1,720,998 research outputs found
Nanocomposite systems based on polysaccharides and organic/inorganic nanostructures for biomedical applications
No full textThis PhD thesis deals with the development of bioactive polysaccharide-based biomaterials for bone tissue and neural tissue engineering. Alginate was chosen for its gel forming properties; hyaluronic acid and chitlac (a lactose-modified chitosan) were chosen for their bioactive properties. The properties of these polysaccharides have been implemented by introducing gelatin, functionalized Carbon Nanotubes (f-CNTs) and silver nanoparticles (nAg).
In the first part of the work, the dispersibility and aggregation tendency of f-CNTs have been characterized by means of Low Field Nuclear Magnetic Resonance (LF-NMR). It was also possible to correlate the f-CNTs concentration to the proton transversal relaxation rate of water. Alginate/f-CNTs solutions and hydrogels have been analyzed by LF-NMR, rheology and uniaxial compression tests; these investigations showed that the f-CNTs are able to affect nanocomposite properties depending on their concentration and functionalization.
In the second part of the work, the preparation of a bioactive (bridging) implant for the treatment of Spinal Cord Injury is described. Neuronal cells and mesoangioblasts (MABs) engineered for the production of neurotrophines have been cultured and co-cultured on polysaccharide-coated glass substrates in order to evaluate the biological effects of chitlac. Chitlac-coated surfaces where shown to possess higher surface energies if compared to chitosan-coated ones and enable the formation of wider neural networks with improved electrical activity. The co-cultures confirmed the higher bioactivity of chitlac/alginate substrates and the biological role of neurotrophines. Porous scaffolds of alginate/chitlac have been prepared; these scaffolds where shown to be stable in simulated body fluid for over a month. The mechanical properties of rehydrated scaffolds where proved to be similar to those of neural tissue. Biological properties of chitlac substrates enriched with f-CNTs are currently under investigation.
In the third part of the work, tridimensional scaffolds and injectable fillers were developed for the treatment of non-critical bone defects. Porous scaffolds with different pore morphologies have been prepared by freeze casting of alginate/HAp hydrogels. Isotropic porosity was obtained by freezing the constructs in a cryostat, while anisotropic porosity was obtained by the Ice Segregation Induced Self Assembly process. Physical, mechanical and biological analyses revealed that the differences in pore morphology determine differences in the mechanical properties of the scaffolds. Biocompatible f-CNTs have been used to implement the isotropic scaffolds; the biological analyses showed that the presence of f-CNTs does not affect scaffold properties.
Osteoconductive/antimicrobial injectable bone fillers, based on alginate/HAp microbeads dispersed in polysaccharide mixtures, have been developed. Microbeads were enriched with nAg synthesized in chitlac. Antimicrobial assays proved the antibacterial properties of the microbeads towards bacteria in suspension and on pre-formed biofilms. Biological assays showed the biocompatibility of the microbeads and their ability to sustain osteoblast proliferation. The fillers prepared by dispersing microbeads in polysaccharide mixtures were shown to be easily injectable through surgical syringes. In vivo studies on a rabbit model of non-critical bone defect pointed out the biocompatibility and the osteoconductivity of the composite materials. Further studies are ongoing in order to evaluate the possibility to further implement the bioactive properties of the microbeads by addiction of gelatin
A Resin Infiltration Technique for Molar Hypomineralization Treatment: A Preliminary Study in a Pediatric Population
No full textPurpose: The purpose of this study was to evaluate resin infiltration (RI) technique's effects on the in vivo functional treatment of molar hypomineralization (MH)-affected permanent first molars (PFMs). Methods: Fifteen MH-affected PFMs were resin-infiltrated and evaluated for a three-month follow-up (FU). In vivo resin replicas were used for profilometric and scanning electron microscope (SEM) analysis of PFM surfaces; any variation of clinical aspect and dentin hypersensitivity was registered as: T0 equals baseline; T1 equals right after treatment; T2 equals oneweek follow-up; and T3, T4, and T5 equal one-, two-, and three-month FU. Results: At T0, MH-affected surfaces were rougher and more irregular than sound ones; at T1, resin-infiltrated surfaces were smoother while a progressive increase of superficial roughness was observed over time. Hypersensitivity improved at T1 and remained stable over time in severe MH cases. Conclusions: Resin infiltration seems to be a promising treatment, especially in managing severe molar hypomineralization cases for the evaluated follow-up
Influence of sealer placement technique and powder/liquid mixing ratio on the quality of single cone root canal filling: a micro-CT analysis
Full text linkAim: To assess the influence of two different placement techniques and powder/liquid mixing ratio of a bioceramic sealer on the quality of root canal filling by single-cone using a micro-CT analysis.
