Search

Antimicrobial photodynamic therapy (aPDT) using aminolaevulinic acid (ALA) is a promising alternative to antibiotic therapy. ALA administration induces protoporphyrin IX (PpIX) accumulation in bacteria, and light excitation of the accumulated PpIX generates singlet oxygen to bacterial toxicity. Several factors, including drug administration and light irradiation conditions, contribute to the antibiotic effect. Such multiple parameters should be determined moderately for effective aPDT in clinical practice.A mathematical model to predict bacterial dynamics in ALA-aPDT following clinical conditions was constructed. Applying a pharmacokineticspharmacodynamics (PK-PD) approach, which is widely used in antimicrobial drug evaluation, viable bacteria count by defining the bactericidal rate as the concentration of singlet oxygen produced when PpIX in bacteria is irradiated by light.The in vitro experimental results of ALA-aPDT for Pseudomonas aeruginosa demonstrated the PK-PD model validity. The killing rate has an upper limit, and the lower power density for a long irradiation time can suppress the viable bacteria number when the light dosages are the same.This study proposed a model of bacterial viability change in ALA-aPDT based on the PK-PD model and confirmed, by in vitro experiments using PA, that the variation of bacterial viability with light-sensitive substance concentration and light irradiation power densities could be expressed. Further validation of the PK-PD model with other gram negative and gram positive strains will be needed.

The increase in root caries is a serious problem as society ages. Root caries is diagnosed by inspection and palpation, which are qualitative. A method to objectively and quantitatively evaluate the progress of root caries in a clinical setting is strongly desired. The root caries could be diagnosed by measuring hardness because dentin becomes softer as the caries progresses. Vickers hardness has been customarily used as an indicator of tooth hardness. However, this method cannot be used to in vivo teeth because the teeth must be dried prior to measurement to make the indentation. A hardness meter using an indenter with light for tooth monitoring (HAMILTOM) is proposed as an optical device. HAMILTOM could measure hardness of teeth in wet condition as a dark area while applying a load to dentins without drying. Therefore, HAMILTOM may realize hardness measurements of in vivo teeth in a clinical setting quantitatively.The aim of our study is to demonstrate the optical dentin hardness measuring device HAMILTOM using bovine dentin with different demineralization times and to evaluate the correlation between the dark areas measured by HAMILTOM and the Vickers hardness measured by the Vickers hardness tester.The samples were 20 bovine dentins. They were demineralized by a lactic acid solution with different times and divided into groups 1 and 2 of 10 samples each. In both groups, the dark areas and Vickers hardness were measured for each sample. Group 1 was used to obtain a calibration curve to calculate Vickers hardness from the dark area. Group 2 was used to validate the calibration curve obtained from the dentin samples of group 1.The areas appearing black without a total internal reflection of the indenter measured by HAMILTOM increased as the demineralization time increased. Additionally, the Vickers hardness of group 2 calculated by the dark areas of group 2 and the calibration curve obtained in group 1 and the Vickers hardness of group 2 measured by the Vickers hardness tester were strongly correlated with a determination coefficient of 0.99.The results demonstrate that HAMILTOM may be a suitable alternative to the conventional method. Unlike the conventional method, which cannot be used for in vivo teeth, HAMILTOM holds potential to quantitatively evaluate the progress of caries in in vivo teeth.

