Browsing by Author "Tobaldi, D. M."
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- Bacteria immobilisation on hydroxyapatite surface for heavy metals removalPublication . Piccirillo, C.; Pereira, S. I. A.; Marques, A. P. G. C.; Pullar, R. C.; Tobaldi, D. M.; Pintado, M. E.; Castro, P. M. L.Selected bacterial strains were immobilised on the surface of hydroxyapatite (Ca-10(PO4)(6)(OH)(2) - HAp) of natural origin (fish bones). The capacity of the material, alone and in combination with the bacterial strains to act as heavy metal removers from aqueous streams was assessed. Pseudomonas fluorescens (S3X), Micro bacterium oxydans (EC29) and Cupriavidus sp. (1C2) were chosen based on their resistance to heavy metals and capacity of adsorbing the metals. These systems were tested using solutions of Zn(II), Cd(II) and in solutions containing both metals. A synergistic effect between the strains and HAp, which is effective in removing the target heavy metals on its own, was observed, as the combination of HAp with the bacterial strains led to higher adsorption capacity for both elements. For the solutions containing only one metal the synergistic effect was greater for higher metal concentrations; 1C2 and EC29 were the most effective strains for Zn(II) and Cd(II) respectively, while S3X was less effective. Overall, an almost four-fold increase was observed for the maximum adsorption capacity for Zn(II) when 10 was employed - 0.433 mmol/g in comparison of 0.121 mmol/g for the unmodified HAP. For Cd(II), on the other hand, an almost three-fold increase was registered with EC29 bacterial strain - 0.090 vs 0.036 mmol/g for the unmodified HAp. When the solutions containing both metals were tested, the effect was more marked for lower concentrations.
- Chitosan-hydroxyapatite composites made from sustainable sources: a morphology and antibacterial studyPublication . Scalera, F.; Pereira, S. I. A.; Bucciarelli, A.; Tobaldi, D. M.; Quarta, A.; Gervaso, F.; Castro, P. M. L.; Polini, A.; Piccirillo, C.Chitosan (Cs) and hydroxyapatite (HA) 3D scaffolds/composites were prepared with a sustainable process, as HA was obtained using CaCO3 derived from cork, a natural material used as a template agent. The HA@Cs composites were prepared with HA in situ formation in a Cs solution, with a dissolution-precipitation mechanism. Different reaction times were considered, with time of 72 h leading to the best materials (sample CsHA_72). X-ray Diffraction (XRD) analysis confirmed HA formation. The analysis of Cs unit cell parameters showed that, for the unmodified Cs, the cell had larger dimensions and a higher degree of distortion than previously reported in literature; HA incorporation in the CsHA_72 composite led to a further increase in the cell dimensions. The morphology of the scaffolds was studied with Scanning Electron Microscopy (SEM) and a high level of porosity was observed; a statistical comparison was performed between the unmodified Cs and CsHA_72 to determine the pore size, structure, and distribution. This analysis, the first of this kind for this type of composites, showed smaller and more circular pores for the CsHA_72 composite (average diameter of 70 μm vs. 88 μm for unmodified Cs). The overall level of porosity, however, did not change (>77%); likewise, the Young modulus was not affected by HA incorporation (about 11 kPa). Antibacterial tests, performed on Escherichia coli and Staphylococcus aureus, showed that HA presence did not significantly reduce the antimicrobial properties; the composites were particularly effective towards S. aureus, as a >90% the bacterial population reduction was observed for an incubation time of 2 h. HA@Cs also showed excellent biocompatibility and good cell proliferation. The properties of these 3D scaffolds make them suitable for application as biomaterials.