Methods: Thirty-two single-rooted elements with a mesio-distal diameter of 5,00±0,50 mm, a buccallingual diameter of 6,50 ±0,50 mm and a root length of 14,50±0,50 mm measured at CEJ level were selected to be included in the study. After creating the coronal access cavity, root canals were scouted with manual files and the working length was acquired. Root canals were shaped with R40 Reciproc Blue and irrigated with NaOCl 5% and EDTA 17% solutions. Prepared samples were randomly assigned into four experimental groups (n=8), according to the sealer placement technique and the powder/liquid mixing ratio: G1, the sealer (BioRoot RCS, Septodont) was mixed in a 1:5 ratio, as suggested by the manufacturer, and carried into the root canal by a dedicated gutta-percha cone up to the working length; G2, sealer placement as group G1, but using 1:6 mixing ratio; G3, the sealer was mixed in a 1:5 ratio and carried into the root canal by a syringe with a cannula (Apexcal, Ivoclar) up to its complete filling, then a dedicated gutta-percha cone was inserted into the canal; G4, sealer placement as group G3, but using 1:6 mixing ratio. All the samples were submitted to micro-CT analysis. Micro-CT scans were acquired after shaping procedures (t0) and after canals obturation (t1) and then compared to evaluate the presence of voids in the gutta-percha, sealer and dentin interfaces. The normality of the distribution and the equality of variance of the microtomographic datasets were tested with a Shapiro-Wilk and Levene test, respectively; the significance of the differences between groups in terms of the formation of voids was ascertained with the Kruskal-Wallis test. The results were considered statistically significant for a p-value < 0.05.
Results: Minimal void volumes were observed among groups. G1 performed the best result: total void volumes were 0,253±0,175% of the entire canal space. The other experimental groups follow in order of increasing volume: G3 (0,260±0,254%), G2 (0,532±0,528%), G4 (0,840±0,705%), but no statistically significant difference was observed. All groups showed a similar distribution of voids: in the apical and middle third of the root canal the presence of voids was minimal while the greatest void volumes were detected in the coronal third, due to the canal anatomy and the larger amount of sealer. In this canal portion voids were mainly distributed within the sealer. Concerning the sealer viscosity, the more fluid formulation (1:6) showed an increase of void volumes, although without statistical significance. Likewise, no statistically relevant influence was registered regarding the sealer placement technique.
Conclusion: All the examined techniques should be considered effective for the clinician. Under the conditions of the present study, the 1:5 powder/liquid mixing ratio should be preferred when associated with both the sealer placement techniques, according to the clinical situation and the operator preferences. When using the low viscosity formulation, the clinician should insert the sealer slowly and in a controlled way, in order to minimize the formation of voids
Alginate bone scaffolds coated with a bioactive lactose modified chitosan for human dental pulp stem cells proliferation and differentiation
Full text linkBioactive and biodegradable porous scaffolds can hasten the healing of bone defects; moreover, patient stem cells seeded onto scaffolds can enhance the osteoinductive and osteoconductive properties of these biomaterials. In this work, porous alginate/hydroxyapatite scaffolds were functionalized with a bioactive coating of a lactose-modified chitosan (CTL). The highly interconnected porous structure of the scaffold was homogeneously coated with CTL. The scaffolds showed remarkable stability up to 60 days of aging. Human Dental Pulp Stem Cells (hDPSCs) cultured in the presence of CTL diluted in culture medium, showed a slight and negligible increase in terms of proliferation rate; on the contrary, an effect on osteogenic differentiation of the cells was observed as a significant increase in alkaline phosphatase activity. hDPSCs showed higher cell adhesion on CTL-coated scaffolds than on uncoated ones. CTL coating did not affect cell proliferation, but stimulated cell differentiation as shown by alkaline phosphatase activity analysis
Toward a new generation of nanoparticles for therapy and diagnosis
No full textProgress in utilizing inorganic nanoparticles for biomedical applications has advanced rapidly due to the extensive amount of work done in the synthesis and modification of the materials.1 These nanosized materials provide a robust framework in which two or more components can be incorporated to give multifunctional capabilities. An example can be seen in gold nanomaterials.2 Gold nanoparticles are bioinert, nontoxic, and readily synthesized and functionalized.3 They also provide a multifunctional platform for both therapeutic and diagnostic purposes. Indeed, through proper functionalization, these particles can be engineered to accumulate at illness cells using targeting ligands providing a powerful tool, for example, for gene therapy.4 The biophysico-chemical properties of the vehicle, such as size, charge, surface hydrophilicity, and the nature and density of the ligands on their surface, can all impact the circulating half-life of the particles as well as their biodistribution.