Background and objectives In this study, the threshold fluences for disrupting the melanosomes for pigmented skin lesion treatment were determined using a 755-nm picosecond laser for clinical use. Based on the melanosome disruption thresholds, incident fluences corresponding to the target lesion depths were evaluated in silico for different laser spot sizes. Study design/materials and methods Melanosome samples were isolated from porcine eyes as alternative samples for human cutaneous melanosomes. The isolated melanosomes were exposed to 755-nm picosecond laser pulses to measure the mean particle sizes by dynamic light scattering and confirm their disruption by scanning electron microscopy. The threshold fluences were statistically determined from the relationships between the irradiated fluences and the mean particle sizes. Incident fluences of picosecond laser pulses for the disruption of melanosomes located at different depths in skin tissue were calculated through a light transport simulation using the obtained thresholds. Results The threshold fluences of 550- and 750-picosecond laser pulses were determined to be 2.19 and 2.49 J/cm2 , respectively. The numerical simulation indicated that appropriate incident fluences of picosecond laser pulses differ depending on the depth distribution of the melanosomes in the skin tissue, and large spot sizes are desirable for disrupting the melanosomes more deeply located within the skin tissue. Conclusion The threshold fluences of picosecond laser pulses for melanosome disruption were determined. The incident fluence analysis based on the thresholds for melanosome disruption provides valuable information for the selection of irradiation endpoints for picosecond laser treatment of pigmented skin lesions. Lasers Surg. Med. © 2021 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.

An accurate inversion technique in double integrating sphere (DIS) measurement is essential for determining the optical properties of biological tissue. Although there are several established techniques, the computational time and complexity for spectral analysis require some approximations of the anisotropy factor g and refractive index n. We aim to demonstrate an artificial neural network (ANN) based method to determine the absorption $$\mu _\mathrm{a}$$ and scattering $$\mu _\mathrm{s}$$ coefficients of biological tissue from the diffuse reflectance R, total transmittance T, g, and n. ANNs were trained using dataset generated by calculating light transport in the DIS setup with a Monte Carlo method. The measured R and T spectra and the wavelength-dependent g and n were inputted to calculate $$\mu _\mathrm{a}$$ and $$\mu _\mathrm{s}$$ . Due to the simple and fast calculation, the ANN-based method can calculate the $$\mu _\mathrm{a}$$ and $$\mu _\mathrm{s}$$ spectra assuming the wavelength dependence of g and n. The relative errors of reconstruction by the trained networks were 1.1% and 0.95% for $$\mu _\mathrm{a}$$ and $$\mu _\mathrm{s}$$ , respectively. Each optical property spectra (total 662 points) was obtained in 1.1 ms. The proposed method can determine $$\mu _\mathrm{a}$$ and $$\mu _\mathrm{s}$$ in the DIS measurement assuming wavelength dependent g and n.

Since 2000, Federation Dentaire Internationale has advocated for “minimal intervention” dental treatments. The dental field has demanded less-invasive caries treatment methods. However, recent caries treatments using a microsecond-pulsed free-running Er:YAG laser with a pulse duration of 200–300 μs have issues with non-selectivity for caries due to the thermal effect caused by the laser. To improve the selectivity by reducing the thermal effect, the ablation characteristics of a nanosecond-pulsed Er:YAG laser are investigated. A Q-switched Er:YAG laser with a rotating mirror Q-switching system attached to a flash lamp-pumped Er:YAG laser and a free-running Er:YAG laser were used. The pulse duration of the Q-switched Er:YAG laser was 80–130 ns, while that of the free-running Er:YAG laser was around 200 μs. The pulse repetition rate of the free-running Er:YAG laser was constant at 10 Hz, but that of the Q-switched Er:YAG laser fluctuated between 10 and 23 Hz. The fluence was 6, 10, or 14 J/cm2. The samples were bovine sound dentin slices and caries models. Caries models were prepared by immersing sound dentin slice samples into a 0.1-M lactic acid solution for 24 h at 37 °C. The samples were irradiated with the two lasers horizontally without water spray for 1, 2, or 4 s. Laser irradiation experiments indicate that the selectivity towards caries occurs at the fluence of 6 J/cm2 without water spray. The ablation depth of a demineralized dentin slice by the Q-switched Er:YAG laser is about three times that by the free-running Er:YAG laser at the fluence of 10 J/cm2. In addition, the Q-switched Er:YAG laser suppresses the thermal effect reducing the range of the thermal melting area. Caries dentin may be selectively removed without water spray using the Q-switched Er:YAG laser with suppressing dental pulp necrosis because the temperature increase is below 5 °C. The ablation depths by the Q-switched Er:YAG are about three times larger than those using the free-running Er:YAG laser.

