Results of theoretical and experimental investigations are reported on the feasibility and the performance of a highly sensitive and stable `standardized' sensing pad suitable for integration into a great variety of miniature hybrid and monolithic integrated optical sensors for biochemical and clinical analysis. The basic type of sensing pad structure consists of sensing layers immobilized at the surface of waveguiding films with a high refractive index deposited on low index substrates. As a simple biochemical model system for the sensing pad development, the binding of immunoglobulin (IgG) to immobilized protein A was chosen. Results obtained for TiO₂ waveguides at wavelengths of 633 nm and 785 nm show that these sensing pads feature very high sensitivities and an excellent stability, and that infrared laser diodes are adequate light sources. Resolutions and stabilities in the order of 1/4000 of a monolayer have been demonstrated by performing experiments for such chips in an input grating coupler configuration. Based on these results, surface coverage resolutions in the < 100 fg/mm² range have been estimated if such sensing pads were used in integrated optical interferometers.

An optical fiber biosensor for the selective determination of hydrogen peroxide has been developed as the base sensor for the construction of multienzyme optodes involving lactate converting enzymes for the analysis of lactic acid. The optode uses the H₂O₂ dependent oxidation of homovanillic acid by horseradish peroxidase (HRP) as the sensing reaction. The fluorescence of the dimeric product formed is used as the measuring signal related to the concentration of H₂O₂. HRP was immobilized on a membrane and combined with a bifurcated fiber optic probe. Under optimized conditions the sensor responds linearly to hydrogen peroxide between 1 micrometers ol/l and 0.12 mmol/l and exhibits a half life of 90 days. Using a lactate oxidase-HRP membrane, the sensor is suitable for lactate measurement with a linear range of 3 micrometers ol/l-0.2 mmol/l. To increase the sensitivity for lactate, lactate dehydrogenase was coimmobilized on the sensor membrane. In the presence of NADH the signal for lactate is amplified fourfold through the internal analyte recycling accomplished by the lactate-converting enzymes.

Much interest has been shown in the development of rapid, one step immunoassay systems for the point-of-care market. The fluorescence capillary fill device (FCFD) is a technology that fulfills the requirements for a system to penetrate this market. The performance of the FCFD is demonstrated in an assay for prostate specific antigen (PSA) in whole blood, the FCFD assay has adequate analytical (a detection limit of less than 0.4 ng/mL PSA and reasonable precision over the clinically relevant range of the assay) and clinical performance (good correlations with commercial PSA assays).

Surface plasmon resonance is an optical phenomenon which can be used to monitor the increase in the thickness of a dielectric layer, as an antigen binds to an immobilized antibody. In the present work, the preparation of a reactive surface which permits covalent immobilization of proteins and antigen-antibody reactions is described. In a first step, cysteamine a bifunctional reagent, is linked to a thin gold film via thiol groups. A reactive polymer is then covalently bound to the cysteamine layer. The resulting surface permits immobilization of proteins through their amino groups. The polymer layer is hydrophilic and not ionic in order to prevent hydrophobic and/or electrostatic interactions with proteins. After deactivation of the residual reactive functions, the binding of rabbit immunoglobulin G (IgG) onto this surface, rabbit IgG-anti rabbit IgG interactions and specificity of the system were studied. Preliminary results concerning stability and regeneration of the biosensor are reported.

In this study a direct immunosensor for heart-type fatty acid binding protein (FABP) based on surface plasmon resonance spectroscopy (SPRS) is presented. FABP can be used as a heart infarction marker in clinical diagnostics. The development of a simple and cheap direct optical sensor device is reported in this paper as well as immobilization procedures and optimization of the measuring conditions. The correct working of the SPRS device is controlled by comparing the signals with theoretical calculated values. Two different immunoassay techniques were optimized for a sensitive FABP-analysis. The competitive immunoassay was superior to the sandwich configuration as it had a lower detection limit (100 ng/ml), needed less antibodies and could be carried out in one step.

