Sharad Gupta | Indian Institute of Technology Indore (original) (raw)

Papers by Sharad Gupta

Applied optics, Jan 9, 2009

The alignment of deposited minerals in tissues such as bone and teeth plays a critical role in th... more The alignment of deposited minerals in tissues such as bone and teeth plays a critical role in the mechanical properties of these tissues. Therefore, assessment of features that are characteristic of aligned biominerals could aid in the development of novel biomaterials and engineered tissues that can be used to replace damaged or defective human tissues. In this study, we demonstrate that light scattering spectroscopy can serve as a useful tool for the noninvasive characterization of mineralization on aligned organic substrates. Specifically, we used silk films with oriented and nonoriented secondary structures as a protein matrix for control of mineralization. The mineral deposits displayed self-affine fractal morphologies with the oriented films yielding a significantly higher Hurst parameter, which in turn suggests higher levels of fractal organization. In addition, the value of the upper bound of fractal correlation lengths was significantly smaller for the oriented than for the nonoriented films and correlated well with the size of the corresponding nanocrystalline mineral beads identified by scanning electron microscope imaging.

Journal of Biomedical Optics, 2005

Fluorescence intensity fluctuations in the visible wavelength regime in normal, benign, and cance... more Fluorescence intensity fluctuations in the visible wavelength regime in normal, benign, and cancerous human breast tissue samples are studied through wavelet transform. The analyses have been carried out in unpolarized, parallel and perpendicularly polarized channels, for optimal tissue characterization. It has been observed that polarized fluorescence data, particularly the perpendicular components, differentiate various tissue types quite well. Wavelet transform, because of its ability for multiresolution analysis, provides the ideal tool to separate and characterize fluctuations in the fluorescence spectra at different scales. We quantify these differences and find that the fluctuations in the perpendicular channel of the cancerous tissues are more randomized as compared to their normal counterparts. Furthermore, for cancerous tissues, the same is very well described by the normal distribution, which is not the case for normal and benign samples. It has also been observed that, up to a certain point, fluctuations at larger scales are more sensitive to tissue types. The differences in the average, low-pass wavelet coefficients of normal, cancerous, pericanalicular, and intracanalicular benign tissues are also pointed out.

International Journal of Nanomedicine, Apr 1, 2013

Near-infrared nanoconstructs present a potentially effective platform for site-specific and deep ... more Near-infrared nanoconstructs present a potentially effective platform for site-specific and deep tissue optical imaging and phototherapy. We have engineered a polymeric nanocapsule composed of polyallylamine hydrochloride (PAH) chains cross-linked with sodium phosphate and doped with indocyanine green (ICG) toward such endeavors. The ICG-doped nanocapsules were coated covalently with polyethylene glycol (5000 daltons) through reductive amination. We administrated the constructs by tail vein injection to healthy mice. To characterize the biodistribution of the constructs, we performed in vivo quantitative fluorescence imaging and subsequently analyzed the various extracted organs. Our results suggest that encapsulation of ICG in these PEGylated constructs is an effective approach to prolong the circulation time of ICG and delay its hepatic accumulation. Increased bioavailability of ICG, due to encapsulation, offers the potential of extending the clinical applications of ICG, which are currently limited due to rapid elimination of ICG from the vasculature. Our results also indicate that PAH and ICG-doped nanocapsules (ICG-NCs) are not cytotoxic at the levels used in this study.

IEEE Journal of Selected Topics in Quantum Electronics, Mar 1, 2003

Polarized fluorescence spectra of malignant, benign, and normal human breast tissues in the emiss... more Polarized fluorescence spectra of malignant, benign, and normal human breast tissues in the emission range of 500-700 nm, with an excitation wavelength of 488 nm, are analyzed through discrete wavelet transform. The multiresolution and localization properties of the wavelets are shown to be ideally suited for identifying characteristic features distinguishing these tissue types. Analysis of a number of data sets, belonging to both parallel and perpendicular polarized spectra, have led to several key distinctions between different tumors and corresponding normal breast tissues, revealing the usefulness of polarized fluorescence in the diagnosis of tumors. Wavelet transform also naturally leads to the dimensional reduction of the data set, in the form of low-pass coefficients, making it amenable for physical modeling.

