Photomechanical Waves Research Articles

Transvascular delivery of talaporfin sodium to subcutaneous tumors in mice by nanosecond pulsed laser-induced photomechanical waves

BackgroundWe previously developed a site-specific transvascular drug delivery system (DDS) based on photomechanical waves (PMWs) or laser-induced stress/shock waves (LISWs). In this study, we investigated the validity of this method to deliver a clinical photosensitizer, talaporfin sodium (TS), to subcutaneous tumors in mice and to enhance the efficacy of photodynamic therapy (PDT). MethodsTS solution (2.5 mg/kg) was intravenously injected into mice. Immediately thereafter, PMWs were applied to the tumor by irradiating a laser target with a Q-switched ruby laser pulse (0.8 J/cm2). Five hours after TS administration, some tumors were excised to evaluate the depth distribution of the delivered TS under a fluorescence microscope. Other tumors were subjected to PDT by irradiating the tissues with a 665 nm continuous-wave laser diode (75 mW/cm2, 667 s) at this timepoint. The effects of PDT were evaluated on the basis of the two primary therapeutic mechanisms of TS-mediated PDT: i) damage to tumor cells and ii) damage to endothelial cells of tumor vessels, i.e., the vascular shutdown effect on tumors. ResultsPMW application significantly increased the accumulation of TS in the tumor parenchyma but not in the tumor vessel walls; the endothelial cell junctions of tumor vessels should be the route of TS delivery enhanced by PMWs. Thus, as a result of PMW application followed by PDT, while the vascular shutdown effect on the tumors was not enhanced, direct damage to the tumor cells was increased, resulting in significant tumor growth retardation without body weight loss for 7 days after treatment.

Transdermal Drug Delivery Systems: A Focused Review of the Physical Methods of Permeation Enhancement.

The skin is the body's largest organ and serves as a site of administration for various medications. Transdermal drug delivery systems have several advantages over traditional delivery systems. It has both local and systemic therapeutic properties. Controlled plasma drug levels, reduced dosing frequency, and avoidance of hepatic first-pass metabolism are just a few of these systems' advantages. To achieve maximum efficacy, it is critical to understand the kinetics, physiochemical properties of the drug moiety, and drug transport route. This manuscript focused on the principles of various physical means to facilitate transdermal drug delivery. Some examples are iontophoresis, electrophoresis, photomechanical waves, ultrasound, needleless injections, and microneedles. Mechanical, chemical, magnetic, and electrical energy are all used in physical methods. A major advantage of physical methods is their capability to abbreviate pain, which can be used for effective disease management. Further investigation should be carried out at the clinical level to understand these methods for effective drug delivery.

Molecular delivery systems by the use of nanosecond pulsed laser-induced photomechanical waves

Molecular delivery systems by the use of nanosecond pulsed laser-induced photomechanical waves

Theranostic system for drug delivery and pharmacokinetic imaging based on nanosecond pulsed light-induced photomechanical and photoacoustic effects

For efficient and side effects-free pharmacological treatment, we here propose a theranostic system that enables transvascular drug delivery by photomechanical waves (PMWs) and photoacoustic (PA) imaging of the drug distribution; both functions are based on nanosecond laser pulses and can therefore be integrated in one system. Through optical fibers arranged around an ultrasound sensor, low-energy and high-energy nanosecond light pulses were transmitted respectively for PA imaging and PMW-based drug delivery by temporal switching. With the system, we delivered a test drug (Evans blue) to tumors in mice and visualized distributions of both the blood vessels and drug in the tissue in vivo, showing the validity of the system.