Most affinity sensor principles demand immobilized receptor molecules. A widely used multiple-step technique for covalent immobilization of proteins is based on a silanization procedure and a crosslinking agent, e.g., glutardialdehyde. In the presented work non- amphophilic Langmuir-Blodgett films based on phthalocy-aninato-polysiloxane derivatives or copolyglutamates are used to immobilize antibodies as monolayers. Due to a photopolymerization process of terminal C-C-double bonds at alkylic side chains of the non- amphophilic substance the stability of the films is improved compared to conventional LB films. Antibodies can be immobilized by a one-step-method subsequent to illumination. Polymethyl-methacrylate (PMMA) fibers are found to be ideal substrates for the antibody transfer. Enzyme-linked immunosorbent assays (ELISA) give quite good specificities and densities of active immobilized immunoglobulin (IgG). For antigen detection these films are combined with compact evanescent wave sensors. Antibodies were immobilized at the surface of a waveguide using the Langmuir-Blodgett (LB) technique. The light source is a diode laser, which results in a small and compact set-up and due to the red excitation wavelength the background fluorescence is reduced.

In the present paper optical fiber sensors for monitoring and detection of foregut functional diseases are described. Bile-containing refluxes and pH are the parameters already investigated with optical fibers and both in vitro and in vivo performances of these sensors are described.

The measurement of blood component concentrations is of great interest for medical applications such as anaesthetizing monitoring, heart disease evolution, respiratory insufficiency, etc. The common system is the spectroscopic analysis of blood samples. Analyzing the absorption versus wavelengths permits the determination of blood component concentrations by comparison to the theoretical extinction coefficients of the investigated components. The functional saturation rate of oxyhemoglobin HbO₂ called SfO₂ is therefore accessible. A new system is presented in this paper utilizing three laser diodes at wavelengths 660, 830, and 1060 nm. We have, therefore, access to a supplementary parameter which is the concentration of carboxyhemoglobin HbCO. The set-up can be portable because it utilizes small light sources, optical fibers, and integrated electrical supply and signal processing device. The performances reach a SfO₂ resolution of 2% and 1% on HbCO measurement.

The photoplethysmographic signal (PPG) from forearm skin and the ECG were recorded simultaneously from healthy subjects. The optical signal was derived with a fiber-optic probe which consisted of 61 fiber pairs. The peak-to-peak averaged AC-signal was calculated. The dependency of this signal on light wavelength and on sample volume was studied. The light intensities used at 560 nm were 0.015 and 0.029 mWmm^-2 and at 940 nm we used 0.029, 1.37 and 2.77 mWmm^-2. A theoretical model for calculation of the sample volumes was also developed. The amplitude of the AC-signal at 560 nm is larger than at 940 nm at the same intensity (0.029 mWmm^-2). At 560 nm and small sample volumes (7 fiber pairs) the amplitude did not increase with increased intensity. At 940 nm using 1.37 and 2.77 mWmm^-2 the AC-signal increased with the number of fiber pairs (volume).

A new sensor for respiratory rate monitoring based on optical fiber technique was simultaneously compared with an acoustic sensor and a transthoracic impedance plethysmograph during normoventilation in the respiratory rate range of 9 - 17 breaths per minute. The response characteristics of the optical sensor were then measured during simulation of central apnoea and tachypnoea. Visual observation was chosen as the reference method for monitoring the respiratory rate. The measurements were performed in ten healthy volunteers and the respiratory signals recorded on an analogue tape and strip-chart recorder and analyzed off-line. The response characteristics of the fiber optic sensor corresponded well with those of the acoustic sensor and impedance plethysmograph. All three methods responded rapidly to a simulated apnoeic event.

In an extension of previous work on optical chemical sensors based on the use of potential- sensitive dyes incorporated in Langmuir-Blodgett films, we now describe solid-state potassium-sensitive membranes. The sensing scheme again is based on the use of valinomycin as the potassium carrier, but a plasticized pvc membrane is being used as a membrane material rather than a Langmuir-Blodgett film. A potential-sensitive dye detects the potential created at the sensor/sample interface. Unlike many other kinds of potassium optrodes, the response function is virtually independent of pH. Potassium can be continuously monitored over the concentration range from 10 - 50 (mu) M up to 10 mM, although relative signal changes do not exceed -20% at present. Membranes are designed in a way that they can be manufactured in large quantities, and the dye is compatible with LED light sources.

