiation was similar to that displaced inside the thin TiO2 excited layer. Relative conductivity of the TiO2 excited layer versus Ti6Al4V showed a difference of up to five orders of magnitude between the two samples. The model is suitable for application to any metal and any excited semiconductor, thus increasing the usefulness of electrokinetic characterization based on streaming potential/current measurements. [ABSTRACT FROM AUTHOR]

Controlling initial bacterial adhesion is essential to prevent biofilm formation and implant-related infection. The search for surface coatings that prevent initial adhesion is a powerful strategy to obtain implants that are more resistant to infection. Tracking the progression of adhesion on surfaces from the beginning of the interaction between bacteria and the surface provides a deeper understanding of the initial adhesion behavior. To this purpose, we have studied the progression over time of bacterial adhesion from a laminar flow of a bacterial suspension, using a modified Robbins device (MRD). Comparing with other laminar flow devices, such as the parallel plate flow chamber, MRD allows the use of diverse substrata under the same controlled flow conditions simultaneously. Two different surfaces of Ti6Al4V and two strains of Staphylococcus epidermidis with different exopolymer production were tested. In addition, the modified Robbins device was examined for its convenience and suitability for the purpose of this study. Results were analyzed according to a pseudofirst order kinetic. The values of the parameters obtained from this model make it possible to discriminate the adhesive behavior of surfaces and bacteria. One of the fitting parameters depends on the bacterial strain and the other only on the surface properties of the substrate. [ABSTRACT FROM AUTHOR]

In this work, we investigated a new approach to incorporate Mg particles within a PDLLA matrix using a solvent-free commercially available process. PDLLA/Mg composites were manufactured by injection moulding and the effects of Mg incorporated into PDLLA on MSC and macrophage responses were evaluated. Small amounts of Mg particles (≤1 wt %) do not cause thermal degradation of PDLLA, which retains its mechanical properties. PDLLA/Mg composites release hydrogen, alkaline products and Mg2+ ions without changing pH of culture media. Mg-containing materials provide a noncytotoxic environment that enhances MSC viability. Concentration of Mg2+ ions in extracts of MSCs increases with the increment of Mg content in the composites. Incorporation of Mg particles into PDLLA stimulates FN production, ALP activity, and VEGF secretion in MSCs, an effect mediated by degradation products dissolved from the composites. Degradation products of PDLLA induce an increase in MCP-1, RANTES, and MIP-1α secretion in macrophages while products of composites have minimal effect on these chemokines. Regulation of MSC behavior at the biomaterial's interface and macrophage-mediated inflammatory response to the degradation products is related to the incorporation of Mg in the composites. These findings suggest that including small amounts of Mg particles into polymeric devices can be a valuable strategy to promote osseointegration and reduce host inflammatory response. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 866-878, 2016. [ABSTRACT FROM AUTHOR]

Biomaterial implant-associated infections, a common cause of medical devices' failure, are initiated by bacterial adhesion to an adsorbed protein layer on the implant material surface. In this study, the influence of protein surface orientation on bacterial adhesion has been examined using three clinically relevant bacterial strains known to express specific binding sites for human plasma fibronectin (HFN). HFN was allowed to adsorb on hydrophobic Ti6Al4V and physically modified hydrophilic Ti6Al4V substrata. Ellipsometric data reveal that the characteristics of the adsorbed protein layers primary depend on solid surface tension and the initial protein concentration in solution. In particular, HFN molecules adopt a more extended conformation on hydrophobic than hydrophilic surfaces, an effect that is more pronounced at low than at high initial protein concentrations. Moreover, the extended conformation of the protein molecules on these surfaces likely facilitates the exposure of specific sites for adhesion, resulting in the higher bacterial-cell attachment observed regardless of the strain considered. Contact angle measurements and the analysis of the number of remaining adhering cells after being subjected to external forces further suggest that both specific and nonspecific (hydrophobic) interactions play an important role on bacterial attachment. This study is the first one to evaluate the influence of surface hydrophobicity on protein adsorption and its subsequent effect on bacterial adhesion using a material whose hydrophobicity was not modified using chemical treatments that potentially led to surface properties changes other than hydrophobicity. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

The effects of growth in the presence of sub-inhibitory concentrations of ampicillin and vancomycin on physico-chemical cell surface properties of Enterococcus faecalis 1131 have been determined. Growth in the presence of antibiotics yielded increased exposure of nitrogen and oxygen at the cell surface, proportional to the amount of antibiotic added to the growth medium, probably as a result of progressive removal of lipoteichoic acid (LTA) by ampicillin and vancomycin. Bacterial isoelectric points (IEP''s), derived from particulate microelectrophoresis at different suspension pH, increased concurrently. Water contact angles on bacterial lawns only varied slightly in the presence of antibiotic during growth, whereas formamide contact angles after growth in the presence of vancomycin were significantly higher than after growth in the absence of this antibiotic, yielding a strongly electron-donating character of the cell surface. Surface thermodynamical analyses indicated favourable conditions for adhesion to hexadecane and chloroform, but more negative values of interaction free energies did not necessarily coincide with increased adhesion. Bacterial adhesion to hexadecane and chloroform increased when the pH of the bacterial suspension approached the isoelectric point of the organisms, because of the minimal electrostatic interactions. [Copyright &y& Elsevier]