Photoradiation Therapy Research Articles

Disinfection by methylthionine chloride and chitosan in combination with Photo radiation therapy on caries affected dentin nano hardness, adhesive integrity, and bond failure.

The aim of the study was to assess the disinfection efficacy, bond integrity, and nano hardness of caries-affected dentin (CAD) surface bonded to resin cement when disinfected with chlorhexidine (CHX), Methylene blue activated by Photodynamic therapy (MB-PDT), chitosan, silver diamine fluoride (SDF), chitosan activated by PDT, and SDF-diode laser against S. mutans. A total of 60 human mandibular molars were extracted non-traumatically and gathered using ICDAS criteria. The dentin surface was prepared, leaving CAD to receive a disinfection procedure. After inoculation with S. mutans, the CAD samples were divided into six groups and disinfected with various disinfectants (n = 10) CHX, MB-PDT, chitosan, chitosan-PDT, SDF, and SDF+ diode laser. Survival rates of S. mutans were analyzed following the restoration of samples with resin cement via the etch and rinse method to assess SBS. Also, nano hardness was analyzed. Statistical analysis was performed by using the ANOVA and the Tukey multiple test (p<0.05). The Kruskal-Wallis test was used to evaluate the change in survival rate. Related to the survival rates, the SDF+ diode laser displayed the highest reduction in S. mutans levels and chitosan presented the lowest level of disinfection. The intergroup comparison revealed that CHX and chitosan-PDT displayed comparable outcomes of S. mutans survival rate to that of SDF+ diode laser (p>0.05). Likewise, MB-PDT and SDF displayed a comparable survival rate of S. mutans to Chitosan disinfection (p>0.05). Considering SBS and nano hardness, the highest SBS and NH were exhibited by the SDF+ diode laser, and the lowest SBS and NH values were exhibited by MB-PDT. The intragroup comparison revealed that CAD specimens disinfected with Chitosan-PDT showed comparable SBS and NH values to the SDF+ diode laser (p>0.05). CHX, chitosan, and SDF exhibited bond values and NH comparable to MB-PDT (p<0.05). Synergistic use of Silver diamine fluoride with diode laser and chitosan activated by PDT can be used as an alternative to CHX for controlling S. mutans growth, promoting enhanced bond efficacy and nano hardness for bonding resin cement to the caries-affected dentin.

Role of Photodynamic Therapy in Endodontics―A Review

The irrigants used commonly do not always eradicate the entire microbial flora in infected root canals. Thus in quest other strategies, such as photodynamic therapy (PDT) have been developed. The word photodynamic means the applications of the dynamics of photons of light on the biological molecules. German physician Friedreich Mayer performed the first study, which was first called as photo-radiation therapy with porphyrins (1913) in humans. Photoactivated disinfection is based primarly on the interaction of a photosensitive antibacterial agent and a light source which uses a nontoxic dye named photosensitizer (PS) and lowintensity visible light. In the presence of oxygen, these combine to produce some cytotoxic species. The PS molecules attach to the bacteria membrane. Irradiation with a specific wavelength of the light may result in the production of singlet oxygen, resulting in rupture of the microbial cell wall. There are several applications for PDT in dentistry.. Photodynamic therapy has also been used to disinfect caries dentin before the restoration, disinfecting oral tissues before or during surgical procedures, treating denture stomatitis, and treating oral candidiasis in immunocompromised patients. Photodynamic therapy can also be used in combination with mechanical instrumentation and chemical antimicrobial agents, such as sodium hypochlorite.

A Gel‐Based Model of Selective Cell Motility: Implications for Cell Sorting, Diagnostics, and Screening

AbstractThe ability to precisely control cell‐loaded material systems is essential for in vitro testing of novel therapeutics poised to advance to clinic. In this report, unique patterns of cell migration are devised into an in vitro gel‐in‐gel model for the purpose of obtaining cell response data to potentially therapeutic chemical agonists. The model consists of co‐cultures in a cell‐loaded microgel invading an acellular “sorting” gel. Material properties including biophysical and chemical compositions of the sorting gel are carefully controlled to guide a desired cell‐specific behavior, leading to massive tumor cell invasion by amoeboid migration mechanisms. Optical transparency enables straightforward and high‐throughput measurements of outgrowth response in the presence of either chemical and photoradiation therapy. Important dosing and drug sensitivity information are obtained with the gel‐in‐gel model using no more than a light microscope, without further need for arduous genomic or proteomic screening of the tissue samples.

