Ramapurath S. Jayasree

Fluorescence Imaging Assisted Photodynamic Therapy Using Photosensitizer-Linked Gold Quantum Clusters

Fluorescence imaging assisted photodynamic therapy (PDT) is a viable two-in-one clinical tool for cancer treatment and follow-up. While the surface plasmon effect of gold nanorods and nanoparticles has been effective for cancer therapy, their emission properties when compared to gold nanoclusters are weak for fluorescence imaging guided PDT. In order to address the above issues, we have synthesized a near-infrared-emitting gold quantum cluster capped with lipoic acid (L-AuC with (Au)18(L)14) based nanoplatform with excellent tumor reduction property by incorporating a tumor-targeting agent (folic acid) and a photosensitizer (protoporphyrin IX), for selective PDT. The synthesized quantum cluster based photosensitizer PFL-AuC showed 80% triplet quantum yield when compared to that of the photosensitizer alone (63%). PFL-AuC having 60 μg (0.136 mM) of protoporphyrin IX was sufficient to kill 50% of the tumor cell population. Effective destruction of tumor cells was evident from the histopathology and fluorescence imaging, which confirm the in vivo PDT efficacy of PFL-AuC.

The influence of photodynamic therapy on the wound healing process in rats

In photodynamic therapy (PDT), photosensitisers (PS) are used along with lasers for the treatment of tumors. The combined effect of photosensitisers and lasers on the wound healing process is studied using δ-aminolevulinic acid (ALA) (5 mg/kg) and hematoporphyrin derivative (HPD) (5 mg/kg) as photosensitisers in the open excision wounds of rats. The lasers used were He-Ne laser (3 J/cm2) and Nd: YAG laser (30 J/cm2). This study is important for understanding the healing process involved after PDT. Open excision wounds treated with He-Ne lasers in animals that received ALA as photosensitiser showed complete wound closure at the earliest by 13 ± 1 days, and with results obtained for HPD and the combination of lasers with complete closing by 14 ± 1 days. However, the control group of animals that received ALS or HPD with no laser treatment showed wound healing on the twentieth and eighteenth days with a deviation of one day and two days, respectively. ALA with the combination of Nd: YAG and He-Ne lasers and HPD with He-Ne laser alone does not show quicker wound healing effects. Histopathological results also gave similar results. Tensile strength measurements do not vary significantly from control group to the test group. ALA along with He-Ne laser of HPD along with the combination of He-Ne and low power Nd-YAG lasers are found to be ideal methods for quickening the wound healing process in rat.

Synthesis and characterization of dextran stabilized superparamagnetic iron oxide nanoparticles for in vivo MR imaging of liver fibrosis.

The field of medical imaging has recently seen rapid advances in the development of novel agents for enhancing image contrast. In particular, superparamagnetic iron oxide nanoparticles (SPIONs) with a variety of surface properties have been tried as effective contrast agents for magnetic resonance imaging, but with major side effects. In this study, the surface chemistry of SPIONs of size 12 nm was modified with high molecular weight dextran to yield particles of size 50 nm, without compromising the magnetic properties. A systematic characterization of the material for its size, coating efficiency, magnetic properties and biocompatibility has been carried out. The magnetic relaxivity as evaluated on a 1.5 T clinical magnet showed r2/r1 ratio of 56.28 which is higher than that reported for any other dextran stabilized ironoxide nanoparticles. Liver uptake and magnetic resonance imaging potential of dextran stabilized SPIONs (D-SPIONs) has been evaluated on liver fibrosis induced animal model, which is further supported by histopathology results.

