Shamaraz Firdous

Non-invasive characterization of structure and morphology of silk fibroin biomaterials using non-linear microscopy.

Designing biomaterial scaffolds remains a major challenge in tissue engineering. Key to this challenge is improved understanding of the relationships between the scaffold properties and its degradation kinetics, as well as the cell interactions and the promotion of new matrix deposition. Here we present the use of non-linear spectroscopic imaging as a non-invasive method to characterize not only morphological, but also structural aspects of silkworm silk fibroin-based biomaterials, relying entirely on endogenous optical contrast. We demonstrate that two photon excited fluorescence and second harmonic generation are sensitive to the hydration, overall beta sheet content and molecular orientation of the sample. Thus, the functional content and high resolution afforded by these non-invasive approaches offer promise for identifying important connections between biomaterial design and functional engineered tissue development. The strategies described also have broader implications for understanding and tracking the remodeling of degradable biomaterials under dynamic conditions both in vitro and in vivo.

Ex Vivo Assessment of Carbon Tetrachloride (CCl 4 )-Induced Chronic Injury Using Polarized Light Spectroscopy

The liver performs various functions, such as the production and detoxification of chemicals; therefore, it is susceptible to hepatotoxins such as carbon tetrachloride (CCl4), which causes chronic injury. Thus, assessment of injury and its status of severity are of prime importance. Current work reports an ex vivo study for probing the severance of hepatic injury induced by CCl4 with polarized light over the spectral range 400–800 nm. Different concentrations of CCl4 were used to induce varying severity of hepatic injury in a rat model. Linear retardance, depolarization rates, and diagonal Mueller matrix elements (m22, m33, and m44), were successfully used as the distinguishing criterion for normal and different liver injuries. Our results show that linear retardance for injured liver samples with lower doses of CCl4 tends to increase when compared with normal liver samples, while samples injured at higher doses of CCl4 offer almost no retardance. Total, linear, and circular depolarizations follow decreasing trends with increased liver injury severity over the entire investigated wavelength range. Linear polarization states were observed to be better maintained as compared to circular polarization states for all samples. Furthermore, numerical values of diagonal elements of the experimentally measured Mueller matrix also increase with increasing doses of CCl4. Liver fibroses, change in transport albedo, and the relative refractive index of the extracellular matrix caused by CCl4 are responsible for the observed differences. These results will provide a pathway to gauge the severity of injury caused by toxic chemicals.

Stokes polarimetry for the characterization of bio-materials using liquid crystal variable retarders

We demonstrate significant differences in the propagation of polarized laser light through biological tissue phantom. The Stokes vectors along with degree of linearly and circularly polarized light were measured with stokes polarimetry techniques. The measurements were performed on dense and diluted tissue phantoms that consisted of soybean oil interloped. Liquid crystal variable retarder (LCVR) Stokes polarimeter is used for either rotating the major axis of elliptically polarized light or for converting an input linearly polarized beam into an arbitrary elliptically polarized beam. This system makes possible a direct measurement of a component of the Stokes vector with phase change detection of polarization modulation for polarimetric measurements of turbid media and biological tissue.

Formulation of a Mueller matrix for modeling of depolarization and scattering of nitrobenzene in a Kerr cell

We have studied the depolarization of light from nitrobenzene in a Kerr cell. We observed that absorption in nitrobenzene is electric-field dependent. For modeling a nitrobenzene device we formulated a Mueller matrix for the Kerr-cell assembly, and by operating it on a Stokes vector of the input light we obtained a corresponding Stokes vector for the output light. The first parameter of the output Stokes vector corresponds to the intensity transmittance. It was simulated and compared with the measured intensity transmittance for several orientations of the polarizer-analyzer pair with respect to the applied voltages. The measurement of all unknown coefficients in a Mueller matrix consisting of the superposition of nondepolarizing and depolarizing components predicts the depolarization, scattering, and absorption in the nitrobenzene electro-optic device. The output intensities of the orthogonally polarized and cross-coupled depolarizing coefficients are in good agreement for a semi-isotropic medium. The formulated Mueller matrix agrees with the experimentally measured transmittance.

Transmission and scattering matrix of polarization imaging for biological turbid medium

Laser transmittion and scattering technique, including depolarization of wave applied to biological particles provide a sample way for diagnostic and treatment of skin lesion and breast cancer. Laser polarization imaging system is described for non invasive and non radioactive detection. The system described in this paper generates 16 full out put Mueller matrix for characterization of turbid medium. In this work we describe the scattering and depolarization of electromagnetic radiation through biological turbid medium. This research work provides a base work for designing quick model of polarized laser tissues imaging.

