Jonathan Knowles
University College London, Eastman Dental Institute, Faculty Member
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... 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...
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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... 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...
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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... 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...
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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... 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 ...
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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.
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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... 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...
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Research Interests: Chemistry, Biomedical Engineering, Cell Biology, Medicine, Bone Regeneration, and 15 moreIn Vitro, Cell Differentiation, Humans, Peptide, Amelogenin, Cementum, Adult, Biological markers, Osteogenesis, Molecular weight, Amino Acid Sequence, Bone and Bones, Osteocytes, Biochemistry and cell biology, and Molecular Sequence Data
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Research Interests: Chemistry, Biomedical Engineering, Electrophysiology, Glass, Regeneration (Biology), and 13 moreMedicine, Female, Animals, Medical Physiology, Tissue engineering and regenerative medicine, Clinical Sciences, In Vivo, Rats, Neurite, Time Factors, Sciatic Nerve, Peripheral nerve injuries, and Recovery of Function
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... 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.
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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... 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.
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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... 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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Glasses from the CaO-TiO2-P2O5 system have potential use in biomedical applications. Here a method for the sol-gel synthesis of the ternary glass (CaO)0.25(TiO2)0.25(P2O5)0.5 has been developed. The structures of the dried gel and... more
Glasses from the CaO-TiO2-P2O5 system have potential use in biomedical applications. Here a method for the sol-gel synthesis of the ternary glass (CaO)0.25(TiO2)0.25(P2O5)0.5 has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction. The structure of the binary (TiO2)0.5(P2O5)0.5 sol-gel was studied for comparison. The results reveal that the heat-treated (CaO)0.25(TiO2)0.25(P2O5)0.5 glass has a structure based on chains and rings of PO4 tetrahedra, held together by a combination of electrostatic interaction with Ca2+ ions and by corner-sharing oxygen atoms with TiO6 octahedra. In contrast, the (TiO2)0.5(P2O5)0.5 glass has a structure based on isolated P2O7 units linked together by corner-sharing with TiO6 groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)0.25(TiO2)0.25(P2O5)0.5 sample there is a significant increase in Ca-O coordination number with heat treatment.
Research Interests: Materials Engineering, Materials Science, Biomedical Engineering, Crystallography, Glass, and 15 moreCalcium, Heat Treatment, Medicine, Phase transition, Gels, Oxygen, Coordination number, Oxides, Materials Testing, Calcium Compounds, Biocompatible Materials, Ions, Biomedical Application, High energy, and Electrostatic interaction
Ti K-edge XANES (X-ray absorption near edge structure) spectroscopy has been used to study the local coordination of titanium in biocompatible and bioresorbable TiO2-CaO-Na2O-P2O5 glasses. Both conventional melt-quenched glasses of... more
Ti K-edge XANES (X-ray absorption near edge structure) spectroscopy has been used to study the local coordination of titanium in biocompatible and bioresorbable TiO2-CaO-Na2O-P2O5 glasses. Both conventional melt-quenched glasses of composition (TiO2)x(CaO)0.30(Na2O)0.20-x(P2O5)0.50, where x = 0.01, 0.03 and 0.05, and sol-gel derived (TiO2)0.25(CaO)0.25(P2O5)0.50 glass have been studied. The results show that in all the materials studied, titanium is surrounded by an octahedron of oxygen atoms. Further analysis reveals that the TiO6 site in the amorphous samples is not heavily distorted relative to that in rutile, anatase or CaSiTiO5. The spectra from the (TiO2)0.25(CaO)0.25(P2O5)0.50 sol-gel samples reveal greater distortion in the TiO6 site in the dried gel compared to the heat-treated sol-gel glass. The XANES spectra from melt-quenched glass samples soaked in distilled water for various times do not shown any evidence of degradation of the titanium site over periods of up to 14 days.