Effect of substrate roughness on photoluminescence spectra of silicon nanocrystals grown by off axis pulsed laser deposition

Silicon nanoparticles were prepared by off axis pulsed laser deposition (PLD) technique. The optical properties of Si nanoparticles grown on quartz substrate have been characterized by optical absorption, photoluminescence, Raman, and transmission electron microscopy. TEM has demonstrated that the radius of nanocrystals decreases from 4to0.8nm as the off axis target to substrate distance increases. A blueshift up to 4.2eV is observed in the optical absorption spectra of the Si quantum dots. The slope of log(hν) vs log(α) graph shows that the optical transitions in Si quantum dots are allowed direct, allowed indirect, and direct forbidden transitions which depend on the nature of the substrate used for the growth of silicon. Relaxation of k selection rule is observed in these samples. Photoluminescence (PL) emission consists of an intense broad emission extending over visible to ultraviolet region. The photoluminescence peak energy and intensity are found to be sensitive to the nature of substrate. Possibl...

Citrate coated iron oxide nanoparticles with enhanced relaxivity for in vivo magnetic resonance imaging of liver fibrosis.

Superparamagnetic iron oxide nanoparticles are widely used for the magnetic resonance imaging (MRI) applications. The surface characteristics, magnetic properties, size and targeting efficiency of the material are crucial factors for using the same as contrast agents. We report a simple synthesis method of citrate coated iron oxide nanoparticles and its systematic characterization. The developed system is highly water dispersible with an average particle size of 12 nm. The particles in water are monodisperse and are found to be stable over long periods. The efficiency of the material to de-phase water proton has been studied for various concentrations of iron using longitudinal (T1) and transverse (T2) weighted MRI. The coating thickness of the nanoparticle was optimized so that they exhibited a high transverse to longitudinal relaxivity (r2/r1) ratio of 37.92. A clear dose-dependent contrast enhancement was observed in T2 weighted in vivo MR imaging of liver fibrosis model in rodents. The labelling efficacy of the particle and the intracellular magnetic relaxivity were also investigated and presented. The particles were also tested for blood and cellular compatibility studies. Development of fibrosis and presence of iron in the liver was confirmed by histopathological analysis. From this study, we conclude that the citrate coated ultra small superparamagnetic iron oxide nanoparticles (C-USPION) with optimized parameters like particle size and magnetic property are capable of producing good MR contrast in imaging of liver diseases.

Quantum dot tailored to single wall carbon nanotubes: a multifunctional hybrid nanoconstruct for cellular imaging and targeted photothermal therapy.

Hybrid nanomaterial based on quantum dots and SWCNTs is used for cellular imaging and photothermal therapy. Furthermore, the ligand conjugated hybrid system (FaQd@CNT) enables selective targeting in cancer cells. The imaging capability of quantum dots and the therapeutic potential of SWCNT are available in a single system with cancer targeting property. Heat generated by the system is found to be high enough to destroy cancer cells.

Segmentation and volumetric analysis of the caudate nucleus in Alzheimer's disease

OBJECTIVES A quantitative volumetric analysis of caudate nucleus can provide valuable information in early diagnosis and prognosis of patients with Alzheimers diseases (AD). Purpose of the study is to estimate the volume of segmented caudate nucleus from MR images and to correlate the variation in the segmented volume with respect to the total brain volume. We have also tried to evaluate the caudate nucleus atrophy with the age related atrophy of white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) in a group of Alzheimers disease patients. METHODS 3D fast low angle shot (3D FLASH) brain MR images of 15 AD patients, 15 normal volunteers and 15 patients who had normally diagnosed MR images were included in the study. Brain tissue and caudate nuclei were segmented using the statistical parametric mapping package and a semi-automatic tool, respectively and the volumes were estimated. Volume of segmented caudate nucleus is correlated with respect to the total brain volume. Further, the caudate nucleus atrophy is estimated with the age related atrophy of WM, GM and CSF in a group of AD patients. RESULTS Significant reduction in the caudate volume of AD patients was observed compared to that of the normal volunteers. Statistical analysis also showed significant variation in the volume of GM and CSF of AD patients. Among the patients who had normal appearing brain, 33% showed significant changes in the caudate volume. We hypothesize that these changes can be considered as an indication of early AD. CONCLUSION The method of volumetric analysis of brain structures is simple and effective way of early diagnosis of neurological disorders like Alzheimers disease. We have illustrated this with the observed changes in the volume of caudate nucleus in a group of patients. A detailed study with more subjects will be useful in correlating these results for early diagnosis of AD.

