Innovative Anodic Treatment to Obtain Stable Metallic Silver Micropatches on TiO2 Nanotubes: Structural, Electrochemical, and Photochemical Properties.

Electrochemical modification of the Ti surface to obtain TiO2 nanotubes (NT-Ti) has been proposed to enhance osseointegration in medical applications. However, susceptibility to microbial adhesion, linked to biomaterial-associated infections, and the high TiO2 band gap energy, which allows light absorption almost exclusively in the ultraviolet (UV) region, limit its applications. Modifying the TiO2 semiconductor with metals such as Ag has been suggested both for antimicrobial purposes and for absorbing light in the visible region. The formation of NT-Ti with Ag micropatches (Ag-NT-Ti) is pursued with the objective of enhancing the stability of the deposits and preventing cytotoxic levels of Ag cellular uptake. The innovative process proposed here involves immersing NT-Ti in a AgNO3 solution as the initial step. Diverging from previously reported electrochemical methods, this process incorporates anodization within the TiO2 oxide formation region instead of cathodic reduction generally employed by other researchers. The final step encompasses an annealing treatment. The treatments result in the in situ Ag1+ reduction and formation of stable and active micropatches of metallic Ag on the NT-Ti surface. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman, diffuse reflectance spectroscopy (DRS), wettability assessment, and electrochemical characterizations were conducted to evaluate the modified surfaces. The well-known properties of NT-Ti surfaces were enhanced, leading to improved photocatalytic activity across both visible and UV regions, significant stability against detachment, and controlled release of Ag1+ for promising antimicrobial effects.

Patient-reported outcome measures after periodontal surgery.

OBJECTIVES: The present study aimed to explore the impact of different periodontal surgical treatments on the quality of life and postoperative morbidity. MATERIALS AND METHODS: The present study is a single-center, prospective, observational cohort trial. One hundred fifty-five patients, referred to the Periodontal Department of Bologna University who needed periodontal surgical treatment, were recruited. The self-reported perception of the postoperative course was assessed using the following anonymous questionnaires: Italian oral health impact profile (I-OHIP-14), visual analog scale (VAS) to evaluate the intensity of the pain, and 5-point Likert scale. RESULTS: Patients reported a mean OHIP-14 total score of 9.87±8.5 (range 0-42), significantly influenced by the female sex, flap extension, and periodontal dressing. A mean VAS score of 2.96±2.39 (range 0-9) was calculated, and was found to be influenced by the presence of vertical releasing incisions and palatal flap extension. Of the 155 subjects, 40 (25.8%) patients reported bleeding as a post-surgical complication, 96 (61.9%) swelling, 105 (67.7%) eating discomfort, and 44 (28.4%) reported speech discomfort. CONCLUSIONS: Within the limitations of the nature of the present study, periodontal surgical procedures have a low impact on patients' quality of life evaluated through the OHIP-14 and VAS pain questionnaires. CLINICAL RELEVANCE: Periodontal surgical procedures are safe procedures, with a limited duration of postoperative discomfort as well as the incidence of complications.

Complications and treatment errors in root coverage procedures.

Root coverage procedures have become very common in clinical dental practice. Even though these techniques are considered safe, the clinician may face several issues during the therapy due to their surgical nature. Some of these issues can be defined strictly as complications inherent to the procedure, whereas others are medical errors or treatment errors. This review will focus on describing treatment errors and complications that may arise during different phases of the root coverage therapeutic process and on how to prevent and manage them.

Different Impact of Suspended Al2O3 Nanoparticles on Microbial Communities: Formation of 2D-Networks (Without Humic Acids) or 3D-Colonies (With Humic Acids).

