Frontiers in Bioengineering and Biotechnology, 2021
Due to the threat posed by the rapid growth in the resistance of microbial species to antibiotics... more Due to the threat posed by the rapid growth in the resistance of microbial species to antibiotics, there is an urgent need to develop novel materials for biomedical applications capable of providing antibacterial properties without the use of such drugs. Bone healing represents one of the applications with the highest risk of postoperative infections, with potential serious complications in case of bacterial contaminations. Therefore, tissue engineering approaches aiming at the regeneration of bone tissue should be based on the use of materials possessing antibacterial properties alongside with biological and functional characteristics. In this study, we investigated the combination of polyhydroxyalkanoates (PHAs) with a novel antimicrobial hydroxyapatite (HA) containing selenium and strontium. Strontium was chosen for its well-known osteoinductive properties, while selenium is an emerging element investigated for its multi-functional activity as an antimicrobial and anticancer agen...
The biocompatibility and neuron regenerating properties of various bioactive glass (BG)/polyhydro... more The biocompatibility and neuron regenerating properties of various bioactive glass (BG)/polyhydroxyalkanoate (PHA) blend composites were assessed in order to study their suitability for peripheral nerve tissue applications, specifically as lumen structures for nerve guidance conduits. BG/PHA blend composites were fabricated using Bioactive glass® 45 S5 (BG1) and BG 1393 (BG2) with the 25:75 poly(3-hydroxyoctanoate/poly3-hydroxybutyrate), 25:75 P(3HO)/P(3HB) blend (PHA blend). Various concentrations of each BG (0.5 wt%, 1.0 wt% and 2.5 wt%) were used to determine the effect of BG on neuronal growth and differentiation, in single culture using NG108-15 neuronal cells and in a co-culture along with RN22 Schwann cells. NG108-15 cells exhibited good growth and differentiation on all the PHA blend composites showing that both BGs have good biocompatibility at 0.5 wt%, 1.0 wt% and 2.5 wt% within the PHA blend. The Young’s modulus values displayed by all the PHA blend/BG composites ranged f...
Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged ... more Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged cartilage caused by disease, trauma, ageing or developmental disorder. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials and signalling factors to the defect site. Materials and fabrication technologies are therefore critically important for cartilage tissue engineering in designing temporary, artificial extracellular matrices (scaffolds), which support 3D cartilage formation. Hence, this work aimed to investigate the use of poly(3‐hydroxybutyrate)/microfibrillated bacterial cellulose (P(3HB)/MFC) composites as 3D‐scaffolds for potential application in cartilage tissue engineering. The compression moulding/particulate leaching technique employed in the study resulted in good dispersion and a strong adhesion between the MFC and the P(3HB) matrix. Furthermore, the composite scaffold produced displayed bet...
The homopolymer poly(3‐hydroxyoctanoate), produced from Pseudomonas mendocina with octanoate as a... more The homopolymer poly(3‐hydroxyoctanoate), produced from Pseudomonas mendocina with octanoate as a carbon feed, was studied as a potential biomaterial for soft tissue engineering, that is, as a cardiac patch and as matrices for skin tissue engineering. The polymer was fabricated into neat solvent‐cast films of 5 and 10 wt %. Microstructural studies revealed the films as having a smooth surface topography with a root mean square value of 0.238 μm. The films also possessed moderate hydrophilicity when compared to other monomers of the polyhydroxyalkanoate family. Stress–strain curves of the films obtained was typical of that of elastomeric polymers. This elastomeric and flexible nature of the films makes them promising candidates for the proposed applications. Biocompatibility studies with the human adult low calcium temperature keratinocytes (HaCaT) keratinocyte cell line showed that the films were able to support the attachment, differentiation, and maturation of the HaCaT cells. In ...
The silicate-shelled alginate hydrogel fiber scaffold is highly effective for promoting ion-induc... more The silicate-shelled alginate hydrogel fiber scaffold is highly effective for promoting ion-induced angiogenesis and bone bioactivity, ultimately useful for the repair and regeneration of hard tissues.