To enhance the potency of photosensitizer, we developed a novel photosensitizer, Laserphyrin®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin®, Meiji Seika Pharma) into hemagglutinating virus of Japan envelope (HVJ-E). In this study, we examined the optimal Laserphyrin® concentration for preparation of Laserphyrin®-HVJ-E which had photocytotoxicity and maintained direct cytotoxicity derived from HVJ-E. Then, potency of Laserphyrin®-HVJ-E and Laserphyrin® were compared in vitro using castration-resistant prostate cancer cell line (PC-3). A laser diode (L660P120, Thorlabs, USA) with a wavelength of 664 nm was used for light activation of Laserphyrin®, which corresponds to an absorption peak of Laserphyrin® and provides a high therapeutic efficiency. The photocytotoxicity and direct cytotoxicity of Laserphyrin®-HVJ-E prepared using various Laserphyrin® concentrations were evaluated using PC-3 cell in vitro. We categorized the treatment groups as Group 1: 50 μL of D-MEM treatment group, Group 2: HVJ-E treatment group, Group 3: Laserphyrin®-HVJ-E treatment group, and Group 4: Laserphyrin® treatment group. Group 3 was subjected to different concentrations of Laserphyrin®-HVJ-E suspension, and all groups were subjected to different incubation periods (24, 48 h), (30 min, 1 h, or 3 h,) respectively, without and after PDT. Laserphyrin®-HVJ-E prepared using 15 mM Laserphyrin® had high photocytotoxicity and maintained HVJ-E’s ability to induce direct cytotoxicity. Therapeutic effect of Laserphyrin®-HVJ-E was substantially equivalent to that of Laserphyrin® alone even at half Laserphyrin® concentration. By utilizing Laserphyrin®-HVJ-E, PDT could be performed with lower Laserphyrin® concentration. In addition, Laserphyrin®-HVJ-E showed higher potency than Laserphyrin® by combining cytotoxicities of HVJ-E and PDT.

The possibility of using photoacoustic imaging for functional diagnosis has attracted much attention especially in the clinical field. Among such imaging systems, a system, which offers real-time imaging using compact and low-priced LEDs as a light source, has appeared. Compared to solid state lasers, the LED pulse energy was extremely small, so it had been thought that imaging would be extremely difficult, but by adding a pre-amplifier, real time photoacoustic imaging became possible. However the signal-to-noise ratio (SNR) and the amplifier gain needed for making real time imaging possible have remained unclear. The present study was designed to clarify these data. The results showed that, using a tissue phantom and human fingers, an SNR > 4 and amplifier gain > 80dB were required, and demonstrated why making an image without a pre-amplifier had proved difficult.

In photodynamic therapy (PDT), singlet oxygen ([Formula: see text]) is the main species responsible for promoting tumor cell death. The determination of the quantum yield (ΦΔ) of a photosensitizer (PS) is important for dosimetry. The purpose of this paper is to quantify the [Formula: see text] generated by the PS by near-infrared spectroscopy (NIRS). The ΦΔ of different PS species were measured by the detection of near-infrared [Formula: see text] luminescence. From the measurement results, the ΦΔ of talaporfin sodium, protoporphyrin IX (PpIX), and lipidated PpIX (PpIX lipid) were measured as 0.53, 0.77, and 0.87, respectively. In addition, the ΦΔ values of PpIX in a hypoxic and oxic solution were evaluated, since tumors are associated with regions of hypoxia. The measured ΦΔ indicated a same value at high (DO: 20%) and low (DO: 1%) oxygen concentrations. Using the measured ΦΔ, the amount of [Formula: see text] generated by the PSs was estimated using [[Formula: see text]] = D*ΦΔ, where D* is the total excited PS concentration. The generated [Formula: see text] amounts were little different at the high and the low oxygen concentrations, and the generated [Formula: see text] amount for each PS was different depending on each ΦΔ. The NIRS measurement determined the ΦΔ of talaporfin sodium, PpIX, and PpIX lipid. The quantitative evaluation based on the measured ΦΔ will support the development of PDT treatment monitoring and design.