Photodynamic Therapy in Dentistry

Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemotherapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly: the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis (PDD) of the malignant transformation of oral lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. Photodynamic antimicrobial chemotherapy (PACT) has been efficacious in the treatment of bacterial, fungal, parasitic, and viral infections. The absence of genotoxic and mutagenic effects of PDT is an important factor for long-term safety during treatment. PDT also represents a novel therapeutic approach in the management of oral biofilms. Disruption of plaque structure has important consequences for homeostasis within the biofilm. Studies are now leading toward selective photosensitizers, since killing the entire flora leaves patients open to opportunistic infections. Dentists deal with oral infections on a regular basis. The oral cavity is especially suitable for PACT, because it is relatively accessible to illumination.

Chloroplast biogenesis 91: Detection of δ-aminolevulinic acid esterases activity in higher plant and insect tissues

δ-Aminolevulinic acid (ALA) esterase(s) is an enzyme or a family of enzymes that regenerate ALA from ALA esters by hydrolysis. These enzyme(s) are highly active in cancer cells. As a consequence ALA esters have been used to advantage in ALA-dependent photoradiation therapy, since ALA esters translocate better to sites of metabolism in cancer cells and tissues than free ALA. In this work, it is shown that ALA esterase(s) also occur in insect and plant tissues, but are less active than in cancer cells. In plant cells ALA esterase activity is observed in the cytosol as well as in the plastids where most of the activity is observed in the plastid stoma. The ALA esterase activity appears to be sensitive to the nature of the esterifying alcohol as well as to components of the incubation medium. The observed lower activity of ALA ester conversion to tetrapyrroles in insect and plant cells, in comparison to free ALA, suggests that the use of ALA esters in photodynamic insecticidal and herbicidal applications may not be as advantageous as their use in cancer photodynamic therapy treatments. It is proposed that ALA esterase(s) may be involved in the mobilization of sequestered and esterified ALA. Esterification and sequestering of excess ALA may be visualized as a mean of cellular detoxification.

Methotrexate-loaded, photosensitized erythrocytes: a photo-activatable carrier/delivery system for use in cancer therapy

With a view towards the design of a system incorporating both the use of chemotherapeutics and photodynamic therapy for use in cancer treatment modalities, erythrocytes have been loaded with methotrexate and subsequently photosensitized by exposure to hematoporphyrin derivative. Loading of methotrexate into erythrocytes has been optimized by examining variations in electroporation conditions. Maximum loading indices observed were in the region of 64%. In order to obtain rapid pre-defined release of chemotherapeutic from the system, the erythrocytes were photosensitized. Light-dependent release of methotrexate from the system was examined. In addition, studies measuring the cytotoxic effects of light-activated release from the system using Hela cells as a target, suggested that decreases in cell viability following exposure to light resulted from the combined effects of chemotherapy and photoradiation therapy. Potential applications and advantages associated with this novel system are discussed.

Magnetically responsive photosensitizing reagents for possible use in photoradiation therapy

The ability of a magnetically responsive material to function as a carrier for photosensitizing agents for use in photoradiation therapy (PRT) has been examined in vitro. The photosensitizer has been attached to the magnetically responsive matrix (Dynabeads) by non-specific adsorption, Intralipid-mediated adsorption and poly- l-lysine mediated adsorption. In these studies, it has been demonstrated that conditions of attachment of photosensitizer to the matrix may be adapted in order to facilitate a diffuse or highly localized photo-toxic effect on target cells in vitro. The authors believe that this system may represent a novel approach to targeting photosensitizing agents to specific areas, thereby circumventing some of the problems associated with conventional photoradiation therapy (PRT), particularly in hollow organs.

Newer options for treating drug-resistant (MDR+) cancer cells using photoradiation therapy.

Emergence of drug resistance with conventional cytotoxic therapy is a major challenge towards the curability of many cancers, especially in patients undergoing autologous BMT with ex-vivo purged hematopoietic support. We have explored the potential role of photoradiation therapy in purging hematopoietic stem cells of various hematological malignancies. Benzoporphyrin derivative, monoacid ring A (BPD-MA), dihematoporphyrin ether (DHE), and MC-540 were evaluated for the "ex-vivo" purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large cell lymphoma cell lines and colony forming-unit leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments four log elimination of tumor cell lines was observed after 1 hr of incubation with BPD-MA or DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA or DHE, the mean recovery of normal BM progenitors was 4-5.2% for granulocyte-macrophage colony forming unit (CFU-GM) and 5-9.8% for burst forming unit erythroid (BFU-E). The T lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL100, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. Our results demonstrated the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)