The use of metal-based and, particularly, Al2O3 nanoparticles (Al2O3-NP) for diverse purposes is exponentially growing. However, the growth of such promissory market is not accompanied by a parallel extensive investigation related to the impact of this pollution on groundwater and biological systems. Pseudomonas species, ubiquitous, environmentally critical microbes, frequently respond to stress conditions with diverse strategies that generally include extracellular polymeric substances (EPS) formation. The aim of this study is to report that changes in the aqueous environment, particularly, the addition of Al2O3-NP without and with humic acids, induce different adaptive strategies of Pseudomonas aeruginosa early biofilms. To this purpose, early biofilms were incubated in diluted culture media without (control) and with Al2O3-NP, and with humic acids (HA-control, HA-Al2O3-NP) for 24 h. 3D colonies with EPS strings and isolated bacteria in their surroundings were detected in the control biofilms. Unlikely, an unusual adaptive behaviour was developed in the presence of Al2O3-NP. Bacteria opt to disassemble the 3D arrangements and to implement a 2D network promoting morphological and size changes of bacterial cells (small coccoid shapes). Remarkably, this strategy allows their temporarily non-EPS-depending survival without decreasing the number of cells. This behaviour was not observed with ZnO-NP, HA-Al2O3-NP, or HA-ZnO-NP. Physicochemical analysis revealed that HA were adsorbed on Al2O3-NP and promoted the Al(III) ions complexation. This supports the hypothesis that the reduction of toxicity of Al ions and the 3D colony formation in the presence of HA-Al2O3-NP is promoted by the complexation of the metal ions with HA components.

Vertically Coronally Advanced Flap (V-CAF) to Increase Vestibule Depth in Mandibular Incisors.

Treatment of gingival recessions affecting mandibular incisors is scarcely documented. Despite a shallow vestibule depth being considered a poor anatomical condition, it has never been measured nor deemed a clinical parameter affecting the outcome of root coverage procedures. This study describes a vertically and coronally advanced flap (V-CAF) + connective tissue graft (CTG) technique to obtain root coverage and increased vestibule depth in the treatment of gingival recessions affecting mandibular incisors. Twenty patients with single gingival recessions were treated. The results showed that V-CAF+CTG is effective in increasing residual vestibule depth and in reducing recession depth. Immediately after surgery, a vestibule-depth increase of 5.9 ± 1.2 mm was reported, which was statistically significant compared to baseline, and it remained stable after 12 months (4.8 ± 1.1 mm). The mean percentage of root coverage was 98.3% ± 5.2% for all treated recessions, and complete root coverage (CRC) was achieved in 90% of cases (18 of 20). V-CAF+CTG could be considered a successful technique in terms of vestibule depth increase and CRC for the treatment of single gingival recessions in the mandibular incisors.

Environmentally Induced Changes of Commercial Carbon Nanotubes in Aqueous Suspensions. Adaptive Behavior of Bacteria in Biofilms.

The effects of environmental factors such as sunlight irradiation and the presence of humic acid (HA) on the physicochemical properties of commercial multiwall carbon nanotubes (MWCNT) suspended in a simulated inorganic matrix (SIM) and their impacts on bacteria growing in biofilms were evaluated. Both solar irradiation and the presence of HA lead to the dissolution of adsorbed metals on the MWCNT, which are residues of synthesis catalysts. Also, preferential adsorption of certain HA components on the MWCNT induces important modifications in the aliphatic/aromatic relationship of HA components in solution and the generation and release of new moieties. Results demonstrated that the variation of such physicochemical parameters strongly affects the interactions of MWCNT with Pseudomonas aeruginosa sessile bacteria. Thus, the number of attached bacteria increased, and stress responses such as decrease in bacterial size were found in the presence of sunlight-irradiated MWCNT with a particular distribution of extracellular polymeric substances (EPS) strands. A shielding effect was observed when HA was added. It was concluded that physicochemical alterations caused by environmental conditions (with/without irradiation, presence/absence of HA) on MWCNT-containing SIM trigger distinctive adaptive behavior of bacteria in biofilms. This information must be taken into account in the development of biologically assisted treatments for organic metal co-contamination of MWCNT-containing media since MWCNT discharge alters the physicochemical properties and composition of the aqueous environment and the response of the biofilms that interact with it.

