The Facts and Myths for the Use of Lasers in Orthopedic Surgery.

For the past three decades, laser use has been investigated, mainly on implant applications, as well as hard and soft tissue processing on orthopedics. However, despite significant technological advances and achievements in Biophotonics, lasers have yet to emerge as a successful tool for hard-tissue manipulation (e.g., osseous tissue). Indeed, a careful search in relevant literature reveals a limited number of laser-based clinical applications in orthopedics, except for the low-level laser therapy applications. In this review article, we give a brief overview of the biophysical mechanisms of bone tissue and biocompatible implants laser surgery and, in parallel, we summarize some specific pre-clinical and clinical laser applications in orthopedics. Taking into consideration the complexity of laser-based applications in inhomogeneous musculoskeletal biostructures and/or implants, it is justified to state that applying laser radiation is still an open field of multidisciplinary research before performing interventions in clinical praxis. The evidence from this study indicates the need for more experimental and theoretical studies regarding light transport on soft and hard tissues, in order to further enhance safe and efficient laser applications in orthopedics. This undoubtedly implies the need for developing modern light delivery devices for laser surgery, by means of implementing robotic guidance, specialized for medical procedures on various anatomic structures. The aforementioned studies could eventually revolutionize the clinical applications of laser technology in orthopedics.

Requirements for Designing an Effective Metallic Nanoparticle (NP)-Boosted Radiation Therapy (RT).

Many different tumor-targeted strategies are under development worldwide to limit the side effects and improve the effectiveness of cancer therapies. One promising method is to enhance the radiosensitization of the cancer cells while reducing or maintaining the normal tissue complication probability during radiation therapy using metallic nanoparticles (NPs). Radiotherapy with MV photons is more commonly available and applied in cancer clinics than high LET particle radiotherapy, so the addition of high-Z NPs has the potential to further increase the efficacy of photon radiotherapy in terms of NP radiosensitization. Generally, when using X-rays, mainly the inner electron shells are ionized, which creates cascades of both low and high energy Auger electrons. When using high LET particles, mainly the outer shells are ionized, which give electrons with lower energies than when using X-rays. The amount of the produced low energy electrons is higher when exposing NPs to heavy charged particles than when exposing them to X-rays. Since ions traverse the material along tracks, and therefore give rise to a much more inhomogeneous dose distributions than X-rays, there might be a need to introduce a higher number of NPs when using ions compared to when using X-rays to create enough primary and secondary electrons to get the desired dose escalations. This raises the questions of toxicity. This paper provides a review of the fundamental processes controlling the outcome of metallic NP-boosted photon beam and ion beam radiation therapy and presents some experimental procedures to study the biological effects of NPs' radiosensitization. The overview shows the need for more systematic studies of the behavior of NPs when exposed to different kinds of ionizing radiation before applying metallic-based NPs in clinical practice to improve the effect of IR therapy.

Combined radiation strategies for novel and enhanced cancer treatment.

Numerous studies focus on cancer therapy worldwide, and although many advances have been recorded, the complexity of the disease dictates thinking out of the box to confront it. This study reviews some of the currently available ionizing (IR) and non-ionizing radiation (NIR)-based treatment methods and explores their possible combinations that lead to synergistic, multimodal approaches with promising therapeutic outcomes. Traditional techniques, like radiotherapy (RT) show decent results, although they cannot spare 100% the healthy tissues neighboring with the cancer ones. Targeted therapies, such as proton and photodynamic therapy (PT and PDT, respectively) present adequate outcomes, even though each one has its own drawbacks. To overcome these limitations, the combination of therapeutic modalities has been proposed and has already been showing promising results. At the same time, the recent advances in nanotechnology in the form of nanoparticles enhance cancer therapy, making multimodal treatments worthy of exploring and studying. The combination of RT and PDT has reached the level of clinical trials and is showing promising results. Moreover, in vitro and in vivo studies of nanoparticles with PDT have also provided beneficial results concerning enhanced radiation treatments. In any case, novel and multimodal approaches have to be adopted to achieve personalized, enhanced and effective cancer treatment.