Photocoagulation with a copper vapour laser in rabbit liver: A comparative study between the 510 nm and the 578 nm wavelengths

The coagulation effect, penetration depth and healing process of the 510.6 nm (green) and 578.2 nm (yellow) wavelengths of copper vapour laser (CVL) were compared in vivo in rabbit liver (n=15). A pulsed CVL, the Cu 15 from Oxford Laser—pulse repetition 10 kHz, peak-power 70 kW, pulse width 25 ns, and average maximal power 16W—was used connected to a dichroic system. The beam was transmitted through a 1000 μm quartz fibre and focused with a handpiece providing a 2 mm diameter spot size. By means of this delivery system 270 focused lesions are achieved at a power output of 2.65 W (power density 80 W cm−2) with irradiation times of 3, 5 and 10 s. The operative and microscopic verifications were achieved at 0 hour, and on days 3, 10, 20 and 30. Immediately after laser application, the lesions were triangular, well demarcated, and characterized by a central vaporization surrounded by four peripheral zones: carbonization; coagulation; oedema; and transition. The penetration depth was noticeably bigger in the yellow wavelength than with green wavelength, evidenced on day 10 by superior size of yellow wavelength photocoagulations and coagulation necrosis. Fibrosis appeared by day 3 and was gaining ground quickly and intensively after yellow wavelength while the fibrotic reaction was delayed on day 10 after green wavelength. The more penetrating effect of yellow wavelength advocates for its use in liver tumour destruction and photoradiation therapy while the green wavelength, inducing less aggressive effect on the surrounding tissue, seems more suitable for liver resection.

Dye-Mediated Photolysis Is Capable of Eliminating Drug-Resistant (MDR +) Tumor Cells

Abstract We evaluated the potential role of photoradiation therapy with a benzoporphyrin derivative, monoacid ring A (BPD-MA), and dihematoporphyrin ether (DHE), for the ex vivo purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large-cell lymphoma cell lines and colony-forming unit-leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments, 4-log elimination of tumor cell lines was observed after 1 hour of incubation with 75 ng/mL of BPD-MA or 30 minutes of treatment with 12.5 micrograms/mL of DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA, the mean recovery of normal BM progenitors was 4% +/- 0.8% (mean +/- SD) for granulocyte- macrophage colony-forming unit (CFU-GM) and 5% +/- 0.8% for burst- forming unit-erythroid (BFU-E). Similarly, DHE treatment resulted in the recovery of 5.2% +/- 2% and 9.8% +/- 3% of CFU-GM and BFU-E, respectively. Furthermore, equivalently cytotoxic concentrations of both DHE and BPD-MA and light were found not to kill normal pluripotent stem cells in BM, as demonstrated by their survival in two-step long- term marrow culture at levels equal to untreated controls. The T- lymphoblastic leukemia cell line CEM and its vinblastine (VBL)- resistant subline CEM/VBL, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. BPD-MA at 75 ng/mL was able to provide a greater than 4-log elimination of the drug-sensitive cell lines, but only a 34% and 55% decrease of the drug-resistant HL-60/VCR and CEM/VBL cell lines, respectively. On the contrary, 12.5 micrograms/mL of DHE reduced the clonogenic growth of all the cell lines by more than 4 logs. Further experiments demonstrated decreased uptake of both BPD-MA and DHE by the resistant cell lines. However, all the cell lines took up more DHE than BPD-MA under similar experimental conditions. Our results demonstrate the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation with DHE would be useful for in vitro purging of residual drug-resistant leukemia and lymphoma cells.

Dye-mediated photolysis is capable of eliminating drug-resistant (MDR+) tumor cells

We evaluated the potential role of photoradiation therapy with a benzoporphyrin derivative, monoacid ring A (BPD-MA), and dihematoporphyrin ether (DHE), for the ex vivo purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large-cell lymphoma cell lines and colony-forming unit-leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments, 4-log elimination of tumor cell lines was observed after 1 hour of incubation with 75 ng/mL of BPD-MA or 30 minutes of treatment with 12.5 micrograms/mL of DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA, the mean recovery of normal BM progenitors was 4% +/- 0.8% (mean +/- SD) for granulocyte-macrophage colony-forming unit (CFU-GM) and 5% +/- 0.8% for burst-forming unit-erythroid (BFU-E). Similarly, DHE treatment resulted in the recovery of 5.2% +/- 2% and 9.8% +/- 3% of CFU-GM and BFU-E, respectively. Furthermore, equivalently cytotoxic concentrations of both DHE and BPD-MA and light were found not to kill normal pluripotent stem cells in BM, as demonstrated by their survival in two-step long-term marrow culture at levels equal to untreated controls. The T-lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL, along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. BPD-MA at 75 ng/mL was able to provide a greater than 4-log elimination of the drug-sensitive cell lines, but only a 34% and 55% decrease of the drug-resistant HL-60/VCR and CEM/VBL cell lines, respectively. On the contrary, 12.5 micrograms/mL of DHE reduced the clonogenic growth of all the cell lines by more than 4 logs. Further experiments demonstrated decreased uptake of both BPD-MA and DHE by the resistant cell lines. However, all the cell lines took up more DHE than BPD-MA under similar experimental conditions. Our results demonstrate the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation with DHE would be useful for in vitro purging of residual drug-resistant leukemia and lymphoma cells.

