Abha Uppal

Breast cancer diagnosis using N2 laser excited autofluorescence spectroscopy

This article reports results of an in vitro study involving 63 patients for the evaluation of the diagnostic potential of N2 laser excited autofluorescence spectroscopy of human breast tissues.

Self-rotation of red blood cells in optical tweezers: prospects for high throughput malaria diagnosis

A simple and sensitive approach for detection of malarial parasite in blood samples is demonstrated. The approach exploits our finding that, in hypertonic buffer, a normal red blood cell (RBC) rotates by itself when trapped by an optical tweezers. The rotational speed increases linearly at lower trap-beam powers and more rapidly at higher powers. In contrast, under the same experimental conditions, RBC having a malarial parasite does not rotate. The rotational speeds of other RBCs from malaria-infected sample are of an order of magnitude less than that for normal RBC and also increase much more slowly with an increase in trap beam power than that for normal RBC. The difference in rotational speeds could be exploited for the diagnosis of malaria.

Polar decomposition of 3×3 Mueller matrix: a tool for quantitative tissue polarimetry

The polarization properties of any medium are completely described by the sixteen element Mueller matrix that relates the polarization parameters of the light incident on the medium to that emerging from it. Measurement of all the elements of the matrix requires a minimum of sixteen measurements involving both linear and circularly polarized light. However, for many diagnostic applications, it would be useful if the polarization parameters can be quantified with linear polarization measurements alone. In this paper, we present a method based on polar decomposition of Mueller matrix for quantification of the polarization parameters of a scattering medium using the nine element (3 x 3) Mueller matrix that requires linear polarization measurements only. The methodology for decomposition of the 3 x 3 Mueller matrix is based on the previously developed decomposition process for sixteen element (4 x 4) Mueller matrix but with an assumption that the depolarization of linearly polarized light due to scattering is independent of the orientation angle of the incident linear polarization vector. Studies conducted on various scattering samples demonstrated that this assumption is valid for a turbid medium like biological tissue where the depolarization of linearly polarized light primarily arises due to the randomization of the field vectors direction as a result of multiple scattering. For such medium, polar decomposition of 3 x 3 Mueller matrix can be used to quantify the four independent polarization parameters namely, the linear retardance (delta ), the circular retardance (psi), the linear depolarization coefficient (Delta) and the linear diattenuation (d) with reasonable accuracy. Since this approach requires measurements using linear polarizers only, it considerably simplifies measurement procedure and might find useful applications in tissue diagnosis using the retrieved polarization parameters.

Measurement of NADH concentration in normal and malignant human tissues from breast and oral cavity

We report measurements of the concentration of NADH from malignant and non‐malignant sites of tissues resected from patients suffering from cancer of the breast or oral cavity. The concentration of NADH was found to be significantly higher in malignant breast‐tissue sites as compared with normal breast tissue, whereas the opposite result was obtained with malignant and normal tissues from the oral cavity. These results confirm the inferences made previously, from spectroscopic studies, and are consistent with other biochemical measurements reported in breast and oral cavity tissues.

Photodynamic action of Rose Bengal silica nanoparticle complex on breast and oral cancer cell lines.

Rose Bengal, an anionic photosensitizer was conjugated to organically modified silica nanoparticles having 3‐amino propyl groups by electrostatic or covalent interaction. The drug‐nanoparticle complexes were characterized by FTIR, light scattering and zeta potential measurements. Significant changes were observed in the spectroscopic properties of the drug when it is conjugated with nanoparticles. The toxicity of the free drug and drug‐nanoparticle complex was studied against oral (4451) and breast (MCF‐7) cancer cell lines. Both complexes with nanoparticles were more phototoxic than free Rose Bengal, with the covalent complex being the more effective. Studies carried out on cellular uptake, photostability and singlet oxygen generation suggest that enhanced phototoxicity is primarily due to the enhanced uptake of the drug‐nanoparticle complex.

Hemoglobin degradation in human erythrocytes with long-duration near-infrared laser exposure in Raman optical tweezers

Near-infrared laser (785-nm)-excited Raman spectra from a red blood cell, optically trapped using the same laser beam, show significant changes as a function of trapping duration even at trapping power level of a few milliwatts. These changes in the Raman spectra and the bright-field images of the trapped cell, which show a gradual accumulation of the cell mass at the trap focus, suggest photoinduced aggregation of intracellular heme. The possible role of photoinduced protein denaturation and hemichrome formation in the observed aggregation of heme is discussed.

Studies on erythrocytes in malaria infected blood sample with Raman optical tweezers

Raman spectroscopy was performed on optically trapped red blood cells (RBCs) from blood samples of healthy volunteers (h-RBCs) and from patients suffering from P. vivax infection (m-RBCs). A significant fraction of m-RBCs produced Raman spectra with altered characteristics relative to h-RBCs. The observed spectral changes suggest a reduced oxygen-affinity or right shifting of the oxygen-dissociation curve for the intracellular hemoglobin in a significant fraction of m-RBCs with respect to its normal functional state.

Polarized diffuse reflectance measurements on cancerous and noncancerous tissues

We report the measurement of polarization parameters (linear retardance, diattenuation and depolarization) of normal and malignant tissue from human oral cavity and breast over the spectral range 390 nm to 550 nm. These parameters were determined using the 3 x 3 Mueller matrix, the elements of which could be determined using linear polarization measurements only. The significant differences observed in the polarization parameters of the normal and malignant tissues appear to arise because of the changes in the collagen matrix in the two tissue types.

Fluorimetric estimation of the concentration of NADH from human blood samples

We report the quantitative fluorimetric estimation of the concentration of NADH in human blood samples. To measure both free and bound NADH, the 340‐nm‐excited fluorescence spectra was recorded from blood samples to which SDS was added. Diffuse reflectance and the transmittance spectra of the same sample were also recorded over the wavelength range 340–650 nm. These measurements were used to correct the measured fluorescence spectra for the wavelength‐dependent reduction in fluorescence due to absorption and scattering in the blood sample. NADH concentrations estimated using the corrected fluorescence spectra were found to be in reasonable agreement with the concentrations estimated by the biochemical method.

Raman spectroscopic investigations on optical trap induced deoxygenation of red blood cells

Raman spectroscopic investigations on the oxygenation status of optically trapped red blood cells show that the cellular site in the trap beam is more deoxygenated compared to the rest of the cell, and the level of deoxygenation increases with an increase in the trap beam power. These observations and the changes in the Raman spectrum of hemoglobin solution as a function of the trapping beam power suggest that observed deoxygenation may be due to photodissociation of oxygen from hemoglobin at increased trapping power.