Staphylococcus aureus biofilm eradication by the synergistic effect exerted by PEG-coated silicon dots immobilized in silica films and light irradiation.

Immobilization of PEG-covered silicon dots, PEGSiDs, on glass substrates was performed following a simple strategy involving particle embedding by a sol-gel process forming a silica film on glass slides. The obtained films, denoted as fSiO x -PEGSiD, constitute a water-wettable, strongly supported, photoluminescent glass coating. The films showed high capacity for photosensitizing singlet oxygen (1O2) in the UVA when immersed in water. Staphylococcus aureus colonies formed on fSiO x -PEGSiDs modified glasses revealed the inhibition of bacterial adhesion and bacterial growth leading to the formation of loosely-packed and smaller S. aureus colonies. Upon 350 nm light irradiation of the biofilmed fSiO x -PEGSiDs -modified glasses, S. aureus growth was inhibited and bacteria killed reducing the number of living bacteria by three orders of magnitude. Eradication of attached bacteria was achieved by the synergistic effect exerted by a less adherent fSiO x -PEGSiDs surface that inhibits biofilm formation and the ability of the surface to photosensitize 1O2 to kill bacteria.

Effect of degradation products of iron-bioresorbable implants on the physiological behavior of macrophages in vitro.

The degradation of bioresorbable metals in vivo changes the physicochemical properties in the environment of an implant, such as a stent in the artery wall, and may induce the alteration of the functions of the surrounding cells. The Fe-degradation, from bioresorbable stents, is a particularly intricate process because it leads to the release of soluble (SDP) and insoluble degradation products (IDP) of varied composition. Macrophages are involved in the resorption of the exogenous agents coming from degradation of these materials. In the present work an Fe0 ring, made with a pure Fe wire, in contact with macrophage cell cultures was used to simulate the behaviour of a biodegradable Fe-based implant in a biological environment. Non-invasive time-lapse optical microscopy was applied to obtain images of macrophages exposed to Fe-degradation products, without using staining to avoid distortions and artefacts. It was noticed that as metal degraded, the IDP formed in situ accumulated close to the Fe0 ring. In this zone, the macrophages showed a dynamic process of uptake of dark Fe-containing products, confirmed by SEM-EDX. These macrophages showed alterations in the morphology and decrease in the motility and viability. The inability of the macrophages to move and to degrade the engulfed products caused a long persistence of IDP in the zone closest to the metal. The deleterious effects of IDP accumulated close to the ring, were significantly worse than those observed in the experiments made with (1) concentrated salt solutions (Fe3+ salt 3 mM), with the same amount of precipitates but uniformly distributed in the well, and (2) diluted salt solutions (Fe3+ salt 1 mM) with mainly soluble species. The results were confirmed by standard staining protocols that revealed dead cells close to the Fe0 ring and oxidative stress in cells exposed to both soluble and insoluble species.

Characterization and antimicrobial effect of a bioinspired thymol coating formed on titanium surface by one-step immersion treatment.

OBJECTIVE: To develop an antimicrobial and anti-adherent thymol (TOH)-containing coating on titanium (Ti) by a bioinspired one-step biocompatible method. METHODS: A nanolayer of adsorbed TOH (TOH-NL-Ti) was formed by an easy deep coating method on Ti surface. The treatment consists in a simple one-step immersion process in a TOH-containing solution. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), potentiodynamic electrochemical technique, open circuit potential records, Atomic Force Microscopy (AFM) and measurements of TOH release were used to characterize TOH-NL-Ti. Live/Dead staining and plate counting were employed to quantify attached and living adhered bacteria, respectively. Biocompatibility and cytotoxicity in fibroblastic and pre-osteoblastic cell lines were evaluated by acridine orange staining and MTT assay, respectively. RESULTS: TOH adsorbed on TOH-NL-Ti was detected by ATR-FTIR and electrochemical techniques. ATR-FTIR results showed that TOH nanofilms development involves spontaneous production of ketonic structures on Ti surface. AFM analysis revealed that the thickness of the TOH-NL was below 80 nm. Finally, microbiological assays confirmed that TOH-NL-Ti can inhibit the adhesion and kill attached bacteria leading to the eradication of leaving cells on its surface. After 24 h of biocidal release, the antimicrobial effect is also significant (a decrease of 3 orders in the number of attached bacteria). SIGNIFICANCE: The formation of TOH-NL-Ti nanolayer is a simple strategy able to be applied by not specially trained personnel, to reduce implant infection risks, ensure highly effective antimicrobial action and inhibition of bacterial adhesion on Ti surfaces without showing toxic effects for pre-osteoblastic and fibroblastic cells.