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... Further increase of the treatment temperature caused a drop of the transformation temperature. Acknowledgements This work was supported by EU FP6, IEF Marie Curie action, and EPSRC. NT 200C 400C 600C ... 13. T. Kokubo, F. Miyaji, HM... more
... Further increase of the treatment temperature caused a drop of the transformation temperature. Acknowledgements This work was supported by EU FP6, IEF Marie Curie action, and EPSRC. NT 200C 400C 600C ... 13. T. Kokubo, F. Miyaji, HM Kim, J. Am. Ceram. Soc. ...
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To significantly improve the biocompatibility of titanium doped phosphate based glasses, codoping with zinc has been attempted. This study investigated the effect of doping a quaternary 15Na(2)O:30CaO:5TiO(2):50P(2)O(5) glass with zinc... more
To significantly improve the biocompatibility of titanium doped phosphate based glasses, codoping with zinc has been attempted. This study investigated the effect of doping a quaternary 15Na(2)O:30CaO:5TiO(2):50P(2)O(5) glass with zinc oxide (1, 3, and 5 mol %) on bulk, structural, surface, and biological properties; the results were compared with glasses free from ZnO and/or TiO(2). ZnO as adjunct to TiO(2) was effective in changing density, interchain bond forces, degradation behavior, and ions released from the degrading glasses. Incorporation of both TiO(2) and ZnO in T5Z1, T5Z3, and T5Z5 glasses reduced the level of Zn(2+) release by two to three orders of magnitude compared with glasses containing ZnO only (Z5). (31)P NMR results for T5Z1, T5Z3, and T5Z5 glasses showed the presence of Q(3) species suggesting that the TiO(2) is acting as a network former, and the phosphate network becomes slightly more connected with increasing ZnO incorporation. Regardless of their relative lower hydrophilicity and surface reactivity compared with the control glass free from TiO(2) and ZnO (T0Z0), these glasses have significantly higher surface reactivity compared with Thermanox. This has been also reflected in the maintenance of >98% viable Osteoblasts, proliferation rate, and expression level of osteoblastic marker genes in a comparable manner to Thermanox and T5 glasses, particularly T5Z1 and T5Z3 glasses. However, T0Z0 and Z5 glasses showed significantly reduced viability compared to Thermanox. Therefore, it can be concluded that ZnO doped titanium phosphate glasses, T5Z1 and T5Z3 in particular, can be promising substrates for bone tissue engineering applications.
Research Interests: Materials Science, Biomedical Engineering, Glass, Cell Adhesion, Titanium, and 15 moreMedicine, Doping, Zinc Oxide, Humans, Wettability, Calcium Phosphates, Zinc, Anions, X ray diffraction, Surface Properties, Biological markers, Cell Proliferation, Surface free energy, Materials Testing, and Biocompatible Materials
Research Interests: Engineering, Materials Science, Titanium, Medicine, Biological Sciences, and 15 moreHumans, Surface modification, Wettability, Temperature, Osteocalcin, Nickel, Alkaline phosphatase, Apatite, Surface Properties, Cell Proliferation, Culture Media, Alloys, Cell Survival, Bone and Bones, and In Vitro Techniques
High nickel content is believed to reduce the number of biomedical applications of nickel–titanium alloy due to the reported toxicity of nickel. The reduction in nickel release and minimized exposure of the cell to nickel can optimize the... more
High nickel content is believed to reduce the number of biomedical applications of nickel–titanium alloy due to the reported toxicity of nickel. The reduction in nickel release and minimized exposure of the cell to nickel can optimize the biocompatibility of the alloy and increase its use in the application where its shape memory effects and pseudoelasticity are particularly useful, e.g., spinal implants. Many treatments have been tried to improve the biocompatibility of Ni–Ti, and results suggest that a native, smooth surface could provide sufficient tolerance, biologically. We hypothesized that the native surface of nickel–titanium supports cell differentiation and insures good biocompatibility. Three types of surface modifications were investigated: thermal oxidation, alkali treatment, and plasma sputtering, and compared with smooth, ground surface. Thermal oxidation caused a drop in surface nickel content, while negligible chemistry changes were observed for plasma-modified samp...