Innovation may be introduced by controlling the surface properties of the monolayer protecting the gold core. Indeed, recently it has been demonstrated that particles coated with a molecularly ordered ligand shell were able to enter cells directly through the membrane without perforating it basing on a novel physical chemistry phenomenon.6 This property is ideal as it provides the particles with minimal if none genotoxicity. Mixed monolayers composed of mixtures of hydrogenated/fluorurated ligands favor the phase segregation and consequently the ordered morphology of the NP surface. 7 In addition, the introduction in the monolayer of perfluorocarbon ligands might enable, for example, the imaging by 19F MRI techniques of the nanoparticles and, consequently, the tracking in vivo of cell fate.
In this communication we will discuss the approaches for the realization of such innovative nanoparticles easy to make, because obtained by self-assembly strategies, but with an unprecedented degree of complexity, with respect to nanotechnology platforms for drug delivery applications know to date, as far as their features is concerned
Polymeric wound dressings, an insight into polysaccharide-based electrospun membranes
Full text linkChronic wounds deeply invalidate patient's quality of life, involving very high costs for the medical system. Numerous wound dressings have been studied over the years, and active wound dressings replaced traditional passive dressings to promote tissue regeneration and wound closure. Aiming at an optimal reproduction of the physiological environment, electrospun wound dressings are emerging since they mimic the architecture of the extracellular matrix and provide a large contact surface area, enabling exudate absorption and permeability as well as good conformability to the wound site. The use of polysaccharides offers an excellent biomimicry, as they ensure good biocompatibility, biodegradability, and non-immunogenicity. Furthermore, they possess bioactive properties, such as antimicrobial, anti-inflammatory, and antioxidant properties, which can promote and enhance the healing process. The aim of this review is to present the morphological, physical, and chemical features of an ideal wound dressing together with the traditional and the current strategies, and the already commercialized wound dressings. Moreover, the review is focused on the preparation of polysaccharide-based electrospun nanofibrous devices and on the strategies for the modulation and improvement of membrane stability and bioactivity. Lastly, a comprehensive consideration on the process and requirements that lead to the commercialization of the wound dressings is reported
Reuse of Implant Healing Abutments: Comparative Evaluation of the Efficacy of Two Cleaning Procedures
No full textPURPOSE: To compare the efficacy of two systems in cleaning used healing abutments (HAs).
MATERIALS AND METHODS: A total of 60 used HAs were randomized into two groups: one treated with an automatic cleaning system, and the other with conventional decontamination procedures. After sterilization and staining, the HAs were microscopically analyzed and underwent a cellular adhesion in vitro assay.
RESULTS: Contaminated areas were observed with different frequencies in the two groups (3.6% test; 78.2% control; P < .001). In vitro assay showed a uniform cell distribution in test HAs, while areas of debris without adhering cells were a common finding in the control HAs.
CONCLUSION: Further studies investigating the chemical composition and clinical influence of biologic remnants are necessary before considering reusing HAs
Antibacterial and bioactive multilayer electrospun wound dressings based on hyaluronic acid and lactose-modified chitosan
Full text linkAntibacterial multilayer electrospun matrices based on hyaluronic acid (HA) and a lactose-modified chitosan (CTL) were synthetized (i) by combining electrospun polycaprolactone (PCL) and polysaccharidic matrices in a bilayer device and (ii) by sequentially coating the PCL mat with CTL and HA. In both cases, the antibacterial activity was provided by loading rifampicin within the PCL support. All matrices disclosed suitable morphology and physicochemical properties to be employed as wound dressings. Indeed, both the bilayer and coated fibers showed an optimal swelling capacity (3426 ± 492 % and 1435 ± 251 % after 7 days, respectively) and water vapor permeability (160 ± 0.78 g/m2h and 170 ± 12 g/m2h at 7 days, respectively). On the other hand, the polysaccharidic dressings were completely wettable in the presence of various types of fluids. Depending on the preparation method, a different release of both polysaccharides and rifampicin was detected, and the immediate polysaccharide dissolution from the bilayer structure impacted the antibiotic release (42 ± 4 % from the bilayer structure against 25 ± 2 % from the coated fibers in 4 h). All the multilayer matrices, regardless of their production strategy and composition, revealed optimal biocompatibility and bioactivity with human dermal fibroblasts, as the released bioactive polysaccharides induced a faster wound closure in the cell monolayer (100 % in 24 h) compared to the controls (78 ± 8 % for untreated cells and 89 ± 5 % for cells treated with PCL alone, after 24 h). The inhibitory and bactericidal effects of the rifampicin loaded matrices were assessed on S. aureus, S. epidermidis, E. coli, and P. aeruginosa. The antibacterial matrices were found to be highly effective except for E. coli, which was more resistant even at higher amounts of rifampicin, with a bacterial concentration of 6.4 ± 0.4 log CFU/mL and 6.8 ± 0.3 log CFU/mL after 4 h in the presence of the rifampicin-loaded bilayer and coated matrices, respectively