Synergistic effect of carboxypterin and methylene blue applied to antimicrobial photodynamic therapy against mature biofilm of Klebsiella pneumoniae.

The control of multidrug-resistant (MDR) bacteria is a growing public health problem, and new strategies are urgently needed for the control of the infections caused by these microorganisms. Notoriously, some MDR microorganisms generate complex structures or biofilms, which adhere to surfaces and confer extraordinary resistance properties that are fundamental challenges to control infections. One of the promising strategies for the control of MDR bacteria is antimicrobial photodynamic therapy (aPDT), which takes advantage of suitable photosensitizers (PS), oxygen and radiation to eradicate microorganisms by the generation of highly reactive species, including reactive oxygen species (ROS) that cause cytotoxic damage and cell death. Habitual aPDT treatments use only methylene blue (MB), but MDR microorganism eradication is not completely achieved. The key result of this study revealed that a combination of two known PSs, 6-carboxypterin (Cap, 100 µM) and MB (2.5-10 µM) exposed to ultraviolet and visible radiation, presents a synergistic effect on the eradication of a MDR Klebsiella pneumoniae strain. Similar effect was observed when the treatment was performed either with planktonic or biofilm growing cells. Moreover, it was found that after treatment the killing action continues in the absence of irradiation leading to the eradication of the microorganisms growing in biofilm. Therefore, the combined aPDT represents a promising strategy for the management of clinical contact surfaces, disinfection of surgical instruments, biofouling and even antimicrobial wastewater treatment.

Comparative study of transdermal drug delivery systems of resveratrol: High efficiency of deformable liposomes.

Trans-resveratrol (3, 5, 4' trihydroxystilbene, RSV) is a natural compound that shows antioxidant, cardioprotective, anti-inflammatory and anticancer properties. The transdermal, painless application of RSV is an attractive option to other administration routes owing to its several advantages like avoiding gastrointestinal problems and first pass metabolism. However, its therapeutic potential is limited by its low solubility and low stability in water and the reduced permeability of stratum corneum. To overcome these inconveniences the encapsulation of this compound in a drug delivery system is proposed here. In order to find the best carrier for transdermal application of RSV various liposomal nanoparticulate carriers like conventional liposomes (L-RSV), deformable liposomes (LD-RSV), ultradeformable liposomes (LUD-RSV) and ethosomes (Etho-RSV) were assayed. Transmission electron microscopic (TEM) and dynamic light scattering (DLS) studies were performed to analyze the surface morphology of these carriers. Structural characterization for these formulations was performed by confocal Raman spectroscopy. The spectroscopic results were analysed in conjunction with calorimetric data to identify the conformational changes and stability of formulations in the different nanoparticles induced by the presence of RSV. Comparison of the results obtained with the different carrier systems (L-RSV, LD-RSV, LUD-RSV and Etho-RSV) revealed that the best RSV carrier was LD-RSV. The increase in the fluidity of the bilayers in the region of the hydrophobic chains of the phospholipid by ethanol probably facilitates the accommodation of the RSV in the bilayer and contributes to the improved encapsulation of RSV without affecting the mobility of this carrier.

Esthetic treatment of altered passive eruption.