Research Interests: Materials Science, Biomedical Engineering, Titanium, Medicine, Surface Roughness, and 15 moreBiocompatibility, Cell Differentiation, Humans, Surface modification, Sputtering, Nickel, Surface Properties, Shape Memory Effect, Cell Proliferation, Osteoblasts, Materials Testing, Biocompatible Materials, Biomedical Application, Cell Growth, and Titanium alloy
This study investigated the use of a Ti-containing quaternary phosphate glass system P2O5—Na2O—CaO—TiO 2 as a vehicle for strontium ion delivery to cells. Four glass compositions were manufactured: 0.5P2O5— 0.15Na2O—0.05TiO 2—(0.3 -... more
This study investigated the use of a Ti-containing quaternary phosphate glass system P2O5—Na2O—CaO—TiO 2 as a vehicle for strontium ion delivery to cells. Four glass compositions were manufactured: 0.5P2O5— 0.15Na2O—0.05TiO 2—(0.3 - x)CaO—xSrO (x = 0, 0.01, 0.03, and 0.05). Structural characterization revealed that sodium calcium phosphate is the dominant phase in all the glasses. Degradation studies demonstrated highly linear glass degradation, with Sr-containing glasses degrading at higher rates than the Sr-free glass. Biocompatibility studies using MG63 cells showed that the Sr-containing glasses possess excellent cell attachment and growth, particularly over short periods (~4 days).
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A 31P refocused INADEQUATE pulse sequence has been used in combination with XRD to identify and quantify the crystalline phases present in a ternary sodium calcium phosphate ceramic of composition (CaO) 0.4 (Na2O) 0.1 (P2O5) 0.5. Both the... more
A 31P refocused INADEQUATE pulse sequence has been used in combination with XRD to identify and quantify the crystalline phases present in a ternary sodium calcium phosphate ceramic of composition (CaO) 0.4 (Na2O) 0.1 (P2O5) 0.5. Both the NMR and XRD ...
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It has been shown that the addition of zinc to hydroxyapatite promotes osteoblast cell adhesion (Ishaug et al 1994 J. Biomed. Mater. Res. A 28 1445-53). Therefore, this study presents a series of phosphate-based glass compositions that... more
It has been shown that the addition of zinc to hydroxyapatite promotes osteoblast cell adhesion (Ishaug et al 1994 J. Biomed. Mater. Res. A 28 1445-53). Therefore, this study presents a series of phosphate-based glass compositions that contain varying amounts of zinc in order to promote osteoblast cell adhesion. The compositions investigated were P(50)Ca((40-x))Na(10) where x = 0, 1, 2, 3, 4 and 5 mol%. The dissolution rate and effect on pH of glass discs were investigated and ion release from the glass discs was examined in distilled water at 37 degrees C after 1, 2, 3, 4 and 7 days. The attachment of osteoblast-like cells (HOB) was observed by SEM on the glass discs. A linear decrease in the %mass of the glass discs was observed for all compositions for the duration of the study. The dissolution rates were similar for all the compositions. After 7 days, a mass loss of 3-6% was observed for all the compositions. The pH of distilled water decreased to a range of pH 4.5-5.5 from pH 7 after 1 day, and remained in this range for the duration of the study. The composition containing 0 mol% Zn reduced the pH to a lesser extent than the composition containing the highest amount of Zn. Furthermore, Zn(2+) ion release was observed from all the Zn-containing compositions. These glass compositions may therefore be suitable for tissue engineering applications.