Characterization of turbid medium through diffusely backscattering polarized light with matrix calculus-II

A diffusely backscattered polarized beam of laser radiation from a turbid medium has been characterized by optics calculus. The Stokes and Mueller parameters of polarized light are represented as a column matrix and the optical turbid medium as a 4/spl times/4 matrix. The tissue like turbid phantom system is considered homogeneous and the scattering medium contains one kind of randomly distributed asymmetric particles. We use polarized light from a He-Ne laser (/spl lambda/=632.5 nm) focused on the scattering medium. Different polarization components of backscattered light are obtained by varying the polarization state of the incident laser light and the analyzer configuration. The calculation of the 16 elements of the output Mueller matrix shows that theoretically only seven elements of backscattered light are independent and the remaining nine can be calculated through a symmetry relation. It is also confirmed through experiments. The matrix calculus concept for diffusely backscattered light fully characterizes the turbid medium. The experimental and theoretical results are in good agreement.

Optical diagnosis of dengue virus infected human blood using Mueller matrix polarimetry

Currently dengue fever diagnosis methods include capture ELISAs, immunofluorescence tests, and hemagglutination assays. In this study optical diagnosis of dengue virus infection in the whole blood is presented utilizing Mueller matrix polarimetry. Mueller matrices of about 50 dengue viral infected and 25 non-dengue healthy blood samples were recorded utilizing light source from 500 to 700 nm with scanning step of 10 nm. Polar decomposition of the Mueller matrices for all the blood samples was performed that yielded polarization properties including depolarization, diattenuation, degree of polarization, retardance and optical activity, out of which, depolarization index clusters up the diseased and healthy in to different separate groups. The average depolarized light in the case of dengue infection in the whole blood at 500 nm is 18%, whereas for the healthy blood samples it is 13.5%. This suggests that depolarization index of polarized light at the wavelengths of 500, 510, 520, 530 and 540 nm, we find that in case of depolarization index values are higher for dengue viral infection as compared to normal samples. This technique can effectively be used for the characterization of the dengue virus infected at an early stage of disease.

Optical Diagnostic of Dengue Virus Infected Human Blood using Raman, Polarimetric and Fluorescence Spectroscopy

In this chapter, we present the optical diagnosis of normal and dengue viral‐infected human blood using Raman, Polarimetric, Transmission, and Fluorescence Spectroscopic techniques. The possibility of using light in diagnosis and treating illness has been known for thousands of years. The properties of light and lasers provided many modern applica‐ tions at home, in industry, and in the field of medicine. Laser use in the field of medicine is large and steadily growing. This growth is based on the versatility of laser light. Efficient and accurate diagnosis of dengue is of primary importance for clinical care. A range of laboratory diagnostic methods has been developed to support patient management and disease control. The choice of diagnostic method depends on the purpose for which the testing is done, the type of laboratory facilities and technical expertise available, costs, and the time of sample collection. The dengue viral infection is mostly diagnosed through laboratory tests; these tests include detection of the virus, virus antigen, anti‐dengue virus antibody, complement fixation test, neutralization tests, and detection of virus nucleic acid. As dengue infection most rapidly increases in different regions, early diagnostic con‐ firmation of dengue infection in patients allows for timely clinical intervention, etiological investigation, and disease control. Hence, diagnosis of dengue disease during the acute phase should be a priority and is a public health concern. Lasers and optics have many applications in medical sciences; diagnosis and treatment of diseases with lasers and light are latest and noninvasive techniques. Development of light‐based apparatus has evolved into tools for improved diagnosis and treatment modalities in medical sciences. The meth‐ ods of the laser spectroscopy make it possible to obtain direct information regarding the structure and dynamics of the functional groups of biomolecules. Development of new light sources, optics, and diode laser of different wavelengths makes them attractive for spectroscopy of biological molecules. In our study, more than 600 dengue viral‐infected blood or blood sera samples and 25 non‐dengue healthy blood samples were analyzed using four different optical methodologies. In the first study, Raman spectrum peaks for normal samples observed at 1527, 1170, and 1021 cm−1 show the presence of different bio‐ logical materials, including lipids, carbohydrates, skeletal C–C stretch of acyl chains, and

Imaging of biological tissues with optical coherence tomography system using Jones-Mueller calculus

The polarization sensitive optical coherence tomography (OCT) system provides useful informations about the biological tissues. The exact tissue parameters measurement and comparison predicts about the malignant and normal tissues. The degree of polarization changes with the depth of tissue samples. We have established the analytical modeling with Jones-Mueller matrix for imaging technique, which experimentally extract the birefringence, depolarization, absorption and scattering information of tissues. The Jones matrix of thermally treated porcine tendon showed a reduction of birefringence from thermal damage. The Jones matrices of porcine skin and bovine cartilage also revealed that the density and orientation of the collagen fibers in porcine skin and bovine cartilage are not distributed as uniformly as in porcine tendon. Birefringence is sensitive to changes in tissue because it is based on phase contrast.