This study investigated the mixed alkali effect in a series of phosphate based glasses. These gla... more This study investigated the mixed alkali effect in a series of phosphate based glasses. These glasses were of the composition 0.5P2O5-0.2CaO-0.3-xNa2O-xK2O where x=0 to 0.3 in steps of 0.05. This study considered density measurements using Archimedes’s principle, thermal characterisation using differential scanning calorimetry, phase analysis following crystallisation using X-ray powder diffraction (XRD), and degradation studies combined with ion release. The results showed that these mixed alkali glasses showed a linear decrease in density, with the ternary single alkali glass with 0.3mol K2O showing a 3% reduction in density as compared to that with 0.3mol Na2O which correlated well with the difference in ionic diameter and atomic weight of both cations. These glasses also showed intermediate glass transition temperature (Tg) values, compared to those of the ternary single alkali glasses having the same alkali oxide content, and the minimum Tg value was recorded for equimolar amou...
ABSTRACT (Nb2O5) x ·(SiO2)1−x gels of four different compositions with x=0.025 (2.5Nb), 0.050 (5N... more ABSTRACT (Nb2O5) x ·(SiO2)1−x gels of four different compositions with x=0.025 (2.5Nb), 0.050 (5Nb), 0,10 (10Nb) and 0.20 (20Nb) were synthesized at room temperature from niobium penta-chloride and tetra-ethoxysilane and their structural evolution with the temperature was examined by X-ray diffraction, thermogravimetry/differential thermal analysis, Raman and IR spectroscopy (Fourier transform). The synthesis procedure tuned in this work allowed to obtain for each studied composition transparent chemical gels in which the niobium dispersion resulted to be strongly dependent on the Nb2O5 loading: it was on the atomic scale for the 2.5Nb and 5Nb gel samples whereas the gel structure of the 10Nb and 20Nb appears formed by phase separated niobia-silica nanodomains. All dried gels keep their amorphous nature up to 873K, while at higher temperatures crystallization of T- and H-Nb2O5 polymorphs were observed according to the Nb2O5 loading: at low loading T-Nb2O5 was the main crystallising phase, whereas at higher one the H-Nb2O5 prevails. Particularly, T-Nb2O5 was the sole crystallising phase in the whole explored temperature range for the 2.5Nb, keeping its nanosize up to 1273K for all samples except for the 20Nb.
ABSTRACT Phosphosilicate gels with high phosphorus content (P mol% > Si mol%) have been pr... more ABSTRACT Phosphosilicate gels with high phosphorus content (P mol% > Si mol%) have been prepared using phytic acid as the phosphorus precursor, with tetraethyl orthosilicate (TEOS). It is shown that the structure of phytic acid is maintained in both the sols and those gels dried at a low temperature (i.e. ≤120 °C). Solid state 29Si and 31P NMR suggest that the gel network is primarily based on tetrahedral silicon and that phosphorus is not chemically incorporated into the silicate network at this point. X-ray diffraction shows the gel to be amorphous at low temperatures. After heat treatment at higher temperatures (i.e. up to 450 °C), P–O–Si linkages are formed and the silicon coordination changes from tetrahedral to octahedral. At the same time, the gel crystallizes. Even after this partial calcination, 31P NMR shows that a large fraction of phytic acid remains in the network. The function of phytic acid as chelating agent is also maintained in the gels dried at 120 °C such that its ability to absorb Ca2+ from aqueous solution is preserved.
The loss of tooth structure can increase cuspal flexure, thereby reducing the fracture resistance... more The loss of tooth structure can increase cuspal flexure, thereby reducing the fracture resistance of the tooth, or open the tooth-restoration interface, leading to microleakage. The purpose of this study was to evaluate tooth strain in teeth with different cavity preparations after loading and unloading. Ten intact human maxillary premolars were selected and embedded in epoxy resin molds. Constantan strain gauges were used and tested as an intact tooth (group I), occlusal cavity (group O), mesio-occlusal cavity (group MO), and finally mesio-occluso-distal cavity (group MOD). All teeth were subjected to gradual nondestructive occlusal loading and unloading (50 N, 70 N, 90 N, 110 N, 130 N, 50 N, 0 N) in a servohydraulic testing machine. All data were analyzed statistically by performing a repeated measures ANOVA with load and cavity as factors to compare the relevant mean strains, and a Bonferroni post hoc test was performed for multiple comparisons (α=.05). The repeated measures ANOVA did not provide any evidence of an interaction between load and cavity but indicated a significant difference in the mean strains both between the loads (P<.001) and between the cavity groups (P<.001). MOD cavities presented statistically significantly higher values of strain than MO, O, or intact teeth, and a significant increase in the values of mean strain for all cavities was observed, even with intact teeth, when nondestructive occlusal loading was increased.
