This study reports the effects of substrate temperature and laser ablation wavelength on the structural and bioactivity properties of hydroxyapatite (HAP) coatings. The coatings were obtained using a pulsed laser deposition technique on Ti6Al4V and Si(100) substrates. Different substrate temperatures were used ranging from 25°C to 800°C. Three wavelengths of Nd:YAG pulsed laser (1064 nm, 532 nm, and 355 nm) were employed to study the ablation mechanisms and their effects on film morphology. Surface morphology was investigated by SEM with EDX Analysis and AFM. All coatings were confirmed to be grown in a granular system and it was observed that 355 nm and 532 nm produce smoother coatings. The XRD measurements showed the transition from amorphous to crystalline HAP beyond 500°C. The adhesion strength of the coatings to the substrates was analyzed by pull-out tests. Although as substrate temperature increased, adhesion also got better, further increase of temperature to 800 °C resulted in a significant decrease in bonding. Finally, the bioactivity of the coatings was assessed on multiple levels such as protein adsorption, dissolution in simulated body fluid, and cell proliferation.
Bacterial antibiotic resistance poses a pressing global health crisis, challenging conventional therapies. Efflux pumps diminish antimicrobial effectiveness by expelling drugs from bacterial cells. Multidrug efflux pumps (MEPs) have been found to transport diverse compounds, including phenothiazinium dyes like methylene blue, out of bacteria. Inhibition of MEPs offers a promising strategy to bolster the efficacy of antimicrobial photodynamic inactivation (PDT). This research adopts a synergistic approach, combining the efflux pump inhibitor (EPI) , reserpine, with silver nanoparticles (Ag NPs) and methylene blue (MB) to enhance PDT efficiency. Ag NPs were synthesized via pulsed laser ablation and characterized using TEM, UV-Vis, and PL spectra. E. coli was treated with MB, Ag NPs, and reserpine, followed by LED light irradiation. MB was twice as effective, and AgNPs/MB was six times more effective with reserpine during a sixminute irradiation. Ongoing experiments on morphological changes will be presented. AgNPs/MB with reserpine could effectively combat bacterial pathogens in open wounds and prosthetic joint infections.
Using Pulsed Laser Deposition (PLD), Zr films were deposited on silicon with laser wavelengths of 1064 nm and 532 nm, at substrate temperatures of 25 °C, 300 °C, and 500 °C, and fluences of 0.25, 0.5, and 1.0 J/cm2. The 1064 nm wavelength yielded smoother films, with surface roughness growing at higher fluences. The 300 °C temperature was ideal for crystal quality. Analyses through XRD, SEM, and AFM showed unique morphologies due to laser variables. Computations using a thin film growth model matched the empirical data, underscoring the factors critical to Zr film deposition and guiding PLD optimization for superior film quality.
Zirconia is known to be a hard-to-machine in the sintered state. In this study, the zirconia samples were patterned and then sintered. A nanosecond Nd:YAG laser operating at 1064 and was used to pattern the zirconia surface. A confined plasma was formed through the interaction between the laser beam and a copper grid template. The template was covered by a sacrificial aluminum layer, and the plasma was confined using a glass slide. The size and depth of the pattern were shown to be dependent on the shape of the grid, fluence, exposure time, confinement medium, wavelength, and beam spot size. We successfully achieved patterns ranging in size from 7 μm to 40 μm with depths of up to 3 μm. The resulting patterned surfaces were characterized using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The findings on the nature of the patterning will help in controlling functionality of zirconia, such as hardness, biofilm formation, and osteointegration.
This conference presentation was prepared for the Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXXI conference at SPIE BiOS, SPIE Photonics West 2023.
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