Background: Drug-resistant bacterial infections are a global problem. Novel treatment methods that simultaneously control infection and promote wound healing without leading to new resistant bacteria are needed. Photodynamic therapy (PDT) is a useful antibiotic-free treatment approach. Our previous studies have shown that PDT for skin ulcers infected with methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA) can achieve infection control and promoting wound healing in vitro and in vivo murine model. Here, we investigated the safety and effectiveness of PDT with 5-aminolevulinic acid (ALA-PDT) for human skin ulcers infected with MRSA and PA. Methods: ALA-PDT with macrogol ointment containing 0.5% ALA-HCl and 0.005% EDTA-2Na (wavelength 410 nm, 10 J/cm2) was performed on consecutive days in patients aged ≥20 years who had skin ulcers infected with MRSA and PA. Results: Six of our seven patients showed a clear tendency for ulcer area reduction to ≤60% of that measured at baseline. ALA-PDT was judged to be completely safe in all patients; only one patient had an increase in bacterial count. Conclusions: ALA-PDT is safe and effective for MRSA and PA infected skin ulcers to control and heal wound.

Endoscopic submucosal dissection (ESD) has been at the forefront of international attention as a less invasive treatment for early gastrointestinal cancer. Currently, ESD involves the use of an electrosurgical knife for mucosal incision and subsequent submucosal dissection. However, it has been reported that perforation occurs in approximately 5% of cases. To enhance tissue selectivity with this modality, we focused on applying a laser to ESD (laser ESD). A CO2 laser was chosen as the surgical knife because the saline or sodium hyaluronate solution injected into the submucosal layer during the current ESD procedure has a high absorption coefficient at the wavelength of the CO2 laser. Thus, the purpose of this study is to quantitatively clarify the safety and efficacy of laser ESD for the colon. First, we validated a porcine colon as a model of the human colon in terms of optical and thermal properties. Next, ex vivo experiments on the safety and efficacy of laser ESD were performed. In ex vivo experiments using extracted porcine colon tissue, an incision depth of 0.5–1.0 mm was obtained without thermal damage to the muscle layer when the power density was set at 17, 22, or 28 W/mm2. In addition, less thermal damage was observed in tissue incised with this method compared with electrosurgical knives. These results might be explained by the strong absorption of the CO2 laser by the saline injected into the submucosa. Therefore, laser ESD is expected to be a safer method for the treatment of early colon cancer.

Diffuse reflectance spectroscopy is a widely used technique for medical applications that may analyze the optical characteristics of biological tissues. By using diffuse reflectance spectroscopy, different tissue types can be distinguished based on specific changes on reflected light spectrum that are a result of differences on a molecular level between compared tissues. Identification of the structural features of tissue can be performed by applying diffuse reflectance spectroscopy, and the spectra obtained from this technique could provide important diagnostic information about the tissue morphology and physiology. Moreover, different tissue types can be classified using diffuse reflectance spectroscopy, during surgery on the basis of their optical properties that are related to the tissue morphology and constituents. In recent years, several research groups have been shown the feasibility of diffuse reflectance spectroscopy in discriminating benign and malignant tissue, and thus making it a good competitor for margin assessment. Therefore, the diffuse reflectance spectroscopy has the possibility to become an important optical means for disease diagnosis, treatment and prognosis monitoring. This review represents a summary of the literature on diffuse reflectance spectroscopy and its important clinical applications.

