Fabrication and deposition of copper and copper oxide nanoparticles by laser ablation in open air

The proximity of the “post-antibiotic era”, where infections and minor injuries could be a cause of death, there are urges to seek an alternative for the cure of infectious diseases. Copper nanoparticles and their huge potential as a bactericidal agent could be a solution. In this work, Cu and Cu oxide nanoparticles were synthesized by laser ablation in open air and in argon atmosphere using 532 and 1064 nm radiation generated by nanosecond and picosecond Nd:YVO4 lasers, respectively, to be directly deposited onto Ti substrates. Size, morphology, composition and the crystalline structure of the produced nanoparticles have been studied by the means of field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), the energy dispersive spectroscopy of X-rays (EDS), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The UV-VIS absorbance of the thin layer of nanoparticles was also measured, and the antibacterial capacity of the obtained deposits tested against Staphylococcus aureus. The obtained deposits consisted of porous coatings composed of copper and copper oxide nanoparticles interconnected to form chain-like aggregates. The use of the argon atmosphere contributed to reduce significantly the formation of Cu oxide species. The synthesized and deposited nanoparticles exhibited an inhibitory effect upon S. aureus.Peer ReviewedPostprint (published version

Production of nanoparticles from natural hydroxylapatite by laser ablation

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism

Palladium nanoparticles synthesized by laser ablation in liquids for antimicrobial applications

Antibiotic resistance is a leading cause of death worldwide. In this paper, we explore new alternatives in the treatment of infections. Noble metal nanoparticles could help to mitigate this problem. In this work, palladium nanoparticles were synthesized by laser ablation in order to explore their antimicrobial capacity. To obtain palladium nanoparticles, a palladium plate immersed in water, or methanol, was ablated, using two pulsed lasers that emit radiation with wavelengths of 532 nm and 1064 nm, respectively. Pure Pd-NPs with crystalline microstructure and rounded shape were obtained. The nanoparticles’ size is more homogeneous if the laser wavelength is 532 nm, and it decreases when methanol is used as solvent, reaching mean diameters smaller than 6 nm. With the objective of studying antimicrobial activity against Staphylococcus aureus, the Pd-NPs were immobilized on the surface of titanium discs. The release of palladium ions was recorded during the first seven days, and the cytotoxicity of the immobilized NPs was also tested with L929 mouse fibroblast cell line. Palladium nanoparticles synthesized by means of the infrared laser in methanol showed a strong inhibitory effect on S. aureus and good cytocompatibility, with no toxic effect on fibroblast cells.Peer ReviewedPostprint (published version

Development of marine-based nanocomposite scaffolds for biomedical applications

Despite the increasing attention that marine organisms are receiving, many of those are not efficiently exploited and subproducts with valuable compounds are being discarded. Two examples of those subproducts are the endoskeleton of squid, from which β-­‐chitin and consecutively chitosan can be obtained; and fish-­‐bones, as a source for the production of nano-­‐ hydroxyapatite. In this work, inspired in the nanocomposite structure of human bone, marine-­‐ based nanocomposite scaffolds composed by chitosan and nano-­‐hydroxyapatite (nHA) were developed using particle aggregation methodology. Chitosan was obtained from endoskeleton of giant squid Dosidicus Gigas while fish hydroxyapatite nanoparticles were synthesized from fish-­‐bones by pulsed laser in deionized water. An innovative methodology was used based on the agglomeration of prefabricated microspheres of chitosan/nHA, generally based on the random packing of microspheres with further aggregation by physical or thermal means to create a marine nanocomposite (CHA) .The morphological analysis of the developed nanocomposites revealed a low porosity structure, but with high interconnectivity, for all produced scaffolds. Furthermore, the nanocomposite scaffolds were characterized in terms of their mechanical properties, bioactivity, crystallinity and biological behavior. The obtained results highlight that the chitosan/nHA-­‐based marine nanocomposite can be a good candidate for biomedical applications, namely on bone regeneration

Semiconductor gellan gum based composite hydrogels for tissue engineering applications

