Photodynamic therapy (PDT) is a medical treatment that utilizes photosensitizing agents, along with light, to produce reactive oxygen species that can kill nearby cells. When the photosensitizer is exposed to a specific wavelength of light, it becomes activated and generates reactive oxygen that can destroy cancer cells, bacteria, and other pathogenic micro-organisms. PDT is commonly used in dermatology for treating actinic keratosis, basal cell carcinoma, and other skin conditions. It is also being explored for applications in oncology, such as treating esophageal and lung cancers, as well as in ophthalmology for age-related macular degeneration. In this study, we provide a comprehensive review of PDT, covering its fundamental principles and mechanisms, as well as the critical components for its function. We examine key aspects of PDT, including its current clinical applications and potential future developments. Additionally, we discuss the advantages and disadvantages of PDT, addressing the various challenges associated with its implementation and optimization. This review aims to offer a thorough understanding of PDT, highlighting its transformative potential in medical treatments while acknowledging the areas requiring further research and development.

In this study, the effects of substrate temperature and ablation wavelength/mechanism on the structural, mechanical, and bioactivity properties of hydroxyapatite (HA) coatings were investigated. HA coatings were deposited on both Si(100) and Ti6Al4V surfaces. Substrate temperature varied from room temperature to 800 °C. Depositions were performed in Ar/H₂O and vacuum environments. X-ray diffraction, scanning electron microscopy, and atomic force microscopy techniques were used to analyze structural and morphological variations. The adherence of coatings to the substrates was assessed by the pull-out method. The obtained data indicated that with the temperature increase, the coatings steadily crystallized. However, temperatures above 700 °C adversely affected protein adsorption and adhesion properties. Similar trends were confirmed via pull-out testing, protein adsorption, and cell proliferation tests. The ablation mechanism was also proven to play an important role in the deposition process. Overall, this study provides further evidence that crystallinity is a vital factor in the functionality of the coatings and depends on the deposition conditions. However, all measurements directly indicated that beyond 700 °C, the morpho-structural, mechanical, and bioactivity properties degrade.

Zirconium (Zr) thin films were deposited on silicon using pulsed laser deposition (PLD) with two laser wavelengths (1064 nm and 532 nm) and varying substrate temperatures (25 °C, 300 °C, and 500 °C) and laser fluences (0.25, 0.5, 1.0 J/cm²). Results indicate that smoother films were obtained with 1064 nm and surface roughness increased with higher fluences. Optimal crystalline films were obtained at 300 °C. XRD, SEM, and AFM analysis revealed distinct patterns and peaks related to laser parameters. The growth mechanisms of a Zr film were computed based on a well-known continuum model of thin film growth. Our simulations agree with experimental observations. The study highlights crucial factors affecting Zr thin film deposition and provides insights for optimizing PLD parameters to achieve high-quality films.

Zirconia is increasingly favored for dental implants owing to its corrosion resistance, hypoallergenic properties, and superior esthetics, but its biocompatibility remains a challenge. This study explores laser-assisted surface modification to enhance zirconia bioactivity. Zirconia transitions from the monoclinic to the tetragonal phase during sintering, with mixed phases observed in the pre-sintered stage. These transitions are critical for understanding its structural stability and malleability. Grid patterns were imprinted on the green body implant surface using a 1064 nm Nd-YAG laser (Continuum Surelite II, San Jose, CA, USA), with mesh sizes ranging from 7 to 50 µm and depths up to 2 µm, controlled by varying laser fluence, irradiation time, and templates. SEM, AFM, and XRD analyses were used to characterize the surface morphology and crystallography. Protein adsorption studies compared two patterned samples with different surface coverage—the first sample had a patterned area of 0.212 cm² (27%), while the second sample had a patterned area of 0.283 cm² (36%)—to a control sample. Protein adsorption increased by 92% in the first and 169% in the second sample, demonstrating a direct correlation between increased pattern area and bioactivity. Enhanced protein adsorption facilitates cell attachment and growth, which are crucial for improving osseointegration. These results underscore the potential of laser-assisted surface modification to optimize zirconia’s performance as a medical implant material.

Gold nanoparticles (AuNPs) synthesized via picosecond pulsed laser ablation were investigated as enhancers of methylene blue (MB)-mediated photodynamic therapy (PDT) against Escherichia coli. AuNPs produced at 532 and 1064 nm with frequencies of 20–50 kHz showed frequency- and size-dependent effects, with 50 kHz yielding the highest particle concentrations and smaller particles enhancing reactive oxygen species (ROS) generation. UV-Vis and fluorescence spectroscopy confirmed nanoparticle formation and plasmonic properties consistent with TEM measurements. Photobleaching assays demonstrated that AuNPs significantly increased MB singlet oxygen generation, while the efflux pump inhibitor INF-55 further amplified bacterial killing without altering net ROS yield. In vitro assays revealed that INF-55 combined with MB/AuNPs achieved ~59% higher bacterial deactivation compared to MB/AuNPs alone. Molecular docking confirmed stronger binding of INF-55 to the AcrB efflux pump (−9.1 kcal/mol) than MB, supporting its role as a competitive inhibitor that promotes intracellular MB retention. These findings establish a dual-action PDT strategy in which AuNPs enhance ROS production and INF-55 augments antibacterial efficacy via efflux pump inhibition. Together, this platform provides a proof of concept for future translation to biofilm- and tissue-based infection models, and potentially to localized clinical applications such as prosthetic joint, catheter-associated, or chronic wound infections where conventional sterilization or systemic antibiotics are insufficient.