Probing the Effects of Ionizing Radiation on Young's Modulus of Human Erythrocytes Cytoskeleton using Atomic Force Microscopy.

PURPOSE/AIM: In this work, we examined the possible effects of ionizing radiation (IR) on biomechanical properties of the membrane-cytoskeleton of human erythrocytes, after X-ray irradiation. MATERIALS AND METHODS: Whole human blood from three healthy middle-aged volunteers was drawn by venipuncture and stored in tubes containing anticoagulant. Six blood samples were collected for each volunteer. Five of them were irradiated in the range of 0.1 Gy-2.0 Gy doses and one was used as control. The morphology and the elastic modulus of the erythrocytes were examined using atomic force microscopy and just few drops of whole blood. RESULTS: No morphological changes appeared according to the shape and the morphology of the erythrocytes. The elastic modulus of the irradiated samples was reduced with the increase of radiation dose. The findings indicate that X-ray irradiation affects the biomechanical properties of erythrocyte cytoskeleton. The mean value of Young's modulus of all the irradiated blood samples was significant difference from the control at a level, P < 0.01. CONCLUSIONS: The elastic modulus of the erythrocytes could be an indicator of the adverse effect in the human blood generated by IR exposure through a radiotherapy treatment.

Computational study of necrotic areas in rat liver tissue treated with photodynamic therapy.

BACKGROUND: Photodynamic therapy (PDT) is an alternative treatment method for liver metastatic cancer worth exploring. METHODS: This study implements a computational model of metastatic rat liver tissue subjected to superficial irradiation, after administration of 5,10,15,20-Tetrakis(3-hydroxyphenyl)chlorine (mTHPC). Spatial and temporal distributions of fundamental PDT dosimetric parameters are presented, along with calculation of necrotic distance and necrotic area percentage. Moreover, an algorithm able to calculate the minimum irradiation time needed in order to achieve various values of necrotic depth is coded. RESULTS: The intratissue distributions show that light penetration depth is approximately 1.5 mm for all fluence rate (φ) values in direction of z axis. Moreover, necrosis at r axis (horizontal axis) extends outside beam's geometrical edges at distance equal up to 55.3% of its radius. It is also noticed that both φ and concentration of ground-state photosensitizer ([S0]) can increase the necrotic distance, in a steeper manner at lower [S0] values. The irradiation time needed in order to achieve various values of necrotic depth is independent of φ for the upper tumor layers but is greater in orders of magnitude for deeper lying layers and low φ values. CONCLUSIONS: Increasing light fluence rate appears to be a more productive method than increasing photosensitizer concentration for inducing necrosis, especially in larger tumors. Finally, our results show that high φ values are necessary in order to maintain clinically applicable irradiation times.

Assessment of singlet oxygen dosimetry concepts in photodynamic therapy through computational modeling.

BACKGROUND: In photodynamic therapy (PDT) oxygen plays a vital role in killing tumor cells. Therefore oxygen dosimetry is being thoroughly studied. METHODS: Light distribution into tissue is modelled for radiation-induced fibrosarcoma (RIF) and nodular basal cell carcinoma (nBCC), in order to study the influence of blood flow on singlet oxygen concentration effectively leading to cell death ([1O2]rx) from PDT, within this light distribution. This is achieved through initial oxygen supply rate (g0) and initial molecular oxygen concentration ([3O2]0) calculations. Monte Carlo simulations and mathematical models are used for spatial and temporal distributions of [1O2]rx. Hypoxia conditions are simulated by minimizing [3O2]0 and g0. Furthermore, an optimization algorithm is developed to calculate minimum initial molecular oxygen concentration needed ([3O2]0,min) for constant [1O2]rx, when blood flow changes. RESULTS: Our results validate that in initially well-oxygenated scenarios with normal blood flow maximum [1O2]rx values are significantly higher than corresponding values of hypoxic scenarios both for RIF and nBCC models, with maximum oxygen supply rate percentage variations being independent from g0. Moreover, [1O2]rx appears to be more affected by an increase of g0 than of [3O2]0 values. For low blood flow there is a linear relationship between [3O2]0,min and g0, while for better oxygenated areas high blood flow reduces [3O2]0,min needed in exponential manner. CONCLUSIONS: Blood flow appears to be able to compensate for oxygen consumption. The developed optimization protocol on oxygen dosimetry offers a suitable combination of [3O2]0,min and g0 to achieve constant [1O2]rx, despite possible blood flow variations.