Fluorospectral study of the rat brain and glioma in vivo

An animal model of cerebral glioma was utilized by implanting C6 glioma cells into the brains of adult Wistar rats. Once tumors developed to 7-12 mm in diameter, we conducted continuous fluorimetry monitoring of glioma up to 24 hours using a fibre-optic system connected to an intensified multichannel photodetector after an intravenous injection of hematoporphyrin derivative (HPD) into the rats. The intensity of the fluorescence in normal brain reached a plateau 6 hours after intravenous injection of HPD while that in glioma reached a plateau 80 minutes after injection. These fluorescence intensities of glioma, brain adjacent to tumor (BAT), and surrounding normal brain were measured in vivo 24 hours after intravenous administration of 5 mg/kg of HPD. The ratio of fluorescence intensities between glioma and brain was 6.1 while the ratio between BAT and brain was 3.9. There were no obvious differences in shapes between the spectra of the natural fluorescence (autofluorescence) of rat glioma and brain but the intensity of autofluorescence was much weaker in glioma. There are many problems in spectroscopic studies of biological tissues in vivo. It cannot be overemphasized that very strict criteria must be applied in order to get accurate data. Fluorescence from HPD administration may be used to discriminate tumor tissue from surrounding normal brain tissue during operation if the measuring conditions could be kept constant. It is important to understand the photospectral properties of glioma and brain tissue in order to get the most benefits in clinical application of light-induced fluorescence or photoradiation therapy.

Lasers in Medicine

Lasers now have a wide variety of medical applications, ranging from the dissolution of coronary artery thrombus to the repair of a detatched retina. The main types of laser in medicine are surgical, photocoagulator, photoradiation therapy, and cold lasers which are used by acupuncturists. Cold lasers act directly on cells to improve healing and reduce inflammation. They are also used as an effective substitute for needling or electrical stimulation.

Photoradiation therapy of brain tumours.

Present methods for treating cerebral glioma are inadequate and the possible benefit of using photosensitization therapy to obtain improved local control of the tumour has been studied in the laboratory and in clinical trials. The biological basis for photoradiation therapy and the laboratory studies and clinical trials using photoradiation to treat cerebral tumours are discussed. Photoradiation therapy results in selective tumour destruction in an intracerebral glioma model with an effect up to 1 cm in depth. Clinical studies using haematoporphyrin derivative and up to 260 J/cm2 of red light from laser sources indicate that the therapy is well tolerated and may be of value as an adjuvant treatment of cerebral tumours.

Stereotactic Intratumoral Photodynamic Therapy for Recurrent Malignant Brain Tumors

Abstract Photodynamic therapy (PDT) using purified hematoporphyrin derivative and stereotactic intratumorally implanted optical laser fiber(s) was used to treat patients with recurrent malignant gliomas and metastatic melanoma of the brain. Tumor response to PDT was evaluated by recording changes in the volume and pattern of tumor enhancement between computed tomographic and magnetic resonance imaging scans done before and after PDT, metabolic changes in tumor tissue by31 P magnetic resonance spectroscopy, and patient outcome. Toxicity of PDT to brain was evaluated on the basis of changes in the patients' neurological examinations and correlated with changes in brain adjacent to tumor seen on postoperative imaging studies. Dramatic tumor responses to PDT were seen in all gliomas, but no response of tumor to treatment was seen with melanoma. Transient signs and symptoms of increased peritumoral cerebral edema caused by PDT were seen in all patients. Two patients suffered permanent neurological sequelae, monocular blindness and a partial visual field defect, as a result of treatment. Two patients with recurrent anaplastic astrocytomas remain in remission at 45 and 35 weeks after PDT. We conclude that intratumoral photoradiation therapy of hematoporphyrin derivative-photosensitized malignant gliomas effectively produces necrosis of the solid component of malignant gliomas: however, intratumoral photoradiation may not reach the portion of tumor that invades normal brain.