J0270204 パルスレーザ誘起フォトメカニカル波によるラットグリオーマモデルの腫瘍およびその周辺組織への経血管ドラッグデリバリー

Glioma remains one of the most deadly malignancies, for which efficacy of traditional chemotherapy is often limited due to the blood-tumor barrier (BTB). Thus, the development of a method for enhancing the BTB permeability is highly needed. In this study, we used a nanosecond pulsed laser-induced photomechanical wave (PMW) to enhance the permeability of BTB in a rat intracranial glioma model using C6 cells. A tumor was grown in the both hemispheres, and a solution of Evans blue (EB), as a test drug, was injected into the tail vein. Thereafter, a PMW was applied to one hemisphere through the cranial window and the other hemisphere served as a control. Four hours later, the rat was perfused and intensity distributions of EB fluorescence in the brain were imaged. We examined the optimum PMW pressure for safe and efficient drug delivery by changing the laser fluence, showing that the application of a PMW with a peak pressure of 〜54 MPa enabled efficient, damage-free delivery. On the basis of fluorescence microscopy, we also confirmed that a drug was delivered into targeted cells in the peripheral region of the tumor by using enhanced green fluorescent protein-expressing C6 cells.

Enhancement of the blood-tumor barrier permeability by photomechanical wave in a rat glioma model

Enhancement of the blood-tumor barrier permeability by photomechanical wave in a rat glioma model

Highly site-selective transvascular drug delivery by the use of nanosecond pulsed laser-induced photomechanical waves.

Photomechanical waves (PMWs), which were generated by irradiation of a light-absorbing material (laser target) with nanosecond laser pulses, were used for targeted transvascular drug delivery in rats. An Evans blue (EB) solution was injected into the tail vein, and laser targets were placed on the skin, muscle and brain. Each laser target was irradiated with a laser pulse(s) and 4h later, the rat was perfused and the distribution of EB fluorescence in the targeted tissues was examined. We observed laser fluence-dependent and hence PMW pressure-dependent extravasation of EB selectively in the tissues that had been exposed to a PMW(s). Uptake of leaked EB into cells in extravascular space was also observed in the targeted tissues. Tissue damage or hemorrhage was not apparent except in the brain exposed to the highest laser fluence used. The results for the brain indicated opening of the blood-brain barrier (BBB). Reverse-order (PMW application before EB injection) experiments showed that the BBB was closed in the duration from 8h to 12h after PMW application at a laser fluence of 0.5J/cm(2). Since EB molecules are strongly bound with serum albumin in blood, the results indicate that the present method can be applied not only to small molecules but also to macromolecules.

J023016 フォトメカニカル波を用いた内視鐃的分子デリバリーシステム([J023]薬剤送達とバイオメカニクス)

We previously developed an optical fiber system for endoscopic molecular delivery based on nanosecond pulsed laser-induced photomechanical waves (PMWs). However, there remained problems associated with the large outer diameter (〜2.7 mm) and rapid decrease in the available peak pressure with increasing pulse number. In this study, we examined a newly designed fiber system to overcome these problems. As a laser target (absorption material), cap-type carbon black contained silicone rubber, which was made by molding, was used; the outer diameter was as small as 1.4 mm. Decreasing rate of the peak pressure with pulse number was smaller than that with the previous system, enabling successive irradiation with at least 30 pulses. This is attributable to persistence of the plasma confinement effect in the new system. With this fiber system, we attempted transvascular delivery of Evans blue to the rat brain and efficient, site-selective extravasation of the drug was observed.

Photomechanical Wave-Driven Delivery of siRNAs Targeting Intermediate Filament Proteins Promotes Functional Recovery after Spinal Cord Injury in Rats

The formation of glial scars after spinal cord injury (SCI) is one of the factors inhibiting axonal regeneration. Glial scars are mainly composed of reactive astrocytes overexpressing intermediate filament (IF) proteins such as glial fibrillary acidic protein (GFAP) and vimentin. In the current study, we delivered small interfering RNAs (siRNAs) targeting these IF proteins to SCI model rats using photomechanical waves (PMWs), and examined the restoration of motor function in the rats. PMWs are generated by irradiating a light-absorbing material with 532-nm nanosecond laser pulses from a Q-switched Nd:YAG laser. PMWs can site-selectively increase the permeability of the cell membrane for molecular delivery. Rat spinal cord was injured using a weight-drop device and the siRNA(s) solutions were intrathecally injected into the vicinity of the exposed SCI, to which PMWs were applied. We first confirmed the substantial uptake of fluorescence-labeled siRNA by deep glial cells; then we delivered siRNAs targeting GFAP and vimentin into the lesion. The treatment led to a significant improvement in locomotive function from five days post-injury in rats that underwent PMW-mediated siRNA delivery. This was attributable to the moderate silencing of the IF proteins and the subsequent decrease in the cavity area in the injured spinal tissue.