- Effect of preparation and processing conditions on UV absorbing properties of hydroxyapatite-Fe2O3 sunscreenPublication . Teixeira, M. A. C.; Piccirillo, C.; Tobaldi, D. M.; Pullar, R. C.; Labrincha, J. A.; Ferreira, M. O.; Castro, Paula M. L.; Pintado, M. M. E.The development of innovative, safe and non-photocatalytic sunscreens is urgently needed, as it is essential to have sunscreen filters offering appropriate UV protection without damaging the environment and/or generating free radicals when in contact with the skin. Hydroxyapatite (Ca-10(PO4)(6)(OH)(2), HAp) when substituted with iron has UV protection properties and is not photocatalytic; HAp was used to make a sunscreen filter by treating cod fish bones in an iron-containing solution, and then calcining them at 700 degrees C. Here we present a systematic and advanced study on this material, to obtain a sunscreen with improved UV absorbing properties, Bones were treated with three different iron salts - Fe(II) chloride, Fe(II) lactate and Fe(III) nitrate - under various pH conditions. Results showed that Fe(II) chloride in basic pH led to the most effective iron inclusion, High energy ball milling or ultrasound were investigated to increase surface area and corresponding UV absorption; high energy ball milling treatment led to the best optical properties. The optimum powders were used to formulate UV protection creams, which showed Sun Protection Factor (SPF) values significantly superior to the control cream (up to 4.1). Moreover the critical wavelength (lambda(crit)) was >370 nm (388-389 nm) and UVA/UVB ratios were very close to 1. With these properties these sunscreens can be classified as broad UV protectors. Results also showed that combining these powders with other sunscreens (i.e. titanium dioxide), a synergic effect between the different components was also observed. This investigation showed that HAp-based sunscreens of marine origin are a valid alternative to commercial products, safe for the health of the customers and, being non-photocatalytic, do not pose a threat to the environment.
- Effects of Cu, Zn and Cu-Zn addition on the microstructure and antibacterial and photocatalytic functional properties of Cu-Zn modified TiO2 nano-heterostructuresPublication . Tobaldi, D. M.; Piccirillo, C.; Rozman, N.; Pullar, R. C.; Seabra, M. P.; Škapin, A. Sever; Castro, Paula M. L.; Labrincha, J. A.Titanium dioxide (TiO2) is well established as one of the most common photocatalysts used for many environmental, anti-pollution and antibacterial applications. However, in this work, novel photocatalytic TiO2 nanopowders were modified with additions of 1 mol% copper, zinc or copper + zinc (with various Cu: Zn ratios). These were prepared via a green sol–gel route and thermally treated at 450 C. For the first time, a direct comparison of the effects of these two modifying agents was performed, both as single and co-substitution. The compounds were thoroughly characterised by means of advanced X-ray diffraction (Whole Powder Pattern Modelling, WPPM) and spectroscopic methods (Raman and UV–vis). For functional properties, the photocatalytic activity in the gas-solid phase (nitrous oxides (NOx) and isopropanol degradation (VOCs)) was tested under UV and visible light, and antibacterial activity against Gram positive and Gram negative bacterial strains was also investigated. Neither copper nor zinc entered into the TiO2 structure, but nucleated as oxides at the surface of titania nanoparticles, thus creating a nano-heterojunction between the semiconductor materials; this also retarded the anatase-to-rutile phase transition. When comparing and contrasting their functional properties, it was found that Zn modification gave greater photocatalytic activity than that with Cu. On the contrary, for antibacterial activity, copper was shown to be a better additive. Co-modification with both metals did not improve the antibacterial behaviour, but did lead to an increase in photocatalytic activity in some cases.
- Hydroxyapatite and chloroapatite derived from sardine by-productsPublication . Piccirillo, C.; Pullar, R. C.; Tobaldi, D. M.; Castro, Paula M. L.; Pintado, M. E.In this paper, phosphate-based compounds used in biomedicine were extracted from bones and scales of European sardines (Sardina pilchardus); this is the first time that different parts of the same fish are used for the extraction of these kinds of materials. The bones and scales behave very differently with processing, producing different materials when annealed between 600 and 1000 °C. The bones formed a mixture of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and β-tri-calcium phosphate (β-Ca3(PO4)2, β-TCP), with a higher content of β-TCP obtained with increasing temperature. This bi-phasic material has a high added value, as it is employed as a bioceramic; in fact HAp has good biocompatibility while β-TCP has better resorbability than HAp, despite being less biocompatible. With scales, on the other hand, either a HAp-based material or a chlorine-substitute HAp containing material (chloroapatite (Ca10(PO4)6Cl2, ClAp) were produced. HAp-based material was obtained with a simple annealing process; for ClAp, on the other hand, a combined washing–annealing process was used. ClAp is also used in biomedicine, due to its improved resorption, mechanical properties and bioactivity. This is the first time ClAp of marine origin was produced.