In picosecond laser treatments for pigmented skin lesions, selective optical absorption by melanin particles packaged in cutaneous melanosomes results in producing treatment effects. The treatment effects have been numerically analyzed by simulating light propagation and thermal diffusion at a tissue scale. During picosecond laser irradiation, cutaneous melanosomes are disrupted by explosive vaporization through optical absorption by melanin particles. A multiscale modeling of picosecond laser skin treatments is required for the quantitative evaluation of picosecond therapeutic laser devices. By the multiscale modeling, the treatment effects can be evaluated based on the interactions with picosecond laser pulses at each scale of molecule, organelle, cell, and tissue. For the multiscale modeling, the purpose of this study is to investigate a response of melanin particles to picosecond laser pulses at a molecular scale. Homogeneous melanin suspensions were prepared to irradiate 550-picosecond laser pulses at a wavelength of 755 nm. As a result of comparing morphological characteristics between unirradiated melanin particles and melanin particles irradiated by picosecond laser pulses with a scanning electron microscope and a particle size analyzer using dynamic light scattering, almost no significant change was found. The results suggested that melanin particles do not change the structures and are involved as a heat source to cause damage on lipid bilayer membranes within melanosomes in picosecond laser treatments for pigmented skin lesions.

Photobleaching and photoproduct formations are considered essential phenomena in improving the efficacy of photodynamic diagnosis and therapy (PDD and PDT). We investigated the photobleaching of protoporphyrin IX (PpIX) by measuring its concentration with mass spectrometry (MS). The reduction in the concentration of PpIX dissolved in dimethyl sulfoxide was measured during PDD and PDT conditions using lasers with wavelengths of 405 and 635 nm, respectively, at a power density of 10, 50, or 100 mW/cm2 . The obtained results were compared with the results of conventional fluorescence spectroscopy and previously reported results. Our results demonstrate the variation in the MS-based photobleaching coefficient of PpIX with the power density, while the fluorescence-based photobleaching coefficient was independent of the power density. The results of MS also show faster photobleaching of PpIX in comparison with that obtained from fluorescence. The difference may be attributed to the change in the fluorescence quantum yield of PpIX with its concentration and the effect of fluorescence emission from the PpIX photoproducts. Thus, an MS-based investigation of the photobleaching poses to be a more stable investigation form. Our finding highlights the importance of recognizing the potential significance of these discoveries in the PDD and PDT dosimetry and efficacy.

To enhance the potency of photosensitizer, we developed a novel photosensitizer, Laserphyrin®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin®, Meiji Seika Pharma) into hemagglutinating virus of Japan envelope (HVJ-E). In this study, we examined the optimal Laserphyrin® concentration for preparation of Laserphyrin®-HVJ-E which had photocytotoxicity and maintained direct cytotoxicity derived from HVJ-E. Then, potency of Laserphyrin®-HVJ-E and Laserphyrin® were compared in vitro using castration-resistant prostate cancer cell line (PC-3). A laser diode (L660P120, Thorlabs, USA) with a wavelength of 664 nm was used for light activation of Laserphyrin®, which corresponds to an absorption peak of Laserphyrin® and provides a high therapeutic efficiency. The photocytotoxicity and direct cytotoxicity of Laserphyrin®-HVJ-E prepared using various Laserphyrin® concentrations were evaluated using PC-3 cell in vitro. We categorized the treatment groups as Group 1: 50 μL of D-MEM treatment group, Group 2: HVJ-E treatment group, Group 3: Laserphyrin®-HVJ-E treatment group, and Group 4: Laserphyrin® treatment group. Group 3 was subjected to different concentrations of Laserphyrin®-HVJ-E suspension, and all groups were subjected to different incubation periods (24, 48 h), (30 min, 1 h, or 3 h,) respectively, without and after PDT. Laserphyrin®-HVJ-E prepared using 15 mM Laserphyrin® had high photocytotoxicity and maintained HVJ-E's ability to induce direct cytotoxicity. Therapeutic effect of Laserphyrin®-HVJ-E was substantially equivalent to that of Laserphyrin® alone even at half Laserphyrin® concentration. By utilizing Laserphyrin®-HVJ-E, PDT could be performed with lower Laserphyrin® concentration. In addition, Laserphyrin®-HVJ-E showed higher potency than Laserphyrin® by combining cytotoxicities of HVJ-E and PDT.