Publicado em "Journal of Tissue Engineering and Regenerative Medicine", vol. 7, supp. 1 (2013)Semiconductor hydrogels can be developed by combining the intrinsic electrical properties of semiconductors with the specific characteristics of hydrogels. These hydrogels have recently attracted much attention for applications in tissue engineering, especially formulations incorporating pyrrole and excellent biocompatibility. Several studies have reported that electrical stimulation influences the migration, proliferation and differentiation of stem cells and other cell lines [1]. The goal of this work is to use in situ chemical polymerization of polypyrrole (PPy) with gellan gum (GG) in order to obtain a new generation of semiconductor composite hydrogels. For the synthesis of GG/PPy composites, GG at 1.25% (w/v) final concentration was prepared in distilled water at room temperature. The solution was then heated under stirring at 90°C for 20 min. Temperature was decreased to 65°C and Py was added under vigorous agitation. The crosslinker solution (CaCl2, 0.18%) was added at 50°C. After 2 h, GG/Py composite hydrogels were obtained. In a further step, GG/Py samples were immersed in a solution of oxidizing agent in PBS and the reaction was carried out for 18 h under agitation at room temperature. Finally, the samples were frozen at -80°C for 48 h and lyophilized. The characterization of GG, GG/PPy and PPy samples was performed by scanning electron microscopy (SEM). The incorporation of PPy in the gellan gum was confirmed by SEM analysis. The coating with PPy increases the thickness of each sheet in 3 fold when compared with GG samples. Conductivity tests were also performed. For cytotoxicity assay, the samples were rehydrated with complete culture medium. MTS and DNA quantification assays were performed to evaluate the metabolic activity and proliferation of L929 fibroblast cells after 1, 3 and 7 days in culture with GG, GG/PPy and PPy samples. MTS assays clearly indicate a proportional relation between the cell viability and the PPy concentration: higher concentrations of PPy resulted in lower cell viability. These results show that lower concentration of PPy incorporated in the GG hydrogels can provide an adequate electrical stimulus to improve cell behavior. In conclusion, semiconductor hydrogels can be an excellent platform for tissue engineering and electrochemical therapy application

Silver nanoparticles produced by laser ablation and re-irradiation are effective preventing peri-implantitis multispecies biofilm formation

Implant-associated infection due to biofilm formation is a growing problem. Given that silver nanoparticles (Ag-NPs) have shown antibacterial effects, our goal is to study their effect against multispecies biofilm involved in the development of peri-implantitis. To this purpose, Ag-NPs were synthesized by laser ablation in de-ionized water using two different lasers, leading to the production of colloidal suspensions. Subsequently, part of each suspension was subjected to irradiation one and three times with the same laser source with which it was obtained. Ag-NPs were immobilized on the surface of titanium discs and the resultant materials were compared with unmodified titanium coupons. Nanoparticles were physico-chemically analysed to determine their shape, crystallinity, chemical composition, and mean diameter. The materials were incubated for 90 min or 48 h, to evaluate bacterial adhesion or biofilm formation respectively with Staphylococcus aureus or oral mixed bacterial flora composed of Streptococcus oralis, Actinomyces naeslundii, Veionella dispar, and Porphyromonas gingivalis. Ag-NPs help prevent the formation of biofilms both by S. aureus and by mixed oral bacterial flora. Nanoparticles re-irradiated three times showed the biggest antimicrobial effects. Modifying dental implants in this way could prevent the development of peri-implantitis.Xunta de Galicia | Ref. ED431C 2019/23Ministerio de Ciencia e Innovación | Ref. PID2020-117900RB-I00Ministerio de Ciencia e Innovación | Ref. EQC2018-004315-PInterreg Atlantic Area | Ref. Bluehuman EAPA_151/201

Solid-phase phosphorus speciation in Saharan Bodélé depression dusts and source sediments

Phosphorus (P) is one of the most important limiting nutrients for the growth of oceanic phytoplankton and terrestrial ecosystems, which in turn contributes to CO2 sequestration. The solid-phase speciation of P will influence its solubility and hence its availability to such ecosystems. This study reports on the results of X-ray diffraction, electron microprobe chemical analysis and X-ray mapping, chemical extractions and X-ray absorption near-edge spectroscopy analysis carried out to determine the solid-phase speciation of P in dusts and their source sediments from the Saharan Bodélé Depression, the world’s largest single source of dust. Chemical extraction data suggest that the Bodélé dusts contain 28 to 60% (mean 49%) P sorbed to, or co-precipitated with Fe (hydr)oxides, < 10% organic P, 21-50% (mean 32%) detrital apatite P, and 10-22% (mean 15%) authigenic-biogenic apatite P. This is confirmed by the other analyses, which also suggest that the authigenic-biogenic apatite P is likely fish bone and scale, and that this might form a larger proportion of the apatite pool (33 +/− 22%) than given by the extraction data. This is the first-ever report of fish material in aeolian dust, and it is significant because P derived from fish bone and scale is relatively soluble and is often used as a soil fertilizer. Therefore, the fish-P will likely be the most readily form of Bodélé P consumed during soil weathering and atmospheric processing, but given time and acid dissolution, the detrital apatite, Fe-P and organic-P will also be made available. The Bodélé dust input of P to global ecosystems will only have a limited life, however, because its major source materials, diatomite in the Bodélé Depression, undergo persistent deflation and have a finite thickness