Biomaterials, May 1, 2008

Designing biomaterial scaffolds remains a major challenge in tissue engineering. Key to this chal... more 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 β sheet content and molecular orientation of the sample. Thus, the functional content and high resolution afforded by these noninvasive 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.

arXiv (Cornell University), Apr 7, 2004

Wavelet transform of polarized fluorescence spectroscopic data of human breast tissues is found t... more Wavelet transform of polarized fluorescence spectroscopic data of human breast tissues is found to reliably differentiate normal and malignant tissue types and isolate characteristic biochemical signatures of cancerous tissues, which can possibly be used for diagnostic purpose. A number of parameters capturing spectral variations and subtle changes in the diseased tissues in the visible wavelength regime are clearly identifiable in the wavelet domain. These investigations, corroborated with tissue phantoms, indicate that the observed differences between malignant tumor and normal samples are primarily ascribable to the changes in concentration of porphyrin and density of cellular organelles present in tumors.

Journal of Clinical Microbiology, Aug 1, 2011

Bacterial endospores are some of the most resilient forms of life known to us, with their persist... more Bacterial endospores are some of the most resilient forms of life known to us, with their persistent survival capability resulting from a complex and effective structural organization. The outer membrane of endospores is surrounded by the densely packed endospore coat and exosporium, containing amyloid or amyloid-like proteins. In fact, it is the impenetrable composition of the endospore coat and the exosporium that makes staining methodologies for endospore detection complex and challenging. Therefore, a plausible strategy for facile and expedient staining would be to target components of the protective surface layers of the endospores. Instead of targeting endogenous markers encapsulated in the spores, here we demonstrated staining of these dormant life entities that targets the amyloid domains, i.e., the very surface components that make the coats of these species impenetrable. Using an amyloid staining dye, thioflavin T (ThT), we examined this strategy. A short incubation of bacillus endospore suspensions with ThT, under ambient conditions, resulted in (i) an enhancement of the fluorescence of ThT and (ii) the accumulation of ThT in the endospores, affording fluorescence images with excellent contrast ratios. Fluorescence images revealed that ThT tends to accumulate in the surface regions of the endospores. The observed fluorescence enhancement and dye accumulation, coupled with the sensitivity of emission techniques, provide an effective and rapid means of staining endospores without the inconvenience of pre-or posttreatment of samples.

Applied Spectroscopy, Jul 1, 2012

Wavelet transform of polarized fluorescence spectra of human breast tissues is found to localize ... more Wavelet transform of polarized fluorescence spectra of human breast tissues is found to localize spectral features that can reliably differentiate normal and malignant tissue types. The intensity differences of parallel and perpendicularly polarized fluorescence spectra are subjected to investigation, since the same is relatively free of the diffusive background. A number of parameters, capturing spectral variations and subtle changes in the diseased tissues in the visible wavelength regime, are clearly identifiable in the wavelet domain. These manifest both in the average low pass and high frequency high pass wavelet coefficients.

Journal of Biomedical Optics, 2011

Leukemia is the most common and deadly cancer among children and one of the most prevalent cancer... more Leukemia is the most common and deadly cancer among children and one of the most prevalent cancers among adults. Improvements in its diagnosis and monitoring of leukemic patients could have a significant impact in their long-term treatment. We demonstrate that light-scattering spectroscopy (LSS)-based approaches could serve as a tool to achieve this goal. Specifically, we characterize the light scattering properties of leukemic (NALM-6) cells and compare them to those of normal lymphocytes and granulocytes in the 440-710 nm range, over ± 4 deg about the exact backscattering direction. We find that the LSS spectra are well described by an inverse powerlaw wavelength dependence, with a power exponent insensitive to the scattering angle but significantly higher for leukemic cells than for normal leukocytes. This is consistent with differences in the subcellular morphology of these cells, detected in differential interference contrast images. Furthermore, the residual light-scattering signal, extracted after subtracting the inverse power-law fit from the data, can be analyzed assuming a Gaussian distribution of spherical scatterers using Mie theory. This analysis yields scatterer sizes that are consistent with the diameters of cell nuclei and allows the detection of the larger nuclei of NALM-6 cells compared to those of lymphocytes and granulocytes.