Vibrational spectroscopic studies of FeClMoO4, Na2MoO4 and Na2MoO4·2H2O/D2O

Abstract FTIR and Raman spectra of FeClMoO4 single crystal and polycrystalline Na2MoO4, Na2MoO4·2H2O and Na2MoO4·2D2O are recorded and analysed. The band positions for different modes suggest that MoO4 tetrahedron is more distorted in FeClMoO4. The larger splitting observed for the bending modes and partial retention of degeneracy of the asymmetric stretching mode indicate that angular distortion is greater than liner distortion in MoO42− ion in FeClMoO4 confirming x-ray data. The non-appearance of the ν1 and ν2 modes in the IR and partial retention of the degeneracies of various modes show that MoO42− ion retains Td symmetry in Na2MoO4. Wavenumber values of the ν1 mode indicate that the distortion of MoO4 tetrahedra in the four crystals are in the order FeClMoO4> Na2MoO4·2H2O>Na2MoO4·2D2O>Na2MoO4. The water bands suggest the presence of two crystallographically distinct water molecules in Na2MoO4·2H2O. They form strong hydrogen bonds.

Raman and infrared spectral analysis of thallium niobyl phosphates: Tl2NbO2PO4, Tl3NaNb4O9(PO4)2 and TlNbOP2O7

Raman and infrared spectra of Tl2NbO2PO4, Tl3NaNb4O9(PO4)2 and TlNbOP2O7 are reported. The observed bands are assigned in terms of vibrations of NbO6 octahedra and PO4 tetrahedra in the first two compounds and in terms of NbO6 octahedra and P2O74− anion in the third compound. The NbO6 octahedra in all the title compounds are found to be corner-shared and distorted. The higher wavenumber values of the ν1 (NbO6) mode and other stretching modes indicate that the NbO6 octahedra in them are distorted in the order TlNbOP2O7>Tl2NbO2PO4>Tl3NaNb4O9(PO4)2. The splitting of the ν3 (PO4) mode indicates that PO4 tetrahedra is distorted more in Tl2NbO2PO4 than in Tl3NaNb4O9(PO4)2. The symmetry of P2O74− anion in TlNbOP2O7 is lowered. Bands indicate that the P–O–P bridge in the above compound has a bent P–O–P bridge configuration.

Flower shaped assembly of cobalt ferrite nanoparticles: application as T2 contrast agent in MRI

Material research has moved from generalization to specificity. Progress of nanoscience from synthesis to application oriented tailored synthesis has generated keen interest in the subject. The electrical and magnetic properties of spinel ferrites is one area of nanoscience that is slowing progress towards application oriented research. In this, CoFe2O4, owing to high magnetocrystalline anisotropy, high coercivity and low to moderate saturation magnetization, has found a variety of applications. Clusters of such nanoparticles are predicted to have revolutionary applications. Herein, we report the designed synthesis of cobalt ferrite clusters with a flower like morphology by employing a starch amylose–CTAB complex as a structure directing agent. The ability of starch amylose–CTAB to assemble nanoparticles from a centric core enabled the enhancement of the cluster diameter, leading to a ten fold increase in the T2 relaxivity when compared to the nanoparticles. The nanoparticles were synthesized from metal–polysaccharide complexes, which led to a narrow particle size distribution, low polydispersity index and positively charged surface, all of which contributed to an enhanced R2/R1 value of 82.43, closer to several commercial products. Using starch as a template, along with a low concentration of CTAB, led to low cytotoxicity and high hemocompatibility. In addition, surface starch could provide easy uptake by stem cells and also be linked to light sensitive motifs for dynamic monitoring with MRI.