Altered passive eruption is described as a condition in which the relationship between teeth, alveolar bone and soft tissues creates an excessive display of gingiva, commonly known as a 'gummy smile'. While there are authors who consider altered passive eruption to be a risk to periodontal health, its impact is greatest in terms of oral esthetics. The aim of periodontal management in such cases is not only to improve patient esthetics but also to restore periodontal health by re-establishing the normal relationship between the gingival margin, alveolar bone crest and cemento-enamel junction. The aim of this article is to present a narrative review of the etiology, classification and management of altered passive eruption.

Self-sterilizing ormosils surfaces based on photo-synzthesized silver nanoparticles.

Medical device-related infections represent a major healthcare complication, resulting in potential risks for the patient. Antimicrobial materials comprise an attractive strategy against bacterial colonization and biofilm proliferation. However, in most cases these materials are only bacteriostatic or bactericidal, and consequently they must be used in combination with other antimicrobials in order to reach the eradication condition (no viable microorganisms). In this study, a straightforward and robust antibacterial coating based on Phosphotungstate Ormosil doped with core-shell (SiO2@TiO2) was developed using sol-gel process, chemical tempering, and Ag nanoparticle photoassisted synthesis (POrs-CS-Ag). The coating was characterized by X-ray Fluorescence Spectroscopy (XRF), Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Microscopy (XPS). The silver free coating displays low antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, in opposition to the silver loaded ones, which are able to completely eradicate these strains. Moreover, the antimicrobial activity of these substrates remains high until three reutilization cycles, which make them a promising strategy to develop self-sterilizing materials, such as POrs-CS-Ag-impregnated fabric, POrs-CS-Ag coated indwelling metals and polymers, among other materials.

Resveratrol enhancement staphylococcus aureus survival under levofloxacin and photodynamic treatments.

Reactive oxygen species (ROS) are an efficient tool to eradicate micro-organisms owing to the capacity of these species to damage almost all types of biomolecules and to kill cells. The increase in mechanisms of antimicrobial resistance has led to the exploration of new strategies to eliminate micro-organisms that involve the production of ROS such as superoxide anion (O2•-) and hydrogen peroxide (H2O2). ROS are produced during several antimicrobial treatments, including antibiotic and photodynamic therapies. Among the natural antioxidants, resveratrol (RSV) is efficient at preventing damage from ROS, and every day more people incorporate it as a dietary or cosmetic supplement. However, the consequences of the administration of RSV during antimicrobial treatment are unknown. To investigate possible antagonistic or synergistic effects of RSV during antibiotic therapy (levofloxacin) or photodynamic therapy (visible radiation and methylene blue), killing of planktonic Staphylococcus aureus bacteria was evaluated in the presence of RSV. The results showed that the antimicrobial capacity of these therapies is significantly diminished when levofloxacin or methylene blue are co-administered with RSV, indicating that consumption of RSV during antimicrobial treatment must be, at least, cautioned. Moreover, considering the ROS antimicrobial activity of antibacterial agents, the topical addition of RSV may also affect the control of pathogens of the human body. The results presented in this article highlight the importance of the evaluation of possible antagonistic effects when an antimicrobial agent with ROS-mediated action is co-administrated with RSV.

Is there any difference in the biological impact of soluble and insoluble degradation products of iron-containing biomaterials?

