Light scattering influence in cyanobacteria suspensions inside a photobioreactor

The application of biotechnology is increasing in areas such as agriculture, biochemistry or biomedicine. Growing bacteria or algae could be beneficial for supplying fuel, drugs, food or oxygen, among other products. An adequate knowledge of biological processes is becoming essential to estimate and control products production. Cyanobacteria are particularly appropriate for producing oxygen and biomass, by consuming mainly carbon dioxide and light irradiation. These capacities could be employed to provide human subsistence in adverse environments, as basic breathing and food needs would be satisfied. Cyanobacteria growing is carried out in bioreactors. As light irradiation is quite relevant for their behavior, photobioreactors are needed. Photobioreactors are designed to supply and control the amounts of elements they need, in order to maximize growth. The adequate design of photobioreactors greatly influences production throughput. This design includes, on the optical side, optical illumination and optical measurement of cyanobacteria growth. The influence of optical scattering is fundamental for maximizing cyanobacteria growing, as long as for adequately measure this growth. In this work, optical scattering in cyanobacteria suspensions is analyzed. Optical properties of cyanobacteria and its relationship with concentration is taken into account. Several types of cyanobacteria are considered. The influence of different beam spatial profiles and irradiances is studied by a Monte Carlo approach. The results would allow the consideration of the influence of optical scattering in the detected optical signal employed for growth monitoring, as a function of cyanobacteria type and optical beam parameters.This work has been partially supported by the project “New active phases in transition metals and rare earth nano-oxides stabilized at high pressure” (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation

Optical propagation analysis in photobioreactor measurements on cyanobacteria

Biotechnology applications are nowadays increasing in many areas, from agriculture to biochemistry, or even biomedicine. Knowledge on biological processes is becoming essential in order to be able to adequately estimate and control the production of these elements. Cyanobacteria present the capability of producing oxygen and biomass, from CO2 and light irradiation. Therefore, they could be fundamental for human subsistence in adverse environments, as basic needs of breathing and food would be guaranteed. Cyanobacteria cultivation, as other microorganisms, is carried out in photo-bioreactors. The adequate design of photobioreactors greatly influences elements production throughput. This design includes optical illumination and optical measurement of cyanobacteria growth. In this work an analysis of optical measurement of cyanobacteria growth in a photobioreactor is made. As cyanobacteria are inhomogeneous elements, the influence of light scattering is significant. Several types of cyanobacteria are considered, as long as several spatial profiles and irradiances of the incident light. Depending on cyanobacteria optical properties, optical distribution of transmitted light can be estimated. These results allow an appropriate consideration, in the optical design, of the relationship between detected light and cyanobacteria growth. As a consequence, the most adequate conditions of elements production from cyanobacteria could be estimated.This work has been partially supported by the project “New active phases in transition metals and rare earth nano-oxides stabilized at high pressure” (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation

Analysis of polarimetric parameters in strongly oriented biological tissues

The use of polarimetry as a diagnostic tool for biological tissues could show increased contrast in several pathologies. In this work polarimetric parameters are used to analyze structurally oriented biological tissues.This work has been partially supported by the project "New active phases in transition metals and rare earth nano-oxides stabilized at high pressure" (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation

Nanoparticle-based photodynamic therapy on non-melanoma skin cancer

There are several advantages of Photodynamic Therapy (PDT) for nonmelanoma skin cancer treatment compared to conventional treatment techniques such as surgery, radiotherapy or chemotherapy. Among these advantages its noninvasive nature, the use of non ionizing radiation and its high selectivity can be mentioned. Despite all these advantages, the therapeutic efficiency of the current clinical protocol is not complete in all the patients and depends on the type of pathology. An adequate dosimetry is needed in order to personalize the protocol. There are strategies that try to overcome the current PDT shortcomings, such as the improvement of the photosensitizer accumulation in the target tissue, optical radiation distribution optimization or photochemical reactions maximization. These strategies can be further complemented by the use of nanostructures with conventional PDT. Customized dosimetry for nanoparticle-based PDT requires models in order to adjust parameters of different nature to get an optimal tumor removal. In this work, a predictive model of nanoparticle-based PDT is proposed and analyzed. Dosimetry in nanoparticle-based PDT is going to be influenced by photosensitizer-nanoparticle distribution in the malignant tissue, its influence in the optical radiation distribution and the subsequent photochemical reactions. Nanoparticles are considered as photosensitizer carriers on several types of non-melanoma skin cancer. Shielding effects are taken into account. The results allow to compare the estimated treatment outcome with and without nanoparticles.This work has been partially supported by the project “New active phases in transition metals and rare earth nano-oxides stabilized at high pressure” (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation

Diffuse reflectance spectroscopy biomarkers for biological tissues characterization: application to ex-vivo animal tissues

Biological tissues characterization can be approached by non-ionizing optical techniques, in a non-invasive, non-contact way. Optical diagnostic techniques include Optical Coherence Tomography, spectroscopy or fluorescence, among others. Tissue differentiation is difficult to achieve in general with high specificity and sensibility. Spectroscopy is of great interest for this aim, as it provides intrinsic molecular contrast. The different composition and/or structure of biological tissues influence the spectral response. However, the interpretation of spectra is difficult from the raw data, and further data processing is needed. Diffuse Reflectance Spectroscopy (DRS) is particularly well-suited for biomedical applications, as it can work with bulk tissues in reflection, reinforcing the non-invasive character of the technique. DRS has been employed for malignant tissue detection and also for healthy tissue discrimination. These applications require an adequate definition of potential biomarkers for the classification algorithms. The classification process depends strongly on the amount of collected spectra and tissue and specimen variability. In this work several types of ex-vivo porcine tissues are extracted and measured by DRS. Spectral measurements are made on different specimens, and on different points of each sample. Spectra are normalized and several algorithms for dimension and variability reduction are applied, such as Principal Component Analysis or Savitzky-Golay filtering. From these spectra, several biomarkers are proposed for tissue classification, and different classifiers are applied. The results are compared, and the classification efficiency is quantified. The considered approaches could be of particular interest in image-guided surgery or other types of optical biopsy applications.This work has been partially supported by the project "New active phases in transition metals and rare earth nano-oxides stabilized at high pressure" (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, an by the San Cándido Foundation

