AbstractA change in the water distribution of the human body, such as water retention in the skin, can be a symptom of a pathological condition including heart failure. Therefore, a sensor for the non-invasive quantification of the water content of the skin could be useful where continuous monitoring of patients is required to detect and avoid life threatening conditions. As water is a major absorber of tissue in the near-infrared wavelength range, the water content can be determined based on reflectance measurements. Measuring the diffuse reflectance at multiple distances from the point of illumination allows the determination of absorption in scattering media such as skin. The aim of this project was to develop a small and portable sensor based on light emitting diodes and photodiodes. Evaluation of the first functional sensor design has showed that the water content of tissue phantoms can be predicted with a prediction error of 1%. Further developments towards a sensor that can be applied in a future field study are ongoing.

We report on the development and production of tissue-like optical phantoms for detection and characterization of fluorescent objects close to the tissue surface. The phantoms mimic bulk optical properties such as light scattering and absorption of female breast tissue and human skin. Fluorescence sources are embedded for a given well-defined localization and volume to simulate pathologic lesions that are marked by specific molecular substances labeled with a fluorescent dye. The phantoms were made of epoxy resin with added titanium dioxide and black epoxy color paste for adjustment of the tissue-like scattering and absorbing properties. Indocyanine green was used as a fluorescent dye. The phantoms were evaluated with an experimental set-up for a new method for in vivo laser fluorescence tomography in the frequency domain.

To validate a Monte Carlo simulation of light propagation in the finger tip, reference transmission and pulsation spectra are required. To obtain them, the following method is applied: A fingertip is illuminated by halogen light, and the light that passes the fingertip is recorded by a spectrometer. By comparing a reference spectrum of the light source and the transmitted spectrum, the static transmission spectrum is calculated. Furthermore, from the variation of the transmitted light spectrum in time, a pulsation amplitude spectrum is deduced which contains the change of transmission due to the pulsation of arterial blood. This spectrum resembles the in-vitro spectrum of the effective attenuation coefficient of arterial blood. In a wavelength range from 600 nm to 1300 nm, the methods described in this paper have shown to produce spectra which are suitable to serve as reference for the Monte Carlo simulation.

The driving force behind the complex system of metabolism is based on the efficient use of potential differences. An intact biological system has a dynamic equilibrium in which the cellular biochemical reactions are in a pseudo-stationary state. The equilibrium can be manipulated by external effects such as, temperature changes brought about radiation absorption. Hot spots can be induced by the absorption of photons in strongly absorbing areas within the tissue or the sub-cellular components. Simulation calculations were carried out and utilized for selective manipulation within a spatially limited target volume, using simplified parameters for observation of the model. A good correlation was established between the results of the simulation and the measuring data based on absorption and scattering values for fibroblasts and liver tissue. Relevant biochemical causes of the stimulation effects at cellular level are considered in the discussion. The effect of stimulation with a laser on tissue such as cartilage, using a simplified two-dimensional tissue model system which is mainly supplied by diffusion processes, is discussed here with a view to its use in medicine.

In view of laser-assisted medical applications, the construction of silica-based sol-gel fiberoptic sensors based on photolon (Ph) and protoporphyrin IX (PP IX) is discussed. Electron microscopy and AFM were used to characterize the silica sol-gel coatings. AFM measurements indicate a change in the surface porosity. The PP IX-based sensors were constructed as a one-layer optode as well as a multilayered structure. An additional hybrid sensor made up of alternate layers of PP IX-and Ph-doped sol-gel was also constructed and examined. Sol-gel matrices were prepared from silicate precursor tetraethylorthosilicate (TEOS) mixed with ethanol in acid-catalyzed hydrolysis. The carrier matrices of photosensitive dyes were produced with factor R = 20, where R denotes the ratio of solvent moles (ethanol) to the number of TEOS moles. A multilayered coating was built up using the reverse-dipping technique. The overall coating thickness was determined by electron microscopy. Doped sol-gels with different PP IX concentrations were used to produce fiberoptic coatings. The film optodes with a different number of layers were examined by fluorescence spectroscopy. It was found that photolon and protoporphyrin IX entrapped in sol-gel preserve their chemical reactivity and have contact with the external environment. The hybrid sensor demonstrated clear fluorescence and a reversible behavior in gaseous environments.