The interactions that could be built between the biomaterials and tissue- microenvironments are very complex, especially in case of degradable metals that generate a broad variety of degradation products. The interfacial problems are particularly relevant for Fe-based materials that have been proposed for the development of biodegradable implants. The cell metabolism could be affected by the accumulation of insoluble Fe-containing degradation products that has been observed in vitro and in vivo as a coarse granular brownish material around the implant. However, the relative importance of each Fe-species (soluble and insoluble) on the cellular behavior of the surrounding cells, particularly on the generation of reactive species (RS), is not completely elucidated. The aim of this study is to evaluate the processes occurring at the Fe-biomaterial/cells interfacial region, and to discriminate the effects of soluble and insoluble corrosion products released by the bulk metal (Fe- microparticles (Fe0p) or Fe0 ring) on the adjacent cells, mainly in relation to RS generation. With this purpose Fe0p and Fe0 ring were incubated with fibroblast cells (BALB/c 3T3 line) for 24 and 48h periods. Then different techniques were used, such as the dichlorofluorescein diacetate assay (DCFH2-DA) for detection of RS, acridine orange dye for cell viability, total protein content determinations, Prussian Blue staining and TEM observations. To individualize the effects of soluble and insoluble species, independent experiments with Fe3+-salts were performed. Overall data indicate that RS generation by cells exposed to the degradation products of Fe-based biomaterials is more dependent on the presence of insoluble products than on soluble Fe species.

Polyethylene glycol-coated blue-emitting silicon dots with improved properties for uses in aqueous and biological environments.

Grafting of polyethylene glycol (PEG) to ultrasmall photoluminescent silicon dots (SiDs) is expected to improve and expand the applications of these particles to aqueous environments and biological systems. Herein we report a novel one-pot synthesis of robust, highly water compatible PEG-coated SiDs (denoted as PEG-SiDs) of (3.3 ± 0.5) nm size. The nanoparticles' synthesis is based on the liquid phase oxidation of magnesium silicide using PEG as reaction media and leading to high PEG density grafting. PEG-SiDs enhanced photophysical, photosensitising, and solution properties in aqueous environments are described and compared to those of 2 nm size PEG-coated SiDs with low PEG density grafting (denoted as PEG-NHSiDs) obtained from a multistep synthesis strategy. PEG-SiDs form highly dispersed suspensions in water showing stable photoluminescence and quantum yields of Φ = 0.13 ± 0.04 at 370 nm excitation in air-saturated suspensions. These particles exhibited the capacity of photosensitising the formation of singlet molecular oxygen, not observed for PEG-NHSiDs. PEG robust shielding of the silicon core luminescent properties is further demonstrated in bio-imaging experiments stressing the strong interaction between PEG-SiDs and Staphylococcus aureus smears by observing the photoluminescence of particles. PEG-SiDs were found to be nontoxic to S. aureus cells at concentrations of 100 mg ml-1, though a bacteriostatic effect on S. aureus biofilms was observed upon UV-A irradiation under conditions where light alone has no effect.

Delivery of fluorophores by calcium phosphate-coated nanoliposomes and interaction with Staphylococcus aureus biofilms.

The delivery capacity and mechanical stability of calcium phosphate (CaP) coated 1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) liposomes free and adsorbed on bacterial surface was investigated introducing either acridine orange (AO) or 5,10,15,20-Tetrakis(1-methyl-4-pyridinio)porphyrin (TMP) in the aqueous core of the liposomes. The obtained nanomaterials were thoroughly characterized by electron and optical microscopy and by fluorescence techniques. Distribution of the AO and TMP molecules between the aqueous liposomes core and the outer solution was demonstrated by the band shifts and broadening of the excitation-emission matrices and the modified Stern-Volmer model for fluorescence quenching. In aqueous suspensions, c.a. 40% of AO was released to the outer solution while only a small percentage of TMP was observed to reach the outer liposome surface. The nanoliposomes adhesion capacity and the leaking of fluorophore molecules to Staphylococcus aureus (S. aureus) biofilms were further evaluated. A close interaction between liposomes and S. aureus biofilm was evidenced by TEM and SEM imaging. Epifluorescence experiments demonstrated that CaP-coated liposomes have good biofilm staining capability after two hours incubation of the biofilms with the liposomes, thus supporting an important release of the fluorophores when in contact with the biofilm. Altogether, the obtained results strongly suggest that CaP-coated liposomes are capable of activating drug release when in presence of S. aureus biofilms and smears. The studies herein presented, indicate that CaP-coated liposomes are potential vehicles for the selective delivery of drugs to S. aureus biofilms, as is the case of the singlet oxygen photosensitizer TMP, a well known photodynamic antibacterial agent.