Considerations of education in the field of biophotonics in engineering: the experience of the subject Fundamentals of Biophotonics

Education in the field of photonics is usually somehow complex due to the fact that most of the programs include just a few subjects on the field, apart from specific Master programs in Photonics. There are also specific doctorate programs dealing with photonics. Apart from the problems shared with photonics in education in general, biophotonics specifically needs an interdisciplinary approach between biomedical and technical or scientific fields. In this work, we present our education experience in teaching the subject Fundamentals of Biophotonics, intended preferentially to engineering Bachelor and Master degrees students, but also to science and medicine students. First it was necessary to join a teaching group coming from the scientific technical and medical fields, working together in the subject. This task was easier as our research group, the Applied Optical Techniques group, had previous contacts and experience in working with medicine professors and medical doctors at hospitals. The orientation of the subject, intended for both technical and medical students, has to be carefully selected. All this information could be employed by other education institutions willing to implement studies on biomedical optics.This work has been partially supported by the project “New active phases in transition metals and rare earth nano-oxides stabilized at high pressure” (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation

Generalized Jones matrices for anisotropic media

The interaction of arbitrary three-dimensional light beams with optical elements is described by the generalized Jones calculus, which has been formally proposed recently [Azzam, J. Opt. Soc. Am. A 28, 2279 (2011)]. In this work we obtain the parametric expression of the 3×3 differential generalized Jones matrix (dGJM) for arbitrary optical media assuming transverse light waves. The dGJM is intimately connected to the Gell-Mann matrices, and we show that it provides a versatile method for obtaining the macroscopic GJM of media with either sequential or simultaneous anisotropic effects. Explicit parametric expressions of the GJM for some relevant optical elements are provided

Mueller matrix differential decomposition for direction reversal: application to samples measured in reflection and backscattering

Mueller matrix differential decomposition is a novel method for analyzing the polarimetric properties of optical samples. It is performed through an eigenanalysis of the Mueller matrix and the subsequent decomposition of the corresponding differential Mueller matrix into the complete set of 16 differential matrices which characterize depolarizing anisotropic media. The method has been proposed so far only for measurements in transmission configuration. In this work the method is extended to the backward direction. The modifications of the differential matrices according to the reference system are discussed. The method is successfully applied to Mueller matrices measured in reflection and backscattering

Optical propagation of partially coherent light through anisotropic biological tissues by Green's functions

Biomedical optical techniques of treatment, characterization and surgery depend on light propagation in biological tissues. As biological tissues are turbid media it is necessary to adequately analyze its influence on optical propagation parameters, such as coherence. The influence of a scatterers distribution can be analyzed using Green's functions. Green's functions are sets of impulse responses of inverse operators of differential linear operators with homogeneous boundary conditions. Optical random beams, mainly Gaussian-based, are employed to model light propagation in turbid biological tissues by Green's functions. Enhanced contrast by coherence could distinguish malignant from healthy tissues or provide diagnostic interpretation.This work has been partially supported by the project “High-pressure driven plasmonic and luminescence properties of naked and core/shell metal-oxide nanocomposites” (PGC2018-101464-B-I00) of the Spanish Ministry of Science, Research and Universities, cofunded by FEDER funds, and by the San Cándido Foundation

Light propagation in highly scattering biological tissues analyzed by Green's functions

Biomedical optical techniques of treatment, characterization and surgery are strongly dependent on light propagation in tissues. Information that goes beyond pure intensity, such as polarization or other coherence parameters, can provide increased contrast. This contrast is critical in clinical applications, as malignant tissue has to be distinguished from healthy one, or a particular component or structure has to be highlighted and detected. The appropriate consideration of these further light-tissue interaction properties requires taking into account phase and coherence. The complexity of the problem increases as biological tissues present usually high scattering. This fact greatly influences optical propagation, and is usually a fundamental limitation in optical diagnostic techniques. Light propagation in static scattering media can be analyzed by Green's functions. Electromagnetic propagation could be then considered, including coherence phenomena. However, analytical solutions are complex and require usually numerical methods to obtain a result. Monte Carlo approaches are particularly well-suited in biological tissues. In this work light propagation in highly scattering biological tissues is analyzed first by Green's functions. The limited geometry of this analytical approach serves as a first approach for more complex structures. More realistic biological tissue models are proposed and solved via a threedimensional time-resolved Monte Carlo approach. The model is applied to dermatological tumoral tissues. The results of scattering by Green's functions and the Monte Carlo approach are compared, and the potential contrast of coherence parameters is analyzed in diagnostic applications.This work has been partially supported by the project “New active phases in transition metals and rare earth nano-oxides stabilized at high pressure” (MAT2015-69508-P) of the Spanish Ministry of Economy and Competitiveness, cofunded by FEDER funds, and by the San Cándido Foundation