Scientific Reports, 2019

Delivery of the theranostic agents with effective concentration to the desired sites inside the b... more Delivery of the theranostic agents with effective concentration to the desired sites inside the body is a major challenge in disease management. Nanotechnology has gained attention for the delivery of theranostic agents to the targeted location. The use of essential amino-acid based homopolymers for the synthesis of biocompatible and biodegradable nanoparticles (NPs) could serve as a nanocarrier for delivery applications. In this study, poly-l-lysine (PLL) and salts were used to fabricate the NPs for the delivery of exogenous contrast agents. Here, indocyanine green (ICG) was encapsulated within these NPs, and a simple two-step green chemistry-based self-assembly process was used for the fabrication. The morphological and biochemical characterizations confirm the formation of ICG encapsulating spherical PLL NPs with an average diameter of ~225 nm. Further, a detailed study has been carried out to understand the role of constituents in the assembly mechanism of PLL NPs. Our results s...

Journal of visualized experiments : JoVE, 2012

In viruses with positive-sense RNA genomes pathogenic to humans, animals and plants, progeny enca... more In viruses with positive-sense RNA genomes pathogenic to humans, animals and plants, progeny encapsidation into mature and stable virions is a cardinal phase during establishment of infection in a given host. Consequently, study of encapsidation deciphers the information regarding the know-how of the mechanism regulating virus assembly to form infectious virions. Such information is vital in formulating novel methods of curbing virus spread and disease control. Virus encapsidation can be studied in vivo and in vitro. Genome encapsidation in vivo is a highly regulated selective process involving macromolecular interactions and subcellular compartmentalization. Therefore, study leading to dissect events encompassing virus encapsidation in vivo would provide basic knowledge to understand how viruses proliferate and assemble. Recently in vitro encapsidation has been exploited for the research in the area of biomedical imaging and therapeutic applications. Non-enveloped plant viruses sta...

Nanoscale, 2013

We report the first proof-of-principle demonstration of photoacoustic imaging using a contrast ag... more We report the first proof-of-principle demonstration of photoacoustic imaging using a contrast agent composed of a plant virus protein shell, which encapsulates indocyanine green (ICG), the only FDA-approved near infrared chromophore. These nano-constructs can provide higher photoacoustic signals than blood in tissue phantoms, and display superior photostability compared to non-encapsulated ICG. Our preliminary results suggest that the constructs do not elicit an acute immunogenic response in healthy mice. In this Communication, we report the first demonstration of near infrared (NIR) photoacoustic imaging (PAI) using a new nano-construct composed of biological and organic materials as the contrast agent. Specifically, the construct is comprised of a protein shell, purified from the plant-infecting brome mosaic virus (BMV), that encapsulates indocyanine green (ICG), the only FDA-approved NIR chromophore. We refer to these virus-resembling nano-constructs as optical viral ghosts (OVGs) since the genomic content of the wildtype BMV is eliminated and replaced with ICG, while the capsid protein (CP) subunits remain as the encapsulating shell. Recently, attention has been given to the use of biological materials, particularly viruses, as a platform for the delivery of imaging and therapeutic agents. 1-5 Plant and recombinant adenoviruses have been investigated as potential vaccine carriers in gene therapy and oncolytic viral therapy. 6-8 Viruses have also been used to encapsulate inorganic materials including quantum dots (QDs), 9 gold, 10 and magnetic nanoparticles. 11 Virus-based protein cages, assembled from the cowpea chlorotic mottle virus, 12 and the capsid of the MS2 bacteriophage coated with gadolinium have been investigated as MRI contrast agents. 12,13 In comparison to animal viruses, plant viruses are easier to produce and purify, and are chemically and structurally more stable. 5,14,15 For example, surface conjugation of the cowpea mosaic virus (CPMV) with a folic acid-PEG moiety has been demonstrated in vitro † Authors have no competing financial interest. ‡ Electronic supplemental information (ESI) available: information on experimental procedure for fabrication of the nano-constructs, photoacoustic imaging, and immunogenic studies. See