Stereotactic intratumoral photodynamic therapy for recurrent malignant brain tumors

Photodynamic therapy (PDT) using purified hematoporphyrin derivative and stereotactic intratumorally implanted optical laser fiber(s) was used to treat patients with recurrent malignant gliomas and metastatic melanoma of the brain. Tumor response to PDT was evaluated by recording changes in the volume and pattern of tumor enhancement between computed tomographic and magnetic resonance imaging scans done before and after PDT, metabolic changes in tumor tissue by 31P magnetic resonance spectroscopy, and patient outcome. Toxicity of PDT to brain was evaluated on the basis of changes in the patients' neurological examinations and correlated with changes in brain adjacent to tumor seen on postoperative imaging studies. Dramatic tumor responses to PDT were seen in all gliomas, but no response of tumor to treatment was seen with melanoma. Transient signs and symptoms of increased peritumoral cerebral edema caused by PDT were seen in all patients. Two patients suffered permanent neurological sequelae, monocular blindness and a partial visual field defect, as a result of treatment. Two patients with recurrent anaplastic astrocytomas remain in remission at 45 and 35 weeks after PDT. We conclude that intratumoral photoradiation therapy of hematoporphyrin derivative-photosensitized malignant gliomas effectively produces necrosis of the solid component of malignant gliomas; however, intratumoral photoradiation may not reach the portion of tumor that invades normal brain.

AN ATOMIC BASIS OF CANCER—PHOTORADIATION THERAPY AND HEMATOPORPHYRIN DERIVATIVE

The principles of photoradiation therapy employing a tumor-seeking agent such as a hematoporphyrin derivative are described. The properties and preparation of hematoporphyrin derivatives and metalloporphyrin synthesis are briefly summarized. We show that PIXE analysis can be used to indicate the degree of a synthesis.

COMPARATIVE KINETICS OF HEMATOPORPHYRIN DERIVATIVE UPTAKE AND SUSCEPTIBILITY OF Bacillus subtilis AND Streptococcus faecalis TO PHOTODYNAMIC ACTION

Hematoporphyrin derivative (HpD) is widely used in photoradiation therapy of tumors and other diseases, and has been shown to affect the viability of gram positive bacteria. This investigation assessed the efficiency of binding of HpD to Bacillus subtilis and Streptococcus faecalis when HpD-treated organisms were exposed to red light. Kinetic studies indicated that the amount of HpD bound increased with increasing external concentration of HpD until saturation of binding sites was reached. S. faecalis had a higher affinity for HpD and was more susceptible to photoinactivation than B. subtilis. The data from this study suggest that differences in susceptibility of microorganisms to photoinactivation are directly related to the affinity of each strain for HpD.

Photoradiation Therapy of Animal Tumors and Nasopharyngeal Carcinoma

Both animal tumors and human nasopharyngeal carcinoma were submitted to a photoradiation therapy (PRT) trial in order to determine the efficacy and side effects of PRT, as well as to elucidate its mechanism of cytotoxicity. In animal tumors, the inhibition rate was 70%, and of 20 patients, eight achieved complete remission, and ten, significant remission, with an overall response rate of 90%. The blood picture and the values of serum IgG, IgM, IgA, and C3 all remained stable post-PRT. Only three patients developed mild generalized skin photosensitive reactions, and these did not affect subsequent treatment. There was no immunosuppressive effect as evidenced by a tritium-labeled thymidine-incorporated lymphocytoblast transformation assay performed both before and after PRT. Ultrastructural studies at different time intervals after PRT highly suggested that the mitochondria and rough endoplasmic reticulum were among the first organelles to be damaged.

Gastrointestinal Laser Endoscopy—Future Horizons

The laser, especially the neodymium:yttrium-aluminum-garnet device, has been a dominant influence on the development of gastrointestinal therapeutic endoscopy. More than 2,000 such procedures were performed in the first 5 years of experience with laser endoscopy at the Mayo Clinic. The major areas for future development are (1) the control of acute and chronic gastrointestinal bleeding, (2) the palliation of malignant gastrointestinal neoplasms, and (3) the management of benign and malignant obstructive lesions of the biliary tract. Refinements in laser devices, delivery systems, and techniques such as photodynamic therapy will be needed to achieve more selective tissue destruction. Improvements in the new adjunctive endoscopic methods of electronic (video) endoscopy and ultrasonography may enhance evolving laser applications by more accurately identifying diseased tissues and guiding their destruction.