8C32 フォトメカニカル波を用いたin vivo遺伝子導入技術の進展(OS19 メカノバイオフォトニクス)

8C32 フォトメカニカル波を用いたin vivo遺伝子導入技術の進展(OS19 メカノバイオフォトニクス)

Optical fiber-based photomechanical gene transfer system for in vivo application

We developed an optical-fiber-based photomechanical gene transfer system for endoscopic or catheter-based application. A fiber tip with a laser-absorbing film covered with a transparent plastic disk for plasma confinement was attached to a quartz fiber; the film was irradiated with nanosecond laser pulses transmitted through the fiber to generate photomechanical waves (PMWs). Characteristics of PMWs emitted from the fiber tip were examined to confirm the necessary conditions for gene transfer. We then attempted to transfer reporter genes to the rat skin as a test tissue in vivo with the fiber system, and the results showed significantly high protein levels and spatially selective pinpoint gene expressions in the tissue.

Propagation Characteristics of Photomechanical Waves and Their Application to Gene Delivery into Deep Tissue

Targeted gene transfection can be achieved by the use of photomechanical waves (PMWs) generated by irradiating a solid material with high-power nanosecond laser pulses. To examine the treatable tissue depth, we investigated propagation characteristics of PMWs and depth-dependent properties of gene transfection with different laser fluences and spot diameters. Pressure characteristics of PMWs were measured at different propagation distances using tissue phantoms and their propagation was imaged by shadowgraphing. Phantoms with various thicknesses were placed on rat dorsal skin that had been injected with plasmid DNA coding for a reporter gene and three pulses of PMWs were applied from the top of each phantom. Significant gene expression was observed in the skin even under a 15-mm-thick tissue phantom and the depth-dependent relationships between PMW parameters and gene expression level were revealed. The data obtained will be useful for determining appropriate laser parameters for PMW-based gene transfer into deep-located tissue.

Physical Approaches to Penetration Enhancement

Transdermal delivery of drugs through the skin to the systemic circulation provides a convenient route of administration for a variety of clinical indications. For transdermal delivery of drugs, stratum corneum is the main barrier layer for permeation of drug. So to circumvent the stratum corneum and to increase the flux through skin membrane, different approaches of penetration enhancement are used. Many reviews had described regarding iontophoresis, electroporation, sonophoresis, phonophoresis but other physical method of penetration enhancement like magnetophoresis, laser radiation and photomechanical waves, radio frequency, thermophoresis, microneedle based devices, skin puncture and perforation, needleless injection, suction ablation, application of pressure, skin stretching, skin abration are not exploited for reviews. These physical methods are used extensively to enhance permeation of drugs through skin. The review presents mainly the routes of penetration through skin and the physical approach of penetration enhancement to optimise the transdermal delivery system. Keywords: Transdermal; Penetration enhancement; Physical method; Skin.

Dynamic study of PLGA/CS nanoparticles delivery containing drug model into phantom tissue using CO2 laser for clinical applications

In this study, cationic nanoparticles (NPs) were prepared by coating chitosan (CS) on the surface of PLGA NPs. To our knowledge most of the work in the field of drug delivery systems using lasers has been performed using short pulses with micron and submicron durations. We carried out an experiment using superlong PLS-R (10 ms) and CW CO₂ laser modes on simulated drug-biogelatin model where drug was encapsulated by PLGA/CS NPs. Maximum depth of drug containing cavitation was achieved faster at higher powers and shorter irradiation time in CWC mode. We believe that the main mechanism at work with superlong pulses is both photothermal due to vaporization and photomechanical due to photophoresis and cavitation collapse. In the case of CW, however, it is purely photothermal. Thus, drug molecules can be transported into tissue bulk by thermal waves which can be described by the Fick's law in 3-D model for a given cavity geometry and the mechanical waves, unlike only by pure photomechanical waves (i.e. photoacoustically) as with short pulses. Therefore, our studies could offer an alternative for currently existing method for drug delivery.

