|
Evaluation of the interactions between
collagen and the surface
of a bioactive glass during in vitro test.
Oréfice R, Hench L,
Brennan A.
Department of
Metallurgical and Materials Engineering, Federal University of
Minas Gerais, R. Espírito Santo 35/206 ‐ Belo Horizonte, MG,
30160‐030, Brazil.
Interactions between biomaterials and the body environment usually determine the
lifetime and performance of biomedical devices used as implants. Among a variety
of different types of interactions that occur whenever biomaterials are
implanted into the body, adsorption of biomacromolcules onto the surface of
biomaterials can guide other relevant processes such as cell attachment, cell
differentiation, cell proliferation, tissue growth and biomaterials degradation.
In this work, fundamental mechanisms associated with the interactions between
collagen and the surface of biomaterials were studied by using Atomic Force
Microscopy (AFM). The ultimate goal of this work is to isolate and simulate
phenomena occurring at the molecular level, when biological entities are brought
in contact with biomaterials. These results can then be used to design and test
new biomedical devices. This manuscript reports the evaluation of interactions
between collagen and the surface of bioactive glasses. These bioactive glasses
are known to bond to soft and hard tissues through the formation of a hydroxy-carbonate-apatite
layer. Collagen was grafted onto AFM cantilevers. AFM force-displacement curves
were obtained using these modified tips against the surface of a bioactive glass
at different stages of an in vitro test performed in a simulated body fluid. The
results showed that the structure of the bioactive glass surface affects the
adsorption of collagen on the biomaterial. The magnitude of the adhesion force
measured is highly dependent on the deposition of a hydroxyl-carbonate-apatite
at the surface of the glass.
J
Biomed Mater Res A. 2008
May 19. [Epub ahead of print]
Microarray-based
gene expression analysis of human osteoblasts in response to
different biomaterials
Bombonato-Prado KF,
Bellesini LS,
Junta CM,
Marques MM,
Passos GA,
Rosa AL.
Department of
Morphology, Stomatology and Physiology, School of Dentistry of Ribeirão Preto, University of São Paulo (USP), Av. do Café, s/n,
14040‐904, Ribeirão Preto, SP, Brazil
Several biomaterials have been widely used in bone regeneration/substitution
procedures in orthopedic and oral surgery. However, how these biomaterials alter
osteoblast gene expression is poorly understood. We therefore attempted to
address this question by using cDNA microarray technique to identify genes that
are differentially regulated in osteoblasts exposed to biomaterials
comprehending the biocompatibility spectrum of bioactive (bioglass and
hydroxyapatite), bioinert (Ti and stainless steel), and biotolerant (polymethylmethacrylate).
By using a cDNA microarray containing 687 human IMAGE sequences, we identified
in primary cultures of osteoblastic cells differentiated from the human bone
marrow and exposed to these biomaterials, genes whose expression was
significantly upregulated or downregulated. Among the differentially expressed
genes we have found those involved with cell cycle regulation, cell
differentiation and proliferation, apoptosis, cell adhesion, bone mineralization
and skeletal development. These results can be relevant to a better
understanding of the molecular mechanism underlying the behavior of osteoblasts
in bone regenerative procedures.
J
Biomed Mater Res A. 2008
Feb 27 [Epub ahead of print]
Antimicrobial effect of
nanometric bioactive glass 45S5.
Waltimo T,
Brunner TJ,
Vollenweider M, Stark WJ,
Zehnder M.
Institute of Oral
Microbiology and Preventive Dentistry, University of Basel
Center of Dental Medicine, Switzerland.
Most recent advances in nanomaterials fabrication have given access to complex
materials such as SiO(2)-Na(2)O-CaO-P(2)O(5) bioactive glasses in the form of
amorphous nanoparticles of 20- to 60-nm size. The clinically interesting
antimicrobial properties of commercially available, micron-sized bioactive glass
45S5 have been attributed to the continuous liberation of alkaline species
during application. Here, we tested the hypothesis that, based on its more than
ten-fold higher specific surface area, nanometric bioactive glass releases more
alkaline species, and consequently displays a stronger antimicrobial effect,
than the currently applied micron-sized material. Ionic dissolution profiles
were monitored in simulated body fluid. Antimicrobial efficacy was assessed
against clinical isolates of enterococci from persisting root canal infections.
The shift from micron- to nano-sized treatment materials afforded a ten-fold
increase in silica release and solution pH elevation by more than three units.
Furthermore, the killing efficacy was substantially higher with the new material
against all tested strains.
J
Dent Res. 2007 Aug;86(8):754-7
Bactericidal effects of bioactive glasses on clinically
important aerobic bacteria.