Photodynamic diagnosis (PDD) of gastric cancer with protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) will lead to a method to estimate the invasive depth. The excitation light for ALA-based PDD is attenuated by absorption and scattering of the mucosal tissue according to its wavelength and the difference contains the fluorophore depth information. To realize the method to estimate the invasive depth for the intramucosal cancer, this study investigated the differences of the attenuation rate between two excitation wavelengths. Considering the optical properties of mucosa and PpIX, relationships between the invasive depths of cancer containing PpIX and the fluorescence intensity ratios detected from the mucosa were estimated using a numerical model. An experiment was also performed using a pellet made of epoxy resin containing PpIX. The excitation lights with wavelengths of 405 and 505 nm having the same power density were each used to irradiate the pellet placed at the fluorophore depth of 0 mm, 1.0 mm, and 1.7 mm from the mucosal surface to obtain fluorescence images, and the average fluorescence intensities of the images were evaluated. The numerical and experimental results suggested the possibility to estimate the fluorophore depth of the PpIX fluorescence source by comparing the fluorescence images with excitation lights at wavelengths of 405 and 505 nm.

Photoacoustic imaging is expected to be a next-generation diagnostic modality. However, systems using a solid state laser (SSL) are expensive, large in size and poor in operability of probes. In addition, protective goggles are required because of laser light. Therefore, we have adopted the LED technology and improved the signal-to-noise-ratio (SNR) of the LED-based system, which had been 1 / 2.3 million of the SSL, to the same level with four innovative technologies. These innovative technologies include a) High power and high density LED array technology: Use of high power LED chips with luminous efficiency comparable to laser diode, high density mounting of LED chips on Aluminum base and compact design, b) Giant and ultra-short-pulse drive circuit technology: High speed on-and-off by low-resistance Metal Oxide Semiconductor Field Effect Transistor (MOSFET), and position separation of high-voltage drive circuit from ultrasonic probe (USP) by series connection of LEDs, c) Optical pulse generation technology optimum for frequency response characteristic of USP, d) Noise reduction technology for faint signals using ultra-amplification: Minimization of quantization noise of Analog-digital-converter (ADC) by wide band ultra-amplification of 86 dB, and noise reduction by averaging of

Photothermal damages in laser skin treatments were evaluated computationally to analyze differences between ethnic groups. Our results revealed the seriousness of photothermal damage was varied between the ethnic groups even on the same irradiation conditions.

Background: Photodynamic therapy (PDT) is a less invasive cancer treatment using photochemical reactions induced by light irradiation to a photosensitizer (PS). Highly selective PDT with fast accumulation of the PS in target site might be a promising treatment option for drug-resistant prostate cancer facing high incidence rate of elderly men who have no effective treatment options and require a minimally invasive treatment. Hemagglutinating virus of Japan envelope (HVJ-E) allows selective and fast drug delivery to the drug-resistant prostate cancer cells via rapid cell membrane fusion. PS named porphyrus envelope (PE) has been developed by insertion of lipidated protoporphyrin IX (PpIX lipid) into HVJ-E. In this study, we investigated the optimal conditions for PE preparation and laser irradiation for highly selective PDT using PE with a short drug-light interval. Materials and Methods: Human hormon refractory prostate cancer cell line PC-3 and human normal prostate epithelial cell line PNT2 were cultured. PpIX lipid uptake and cytotoxicity of PDT in the cells incubated with PE for 10 min were evaluated by measuring fluorescence intensity and by using a cell counting reagent 24 h after PDT, respectively. Results: PpIX lipid uptake and cytotoxicity of PDT were increased with PpIX lipid concentration. Cytotoxicity of PDT using PE was more than 9 times as strong as that with PpIX lipid and PpIX induced by 5-aminolevulinic acid. Much stronger cytotoxicity was induced in PC-3 cells than PNT2 cells with the ratio of cell death rate for cancer to normal cells up to 4.64 ± 0.09. Conclusions: Fast PS delivery with HVJ-E allows highly selective PDT with a short drug-light interval. Therefore, PDT using PE has a potential to shorten treatment period and reduce side effects of PDT.