Biomedical subjects

Lothar Lilge

Publications and source records attributed to Lothar Lilge.

24 records · Page 2Linked to original sources

PubMed2002

Effects of 810 nm laser irradiation on in vitro growth of bacteria: comparison of continuous wave and frequency modulated light.

BACKGROUND AND OBJECTIVES: Low intensity laser therapy may modify growth of wound bacteria, which could affect wound healing. This study compares the effects on bacteria of 810 nm laser using various delivery modes (continuous wave or frequency modulated light at 26, 292, 1000, or 3800 Hz). STUDY DESIGN/MATERIALS AND METHODS: Staphylococcus (S.) aureus, Escherichia (E.) coli, and Pseudomonas (P.) aeruginosa were plated on agar and then irradiated (0.015 W/cm(2); 1-50 J/cm(2)) or used as controls (sham irradiated); growth was examined after 20 hours of incubation post exposure. RESULTS: There were interactions of species and modulation frequency in the overall effects of irradiation (P = 0.0001), and in the radiant exposure mediated effects (P = 0.0001); thus individual frequencies and each bacterium were analysed separately. Bacteria increased following 3800 Hz (P = 0.0001) and 1000 Hz (P = 0.0001) pulsed irradiation; at particular radiant exposures P. aeruginosa proliferated significantly more than other bacteria. Pulsed laser at 292 and 26 Hz also produced species-dependent effects (P = 0.0001; P = 0.0005); however, the effects for different radiant exposures were not significant. Bacterial growth increased overall, independent of species, using continuous mode laser, significantly so at 1 J/cm(2) (P = 0.02). Analysis of individual species demonstrated that laser-mediated growth of S. aureus and E. coli was dependent on pulse frequency; for S. aureus, however, there was no effect for different radiant exposures. Further tests to examine the radiant exposure effects on E. coli showed that growth increased at a frequency of 1000 Hz (2 J/cm(2); P = 0.03). P. aeruginosa growth increased up to 192% using pulsed irradiation at 1000-3800 Hz; whereas 26-292 Hz laser produced only a growth trend. CONCLUSIONS: The findings of this study point to the need for wound cultures prior to laser irradiation of infected wounds. Similar investigations using other common therapeutic wavelengths are recommended.

Dose-Response Relationship, Radiation↗

PubMed2002

Effects of 630-, 660-, 810-, and 905-nm laser irradiation delivering radiant exposure of 1-50 J/cm2 on three species of bacteria in vitro.

OBJECTIVE: To examine the effects of low-intensity laser therapy (LILT) on bacterial growth in vitro. BACKGROUND DATA: LILT is undergoing investigation as a treatment for accelerating healing of open wounds. The potential of coincident effects on wound bacteria has received little attention. Increased bacterial proliferation could further delay recovery; conversely inhibition could be beneficial. MATERIALS AND METHODS: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus were plated on agar and then irradiated with wavelengths of 630, 660, 810, and 905 nm (0.015 W/cm(2)) and radiant exposures of 1-50 J/cm(2). In addition, E. coli was irradiated with 810 nm at an irradiance of 0.03 W/cm(2) (1-50 J/cm(2)). Cells were counted after 20 h of incubation post LILT. Repeated measures ANOVA and Tukey adjusted post hoc tests were used for analysis. RESULTS: There were interactions between wavelength and species (p = 0.0001) and between wavelength and radiant exposure (p = 0.007) in the overall effects on bacterial growth; therefore, individual wavelengths were analyzed. Over all types of bacteria, there were overall growth effects using 810- and 630-nm lasers, with species differences at 630 nm. Effects occurred at low radiant exposures (1-20 J/cm(2)). Overall effects were marginal using 660 nm and negative at 905 nm. Inhibition of P. aeruginosa followed irradiation using 810 nm at 5 J/cm(2) (-23%; p = 0.02). Irradiation using 630 nm at 1 J/cm(2) inhibited P. aeruginosa and E. coli (-27%). Irradiation using 810 nm (0.015 W/cm(2)) increased E. coli growth, but with increased irradiance (0.03 W/cm(2)) the growth was significant (p = 0.04), reaching 30% at 20 J/cm(2) (p = 0.01). S. aureus growth increased 27% following 905-nm irradiation at 50 J/cm(2). CONCLUSION: LILT applied to wounds, delivering commonly used wavelengths and radiant exposures in the range of 1-20 J/cm(2), could produce changes in bacterial growth of considerable importance for wound healing. A wavelength of 630 nm appeared to be most commonly associated with bacterial inhibition. The findings of this study might be useful as a basis for selecting LILT for infected wounds.

Escherichia coli↗

PubMedDate not supplied

Non-ionizing near-infrared radiation transillumination spectroscopy for breast tissue density and assessment of breast cancer risk.

There is increasing attention to prevention as a means to reduce cancer incidence. Prevention interventions or therapies in turn rely on risk assessment programs to identify those women most likely to benefit from education and lifestyle changes. These programs are usually based either on interviews to identify ethnic, genetic, and lifestyle factors contributing to risk or on physical examination of the breast. For the latter it has been shown that the parenchymal density pattern observed in X-ray mammography can be used to assess an individual's risk. Extensive areas of dense, glandular tissue that are relatively radio-opaque are associated with higher breast cancer risk, with an odds ratio of 4 to 6 compared with women in whom the breast density is low owing to an abundance of adipose tissue. Near-infrared optical transillumination spectroscopy has been used previously to investigate the physiological properties of breast tissue. In this study, women were recruited who underwent recently X-ray mammography. The tissue density was assessed by a radiologist. The women then underwent optical transillumination spectroscopy, for which an instrument was developed that delivered visible and near-infrared light to the breast. After being transmitted through the breast craniocaudally in one of four quadrants, the spectrum from 625 to 1050 nm was measured. The spectra were used as input to a Principal Component Analysis (PCA) that used the corresponding mammographic density as the reference standard. The study group consisted of 92 women aged 39 to 72 years. Without further stratification for age, menopausal status, or measurement position, the PCA numerical model predicted the radiological assessment of tissue density in the mid 80% to low 90%.