Recent Advances in Cancer Therapy Based on Dual Mode Gold Nanoparticles.

Many tumor-targeted strategies have been used worldwide to limit the side effects and improve the effectiveness of therapies, such as chemotherapy, radiotherapy (RT), etc. Biophotonic therapy modalities comprise very promising alternative techniques for cancer treatment with minimal invasiveness and side-effects. These modalities use light e.g., laser irradiation in an extracorporeal or intravenous mode to activate photosensitizer agents with selectivity in the target tissue. Photothermal therapy (PTT) is a minimally invasive technique for cancer treatment which uses laser-activated photoabsorbers to convert photon energy into heat sufficient to induce cells destruction via apoptosis, necroptosis and/or necrosis. During the last decade, PTT has attracted an increased interest since the therapy can be combined with customized functionalized nanoparticles (NPs). Recent advances in nanotechnology have given rise to generation of various types of NPs, like gold NPs (AuNPs), designed to act both as radiosensitizers and photothermal sensitizing agents due to their unique optical and electrical properties i.e., functioning in dual mode. Functionalized AuNPS can be employed in combination with non-ionizing and ionizing radiation to significantly improve the efficacy of cancer treatment while at the same time sparing normal tissues. Here, we first provide an overview of the use of NPs for cancer therapy. Then we review many recent advances on the use of gold NPs in PTT, RT and PTT/RT based on different types of AuNPs, irradiation conditions and protocols. We refer to the interaction mechanisms of AuNPs with cancer cells via the effects of non-ionizing and ionizing radiations and we provide recent existing experimental data as a baseline for the design of optimized protocols in PTT, RT and PTT/RT combined treatment.

Measurements of liposome biomechanical properties by combining line optical tweezers and dielectrophoresis.

Liposomes are well-known cell simulators and are currently studied as drug delivery systems, for a targeted delivery of higher drug concentrations, in specific cells. Novel biophotonic techniques for manipulation and characterization of liposomes have been developed; among which are optical tweezers. In our work, we demonstrate a novel use of line optical tweezers to manipulate and cause liposome deformations. Optical forces induce tension on liposomes, which are stretched along the line optical trap. The method of dielectrophoresis, combined with optical tweezers, was used to measure the exerted optical forces. As a consequence, in the case of reversible liposome deformations, the value of the shear and bending moduli of liposomes was calculated. We anticipate that the selective manipulation of liposomes will help us toward a better understanding of the cellular-liposome interactions. Studying the biomechanical properties of liposomes will provide an insight into the mechanical behavior of individual living cells, which have recently been implicated in many aspects of human physiology and patho-physiology. The biomechanical properties of cells (i.e. deformability, stiffness and elasticity) can be useful biomarkers for various disease processes and changes of the cell state.

Dynamic model of thermal reaction of biological tissues to laser-induced fluorescence and photodynamic therapy.

The aim of this work was to evaluate the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed ultraviolet (UV) laser (λ=337 nm) and a continuous-wave (cw) visible laser beam (λ=632.8 nm) using Monte Carlo modeling. Finite-element methodology was used for heat transfer simulation. The analysis of the results showed that heat is not localized on the surface, but is collected inside the tissue in lower skin layers. The simulation was made with the pulsed UV laser beam (used as excitation source in laser-induced fluorescence) and the cw visible laser (used in photodynamic therapy treatments), in order to study the possible thermal effects.