Site-specific gene transfer into the rat spinal cord by photomechanical waves

Nonviral, site-specific gene delivery to deep tissue is required for gene therapy of a spinal cord injury. However, an efficient method satisfying these requirements has not been established. This study demonstrates efficient and targeted gene transfer into the spinal cord by using photomechanical waves (PMWs), which were generated by irradiating a black laser absorbing rubber with 532-nm nanosecond Nd:YAG laser pulses. After a solution of plasmid DNA coding for enhanced green fluorescent protein (EGFP) or luciferase was intraparenchymally injected into the spinal cord, PMWs were applied to the target site. In the PMW application group, we observed significant EGFP gene expression in the white matter and remarkably high luciferase activity only in the spinal cord segment exposed to the PMWs. We also assessed hind limb movements 24 h after the application of PMWs based on the Basso-Beattie-Bresnahan (BBB) score to evaluate the noninvasiveness of this method. Locomotor evaluation showed no significant decrease in BBB score under optimum laser irradiation conditions. These findings demonstrated that exogenous genes can be efficiently and site-selectively delivered into the spinal cord by applying PMWs without significant locomotive damage.

Interference of mycobacterium tuberculosis with the endocytic pathways on macrophages and dendritic cells from healthy donors: role of cathepsins

level. Some newly active rate controlled electrically based transdermal techniques including: iontophoresis, electroporation, ultrasound and photomechanical waves have been developed and commercialized for the delivery of troublesome therapeutic protein and peptide based macromolecular drugs. This study covers the development of different electrically based transdermal techniques for delivery of therapeutic protein and peptide based macromolecular drugs, current status and assesses the pros and cons of each technique and summarises the evidence-base of their drug delivery capabilities.

Assessment of tissue alteration in skin after interaction with photomechanical waves used for gene transfection

We previously delivered a therapeutic gene to skin grafts of rats by using photomechanical waves (PMWs), also called laser-induced stress waves (LISWs), with the objective of enhancing adhesion of grafted tissue. The objective of this study was to evaluate tissue alterations that are possibly caused by PMWs used for gene delivery on the basis of immunohistochemistry and electron microscopy. PMWs were generated by irradiating an elastic laser target (rubber disk) with 532 nm nanosecond laser pulses from a (of) Q-switched Nd:YAG laser. Tissue alterations were evaluated by histological analysis using hematoxylin and eosin (H&E) staining and immunohistochemical stainings, including anti-rat CD68 antibody staining to identify macrophages for detection of inflammation and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining for assessment of apoptosis. Morphological changes of cell membranes and organelles were evaluated by transmission electron microscopy. Skin exposed to PMWs that were generated at a laser fluence of 1.2 J/cm(2) (42 MPa in peak pressure), which is the optimum laser fluence (pressure) for therapeutic gene delivery to skin graft, showed no noticeable damage. At fluences higher than 1.8 J/cm(2) (>51 MPa), fragmentation of nuclei was observed and the number of CD68-positive cells increased remarkably. No significant increases in the numbers of TUNEL-positive keratinocytes and fibroblasts were observed at 1.2 J/cm(2). At fluences higher than 1.8 J/cm(2), the averaged ratio of TUNEL-positive cells also increased. The results of electron microscopy revealed that PMWs generated at 1.2 J/cm(2) caused neither damage to the cell membrane, nuclear membrane, or organelles. We observed no noticeable tissue alteration under the optimum laser irradiation conditions used for therapeutic gene delivery to a skin graft, demonstrating low invasiveness of our PMW-based gene transfection.