Time-Lapse Evaluation of Interactions Between Biodegradable Mg Particles and Cells.

Mg-based implants have promising applications as biodegradable materials in medicine for orthopedic, dental, and cardiovascular therapies. During wear and degradation microdebris are released. Time-lapse multidimensional microscopy (MM) is proposed here as a suitable tool to follow, in fixed intervals over 24-h periods, the interaction between cells and particles. Results of MM show interactions of macrophages (J774) with the magnesium particles (MgPa) that led to modifications of cell size and morphology, a decrease in duplication rate, and cell damage. Corrosion products were progressively formed on the surface of the particles and turbulence was generated due to hydrogen development. Changes were more significant after treating MgPa with potassium fluoride. In order to complement MM observations, membrane damage as detected by a lactase dehydrogenase (LDH) assay and mitochondrial activity as detected by a WST-1 assay with macrophages and osteoblasts (MC3T3-E1) were compared. A more significant concentration-dependent effect was detected for macrophages exposed to MgPa than for osteoblasts. Accordingly, complementary data showed that viability and cell cycle seem to be more altered in macrophages. In addition, protein profiles and expression of proteins associated with the adhesion process changed in the presence of MgPa. These studies revealed that time-lapse MM is a helpful tool for monitoring changes of biodegradable materials and the biological surrounding in real time and in situ. This information is useful in studies related to biodegradable biomaterials.

Degradation of bioabsorbable Mg-based alloys: Assessment of the effects of insoluble corrosion products and joint effects of alloying components on mammalian cells.

This work is focused on the processes occurring at the bioabsorbable metallic biomaterial/cell interfaces that may lead to toxicity. A critical analysis of the results obtained when degradable metal disks (pure Mg and rare earth-containing alloys (ZEK100 alloys)) are in direct contact with cell culture and those obtained with indirect methods such as the use of metal salts and extracts was made. Viability was assessed by Acridine Orange dye, neutral red and clonogenic assays. The effects of concentration of corrosion products and possible joint effects of the binary and ternary combinations of La, Zn and Mg ions, as constituents of ZEK alloys, were evaluated on a mammalian cell culture. In all cases more detrimental effects were found for pure Mg than for the alloys. Experiments with disks showed that gradual alterations in pH and in the amount of corrosion products were better tolerated by cells and resulted in higher viability than abrupt changes. In addition, viability was dependent on the distance from the source of ions. Experiments with extracts showed that the effect of insoluble degradation products was highly detrimental. Indirect tests with Zn ions revealed that harmful effects may be found at concentrations ≥ 150 µM and at ≥ 100 µM in mixtures with Mg. These mixtures lead to more deleterious effects than single ions. Results highlight the need to develop a battery of tests to evaluate the biocompatibility of bioabsorbable biomaterials.

Photodynamic inactivation induced by carboxypterin: a novel non-toxic bactericidal strategy against planktonic cells and biofilms of Staphylococcus aureus.

Microbial related contamination is of major concern and can cause substantial economic losses. Photodynamic inactivation (PDI) has emerged as a suitable approach to inhibit microorganism proliferation. In this work, PDI induced by 6-carboxypterin (Cap), a biocompatible photosensitizer (PS), was analyzed. The growth inhibition of Staphylococcus aureus exposed to artificial UV-A radiation and sunlight in the presence of Cap was investigated. After UV-A irradiation, 50 µM Cap was able to decrease by three orders (with respect to the initial value) the number of S. aureus cells in early biofilms. However, this concentration was 500 times higher than that needed for eradicating planktonic cells. Importantly, under solar exposure, 100 µM Cap was able to suppress sessile bacterial growth. Thus, this strategy is able to exert a bactericidal effect on sessile bacteria and to eradicate planktonic cells by exposing the Cap-containing sample to sunlight.