Frontiers in Bioengineering and Biotechnology, 2021
Due to the threat posed by the rapid growth in the resistance of microbial species to antibiotics... more Due to the threat posed by the rapid growth in the resistance of microbial species to antibiotics, there is an urgent need to develop novel materials for biomedical applications capable of providing antibacterial properties without the use of such drugs. Bone healing represents one of the applications with the highest risk of postoperative infections, with potential serious complications in case of bacterial contaminations. Therefore, tissue engineering approaches aiming at the regeneration of bone tissue should be based on the use of materials possessing antibacterial properties alongside with biological and functional characteristics. In this study, we investigated the combination of polyhydroxyalkanoates (PHAs) with a novel antimicrobial hydroxyapatite (HA) containing selenium and strontium. Strontium was chosen for its well-known osteoinductive properties, while selenium is an emerging element investigated for its multi-functional activity as an antimicrobial and anticancer agen...
The biocompatibility and neuron regenerating properties of various bioactive glass (BG)/polyhydro... more The biocompatibility and neuron regenerating properties of various bioactive glass (BG)/polyhydroxyalkanoate (PHA) blend composites were assessed in order to study their suitability for peripheral nerve tissue applications, specifically as lumen structures for nerve guidance conduits. BG/PHA blend composites were fabricated using Bioactive glass® 45 S5 (BG1) and BG 1393 (BG2) with the 25:75 poly(3-hydroxyoctanoate/poly3-hydroxybutyrate), 25:75 P(3HO)/P(3HB) blend (PHA blend). Various concentrations of each BG (0.5 wt%, 1.0 wt% and 2.5 wt%) were used to determine the effect of BG on neuronal growth and differentiation, in single culture using NG108-15 neuronal cells and in a co-culture along with RN22 Schwann cells. NG108-15 cells exhibited good growth and differentiation on all the PHA blend composites showing that both BGs have good biocompatibility at 0.5 wt%, 1.0 wt% and 2.5 wt% within the PHA blend. The Young’s modulus values displayed by all the PHA blend/BG composites ranged f...
Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged ... more Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged cartilage caused by disease, trauma, ageing or developmental disorder. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials and signalling factors to the defect site. Materials and fabrication technologies are therefore critically important for cartilage tissue engineering in designing temporary, artificial extracellular matrices (scaffolds), which support 3D cartilage formation. Hence, this work aimed to investigate the use of poly(3‐hydroxybutyrate)/microfibrillated bacterial cellulose (P(3HB)/MFC) composites as 3D‐scaffolds for potential application in cartilage tissue engineering. The compression moulding/particulate leaching technique employed in the study resulted in good dispersion and a strong adhesion between the MFC and the P(3HB) matrix. Furthermore, the composite scaffold produced displayed bet...
The homopolymer poly(3‐hydroxyoctanoate), produced from Pseudomonas mendocina with octanoate as a... more The homopolymer poly(3‐hydroxyoctanoate), produced from Pseudomonas mendocina with octanoate as a carbon feed, was studied as a potential biomaterial for soft tissue engineering, that is, as a cardiac patch and as matrices for skin tissue engineering. The polymer was fabricated into neat solvent‐cast films of 5 and 10 wt %. Microstructural studies revealed the films as having a smooth surface topography with a root mean square value of 0.238 μm. The films also possessed moderate hydrophilicity when compared to other monomers of the polyhydroxyalkanoate family. Stress–strain curves of the films obtained was typical of that of elastomeric polymers. This elastomeric and flexible nature of the films makes them promising candidates for the proposed applications. Biocompatibility studies with the human adult low calcium temperature keratinocytes (HaCaT) keratinocyte cell line showed that the films were able to support the attachment, differentiation, and maturation of the HaCaT cells. In ...
The silicate-shelled alginate hydrogel fiber scaffold is highly effective for promoting ion-induc... more The silicate-shelled alginate hydrogel fiber scaffold is highly effective for promoting ion-induced angiogenesis and bone bioactivity, ultimately useful for the repair and regeneration of hard tissues.
