Biofilm-associated
diseases are one of the main causes of implant failure. Currently,
the development of implant surface treatment goes beyond the osseointegration
process and focuses on the creation of surfaces with antimicrobial
action and with the possibility to be re-activated (i.e., light source
activation). Titanium dioxide (TiO2), an excellent photocatalyst
used for photocatalytic antibacterial applications, could be a great
alternative, but its efficiency is limited to the ultraviolet (UV)
range of the electromagnetic spectrum. Since UV radiation has carcinogenic
potential, we created a functional TiO2 coating codoped
with nitrogen and bismuth via the plasma electrolytic oxidation (PEO)
of titanium to achieve an antibacterial effect under visible light
with re-activation potential. A complex surface topography was demonstrated
by scanning electron microscopy and three-dimensional confocal laser
scanning microscopy. Additionally, PEO-treated surfaces showed greater
hydrophilicity and albumin adsorption compared to control, untreated
titanium. Bismuth incorporation shifted the band gap of TiO2 to the visible region and facilitated higher degradation of methyl
orange (MO) in the dark, with a greater reduction in the concentration
of MO after visible-light irradiation even after 72 h of aging. These
results were consistent with the in vitro antibacterial effect, where
samples with nitrogen and bismuth in their composition showed the
greatest bacterial reduction after 24 h of dual-species biofilm formation
(Streptococcus sanguinis and Actinomyces naeslundii) in darkness with a superior
effect at 30 min of visible-light irradiation. In addition, such a
coating presents reusable photocatalytic potential and good biocompatibility
by presenting a noncytotoxicity effect on human gingival fibroblast
cells. Therefore, nitrogen and bismuth incorporation into TiO2 via PEO can be considered a promising alternative for dental
implant application with antibacterial properties in darkness, with
a stronger effect after visible-light application.
The experimental alloys are suitable options for dental implant manufacturing, particularly the binary system, which showed a better combination of mechanical and electrochemical properties without the presence of toxic elements.
This study brings new insights on the development of extra oral protocols for the photocatalytic activity of TiO in oral biofilm-associated disease. Anatase and mixture-TiO showed antibacterial activity on this oral bacterial biofilm, being promising surface coatings for dental implant components.
There is a propensity for fungal adherence to the polymethylmethacrylate used for making denture bases. Therefore, this study investigated whether surface modifications with plasma treatments would reduce the adherence of Candida albicans to a denture base resin. Samples (n = 180) with smooth and rough surfaces were made and divided into five groups: control - non-treated; experimental groups - submitted to plasma treatments to obtain surfaces with different hydrophobicities (Ar/50 W; ArO(2) /70 W; AAt/130 W) or with incorporated fluoride (Ar/SF(6) 70 W). Contact angles were measured immediately after treatments and after samples were immersed in water for 48 h. For each group, half the samples were incubated with saliva before the adherence test. The number of adhered C. albicans was evaluated by counting after crystal violet staining. The plasma treatments were effective in modifying the polymethylmethacrylate surface. However, there was a significant alteration in the contact angle measured after immersion in water. No statistically significant difference in the adherence of C. albicans was observed between the experimental and control groups, irrespective of the presence or absence of saliva, and surface roughness.
Polymicrobial infections
are one of the most common reasons for inflammation of surrounding
tissues and failure of implanted biomaterials. Because microorganism
adhesion is the first step for biofilm formation, physical–chemical
modifications of biomaterials have been proposed to reduce the initial
microbial attachment. Thus, the use of superhydrophobic coatings has
emerged because of their anti-biofilm properties. However, these coatings
on the titanium (Ti) surface have been developed mainly by dual-step
surface modification techniques and have not been tested using polymicrobial
biofilms. Therefore, we developed a one-step superhydrophobic coating
on the Ti surface by using a low-pressure plasma technology to create
a biocompatible coating that reduces polymicrobial biofilm adhesion
and formation. The superhydrophobic coating on Ti was created by the
glow discharge plasma using Ar, O2, and hexamethyldisiloxane
gases, and after full physical, chemical, and biological characterizations,
we evaluated its properties regarding oral biofilm inhibition. The
newly developed coating presented an increased surface roughness and,
consequently, superhydrophobicity (contact angle over 150°) and
enhanced corrosion resistance (p < 0.05) of the
Ti surface. Furthermore, proteomic analysis showed a unique pattern
of protein adsorption on the superhydrophobic coating without drastically
changing the biologic processes mediated by proteins. Additionally,
superhydrophobic treatment did not present a cytotoxic effect on fibroblasts
or reduction of proliferation; however, it significantly reduced (≈8-fold
change) polymicrobial adhesion (bacterial and fungal) and biofilm
formation in vitro. Interestingly, superhydrophobic coating shifted
the microbiological profile of biofilms formed in situ in the oral
cavity, reducing by up to ≈7 fold pathogens associated with
the peri-implant disease. Thus, this new superhydrophobic coating
developed by a one-step glow discharge plasma technique is a promising
biocompatible strategy to drastically reduce microbial adhesion and
biofilm formation on Ti-based biomedical implants.
Soft-tissue preservation provides palaeobiological information that is otherwise lost during fossilization. In Brazil, the Early Cretaceous Santana Formation contains fish with integument, muscles, connective tissues, and eyes that are still preserved. Our study revealed that soft-tissues were pyritized or kerogenized in different microfacies, which yielded distinct preservation fidelities. Indeed, new data provided the first record of pyritized vertebrate muscles and eyes. We propose that the different taphonomic pathways were controlled by distinct sedimentation rates in two different microfacies. Through this process, carcasses deposited in each of these microfacies underwent different residence times in sulphate-reduction and methanogenesis zones, thus yielding pyritized or kerogenized soft-tissues, and a similar process has previously been suggested in studies of a late Ediacaran lagerstätte.
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