Photolon is one of the new photosensitisers that has found application in photodynamic therapy (PDT). Its chemical structure has a partially reduced porphyrin moiety and its molecular structure is comparable to chlorin e(6), which can be isolated after hydrolysis of the 5-membered exocyclic beta-ketoester moiety of pheophorbide a.For this study, a Photolon doped sol-gel matrix was produced in the form of coatings deposited on silica fibers cores. The material was produced from sols prepared from the silicate precursor TEOS mixed with ethyl alcohol. The sol-gel films were prepared with factor R = 20, where R denotes the solvent-to-precursor molar ratio. Hydrochloric acid was added as a catalyst in the correct proportion to ensure acid hydrolysis (pH approximate to 2). The mixture was stirred at room temperature for 4 h using a magnetic stirrer (speed 400 rpm). The coated fibers were examined in different environments, liquid and gaseous, at different pH values and with various zinc cation concentrations. The chemical reactions were studied by means of spectroscopic methods, whereby the fluorescence response was studied. It was demonstrated that Photolon immobilized in a sol-gel matrix is accessible for the environment and shows visible response to the external changes. Furthermore, it was observed that these reactions are reversible. These biomaterials are also examined as carriers for PDT. It was also proved that a toxic effect is observed an environment with microorganisms, meaning that doped coatings have photodynamic activity. (C) 2007 Elsevier B.V. All rights reserved.

The technology and methods of optical diagnosis, including bio-monitoring and laser supported medical laboratory diagnostics, show a high potential for application and research. Although it is difficult to give an overview of all the possible fields of use, physicians interested in aspects of biotechnology can be shown some of the solutions involved using examples from affiliated work groups.

This chapter contains sections titled: Cancer: Epidemiological, Medical and Biological Background Cancer Incidence, Prevalence and Mortality The Mechanisms of Carcinogenesis Carcinogens and Their Mode of Action Impact of Early Cancer Diagnosis Diagnosing Cancer: State-of-the-Art Principles of Diagnostics Current Techniques for Cancer Diagnosis Lung and Bronchial Cancer Stomach Cancer Liver Cancer Breast Cancer (Female) Colon and Rectal Cancer Leukemia Lymphomas and Multiple Myelomas Esophageal Cancer Head and Neck Cancer Cervical Cancer Pancreatic Cancer Ovarian Cancer Prostate Cancer Bladder Cancer Skin Cancer Uterine Cancer Emerging Optical Techniques in Cancer Diagnosis In situ Microscopy Superficial Microscopy Microscopy of Tissue in Depth Scattered Light Techniques – Diffuse Optical Tomography Spectroscopy Infrared (IR) Spectroscopy Fluorescence Spectroscopic Techniques – Endogenous Fluorescence The Future of Fluorescence Techniques in Cancer Diagnosis Markers and Labelling Strategies Non-specific Labels Specific Labels – Targeting of Receptors at the Cell Surface Specific Labels – Tumor Expression Methods for Fluorescence Imaging – Fluorescence Tomography Summary Glossary Key References References

The study was carried out on Escherichia coli strains isolated from poultry and cows. The bacteria were incubated and treated by Photolon, a plant-based photosensibilizator, and exposed after that to laser light at 662nm. Additionally, the photosensitizer was immobilized in fiberoptic sol–gel coating, constructed as an 8-layer applicator. It was demonstrated that Photolon inhibits bacteria growth. Photolon entrapped into the sol–gel matrix also exhibits photodynamic activity and no bacteria were seen near the doped sol–gel applicator.