Adult↗

PubMedDate not supplied

Bioluminescence imaging of the response of rat gliosarcoma to ALA-PpIX-mediated photodynamic therapy.

Photodynamic therapy (PDT) is a promising modality for the treatment of solid tumors that combines a photosensitizing agent and light to produce cytotoxic reactive oxygen species that lead to tumor cell death. The recent introduction of bioluminescence imaging (BLI), involving the use of the luciferase gene (luc) transferred into target tumor cells, followed by systemic administration of luciferin and detection of the emitted visible chemiluminescence photons, offers the potential for longitudinal imaging of tumor growth and therapeutic response in single animals. We demonstrate in this study the first results of the use of BLI to assess the response of an intracranial brain tumor model (9L rat gliosarcoma) to aminolevulinic acid (ALA)-mediated PDT. Complementary in vitro experiments with the luciferase-transfected 9L cells show that the decrease in the luminescent signal after PDT correlates with cell kill. In vivo imaging shows a decrease in the BLI signal from the tumor after ALA-PDT treatment, followed by tumor regrowth. Furthermore, preliminary studies using cells transfected with a hypoxia-responsive vector show an increase in bioluminescence within 4 h after Photofrin-mediated PDT, demonstrating the ability to observe stress-gene responses. These results suggest that BLI can be used to provide spatiotemporal information of intracranial brain tumor responses after PDT and may serve as a valuable response-endpoint measure.

Aminolevulinic Acid↗

PubMedDate not supplied

Metronomic photodynamic therapy as a new paradigm for photodynamic therapy: rationale and preclinical evaluation of technical feasibility for treating malignant brain tumors.

The concept of metronomic photodynamic therapy (mPDT) is presented, in which both the photosensitizer and light are delivered continuously at low rates for extended periods of time to increase selective tumor cell kill through apoptosis. The focus of the present preclinical study is on mPDT treatment of malignant brain tumors, in which selectivity tumor cell killing versus damage to normal brain is critical. Previous studies have shown that low-dose PDT using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) can induce apoptosis in tumor cells without causing necrosis in either tumor or normal brain tissue or apoptosis in the latter. On the basis of the levels of apoptosis achieved and model calculations of brain tumor growth rates, metronomic delivery or multiple PDT treatments, such as hyperfractionation, are likely required to produce enough tumor cell kill to be an effective therapy. In vitro studies confirm that ALA-mPDT induces a higher incidence of apoptotic (terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate, sodium salt nick-end labeling positive) cells as compared with an acute, high-dose regimen (ALA-aPDT). In vivo, mPDT poses two substantial technical challenges: extended delivery of ALA and implantation of devices for extended light delivery while allowing unencumbered movement. In rat models, ALA administration via the drinking water has been accomplished at very high doses (up to 10 times therapeutic dose) for up to 10 days, and ex vivo spectrofluorimetry of tumor (9L gliosarcoma) and normal brain demonstrates a 3-4 fold increase in the tumor-to-brain ratio of PpIX concentration, without evidence of toxicity. After mPDT treatment, histological staining reveals extensive apoptosis within the tumor periphery and surrounding microinvading colonies that is not evident in normal brain or tumor before treatment. Prototype light sources and delivery devices were found to be practical, either using a laser diode or light-emitting diode (LED) coupled to an implanted optical fiber in the rat model or a directly implanted LED using a rabbit model. The combined delivery of both drug and light during an extended period, without compromising survival of the animals, is demonstrated. Preliminary evidence of selective apoptosis of tumor under these conditions is presented.

Apoptosis↗

PubMedDate not supplied

In vivo study of the inflammatory modulating effects of low-level laser therapy on iNOS expression using bioluminescence imaging.

This study was designed to demonstrate that bioluminescence imaging (BLI) can be used as a new tool to evaluate the effects of low-level laser therapy (LLLT) during in vivo inflammatory process. Here, the efficacy of LLLT in modulating inducible nitric oxide synthase (iNOS) expression using different therapeutic wavelengths was determined using transgenic animals with the luciferase gene under control of the iNOS gene expression. Thirty transgenic mice, FVB/N-Tg(iNOS-luc)Xen, were allocated randomly to one of four experimental groups treated with different wavelengths (lambda = 635, 785, 808 and 905 nm) or a control group (nontreated). Inflammation was induced by intra-articular injection of zymosan A in both knee joints. Laser treatment (25 mW cm(-2), 200 s, 5 J cm(-2)) was applied to the knees 15 min after inflammation induction. Measurements of iNOS expression were performed at various times (0, 3, 5, 7, 9 and 24 h) by measuring the bioluminescence signal using a highly sensitive charge-coupled device (CCD) camera. The results showed a significant increase in BLI signal after irradiation with 635 nm laser when compared to the nonirradiated animals and the other LLLT-treated groups, indicating wavelength dependence of LLLT effects on iNOS expression during the inflammatory process, and thus demonstrating an action spectrum of iNOS gene expression following LLLT in vivo that can be detected by BLI. Histological analysis was also performed and demonstrated the presence of fewer inflammatory cells in the synovial joints of mice irradiated with 635 nm compared with nonirradiated knee joints.

Age Factors↗