Toward smart implant synthesis: bonding bioceramics of different resorbability to match bone growth rates

Craniofacial reconstructive surgery requires a bioactive bone implant capable to provide a gradual resorbability and to adjust to the kinetics of new bone formation during healing. Biomaterials made of calcium phosphate or bioactive glasses are currently available, mainly as bone defect fillers, but it is still required a versatile processing technique to fabricate composition-gradient bioceramics for application as controlled resorption implants. Here it is reported the application of rapid prototyping based on laser cladding to produce three-dimensional bioceramic implants comprising of a calcium phosphate inner core, with moderate in vitro degradation at physiological pH, surrounded by a bioactive glass outer layer of higher degradability. Each component of the implant is validated in terms of chemical and physical properties and absence of toxicity. Pre–osteoblastic cell adhesion and proliferation assays reveal the adherence and growth of new bone cells on the material. This technique affords implants with gradual-resorbability for restoration of low-load-bearing bone.Ministerio de Educación y Ciencia | Ref. MAT2006-10481Xunta de Galicia | Ref. CN2012/29

Influence of laser texturing on the wettability of PTFE

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer showing excellent thermal and electrical insulation properties and a low coefficient of friction. Due to its large stability, and hydrophobic nature, the wettability of PTFE surfaces can be reduced to transform them into superhydrophobic. In this regard, laser texturing is a fast, simple and versatile method to produce superhydrophobic PTFE surfaces in one-step, and over large areas. In this work, we used a CO2 laser to modify the surface of PTFE samples. We studied the effect of the processing parameters (laser power or irradiance, scanning speed, and spacing -overlapping- between scan lines) on the wettability of textured surfaces using water, mineral oil and ethanol/water solutions as test fluids. Laser-treated surfaces showed a hierarchical micro- and nanotopography with a cotton-like appearance. The higher roughness and large quantity of air pockets make these laser-treated surfaces superhydrophobic, and highly oleophobic. Furthermore, they remain unaltered after being in contact with strong alkali and acid solutions or after slight friction. The self-cleaning performance of these surfaces was also demonstrated. The present findings suggest that CO2 laser texturing of PTFE is suitable for the large-scale preparation of surfaces with low-wettability to different liquids.Agencia Estatal de Investigación | Ref. RTI2018-095490-J-I00Xunta de Galicia | Ref. ED431C 2019/23Xunta de Galicia | Ref. ED481D 2017/010Xunta de Galicia | Ref. ED481B 2016/047-0Xunta de Galicia | Ref. POS-A/2013/16

On the fabrication of bioactive glass implants for bone regeneration by laser assisted rapid prototyping based on laser cladding

The processing of bioceramic materials is a topic of great interest for bone regeneration; bioceramic implants are specifically appropriate for low-load applications, such as cranioplasty. In the present study, we investigated the capabilities of rapid prototyping based on laser cladding to generate three-dimensional bioactive glass implants without moulds or preplaced powder bed. 45S5 bioactive glass and lower crystallization tendency S520 bioactive glass particles were successfully injected and melted to obtain glass-derived implants with similar mechanical properties to the precursor materials. The role of processing parameters in the process outcome was analysed: optimization of the assist gas volumetric flow, the precursor glass mass flow, the substrate preheating, and the optical power of the CO2 infrared laser beam, allowed to adjust the material cooling rates to preclude extensive crystallization or cracking. The assessment of calcium hydroxyapatite precipitation ability and ion release in simulated body fluid conclude the potential osteoconductivity of the produced implants.Xunta de GaliciaMinisterio de Educación y Ciencia | Ref. MAT2006-10481EU – ATLANTIC AREA TRANSNATIONAL AREA. European Regional Development | Ref. MARMED 2011-1/16