Research Interests: Chemistry, Biomedical Engineering, Hydroxyapatite, Glass, Osseointegration, and 15 moreCell Adhesion, Medicine, Nuclear Chemistry, Adhesion, Cell line, Humans, Biomedical Materials, Medical Biotechnology, Dissolution, Distilled Water, Materials Testing, Durapatite, Mass Loss, Biocompatible Materials, and Cell culture techniques
Research Interests: Materials Science, Biomaterials, Glass, Life Sciences, Nanoparticles, and 15 moreMicroscale Chemistry, Medicine, Multidisciplinary, Biocompatibility, Cell line, Ceramics, Humans, Nanostructures, Composite Material, Microstructures, Bioactive Glass, Cell Proliferation, Microspheres, Materials Testing, and Body Fluids
Research Interests: Materials Science, Biomaterials, Glass, Cell Adhesion, Medicine, and 15 moreMultidisciplinary, Cell Division, Humans, Bone Tissue Engineering, Osteoblast, Enzyme, Fibroblast, Mouth, In Vitro Studies, Materials Testing, Human Fibroblasts, Biocompatible Materials, Cell Size, fibroblasts, and coculture techniques
Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar... more
Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar cubes as porogen. Bioactive glass (BG) particles of 45S5 Bioglass grade were introduced in the scaffold microstructure, both in micrometer ((m-BG), <5 microm) and nanometer ((n-BG), 30 nm) sizes. The in vitro bioactivity of the P(3HB)/BG foams was confirmed within 10 days of immersion in simulated body fluid and the foams showed high level of protein adsorption. The foams interconnected porous microstructure proved to be suitable for MG-63 osteoblast cell attachment and proliferation. The foams implanted in rats as subcutaneous implants resulted in a non-toxic and foreign body response after one week of implantation. In addition to showing bioactivity and biocompatibility, the P(3HB)/BG composite foams also exhibited bactericidal properties, which was tested on the growth of Staphylococcus aureus. An attempt was made at developing multifunctional scaffolds by incorporating, in addition to BG, selected concentrations of Vitamin E or/and carbon nanotubes. P(3HB) scaffolds with multifunctionalities (viz. bactericidal, bioactive, electrically conductive, antioxidative behaviour) were thus produced, which paves the way for next generation of advanced scaffolds for bone tissue engineering.
Research Interests: Materials Science, Biomaterials, Carbon Nanotube, Medicine, Adsorption, and 15 moreBiocompatibility, Cell line, Ceramics, Humans, Animals, Bone Tissue Engineering, Composite Material, Microbial Sensitivity Tests, Bioactive Glass, Cell Proliferation, Culture Media, Biocompatible Materials, Bacterial Adhesion, Electric Conductivity, and foreign body
Novel poly(3‐hydroxyoctanoate), P(3HO), and bacterial cellulose composites have been developed. P(3HO) is hydrophobic in nature whereas bacterial cellulose is extremely hydrophilic in nature. Therefore, homogenized bacterial cellulose has... more
Novel poly(3‐hydroxyoctanoate), P(3HO), and bacterial cellulose composites have been developed. P(3HO) is hydrophobic in nature whereas bacterial cellulose is extremely hydrophilic in nature. Therefore, homogenized bacterial cellulose has been chemically modified in order to achieve compatibility with the P(3HO) matrix. Modified bacterial cellulose microcrystals and P(3HO) have been physically blended and solvent casted into two‐dimensional composite films. Mechanical characterization shows that the Young's modulus of the P(3HO)/bacterial cellulose composites is significantly higher in comparison to the neat P(3HO) film. The melting temperature (Tm) of the composites is lower while the glass transition temperature (Tg) is higher than the neat P(3HO) film. Also, the composite film has a rougher surface topography as compared to the neat P(3HO) film. A month's in vitro degradation study has been carried out in Dulbeccos modified eagle medium and in phosphate buffer saline. The incorporation of modified bacterial cellulose microcrystal in the P(3HO) film has increased the degradability of the composite film. Finally, in vitro biocompatibility studies using human microvascular endothelial cells established the biocompatibility of the P(3HO)/bacterial cellulose microcrystal films. The cell proliferation was 50–110% higher on the P(3HO)/bacterial cellulose composites as compared to the neat P(3HO) film. Hence, in this study, for the first time, P(3HO)/bacterial cellulose composites have been developed. The addition of bacterial cellulose has resulted in properties that are highly desirable for medical applications including the development of biodegradable stents.