ACS Omega

In recent years, chemo-photothermal therapy (chemo-PTT) has been extensively studied for the upgr... more In recent years, chemo-photothermal therapy (chemo-PTT) has been extensively studied for the upgradation of cancer treatment. The combined therapeutic approach reduces the overall cytotoxicity and enhances the therapeutic effect against the cancerous cells. In chemo-PTT, Indocyanine green (ICG) dye, a near-infrared chromophore, is used for PTT in combination with doxorubicin (DOX), a chemotherapeutic drug. ICG and DOX work very efficiently in synergy against cancer. However, the effect of DOX on the optical properties of ICG has not been studied yet. Here, for the first time, we report the effect of DOX on the optical properties of ICG in detail. DOX interacts with ICG and induces the aggregation of ICG even at a low concentration. The coincubation of both the molecules causes H and J aggregations in ICG. However, the J aggregation becomes more prominent with an increasing DOX concentration. These findings suggest that the optical properties of ICG change upon incubation with the DOX, which might affect the efficacy of PTT.

Journal of Biological Chemistry, 2012

Background: Huntington disease is associated with protein misfolding. Results: We developed an am... more Background: Huntington disease is associated with protein misfolding. Results: We developed an amyloid seeding assay for detecting misfolded huntingtin (HTT) protein and found early protein misfolding in a transgenic mouse model. Conclusion: The amyloid seeding assay allows for sensitive detection of misfolded HTT. Significance: The detection of misfolded HTT in young YAC128 mice suggests that protein misfolding may be an early event in pathogenesis.

RSC Advances

ICG-PLA NPs were synthesized for multiphoton bioimaging. The ICG-PLA NPs were more efficiently ta... more ICG-PLA NPs were synthesized for multiphoton bioimaging. The ICG-PLA NPs were more efficiently taken up by the cells and improved the photostability of the ICG. The ICG-PLA NPs incubated cells display superior contrast in multiphoton imaging.

Lasers in medical science, Jan 22, 2018

The feasibility of continuous wave laser-based photoacoustic (CWPA) response technique in detecti... more The feasibility of continuous wave laser-based photoacoustic (CWPA) response technique in detecting the morphological changes in cells during the biological studies, through the features extracted from CWPA signal (i.e., amplitude) is demonstrated here. Various hematological disorders (e.g., sickle cell anemia, thalesemia) produce distinct changes at the cellular level morphologically. In order to explore the photoacoustic response technique to detect these morphological changes, we have applied CWPA technique onto the blood samples. Results of our preliminary study show a distinct change in the signal amplitude of photoacoustic (PA) signal due to a change in the concentration of blood, which signifies the sensitivity of the technique towards red blood cell (RBC) count (related to hematological disease like anemia). Further hypotonic and hypertonic solutions were induced in blood to produce morphological changes in RBCs (i.e., swollen and shrink, respectively) as compared to the nor...

Viruses, Feb 23, 2018

Modern oncotherapy approaches are based on inducing controlled apoptosis in tumor cells. Although... more Modern oncotherapy approaches are based on inducing controlled apoptosis in tumor cells. Although a number of apoptosis-induction approaches are available, site-specific delivery of therapeutic agents still remain the biggest hurdle in achieving the desired cancer treatment benefit. Additionally, systemic treatment-induced toxicity remains a major limiting factor in chemotherapy. To specifically address drug-accessibility and chemotherapy side effects, oncolytic virotherapy (OV) has emerged as a novel cancer treatment alternative. In OV, recombinant viruses with higher replication capacity and stronger lytic properties are being considered for tumor cell-targeting and subsequent cell lysing. Successful application of OVs lies in achieving strict tumor-specific tropism called oncotropism, which is contingent upon the biophysical interactions of tumor cell surface receptors with viral receptors and subsequent replication of oncolytic viruses in cancer cells. In this direction, few vir...