Munukka E,
Leppäranta O, Korkeamäki M, Vaahtio M, Peltola T, et.al.,
Department of
Medical Microbiology, University of Turku, Kiinamyllynkatu 13,
Turku 20500, Finland. laevmu@utu.fi
Bioactive glasses (BAGs) have been studied for decades for clinical use, and
they have found many dental and orthopedic applications. BAGs have also been
shown to have an antibacterial effect e.g., on some oral microorganisms. In this
extensive work we show that six powdered BAGs and two sol-gel derived materials
have a clear antibacterial effect on 29 clinically important bacterial species.
We also incorporated a rapid and accurate flow cytometric (FCM) method to
calculate and standardize the numbers of viable bacteria inoculated in the
suspensions used in the tests for antibacterial activity. In all materials
tested growth inhibition could be demonstrated, although the concentration and
time needed for the effect varied depending on the BAG. The most effective glass
was S53P4, which had a clear growth-inhibitory effect on all pathogens tested.
The sol-gel derived materials CaPSiO and CaPSiO II also showed a strong
antibacterial effect. In summary, BAGs were found to clearly inhibit the growth
of a wide selection of bacterial species causing e.g., infections on the
surfaces of prostheses in the body after implantation.
J
Mater Sci Mater Med. 2008 Jan;19(1):27-32. Epub 2007 Jun 14
Do
bioactive glasses convey a disinfecting mechanism beyond a mere
increase in pH?
Gubler M, Brunner
TJ, Zehnder M, Waltimo T, Sener B, Stark WJ.
Institute for
Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zurich, Zurich, Switzerland.
Aim To test
whether bioactive glasses kill microbiota via mineralization or
the release of ions other than sodium. Methodology Flame-spray
synthesis was applied to produce nanometric glasses of different
sodium content and constant Ca/P ratio: 28S5, 45S5 and 77S.
Calcium hydroxide and nanometric tricalcium phosphate (TCP) were
used as controls. Apatite induction was monitored by Raman
spectroscopy. Bovine dentine disks with adherent Enterococcus
faecalis cells were exposed to test and control suspensions or
buffered solutions for 1 h, 1 day and 1 week. Colony-forming
units were counted and disks were inspected using scanning
electron microscopy. Suspension supernatants and solutions were
analysed for their pH, osmolarity, calcium and silicon content.
Results Sodium containing glasses induced pH levels above 12,
compared with less than pH 9 with sodium-free 77S. Calcium
hydroxide, 45S5 and 28S5 killed all bacteria after 1 day and
lysed them after 1 week. TCP caused the highest apatite
induction and substantial calcification on bacteria adhering to
dentine, but did not reduce viable counts. 77S achieved
disinfection after 1 week without visible apatite formation,
whilst the buffer solution at pH 9 caused only minimal reduction
in counts. Conclusion Bioactive glasses have a directly and an
indirectly pH-related antibacterial effect. The effect not
directly linked to pH is because of ion release rather than
mineralization.
Int Endod J. 2008 Jun 11. [Epub
ahead of print]
Genetic portrait of osteoblast-like cells cultured on Bioactive
Glass.
Carinci F,
Palmieri A, Martinelli M, Perrotti V, Piattelli A, Brunelli G,
Arlotti M, Pezzetti F.
Department of
Embryology and Morphology, University of Ferrara.
PerioGlas (PG) is an alloplastic material used for grafting periodontal osseous
defects since 1995. In animal models it has been histologically proven that PG
achieves good repair of surgically created defects. In clinical trials, PG has
been shown to be effective as an adjunct to conventional surgery in treating
intrabony defects. Because the molecular events by which PG is able to alter
osteoblast activity to promote bone formation are poorly understood, we
investigated genes that are differently regulated in osteoblast-like cells
exposed to PG. Bone formation can be attributable to ostegenesis (ie, direct
stimulation of osteoblast to produce new bone), osteoconduction (which operates
like a scaffold), or both processes. By using DNA microarrays containing 20 000
oligonucleotides, we identified several genes in which expression was
significantly downregulated in a MG63 cell line cultured with PerioGlas (US
Biomaterials Corp, Alachua, Fla). Specifically, PG is able to downregulate some
functional activities of osteoblast-like cells: it acts on signal transduction,
especially on the transforming growth factor beta (TGFB) paracrine network; it
inhibits apoptosis; it decreases cell adhesion with consequent enhancement of
cell mobility and migration; and it acts on bone marrow stem cells (ie, CD34).
In conclusion, PG acts on bone formation by determining both osteoconduction (as
demonstrated by the reduced cell adhesion) and ostegenesis (as shown by TGFB-related
proteins and stem cell markers).
J
Oral Implantol. 2007;33(6):327-33.
Request
More Info
|
Osteostimulation