Development and characterization of oligonucleotide-tagged dye-encapsulating EPC/DPPG liposomes.

Liposomes applications in health care include meanly their ability to carry drugs and genes inside the human body for therapeutic purposes. Nevertheless their applicability can extend far beyond and could be used as analytical tools in order to perform rapid, low-cost, sensitive and specific analyses. Their physical characteristics, such as large internal volume and extended surface area, render them ideal for these applications and specifically for improving the specificity and sensitivity of the analytical assay. The purpose of this study was to develop a simple, stable and low-cost oligonucleotide-tagged liposomal formulation consisting of EggPC and DPPG with a simple to synthesize thiol-reactive conjugate (Mal-SA) incorporated into the lipid bilayer of liposomes. The prepared liposomes, having also the water soluble dye Sulforhodamine B encapsulated in their inner cavity, were characterized in terms of their physicochemical (size, size distribution, zeta-potential, lipid content) and mechanical (morphology, rigidity) properties. The results showed that the final liposomal formulation could be used in the future as analytical tool for detecting pathogen strains of microorganism in biological milieu.

Atomic force microscopy: a tool to study the structure, dynamics and stability of liposomal drug delivery systems.

Much work has been done during the past few decades to develop effective drug delivery systems (DDS), many of which are based on nanotechnology science. Liposomes are the most attractive lipid vesicles for drug delivery. The multifunctional properties of liposomes have a key role in modifying the bioavailability profile of a therapeutic agent. Different analytical techniques can be used to describe liposomes, not least applied scanning probe microscopy (SPM) techniques. Atomic force microscopy (AFM) seems to be one of the most effectively applied SPM techniques. This review article outlines the applications of AFM in evaluating the physical characteristics and stability of liposomal DDSs. Other well-known microscopy techniques used in evaluating liposome physical characteristics are also mentioned, and the contribution of AFM to evaluating liposomal stability is discussed. Among the advantages of AFM in examining the physicochemical properties of liposomal DDSs is its ability to provide morphological and metrology information on liposome properties. AFM thus appears to be a promising tool in technological characterization of liposomal DDSs.

Evaluation of trapping efficiency of optical tweezers by dielectrophoresis.

A relatively new method for measuring optically induced forces on microparticles and cells, different from the conventional Brownian motion and viscous drag force calibration methods widely used, is introduced. It makes use of the phenomenon of dielectrophoresis for the calibration of optical tweezers through the dielectrophoretic force calculations. A pair of microelectrodes is fabricated by photolithography on a microscope slide and it is connected to a high-frequency generator. The calibration of the optical tweezers setup is performed by the manipulation of polystyrene beads and yeast cells. Calibration diagrams of the transverse forces versus power are deduced for different cell radii and numerical apertures of the objective lenses. The optical system and the related technique provide a fast and easy method for optical tweezers calibration.

Q-switched versus free-running Er:YAG laser efficacy on the root canal walls of human teeth: a SEM study.

Twenty-one teeth with one root canal were prepared by the step-back technique, divided into three groups, and split longitudinally. Group A served as a control. In group B, 20 to 150 pulses of 100 micros, 30 to 70 mJ per pulse at 1 to 4 Hz from a free-running Er:YAG laser were applied to the root-canal dentin. In group C, the Q-switched Er:YAG laser, with the same energy parameters and a 190-ns pulse duration was used. Scanning electron microscopy examination revealed that control specimens had debris and smear layer obscuring the dentinal tubules at all levels in the canals without crack formation. Both groups of laser-treated dentin were clean with opened dentinal tubules except around the lased area in which there was an intact smear layer. Cracks were observed in both laser groups with higher frequency in group C. In group B, craters with different depth levels at the root canal walls were produced and the energy apparently was distributed equally, because craters were well-shaped. In contrast, the ablation efficiency in group C was questionable with the parameters used in this study. Consequently, suitable parameters of the free-running Er:YAG laser must be found before its careful use as an adjunct in endodontic therapy.