J0203-2-1 フォトメカニカル波を用いた標的組織への経血管ドラッグデリバリー([J0203-2]ドラッグデリバリーシステム:技術開発と医療応用(2))

In this study, we examined the use of photomechanical waves (PMWs) to transiently enhance the permeability of blood vessels for drug delivery to target tissues. PMWs were generated by irradiating a laser target (a rubber disk covered with a transparent plastic sheet) with 532-nm, nanosecond laser pulses; a laser target was placed on target tissue. As a test drug, Evans Blue (EB) was injected into a tail vein of a rat, and thereafter PMWs were applied to the dorsal skin, tibial muscle and brain. For brain, a cranial window was made. After perfusion fixation, distributions of fluorescence originating from EB in tissues were analyzed by fluorescence microscopy. The fluorescence was observed in the extravascular spaces in all tissues exposed to PMWs, and in addition, EB molecules were found to be introduced to cells in the tissues. In most cases, tissue damage was not observed. These results demonstrate the capability of PMWs for transvascular drug delivery to target tissue.

Enhancement of Topical Small Interfering RNA Delivery and Expression by Low-Fluence Erbium:YAG Laser Pretreatment of Skin

RNA interference (RNAi) is rapidly becoming an important tool that is advancing research with therapeutic aims. It is necessary to develop efficient ways of guiding small interfering RNA (siRNA) to targeted tissues to induce an RNAi effect. Herein, we report on an active method for delivering macromolecular siRNA and its plasmid vector into the skin, using erbium:YAG (Er:YAG) laser pretreatment. The amount of siRNA transported through nude mouse skin was determined with an in vitro Franz diffusion assembly. Confocal laser scanning microscopy (CLSM) was used to examine the in vivo uptake of siRNA and the vector by the skin. The stratum corneum was partially ablated with the low-fluence laser. The results of in vitro experiments indicated a significant improvement in siRNA permeation with laser exposure, which showed a 2.4- to 10.2-fold increase compared with the nontreated group depending on the fluence used (1.2-1.7 J/cm(2)). A photomechanical wave generated by filtering the laser irradiation was sufficient to enhance siRNA permeation by 5-fold. CLSM revealed intense green fluorescence from naked siRNA within the epidermis and upper dermis after laser pretreatment, producing a 3.5-fold enhancement compared with the control. The green signal intensity in 1.7 J/cm(2)-treated skin was 4.2-fold higher than that in intact skin after the in vivo topical application of the siRNA expression vector. The increased signal was mainly in the dermis. This noninvasive, precisely controlled technique for siRNA therapy provides an efficient way to deliver siRNA and its vector into the skin.

Photomechanical wave-assisted molecular delivery in oral biofilms

Photomechanical waves (PW), the product of an intense light beam interaction with a target material, enhance molecular delivery across biological membranes and skin. The ability to deliver methylene blue (MB), a fluorescent probe and photosensitizer, into bacterial biofilms was demonstrated by applying PW on saliva-derived multi-species biofilms that were developed on agar surfaces in 24-well plates. PW were generated with a Q-switched Nd:YAG laser and were directed into the biofilms in the presence of 25 μg/ml MB. The biofilms were then irradiated with red light at 665 nm. After illumination, adherent bacteria were scraped and spread over the surface of blood agar plates. Survival fractions were calculated by counting bacterial colonies. Microbial analysis was performed via a colony lift method and a DNA checkerboard assay using whole genomic probes to 40 oral microorganisms. Visual analysis by confocal scanning laser microscopy demonstrated that the application of PW enhanced the penetration depth of MB in biofilms. Exposure to MB, PW and light led to a significant reduction of the mean levels of log10 CFU counts compared with the group that received MB and light (P = 0.006). The DNA checkerboard assay showed some benefit from PW-assisted phototargeting in 25 biofilm microorganisms relative to phototreatment alone. Our data provide a basis for further exploration and optimization of PW parameters for complete eradication of microorganisms in oral microcosm biofilms.