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This study reports the relationship between the biocompatibility and surface properties of experimental bone cements. The effect of hydroxyapatite (HA) or alpha-tri-calcium phosphate (alpha-TCP) incorporated into bone cements prepared... more
This study reports the relationship between the biocompatibility and surface properties of experimental bone cements. The effect of hydroxyapatite (HA) or alpha-tri-calcium phosphate (alpha-TCP) incorporated into bone cements prepared with methyl methacrylate as base monomer and either methacrylic acid or diethyl amino ethyl methacrylate (DEAEMA) as comonomers was investigated. The in vitro biocompatibility of these composite cements was assessed in terms of the interaction of primary human osteoblasts grown on the materials over a period of 5 days and compared with a control surface. These results were related to the surface properties investigated through a number of techniques, namely Fourier transform infrared, contact angle measurements, X-ray photoelectron spectroscopy and energy dispersive analysis of X-rays. Complementary techniques of thermal analysis and ion chromatography were also performed. Biocompatibility results showed that the addition of alpha-TCP improves biocompatibility regardless of comonomer type. This is in contrast to HA-based cements where cell proliferation was significantly lower. Surface characterisations showed that structural integrity of the materials was maintained in the presence of the acid and base comonomers, and water contact angles were reduced particularly in DEAEMA containing materials. Furthermore, ion chromatography confirmed higher Ca2+ and PO4(3-) ion release by both types of ceramics, particularly for those containing DEAEMA. In conclusion, the incorporation of acidic and basic comonomers to either HA or alpha-TCP ceramics containing bone cements can have differential effects upon the attachment and proliferation of bone cells in vitro. Moreover, those cements consisting of alpha-TCP and containing DEAEMA comonomer indicated the most favourable biocompatibility.
Research Interests: Materials Science, Hydroxyapatite, Ion Chromatography, Medicine, Cell Division, and 15 moreBiocompatibility, Ceramics, Humans, Calcium Phosphates, Bone Cement, Contact angle, Calcium Phosphate, Fourier transform infrared spectroscopy, Bone Cements, Cell Proliferation, Durapatite, Biocompatible Materials, Methacrylic Acid, Fourier transform infrared, and Methacrylates
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Research Interests: Biomaterials Engineering, Materials Science, Biomedical Engineering, Biomaterials, Medicine, and 15 moreMultidisciplinary, Biomaterials and Tissue Engineering, Biocompatibility, Intestinal Mucosa, Animals, Scaffold, Cell Fractionation, Decellularization, Decellularized Scaffolds, Biomaterials and tissue engineering scaffolds, Esophagus, prosthesis Design, Cell free System, Equipment Failure Analysis, and Peracetic Acid(Multidisciplinary, Biomaterials and Tissue Engineering, Biocompatibility, Intestinal Mucosa, Animals, Scaffold, Cell Fractionation, Decellularization, Decellularized Scaffolds, Biomaterials and tissue engineering scaffolds, Esophagus, prosthesis Design, Cell free System, Equipment Failure Analysis, and Peracetic Acid)
(Multidisciplinary, Biomaterials and Tissue Engineering, Biocompatibility, Intestinal Mucosa, Animals, Scaffold, Cell Fractionation, Decellularization, Decellularized Scaffolds, Biomaterials and tissue engineering scaffolds, Esophagus, prosthesis Design, Cell free System, Equipment Failure Analysis, and Peracetic Acid)
Using microspherical scaffolds as building blocks to repair bone defects of specific size and shape has been proposed as a tissue engineering strategy. Here, phosphate glass (PG) microcarriers doped with 5 mol % TiO2 and either 0 mol %... more
Using microspherical scaffolds as building blocks to repair bone defects of specific size and shape has been proposed as a tissue engineering strategy. Here, phosphate glass (PG) microcarriers doped with 5 mol % TiO2 and either 0 mol % CoO (CoO 0%) or 2 mol % CoO (CoO 2%) were investigated for their ability to support osteogenic and vascular responses of human mesenchymal stem cells (hMSCs). Together with standard culture techniques, cell-material interactions were studied using a novel perfusion microfluidic bioreactor that enabled cell culture on microspheres, along with automated processing and screening of culture variables. While titanium doping was found to support hMSCs expansion and differentiation, as well as endothelial cell-derived vessel formation, additional doping with cobalt did not improve the functionality of the microspheres. Furthermore, the microfluidic bioreactor enabled screening of culture parameters for cell culture on microspheres that could be potentially t...