- A hydroxyapatite–Fe2O3 based material of natural origin as an active sunscreen filterPublication . Piccirillo, C.; Rocha, C.; Tobaldi, D. M.; Pullar, R. C.; Labrincha, J. A.; Ferreira, M. O.; Castro, Paula M. L.; Pintado, M. E.The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO2 or ZnO, although both Fe2O3 and hydroxyapatite (Ca10(PO4)6(OH)2, HAp) doped with metal ions have been reported as being ultraviolet (UV) absorbing materials. HAp is the main component of bone; it is, therefore, highly biocompatible. In the present work, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (a-Fe2O3) form, was successfully developed from waste cod fish bones. This was achieved through a simple process of treating the bones in a Fe(II) containing solution, followed by heating at 700 C. The material showed good absorption in the whole UV range and did not form radicals when irradiated. The sunscreen cream formulated with this material could be used as a broad sunscreen protector (lcrit > 370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with the human skin. These results show that a food by-product such as fish bones could be converted into a valuable product, with potential applications in health care and cosmetics. This is the first time a HAp-based sunscreen cream has been developed and validated as a proof of concept.
- Oxygen vacancies, the optical band gap (Eg) and photocatalysis ofhydroxyapatite: Comparing modelling with measured dataPublication . Bystrov, V. S.; Piccirillo, C.; Tobaldi, D. M.; Castro, P. M. L.; Coutinho, J.; Kopyl, S.; Pullar, R.Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a calcium phosphate employed both in biomedicine and forenvironmental remediation. It is known that HAp can also be photocatalytic under UV light, probablydue to oxygen deficiencies, but the mechanism is unclear, and reported optical band gap energies varygreatly. For the first time we propose the mechanisms and precise kinds of vacancies which may causethe photocatalytic activity of HAp, and compare these theoretical data with our measured data on bothsamples of marine origin and commercial HAp powders. Density functional theory (DFT) (from firstprinciples calculations and Density of States (DOS) modelling) was used to calculate the optical bandgap energy (Eg) created by various possible oxygen vacancies in the HAp lattice: O from PO4, O fromOH, the loss of an entire OH group, or the simultaneous loss of O from PO4and an entire OH group. Themodelled values match the measured values very closely, suggesting that in non-photocatalytic HAp, ifany vacancies exist, they are O atoms from the OH group, resulting in a band gap of ∼5 eV in the UVCregion (not present in solar light at the Earth’s surface). However, in photocatalytic HAp, reduction fromthe combustion of an organic component at 1000◦C led to oxygen deficiency in the phosphate groups,probably in the O15 position, giving an Egof ∼3.45 eV, in the UVA region (present in sunlight). HeatingHAp with no organic component to 1200◦C also led to vacancies, of both an entire OH group and oxygenfrom PO4groups, which led to an intermediate Egvalue of ∼4 eV, on the boundary of the UVA-UVB regions.Absorption peaks were also predicted in the visible-light region with some types of vacancy.
- Silver-containing calcium phosphate materials of marine origin with antibacterial activityPublication . Piccirillo, C.; Pullar, R. C.; Tobaldi, D. M.; Castro, Paula M. L.; Estevez Pintado, M. M.Hydroxyapatite (Ca10(PO4)6(OH)2 – HAp) is a common material for bone replacement in artificial implants and prostheses, due to its high biocompatibility. In this work we report about the preparation of HAp-based materials of marine origin with antibacterial properties. Bones from cod fish (Gadhus morua) were treated with a dilute AgNO3 solution, to obtain HAp-containing samples with silver as a minor component. The samples were characterised by XRD, FT-IR spectroscopy and SEM, indicating the presence of HAp, β–TCP and some metallic silver. The determination of unit cell parameters, however, indicated that the majority of silver is substituted in the β-TCP lattice in ionic form. The antibacterial activity of these materials was tested towards both Gram-positive and Gram-negative bacterias; results showed that the material is very effective with Gram-negative strains such as Escherichia coli (inactivation rates of 99.82% and 99.999% after 2 and 5 h, respectively) and had a smaller but still significant effect on Gram-positive MRSA (91% inactivation rate). These results show the potentials of these samples as infection-resistant bone replacement materials.
- Surface modified hydroxyapatites with various functionalized nanostructures: computational studies of the vacancies in HApPublication . Bystrova, V. S.; Paramonova, E. V.; Bystrova, A. V.; Pullar, R. C.; Kopyl, S.; Tobaldi, D. M.; Piccirillo, C.; Avakyan, L. A.; Coutinho, J.Hydroxyapatite (HAp) has structural features that define its basic physical properties, which have an important role at the surface, and it is one of the most used materials in bone implants. In this work, we present a density functional modeling (DFT) study of HAp both as bulk and with special HAp models with various defects, especially oxygen vacancies in HAp surface layers, which can also determine photocatalytic properties, confirmed experimentally. The first-principles calculations of bulk and modified HAp were carried out using local basis (AIMPRO) and plane-wave (VASP) codes. Data obtained are analyzed using both approaches, and compared.