This study investigated the mixed alkali effect in a series of phosphate based glasses. These gla... more This study investigated the mixed alkali effect in a series of phosphate based glasses. These glasses were of the composition 0.5P2O5-0.2CaO-0.3-xNa2O-xK2O where x=0 to 0.3 in steps of 0.05. This study considered density measurements using Archimedes’s principle, thermal characterisation using differential scanning calorimetry, phase analysis following crystallisation using X-ray powder diffraction (XRD), and degradation studies combined with ion release. The results showed that these mixed alkali glasses showed a linear decrease in density, with the ternary single alkali glass with 0.3mol K2O showing a 3% reduction in density as compared to that with 0.3mol Na2O which correlated well with the difference in ionic diameter and atomic weight of both cations. These glasses also showed intermediate glass transition temperature (Tg) values, compared to those of the ternary single alkali glasses having the same alkali oxide content, and the minimum Tg value was recorded for equimolar amou...
ABSTRACT (Nb2O5) x ·(SiO2)1−x gels of four different compositions with x=0.025 (2.5Nb), 0.050 (5N... more ABSTRACT (Nb2O5) x ·(SiO2)1−x gels of four different compositions with x=0.025 (2.5Nb), 0.050 (5Nb), 0,10 (10Nb) and 0.20 (20Nb) were synthesized at room temperature from niobium penta-chloride and tetra-ethoxysilane and their structural evolution with the temperature was examined by X-ray diffraction, thermogravimetry/differential thermal analysis, Raman and IR spectroscopy (Fourier transform). The synthesis procedure tuned in this work allowed to obtain for each studied composition transparent chemical gels in which the niobium dispersion resulted to be strongly dependent on the Nb2O5 loading: it was on the atomic scale for the 2.5Nb and 5Nb gel samples whereas the gel structure of the 10Nb and 20Nb appears formed by phase separated niobia-silica nanodomains. All dried gels keep their amorphous nature up to 873K, while at higher temperatures crystallization of T- and H-Nb2O5 polymorphs were observed according to the Nb2O5 loading: at low loading T-Nb2O5 was the main crystallising phase, whereas at higher one the H-Nb2O5 prevails. Particularly, T-Nb2O5 was the sole crystallising phase in the whole explored temperature range for the 2.5Nb, keeping its nanosize up to 1273K for all samples except for the 20Nb.
ABSTRACT Phosphosilicate gels with high phosphorus content (P mol% > Si mol%) have been pr... more ABSTRACT Phosphosilicate gels with high phosphorus content (P mol% > Si mol%) have been prepared using phytic acid as the phosphorus precursor, with tetraethyl orthosilicate (TEOS). It is shown that the structure of phytic acid is maintained in both the sols and those gels dried at a low temperature (i.e. ≤120 °C). Solid state 29Si and 31P NMR suggest that the gel network is primarily based on tetrahedral silicon and that phosphorus is not chemically incorporated into the silicate network at this point. X-ray diffraction shows the gel to be amorphous at low temperatures. After heat treatment at higher temperatures (i.e. up to 450 °C), P–O–Si linkages are formed and the silicon coordination changes from tetrahedral to octahedral. At the same time, the gel crystallizes. Even after this partial calcination, 31P NMR shows that a large fraction of phytic acid remains in the network. The function of phytic acid as chelating agent is also maintained in the gels dried at 120 °C such that its ability to absorb Ca2+ from aqueous solution is preserved.
The loss of tooth structure can increase cuspal flexure, thereby reducing the fracture resistance... more The loss of tooth structure can increase cuspal flexure, thereby reducing the fracture resistance of the tooth, or open the tooth-restoration interface, leading to microleakage. The purpose of this study was to evaluate tooth strain in teeth with different cavity preparations after loading and unloading. Ten intact human maxillary premolars were selected and embedded in epoxy resin molds. Constantan strain gauges were used and tested as an intact tooth (group I), occlusal cavity (group O), mesio-occlusal cavity (group MO), and finally mesio-occluso-distal cavity (group MOD). All teeth were subjected to gradual nondestructive occlusal loading and unloading (50 N, 70 N, 90 N, 110 N, 130 N, 50 N, 0 N) in a servohydraulic testing machine. All data were analyzed statistically by performing a repeated measures ANOVA with load and cavity as factors to compare the relevant mean strains, and a Bonferroni post hoc test was performed for multiple comparisons (α=.05). The repeated measures ANOVA did not provide any evidence of an interaction between load and cavity but indicated a significant difference in the mean strains both between the loads (P<.001) and between the cavity groups (P<.001). MOD cavities presented statistically significantly higher values of strain than MO, O, or intact teeth, and a significant increase in the values of mean strain for all cavities was observed, even with intact teeth, when nondestructive occlusal loading was increased.
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