Benjamin Valdez-Salas

Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO2 Nanotubes Using a Super-Oxidative Solution

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials.

Enhanced antifungal activity by disinfected titanium dioxide nanotubes via reduced nano-adhesion bonds

We have provided evidence that the beneficial effect of super-oxidized water (SOW) disinfected Ti6Al4V-TiO2 nanotubes (NTs) can reduce bacterial adhesion and biofilm formation. However, the need of antifungal nanostructured surfaces with osteoactive capabilities is an important goal that has been arising for dental implants (DI) applications. Thus, in the present study we isolated and tested the effects of Candida albicans (C. albicans) on disinfected, wetter and nanoroughness NTs compared to a non-modified control. Moreover, we elucidated part of the fungal adhesion mechanism by studying and relating the mycotic adhesion kinetics and the formation of fungal nanoadhesion bonds among the experimental materials, to gain new insight of the fungal-material-interface. Similarly, the initial behavior of human alveolar bone osteoblasts (HAOb) was microscopically evaluated. NTs significantly reduced the yeasts adhesion and viability with non-outcomes of biofilm than the non-modified surface. Cross-sectioning of the fungal cells revealed promoted nano-contact bonds with superior fungal spread on the control alloy interface; meanwhile NTs evidenced decreased tendency along time; suggesting, down-regulation by the nanostructured morphology and the SOW treatment. Importantly, the initial performance of HAOb demonstrated strikingly promoted anchorage with effects of filopodia formation and increased vital cell on NTs with SOW. The present study proposes SOW treatment as an active protocol for synthesis and disinfection of NTs with potent antifungal capability, acting in part by the reduction of nano-adhesion bonds at the surface-fungal interface; opening up a novel route for the investigation of mycotic-adhesion processes at the nanoscale for bone implants applications.

Silver nanoparticles from Prosopis glandulosa and their potential application as biocontrol of Acinetobacter calcoaceticus and Bacillus cereus

Abstract In the present study the characterization and properties of silver nanoparticles from Prosopis glandulosa leaf extract (AgNPs) were investigated using UV–Vis spectroscopic techniques, energy dispersive X-ray spectrometers (EDS), zeta potential and dynamic light scattering. The UV–Vis spectroscopic analysis showed the absorbance peaked at 487 nm, which indicated the synthesis of silver nanoparticles. The experimental results showed silver nanoparticles had Z-average diameter of 421 nm with higher stability (−200 mV). The EDS analysis also exhibited presentation of silver element. Additionally, the different concentrations of AgNPs (25, 50, 75 and 100 mg/mL) showed antibacterial activity against Acinetobacter calcoaceticus and Bacillus cereus. Finally, AgNPs from leaf extracts of P. glandulosa may be used as an agent of biocontrol of microorganism of importance medical. However, further studies will be needed to fully understand the antimicrobial activity of silver nanoparticles obtain from P. glandulosa.

Disinfection of titanium dioxide nanotubes using super-oxidized water decrease bacterial viability without disrupting osteoblast behavior.

Amorphous titanium dioxide (TiO2) nanotubes (NTs) on Ti6Al4V alloy were synthesized by anodization using a commercially available super-oxidized water (SOW). The NT surfaces were sterilized by ultraviolet (UV) irradiation and disinfected using SOW. The adhesion and cellular morphology of pig periosteal osteoblast (PPO) cells and the behavior of Staphylococcus aureus (S. aureus) cultured on the sterilized and disinfected surfaces were investigated. A non-anodized Ti6Al4V disc sterilized by UV irradiation (without SOW) was used as control. The results of this study reveal that the adhesion, morphology and filopodia development of PPO cells in NTs are dramatically improved, suggesting that SOW cleaning may not disrupt the benefits obtained by NTs. Significantly decreased bacterial viability in NTs after cleaning with SOW and comparing with non-cleaned NTs was seen. The results suggest that UV and SOW could be a recommendable method for implant sterilization and disinfection without altering osteoblast behavior while decreasing bacterial viability.

The promotion of antibacterial effects of ti6al4v alloy modified with TiO 2 nanotubes using a superoxidized solution

The purpose of the present study was to synthetize 80 nm diameter TiO2 nanotubes (NTs) on Ti6Al4V alloy using a commercially superoxidized water (SOW) enriched with fluoride to reduce anodization time and promote the antibacterial efficacy against Staphylococcus aureus (S. aureus). The alloy discs were anodized for 5 min and as a result, NTs of approximately 80 nm diameters were obtained with similar morphology as reported in previous studies using longer anodization times (1-2 h). Filed emissionscanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the materials surfaces. The NTs showed significantly decreased S. aureus viability after 1, 3, and 5 days of culture in comparison to nonanodized alloy. Likewise, SEM analysis also suggested lower bacterial adhesion on the NTs surface. No differences in bacterial morphology and topography were observed on both materials, as analyzed by SEM and atomic force microscopy (AFM). In conclusion, 80 nm diameter NTs were grown on Ti6Al4V alloy in 5 min by using a SOW solution enriched with fluoride, which resulted in a material with promoted antibacterial efficacy against S. aureus for up to 5 days of in vitro culture when compared to nonanodized alloy.