Fibronectin Functionalization: A Way to Enhance Dynamic Cell Culture on Alginate/Hydroxyapatite Scaffolds
Full text linkBone defects are a global health concern; bone tissue engineering (BTE) is the most promising alternative to reduce patient morbidity and overcome the inherent drawbacks of autograft and allograft bone. Three-dimensional scaffolds are pivotal in this field due to their potential to provide structural support and mimic the natural bone microenvironment. Following an already published protocol, a 3D porous structure consisting of alginate and hydroxyapatite was prepared after a gelation step and a freezing-drying step. Despite the frequent use of alginate in tissue regeneration, the biological inertness of this polysaccharide hampers proper cell colonization and proliferation. Therefore, the purpose of this work was to enhance the biological properties by promoting the interaction and adhesion between cells and biomaterial with the use of Fibronectin. This extracellular matrix protein was physically adsorbed on the scaffold, and its presence was evaluated with environmental scanning electron microscopy (eSEM) and the Micro-Bicinchoninic Acid (μBCA) protein assay. The MG-63 cell line was used for both static and dynamic (i.e., in bioreactor) 3D cell culturing on the scaffolds. The use of the bioreactor allowed for a better exchange of nutrients and oxygen and a better removal of cell catabolites from the inner portion of the construct, mimicking the physiological environment. The functionalized scaffolds showed an improvement in cell proliferation and colonization compared to non-functionalized ones; the effect of the addition of Fibronectin was more evident in the dynamic culturing conditions, where the cells clearly adhered on the surface of functionalized scaffolds
Root-end resection without retrograde preparation: a micro-CT study
Full text linkAim: the gold standard in endodontic surgery is characterized by meticulous retrograde procedures that could be not performable in all teeth due to multiple clinical difficulties. The possibility to perform the only apical resection, when feasible, without further retrograde steps might represent a substantial clinical advantage. The present study analyzes the filling quality achieved with standard retrograde technique in comparison with alternative techniques with or without retrograde procedures.
Methods: the sample size was determined using with the following parameters: α=0.05; β=0.20; δ=3.0; σ=1.5. Twenty-four single-rooted teeth were selected from a pool of freshly extracted teeth, discarding those with aberrant anatomy. Selected teeth of comparable size were decoronated to obtain 12 mm long roots. The canals were scouted with manual files and the working length acquired. After mechanical glide path establishment, canal shaping was performed with HyFlex EDM rotary files up to size 40.04 taper (500 rpm; 2.5 Ncm). The roots were analyzed with a computed microtomography scanner to identify the possible presence of dentine microcracks. Afterwards, the roots were randomly assigned to two groups: twelve canals were filled with the single cone technique (SCT) with dedicated cones and BioRoot RCS bioceramic sealer;
twelve canals were filled with MTA cement (ProRoot MTA) for 6mm in the apical portion with the aid of the MAP System; the empty canal portion was backfilled with thermoplasticized gutta-percha (Obtura III Max System). After 24 h, the roots were apically resected with a carbide bur 3 mm from the apex. At this point, the two groups were randomly subdivided into two further groups of six elements each: G1, SCT and bioceramic sealer without retrograde procedures (n=6); G2, SCT and bioceramic sealer with standard retrograde ultrasonic preparation and MTA filling (n=6); G3, orthograde MTA placement without retrograde filling (n=6); G4, orthograde MTA placement and standard retrograde ultrasonic preparation and MTA filling (n=6). Lastly, the formation of internal and external voids was quantified by means of a second computed microtomographic analysis. The normality of the distribution and the equality of variance of the microtomographic datasets were tested with a Shapiro- Wilk and a Levene test, respectively; then, the volumes measured in the groups were statistically compared with the Kruskal-Wallis test and with the Mann-Withney test with Bonferroni’s
correction couple comparison.
Results: All groups showed minimal voids volumes formation. In the groups characterized by standard retrograde procedures, the mean voids volumes were 1.16±0.40 % (G4) and 1.87±1.49 % (G2) of the entire canal space, in the groups with the only root-end resection 0.82±0.58 % (G1) and 1.08 ± 0.50% (G3). The difference between the groups was not statistically significant. Analyzing the volume within the apical 3 mm of the canal after root resection (G1=0.06 ± 0.10%; G2=0.76 ± 0.81%; G3=2.06 ± .92%; G4=1.53 ± 1.79%) the difference between G1 and the other groups was statistically significant (p <0.05).
Conclusion: When suitable, filling the canal with the single cone technique and bioceramic sealer or orthograde MTA placement combined with simple root-end resection appears to provide an efficient seal of the endodontic space. These technique could represent a good alternative to the retrograde preparation and filling
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