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Calcium silicate-based bioactive glass has received significant attention for use in various biomedical applications due to its excellent bioactivity and biocompatibility. However, the bioactivity of calcium silicate... more
Calcium silicate-based bioactive glass has received significant attention for use in various biomedical applications due to its excellent bioactivity and biocompatibility. However, the bioactivity of calcium silicate nanoparticle-incorporated bioactive dental sealer is not much explored. Herein, three commercially available bioactive root canal sealers (Endoseal MTA (EDS), Well-Root ST (WST), and Nishika Canal Sealer BG (NBG)) were compared with a resin-based control sealer (AH Plus (AHP)) in terms of physical, chemical, and biological properties. EDS and NBG showed 200 to 400 nm and 100 to 200 nm nanoparticle incorporation in the SEM image, respectively, and WST and NBG showed mineral deposition in Hank’s balanced salt solution after 28 days. The flowability and film thickness of all products met the ISO 3107 standard. Water contact angle, linear dimensional changes, and calcium and silicate ion release were significantly different among groups. All bioactive root canal sealers rel...
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Research Interests: Chemistry, Biomedical Engineering, Cell Biology, Confocal Microscopy, Medicine, and 15 moreExtracellular Matrix, Cytoskeleton, Humans, Collagen, Mice, Compressive Strength, Animals, Osteoblast, Mesenchymal Stem Cell, Mechanical Stress, Rats, Cell Shape, Cell Survival, Mesenchymal Stromal Cells, and Biochemistry and cell biology
The objective of this work was to investigate the potential application of Poly(3-hydroxybutyrate)/magnetic nanoparticles, P(3HB)/MNP, and Poly(3-hydroxybutyrate)/ferrofluid (P(3HB)/FF) nanocomposites as a smart material for bone tissue... more
The objective of this work was to investigate the potential application of Poly(3-hydroxybutyrate)/magnetic nanoparticles, P(3HB)/MNP, and Poly(3-hydroxybutyrate)/ferrofluid (P(3HB)/FF) nanocomposites as a smart material for bone tissue repair. The composite films, produced using conventional solvent casting technique, exhibited a good uniform dispersion of magnetic nanoparticles and ferrofluid and their aggregates within the P(3HB) matrix. The result of the static test performed on the samples showed that there was a 277% and 327% increase in Young’s modulus of the composite due to the incorporation of MNP and ferrofluid, respectively. The storage modulus of the P(3HB)MNP and P(3HB)/FF was found to have increased to 186% and 103%, respectively, when compared to neat P(3HB). The introduction of MNP and ferrofluid positively increased the crystallinity of the composite scaffolds which has been suggested to be useful in bone regeneration. The total amount of protein absorbed by the P(...