In the past years new materials have been developed for innovative applications in the field of medical technology. The sol–gel-coated applicators were prepared from the silicate precursor tetraethylorthosilicate (TEOS) mixed with the solvent ethanol in acid to catalyze hydrolysis. The sol–gel layers were deposited on the fiber optic core, substituting the original fiber coating which had been removed. In these studies 2m long optical fibers were used from laser components (core diameter 400μm, HCS, low OH). Two types of applicators were produced with 2 and 3cm long tips, respectively. The sol–gel coatings were prepared with factor R=20, the R denoting the number of alcohol moles to the number of TEOS moles. All applicators are produced as eight-layer applicators, denoting that eight single layers of sol–gel material were placed successively onto the pre-cleaned bare fiber. Examinations were carried out to investigate the optical properties of the diffusely emitting applicators. A diode laser (λ=980nm) in continuous as well as in pulsed mode was used for interstitial coagulation in vitro. Excellent results were obtained in view of the simple and low cost preparation procedure for the sol–gel-coated applicators. It was found that the size of coagulated tissue depends on the applicator length, exposure time and laser power.

The influence of laser radiation on human osteoarthrotically changed chondrocytes was investigated using various wavelengths, power density and dependence on the exposure time in order to confirm the positive results obtained in an animal experiment. It was manifested that, if there was a specific parameter constellation (2W; 16W/cm2; 60s; 120J), an enhanced matrix synthesis (cartilage material from 36 patients) could be achieved. The proof succeeded by applying the radioisotope marking method (3H-proline).

In this work we investigated the photoactive properties sol-gel biocoatings doped with Protoporphyrin IX (PP IX). it was demonstrated that PP IX entrapped in sol-gel preserves it's chemical activity and may have contact with the external environment. The chemical reactions with zinc cations and pyridine, as well as protonation, occurred quite fast. This indicates, that the interconnected porous network could be easily penetrated by relatively large molecules (e.g. mentioned pyridine molecule). Further, we observed that PP IX molecules do not leave the pores. Structural changes caused by the addition of PP IX to the sol-gel matrix influence not only on the optical properties, but also on durability of the coatings. The altering of the PP IX doped silica sol-gel coatings is quite slow.

The modification of optical fibers by exploiting various coatings may be important for construction of fiberoptics sensors or applicators for interstitial laser therapy. We report here on sol-gel films placed on fiber cores, replacing the original fiber coatings. The silica sol-gel coatings were prepared from silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The matrices were produced with various ratios R=5, 15, 20, 32, 40, 50, whereas R denotes the number of solvent moles (here ethanol) to the number of TEOS moles. Two types of coatings were produced: pure sol-gel matrices and sol-gel doped with Protoporphyrin IX in two various concentrations. The angular light intensity distribution was examined in order to find out the influence of R factor on the light intensity distribution near the fiber tip. Then, the light pattern was captured by means of CCD camera and the three dimensional luminances were calculated. The same experiments were repeated for silica sol-gel coatings doped with natural porhyrine Protoporphyrin IX and different patterns were observed.

A new type of applicator for interstitial laser coagulation is proposed in this paper. The new fiber optic applicator is made by removing the original fiber cladding and replacing it with a sol-gel coating. The sol-gel coating was prepared from the silicate precursor TEOS (tetraethylorthosilicate), mixed with ethanol in acid, which catalyzes hydrolysis. The material is produced with the factor R = 20, where R denotes the number of solvent moles to the number of TEOS moles. In these studies, optical fibers were used from Laser Components (core diameter 400 µm, HCS, low OH). The external jacket was mechanically removed, leaving a remaining 2-cm length of bare fiber. The modified dip-coating method was used to cover the bare fibers with sol-gel material. Two types of applicators were produced: pure sol-gel coated devices and applicators with sol-gel coating doped with photosensitive dyes. The photodynamic activity of chlorophyll-based Photolon and Protoporphyrin IX (PPIX) incorporated within the sol-gels was studied spectrophotometrically. It was demonstrated that sol-gel applicators are capable of performing laser interstitial coagulation using a semiconductor cw laser at 980 nm. It was also demonstrated that the incorporated photosensibilizers retain their photochemical activity.