Theoretical and experimental aspects of an extrinsic Fabry-Perot optical fiber ultrasound sensor for use in a photoacoustic-guided laser angioplasty system are described. The sensor has been characterized using laser generated thermoelastic waves as a source of wideband ultrasound. A system sensitivity of 25 mV/MPa and an acoustic noise floor of 2 Pa/Hz^1/2 are reported using a transparent polymer film as the sensing element. The system demonstrates the required bandwidth for sensing thermoelastic waves containing frequency components up to 20 MHz.

Percutaneous, single fiber LDF of 632.8 nm (He-Ne) is used for continuous recording of low leg muscle microcirculation. An optical fiber (0 equals 0.5 mm) was placed inside the tibialis ant. muscle 10 cm below the knee joint via a plastic cannula (0 equals 1.0 mm) and using local anaesthesia of the skin. The LDF is sampled continuously by the on-line PC computer one minute before, three minutes during and for four minutes after tourniquet occlusion. Twelve healthy, non-smoking men were examined. The reactive hyperaemia and the flux reactive time after release of tourniquet was examined successfully. To get better signal-to-noise ration and deeper detected volume in the muscle, the optical characteristics of ordinary fiber tips and modified spherical and `pear'-type ends were studied. Compared with the system of 632.8 nm, a new optical system with a laser diode of 790 nm was developed. A PC computer with DSP card was used for all the signal processing in the new system.

This paper describes the development of a double TV camera system incorporated in a standard fundus camera for imaging the choroidal vascular network with very low intensity infrared light. The equipment was employed to perform indocyanine green (ICG) choroidal angiography in several chorioretinal pathologies with particular interest in age related macular degeneration (AMD). An evaluation and comparison of fluorescein and ICG angiograms is carried out for the diagnosis, localization, and laser treatment evaluation of choroidal neovascularizations (CNV).

Since the diagnosis of the intradental blood supply is difficult in dental trauma, we have designed and built a new dental pulp vitalometer based on optical reflectance measurement and exploiting the different absorption spectra of haemoglobins. The device comprises light transmitters, a receiver, electronics and a PC. Pulsed light is transmitted along the fiber optic probe, which illuminates the tooth being tested. The same probe collects the reflected light from the tooth pulp and transfers the light to the receiver. The received signal is divided into AC and DC components and a data acquisition card reads these signals, performs an A/D conversion and writes the results in a text file. A reference plethysmogram signal from a finger is used to help in processing the measured dental signal. The computer program calculates an estimate for the oxygen saturation.

Alongside EMG activity, biting force is the primary parameter used for assessing the biting problems of dentulous patients and patients with dentures. In a highly conductive oral cavity, dielectric measurement methods are preferred, for safety reasons. The maximum biting force for patients with removable dentures is not more than 100 ... 300 N. We report here on an instrument developed for measuring human biting force which consists of three units: a mouthpiece, a signal processing and interface unit (SPI), and a PC. The mouthpiece comprises a sensor head of thickness 3.4 mm, width 20 mm and length 30 mm constructed of two stainless steel plates and with a fiber optic microbending sensor between them. This is connected to the SPI unit by a three-meter fiber optic cable, and the SPI unit to the PC by an RS connection. A computer program has been developed that includes measurement, display, zeroing, and calibration operations. The instrument measures biting force as a function of time and displays the time-dependent force profile and maximum force on a screen or plots it in hard copy. The dynamic measurement range of the mouthpiece is from 0 to 1000 N, and the resolution of the instrument is 10 N. The results of preliminary clinical measurements and repeatability tests are reported.