In Vitro Assessment of Early Bacterial Activity on Micro/Nanostructured Ti6Al4V Surfaces

It is imperative to understand and systematically compare the initial interactions between bacteria genre and surface properties. Thus, we fabricated a flat, anodized with 80 nm TiO2 nanotubes (NTs), and a rough Ti6Al4V surface. The materials were characterized using field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). We cultured in vitro Staphylococcus epidermidis (S. epidermidis) and Pseudomonas aeruginosa (P. aeruginosa) to evaluate the bacterial-surface behavior by FE-SEM and viability calculation. In addition, the initial effects of human osteoblasts were tested on the materials. Gram-negative bacteria showed promoted adherence and viability over the flat and rough surface, while NTs displayed opposite activity with altered morphology. Gram-positive bacteria illustrated similar cellular architecture over the surfaces but with promoted surface adhesion bonds on the flat alloy. Rough surfaces supported S. epidermidis viability, whilst NTs exhibited lower vitality. NTs advocated promoted better osteoblast organization with enhanced vitality. Gram-positive bacteria suggested preferred adhesion capability over flat and carbon-rich surfaces. Gram-negative bacteria were strongly disturbed by NTs but largely stimulated by flat and rough materials. Our work proposed that the chemical profile of the material surface and the bacterial cell wall characteristics might play an important role in the bacteria-surface interactions.

Machine vision system for UAV navigation

Unmanned Aerial Vehicle (UAV) navigation requires Machine Vision Systems to determine physical values of near distanced objects. These machine vision systems must respond in sufficiently amount of time using less scanning data from the observed objects. A novel Technical Vision System (TVS), which uses DC motors and laser triangulation to determine spatial coordinates of these objects, is offered and used for UAV navigation. Present paper thereby shows the implementation of open-loop control algorithm, to position the TVS laser ray in the UAV Field of View (FOV). Issues of this implementation, experimental realization and results are presented, as the theoretical concept of a continuous FOV derived.

UAV remote laser scanner improvement by continuous scanning using DC motors

Previous research have shown the advantages of a novel Technical Vision System (TVS), developed at the Autonomous University of Baja California (UABC), which uses triangulation to determine spatial coordinates on any object under observation. Present paper proposes a new application for the TVS use on drones with remote laser scanner in agriculture to determine a vegetation index of scanned crops. Thereby the needed algorithm to position the laser ray in the TVS field-of-view are proposed, implemented using microcontroller and tested using various experimental factors. Experimentation results shows the advantages and disadvantages of every algorithm comparing the positioning errors after control.

Resolution improvement of accelerometers measurement for drones in agricultural applications

In agricultural tasks, monitoring of large fields is required. In the last years automatic/autonomous monitoring has been researched; where unmanned aerial vehicles (UAV)-commonly known as drones-are used. For these systems, constrains related with autonomy during flight arise. In order to control properly the UAVs during flight, they require to measure physical variables, in a fast and accurate way. Also, the weight of instruments must be reduced for improving autonomy. In general, aerial vehicles obtain parameters like position, velocity and acceleration using inertial navigation systems. Regarding to this concern, in this work application of a novel technique for measurements onboard UAVs-particularly inertial measurement unit or IMU-is proposed. There are accelerometers inside the IMU. These accelerometers have a frequency domain output. The speed and position are calculated by the INS from acceleration. The acceleration is obtained from frequency measurements of the accelerometers output. For this reason an accurate and fast frequency measurement method is required. In this work, for this particular application, frequency measurement using principle of rational approximations is proposed. This technique allows to measure frequency in short time and with high accuracy, using a few electronic components. Due this properties, it perfectly fits requirements for UAVs.

Silver nanoparticles from Justicia spicigera and their antimicrobial potentialities in the biocontrol of foodborne bacteria and phytopathogenic fungi

In the present work, the biosynthesis of silver-nanoparticles (AgNP) was evaluated using the aqueous extract from Justicia spicigera. The obtained silver nanoparticles were characterized using UV-visible spectroscopic techniques, energy dispersive X-ray spectrometers (EDS), zeta potential and dynamic light scattering. The antimicrobial activity of biosynthesized AgNP was tested against foodborne bacteria (Bacillus cereus, Klebsiella pneumoniae and Enterobacter aerogenes) and phytopathogenic fungi (Colletotrichum sp., Fusarium solani, Alternaria alternata and Macrophomina phaseolina). The elemental profile of synthesized nanoparticles using J. spicigera shows higher counts at 3keV due to silver, confirming the formation of silver nanoparticles. Scanning electron microscopy (SEM) analysis showed a particle size between 86 and 100nm with spherical morphology. AgNP showed effective antibacterial and antifungal activity against the tested organisms principally with B. cereus, K. pneumoniae, E. aerogenes, A. alternata and M. phaseolina. Therefore, further studies are needed to confirm the potential of AgNP from J. spicigera in the control of indicator organisms under field conditions.