In this paper, the influence of heating temperature on the properties of sol-gel materials, was investigated. The aim of the study was to examine the production repeatability. All samples were made with factor R = 15, denoting the ratio of the number of precursor (TEOS) moles to solvent (water) moles. The samples were prepared in acid hydrolysis route on water, whereas two groups were considered: in one group the hydrolysis was terminated by addition of NH3 center dot H2O and in the other there was no addition of base. The samples were stored for 1 month at room temperature and then exposed to high temperatures: 11000, 1200 and 1350 degrees C. They were examined by means of scanning electron microscopy (SEM). The electron microphotographs were recorded, digitized and analyzed. The Fisher linear discriminant analysis for evaluation of the microscopic images was exploited. It was shown that the repeatability varied between 83.24% and 95.48%. The analysis demonstrated that the best results were achieved for neutralized samples made at 1000 degrees C.

Laser based fibre-optic surgery procedures are commonly used in minimal invasive surgery. Despite the development of precise and efficient laser systems there are also innovative attempts in the field of bio-medical diagnostics. As a direct result of the tissue's optical properties most applications are focused on the visible wavelength range of the spectrum. The extension of the spectrum up to the mid-infrared (IR) region will offer a broad range of possibilities for novel strategies with a view to non-invasive diagnostics in medicine. We describe a method to detect differences between diseased and normal tissues, which involve Fourier transform IR microspectroscopy and fibre-optics methods. Regions of interest on 10 mu m thin tissue sections were mapped using an IR microscope in transmission mode. After IR-mapping, the samples were analysed using standard pathological techniques. Quadratic discriminant and correlation analyses were applied to the IR maps obtained allowing differentiation between cancerous and normal tissue. The use of optical fibres, transparent in the mid-IR, allowed measurements to be made in the attenuated total reflectance (ATR)-mode at a remote location. The IR sensor is in contact with the sample that shows characteristic absorption lines. The total transmission of the fibre and the sample will decrease at these lines. This method can be used to determine the absorption of a sample in a non-destructive manner. In this paper we report on our efforts to develop an IR fibre-optic sensor for tissue identification as well as to differentiate between malignant and healthy tissue in vivo. We also describe the technical design of the laboratory set-up and the results of developments made. Silver halide fibres and a special sensor tip were used for the ATR measurements on tissue specimens. The results indicate that fibre-optic IR spectrometry will be a useful tool for bio-diagnostics.

Charite – Universitatsmedizin Berlin, Campus Benjamin Franklin, Institute of Laser Physics and Laser Medicine, Freie University Berlin, Fabeckstr. 60-62, 14195 Berlin, Germany One of the promising modalities of modern medical treatment is interstitial laser therapy, where a special fibre-optic applicator is used to ensure a proper curing light distribution in the pathological lesion. Such an applicator can act as a light diffuser, and simultaneously it can serve as a carrier of the therapeutic medium, e.g. a photosensitive dye for photodynamic therapy in situ. For applicator construc-tion, silica based sol-gels coatings are proposed in this paper. The sol-gel applicators were prepared from the silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid-catalysed hydroly-sis. A suitable amount of surfactant (Triton X-100) was used. The carrier matrices were produced with a solvent to precursor molar ratio of 20. In these studies, optical fibres from Laser Components were used (core diameter 400 nm, HCS, low OH). The external jacket was mechanically removed at a distance of 25 mm. The modified dip-coating method was exploited to cover the bare fibres with sol-gel material. Two types of applicators were produced, silica sol-gels with an addition of chlorophyll-derived sensibili-sator (Photolon) in two various concentrations. It was proved that the immobilization of Photolon in a silica sol-gel does not destroy its chemical activity and does not disturb contact with the external envi-ronment. Key words: sol-gel coatings; fibre optic applicator; chlorophyll-based photosensitiser