The fibeated broptic-based multisensor was made of quartz optic fiber capillary with an outer diameter of 250 micrometers and an inner diameter of 10 micrometers through two methods: a capillary and the parallel capillary with another piece of optic fiber. There was a thin layer of tungsten membrane (thickness 1 micrometers ) around the outer surface of the optic fiber or capillary. The metal membrane worked as a micro electrode or an electro-osmosis electrode. Nitrogen laser beam and laser-fluorescent pulses were guided in two ways through optic fiber or the wall of the capillary. The advantage of one capillary was its small tip and measurement of different physiological indices in the same site, but the intensity of laser-fluorescent pulses was diminished by electro-osmosis flow; the parallel optic fiber and capillary avoided the shortage, but the device tip was bigger than a capillary. The multisensor was used to inquire into cognitive brain mechanism in awake animals by simultaneous recording of neuron activities (neuron firing), neuron metabolism rate (laser-fluorescent pulses), and biochemical events through microelectrophore in vivo and field effect electro-osmosis analysis at situ. The effects of nitric oxide biosynthesis-related compounds on neuron efficiency of the cortex were investigated by the multisensor.

Blood analysis has been carried out routinely for decades. Normally, blood samples are taken from patients and sent to the laboratory for processing. Novel analytical methods are facilitated by fiberoptic sensors that are inserted into the human body or in contact with it. In the present work a spectral analysis of human blood serum was undertaken by fiberoptic evanescent wave spectroscopy (FEWS) using a Fourier transform infrared spectrometer (FTIR). A special cell based on IR transmitting non-toxic silver halide fibers was designed. Further improvements in the analysis were obtained by adopting some multivariate calibration techniques that have already been used in clinical chemistry. The partial least-square (PLS) algorithm was used to calculate the concentrations of urea, uric acid, calcium, cholesterol and total protein in human blood serum. Good agreement between our results and the ordinary chemical and enzymatic methods was reached. The average errors obtained were 28 mg/dl for cholesterol (about 16% of the average value), 9 mg/dl for urea (about 29% of the average value), 0.38 g/L for total protein (about 6% of the average value), 1.5 mg/dl for uric acid (about 29% of the average value) and 0.28 mg/dl for calcium (about 3% of the average value).

Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, CO₂, NH₃, CH₄, NO, NO₂ in human and animal exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and CO₂, NH₃ and CO₂ and CO and N₂O, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.

Infrared signal transmission through zirconium glass fiber is used for noncontact temperature measurement. A fiber optic radiometer using a cooled photonic detector was designed and constructed for temperature measurements between 30 degree(s)C and 200 degree(s)C. An acquisition and data processing software allowing calibration, display, and storage of data was developed. In this work we suggest a new approach for signal processing, based on active filters. This method is compared to the synchronous detection technique using a lock-in amplifier. The dependence of the radiometer signal on ambient temperature and detector cooling is presented. The dependence of the radiometer signal on the black-body temperature is given. The radiometer spatial resolution is calculated. Since real time, high-accuracy low- temperature measurement was obtained, we suggest this IR fiber radiometric thermometer may be useful in medical applications.

In this paper, we present a design approach for an ASIC PulCar able to measure in continuous and real time heartbeat rate, and to display it. PulCar gives an audible alarm when this heartbeat rate exceeds a specified threshold. This VLSI circuit processes a digitalized analog signal, provided by an optoelectronic sensor. It is synthesized by Syncirc, a new CAD software which involves the development of the principle layout of a numerical circuit. This ASIC includes about 22,000 transistors in a 2 mm² chip.

It is well known that low-level luminescence is correlated to many physiological and biological parameters, e.g. cell cycle, temperature, oxidation- and UV-stress. We report some new approaches on low-level luminescence measurements and UV influence on different biological systems. One example concerns yeast cultures, which show an increasing intensity of luminescence after UV-treatment with a maximum after 1.5 h. Investigations on normal human fibroblasts and keratinocytes display different longtime kinetics: The former show no changes of the luminescence in time, the latter an increase that reaches the maximum after 9 h. The time-dependent spectral measurement on xeroderma pigmentosum after UV-treatment displays a time-shift of the action-spectra shifting the maximum from 400 nm to 420 nm in 12 h. Some results on neutrophils reveals spectral UV influence on respiratory burst and the cellular repair system. The results on human skin display spectral changes of low-level luminescence after UV-treatment. These results provide a useful tool of analyzing UV influence on human skin.