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SummaryThere is a need for physical standards (reference materials) to ensure both reproducibility and consistency in the production of somatic cell types from human pluripotent stem cell (hPSC) sources. We have outlined the need for... more
SummaryThere is a need for physical standards (reference materials) to ensure both reproducibility and consistency in the production of somatic cell types from human pluripotent stem cell (hPSC) sources. We have outlined the need for reference materials (RMs) in relation to the unique properties and concerns surrounding hPSC-derived products and suggest in-house approaches to RM generation relevant to basic research, drug screening, and therapeutic applications. hPSCs have an unparalleled potential as a source of somatic cells for drug screening, disease modeling, and therapeutic application. Undefined variation and product variability after differentiation to the lineage or cell type of interest impede efficient translation and can obscure the evaluation of clinical safety and efficacy. Moreover, in the absence of a consistent population, data generated from in vitro studies could be unreliable and irreproducible. Efforts to devise approaches and tools that facilitate improved cons...
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Ni-Ti alloy due to its unique mechanical properties, is used for many types of implants. Failure of these implants can be attributed to many different factors; however infections are a common problem. In this paper, the attachment of the... more
Ni-Ti alloy due to its unique mechanical properties, is used for many types of implants. Failure of these implants can be attributed to many different factors; however infections are a common problem. In this paper, the attachment of the bacteria, Staphylococcus aureus, to the Ni-Ti surface modified by a range of processes with and without of light activation (used to elicit antimicrobial properties of materials) was assessed and related to different surface characteristics. Before the light activation the number of bacterial colony forming units was the greatest for the samples thermally oxidised at 600°C. This sample and the spark oxidised samples showed the highest photocatalytic activity but only the thermally oxidised samples at 600°C showed a significant drop of S. aureus attachment. The findings in this study indicate that light activation and treating samples at 600°C is a promising method for Ni-Ti implant applications with inherent antimicrobial properties. Light activation was shown to be an effective way to trigger photocatalytic reactions on samples covered with relatively thick titanium dioxide via accumulation of photons in the surface and a possible increase in defects which may result in free oxygen. Moreover, light activation caused an increase in the total surface energy.
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Research Interests: Chemistry, Biomedical Engineering, Tissue Engineering, Regeneration, Biology, and 15 moreGlass, Medicine, Humans, Animals, Scaffold, Staphylococcus aureus, Medical Physiology, Tissue engineering and regenerative medicine, Staphylococcus epidermidis, Clinical Sciences, Skeletal Muscle, Rats, Phosphates, Myofibrils, and Tissue Scaffolds
Research Interests: Chemistry, Biomedical Engineering, Tissue Engineering, Regeneration, Medicine, and 15 moreCell Differentiation, Humans, Animals, Scaffold, Myosin, Medical Physiology, Tissue engineering and regenerative medicine, Clinical Sciences, Skeletal Muscle, Rats, Adult, Muscle development, Cell Survival, Gene Expression Regulation, and MyoD Protein
Research Interests: Materials Engineering, Chemical Engineering, Materials Science, Biomedical Engineering, Hydroxyapatite, and 15 moreMedicine, Polymer, Porosity, Coating, Compressive Strength, Scaffold, Drug Delivery Systems, Infrared, Durapatite, Polyesters, FT IR Spectroscopy, Drug Release, Fourier transform infrared, pore structure, and Mechanical Property
This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by P(2)O(5)-Na(2)O-CaO-TiO(2). The following four different glass compositions were manufactured:... more
This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by P(2)O(5)-Na(2)O-CaO-TiO(2). The following four different glass compositions were manufactured: 0.5P(2)O(5)-0.17Na(2)O-0.03TiO(2)-(0.3-x)CaO-xSrO where x = 0, 0.01, 0.03 and 0.05. Structural characterisation revealed glass transition temperatures in the range 427-437 degrees C and the presence of sodium calcium phosphate as the dominant phase in all the glasses. Degradation and ion release studies conducted over a 15-day period revealed that the Sr-containing glasses showed significantly higher degradation and ion release rates than the Sr-free glass. Cytocompatibility studies performed over a 7-day period using MG63 cells showed that the addition of 5 mol% SrO yielded glasses with cell viability nearly equivalent to that observed for quaternary TiO(2) glasses.