ORCID Profile
0000-0003-0670-6672
Current Organisation
Nanyang Technological University
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Publisher: Elsevier BV
Date: 11-2015
Publisher: The Optical Society
Date: 29-11-2016
DOI: 10.1364/BOE.7.005308
Publisher: Springer Science and Business Media LLC
Date: 29-07-2016
DOI: 10.1038/SREP30844
Abstract: Direct visualization and assessment of the iridocorneal angle (ICA) region with high resolution is important for the clinical evaluation of glaucoma. However, the current clinical imaging systems for ICA do not provide sufficient structural details due to their poor resolution. The key challenges in achieving high quality ICA imaging are its location in the anterior region of the eye and the occurrence of total internal reflection due to refractive index difference between cornea and air. Here, we report an indirect axicon assisted gonioscopy imaging probe with white light illumination. The illustrated results with this probe shows significantly improved visualization of structures in the ICA including TM region, compared to the current available tools. It could reveal critical details of ICA and expected to aid management by providing information that is complementary to angle photography and gonioscopy.
Publisher: Wiley
Date: 09-10-2012
DOI: 10.1002/LSM.22083
Abstract: The photobiological effect of laser light on cells and tissues originates from light absorption by endogenous chromophores and hence it depends on the wavelength of light source and cell type. Earlier studies regarding the biostimulation effects of green laser light investigated a wide variety of cells but not adipose tissue-derived stem cells (ADSCS). In this study we reported the in vitro effect of 532-nm Nd:YAG laser on proliferation, mitochondrial activity of these mesenchymal stem cells (MSCs) on the autofluorescence emission at wavelengths associated with nicotinamide adenine dinucleotide (NADH) and flavoproteins. ADSCS were exposed to 532 nm second harmonic generation laser light at moderate power density (0.153 W/cm(2)) for periods of 30, 45, 60, 180, and 300 seconds. Mitochondrial membrane potential was measured using JC1 stain and confocal laser scanning microscopy, cell proliferation rates, and cellular autofluorescence emission at 450 and 540 nm wavelengths were measured using micro plate spectrofluorometer 48 hours after irradiation. Shorter (30-60 seconds) exposure times led to significantly increased proliferation, attributed to increased mitochondrial activity (P < 0.05). At longer exposures we observed a significant decrease in proliferation and autofluorescence (P < 0.05). Strong correlation was observed between proliferation rates of cells and autofluorescence intensity. Our results show that autofluorescence of the respiratory chain components and key autofluorescent metabolites offers a non-invasive method to quantify cellular response to laser irradiation.
Publisher: Elsevier BV
Date: 2010
DOI: 10.1016/J.TALANTA.2009.09.020
Abstract: Despite biological variability the spectral characteristics of undiluted human urine show relatively low autofluorescence at short UV (250-300nm) excitation. However with dilution the fluorescence intensity remarkably increases. This paper examines the mechanisms behind this effect, by using excitation-emission matrices. Corrections for the inner filter effect were made for improved understanding of the spectral patterns. We focused on three major fluorophores (tryptophan, indoxyl sulfate and 5-hydroxyindole-3-acetate) that are excited at these wavelengths, and whose content in urine is strongly linked with various health conditions. Their fluorescence was studied both in idually and in combinations. We also examined the effect of ammonium on the fluorescence of these major fluorophores in idually and in combinations. Through these studies we have identified the leading effects that reduce the UV fluorescence, namely higher concentration of indoxyl sulfate producing the inner filter effect and concentration quenching and quenching of fluorophores by ammonium. This result will assist in broader utilisation of UV fluorescence in medical diagnostics.
Publisher: Springer Science and Business Media LLC
Date: 31-03-2016
DOI: 10.1038/SREP23453
Abstract: Automated and unbiased methods of non-invasive cell monitoring able to deal with complex biological heterogeneity are fundamentally important for biology and medicine. Label-free cell imaging provides information about endogenous autofluorescent metabolites, enzymes and cofactors in cells. However extracting high content information from autofluorescence imaging has been hitherto impossible. Here, we quantitatively characterise cell populations in different tissue types, live or fixed, by using novel image processing and a simple multispectral upgrade of a wide-field fluorescence microscope. Our optimal discrimination approach enables statistical hypothesis testing and intuitive visualisations where previously undetectable differences become clearly apparent. Label-free classifications are validated by the analysis of Classification Determinant (CD) antigen expression. The versatility of our method is illustrated by detecting genetic mutations in cancer, non-invasive monitoring of CD90 expression, label-free tracking of stem cell differentiation, identifying stem cell subpopulations with varying functional characteristics, tissue diagnostics in diabetes and assessing the condition of preimplantation embryos.
Publisher: Elsevier BV
Date: 15-08-2010
DOI: 10.1016/J.TALANTA.2010.05.049
Abstract: Urinary tract infections (UTIs) are known to alter the normal urine composition which, in principle, can lead to changes in urine autofluorescence. This paper describes the study of human urine (normal and UTI) by using UV fluorescence excitation/emission matrices and synchronous spectra and proposes a method of diagnosing UTI without any s le preparation. The method is based on excitation in the shorter UV region (250-350 nm) which shows good discrimination between the normal urine and UTI s les. The synchronous scans with an offset of Deltalambda=90 nm were also able to differentiate between normal urines and UTI s les. These differences were observed even though the two known major urine fluorophores, tryptophan and indoxyl sulfate were present in the normal urine and UTI s les in similar concentration as established by HPLC analysis. Although the identity of substances responsible for the altered autofluorescence in UTI is not established, our study shows that autofluorescence has the potential to differentiate between normal human urine s les and those with UTI.
Publisher: Elsevier BV
Date: 03-2009
DOI: 10.1016/J.CCA.2008.11.021
Abstract: A variety of fluorophores are present in normal human urine. Alteration in the autofluorescence of urine could result from physiological or pathological changes. This study investigates the differences in the autofluorescence of 45 normal urine s les from 25 in iduals with bacteriuria. Excitation at 290 nm showed good discrimination between these 2 groups. Principal Component Analysis (PCA) of the data revealed statistically significant differences between the fluorescence spectra for s les with bacteriuria as compared to the control group. The findings indicate the potential of the fluorescence spectrum of urine to be developed as a simple and rapid diagnostic tool.
Publisher: IOP Publishing
Date: 04-04-2007
Abstract: Optical fiber based laser induced fluorescence (LIF) measurements were carried out using Rhodamine B to analyze two different species of bacteria, a Gram-positive bacteria namely Bacillus smithii , and Vibrio alginolyticus, a Gram-negative bacteria. The fiber sensor was clearly able to distinguish between the two species of bacteria. Quenching effect of the dye Rhodamine B by Bacillus smithii was observed. The effect of dye on the s les was also studied in detail.
No related grants have been discovered for SANDEEP MENON PERINCHERY.