Browsing by Author "Nair, RV"

Now showing 1 - 10 of 10
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    An insight into the optical properties of a sub nanosize glutathione stabilized gold cluster
    (DALTON TRANSACTIONS, 2016) Nair, LV; Nair, RV; Jayasree, RS
    In this study, gold quantum clusters with distinct fluorescence properties were developed and their structural and physical behaviour was evaluated. The clusters were prepared by etching gold nanoparticles with glutathione. Three different Au-33 clusters with emission profiles in the NIR region and one blue emitting cluster, Au-8 were developed by varying the geometrical arrangement of atoms within the cluster. These clusters having sizes in the range of 0.7 to 2 nm were synthesized by choosing different reaction temperatures from 0 degrees C to 70 degrees C and pH between 1.5 and 10. In the three cases, formation of self assembled atoms within the cluster and the corresponding changes in optical properties were observed. A detailed evaluation of the number of atoms and the core-ligand ratio using MALDI-MS and a change in the binding energy as seen in the XPS study confirmed this finding. The study demonstrates that the self assembly of atoms and their arrangement is an important factor in determining the characteristics of the cluster. In this communication, we put forward a new concept where the number of atoms and their arrangement within the clusters play a crucial role in tuning their optical properties.
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    Blood brain barrier permeable gold nanocluster for targeted brain imaging and therapy: an in vitro and in vivo study.
    (Journal of Materials Chemistry, 2017-12) Nair, LV; Nair, RV; Shenoy, SJ; Thekkuveettil, A; Jayasree, RS
    Blood brain barrier (BBB) is a dynamic interface, comprising polarized endothelial cells, that separates the brain from the circulatory system. The highly protective nature of this tight junction impairs diagnosis and treatment of brain disorders. In this study, we designed a sub atomic size, near infrared emitting, dual function glutathione gold cluster with high fluorescence yield to facilitate permeability of BBB, for imaging applications and drug delivery. The gold cluster was then modified with Levodopa (L-dopa), to utilize the large amino acid transporter 1 (LAT1) pathways to enhance brain entry. Uptake and permeability of the nanoprobes were demonstrated using an established model of BBB, comprising brain endothelial cells (bEnd.3). The uptake and the clearance of L-dopa modified cluster was faster than the glutathione cluster. L-Dopa modified cluster supports the slow and sustained delivery of a model drug, pilocarpine, to the brain. Results of in vivo imaging and drug release in normal mice hold promise for considering the probe for early diagnosis of brain diseases, when the barrier is not disrupted, and for subsequent drug treatment.
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    A dual signal on-off fluorescent nanosensor for the simultaneous detection of copper and creatinine
    (Materials Science and Engineering : C, 2019-12) Nair, RV; Parvathy, RS; Jayasree, RS
    The transition of conventional medicine to personalized medicine has paved the roadand need for the sensing of newer biomolecules. Hence, this area has attracted wide interestrecently, due to its capacity to provide information on point of care basis. Multi-analytedetection sensors have emerged recently as they can offer the opportunity to perform quickand affordable analysis with minimum blood sample, as compared to traditional sensing ofeach analytes individually. The present study focuses on the development of a quantum dot(Qd) based nanosensor for the simultaneous detection of copper and creatinine; twobiologically relevant molecules. The sensor was designed by forming a complex of Qd withEthyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and picric acid through carboxylic bond formation of Qd-EDC with picric acid. The dual independent emissions of the Qd-EDCcomplex was used for the simultaneous detection of creatinine and copper by a turn on/turnoff method and was successfully demonstrated with a sensitivity of nanomolar to millimolar,and micromolar to millimolar range respectively. The multianalyte sensor thus developed hasquick response and works well under normal conditions of temperature and pH. It is alsoshown to work in cellular environment and blood serum. A mobile App based detection ofcreatinine using the developed sensor strips has also been attempted and validated withhuman blood samples
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    Engineering of Tripeptide-Stabilized Gold Nanoclusters with Inherent Photosensitizing Property for Bioimaging and Photodynamic Therapy
    (ACS Sustainable Chem. Eng, 2023-01) Santhakumar, H; Nair, RV; Govindachar, DM; Periyasamy, G; Jayasree, RS
    Gold nanoclusters have the characteristics of small size, unique optical properties, and eco-friendly synthesis that make them promising candidates for biomedical applications, especially for bioimaging. However, their inherent photochemical activity and therapeutic efficiency are largely unknown and remain unexplored. Here, we report a simple one-step green synthesis procedure for the preparation of two tripeptide-stabilized silver-doped gold nanoclusters (TPGNCs) and their photodynamic therapeutic effect on cancer cells and simultaneous imaging. The custom-designed tripeptides were used for the preparation of silver-doped gold nanoclusters with enhanced fluorescence emission. These TPGNCs exhibited strong red fluorescence with high quantum yield, large Stokes shift, good photostability, and excellent biocompatibility toward normal cells. TPGNCs imparted minimum dark toxicity toward breast cancer cells. These TPGNCs exhibited appreciable photosensitization to generate ROS within the cancer cells triggering loss of mitochondrial membrane potential, leading to apoptotic cell death. The photosensitizing ability of TPGNCs will be a new avenue in the area of photoinduced cancer therapy with negligible side effects.
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    Gold nanorod decorated with cancer drug for multimodal imaging and therapy
    (Faraday Discussions, 2017-12) Nair, RV; Santhakumar, H; Jayasree, RS
    Cancer, a condition with uncontrolled cell division is the second leading cause of death worldwide. The currently available techniques for the imaging and treatment of cancer have their own limitations and hence a combination of more than one modality is expected to increase the efficacy of both diagnosis and treatment. In the present study, we have developed a multimodal imaging and therapeutic system by incorporating a chemotherapeutic drug, mitoxantrone(MTX) onto PEG coated gold nanorods (GNR). Strong absorption in the near-infrared and visible region qualifies GNR as an efficient photo thermal (PTT) agent upon irradiation with either NIR or visible laser. Additionally, enhanced electric field of GNR makes it a suitable substrate for surface enhanced Raman scattering (SERS). Modification of GNR with amino PEG offers biocompatability without affecting its optical property. In order to achieve tumor specificity, GNR-PEG was conjugated with tumor specific marker that can target cancer cells, leaving the normal cells unaffected. The incorporation of fluorescent chemotherapeutic drug mitoxantrone onto GNR-PEG facilitates the chemo therapy as well as fluorescence imaging. The therapeutic efficacy of the developed GNR based system is tracked using fluorescence imaging and Raman imaging. Careful designing of the system also facilitates the controlled release of the drug by photothermal triggering. Llikewise, the imaging modality could be chosen as either Raman or fluorescence to monitor drug release in accordance with irradiation. The physico-chemical properties, and drug release profile under different physiological conditions have been well studied. Finally, the developed system was tested for the therapeutic efficacy using cancer cells, in vitro. The receptor mediated cell uptake was more effective in the folate over expressed cancer cells than in the normal and low expressed cells. Accordingly the percentage of cell death was more in folate over expressed cancer cells which further enhanced due to the effect of dual therapeutic approach. The cell uptake and treatment efficacy was monitored using the fluorescence microscopy and SERS. In conclusion, the developed GNR-PEG-MTX system is found to be an efficient multimodal therapeutic agent against cancer which could be tracked using two different techniques.
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    An insight into the optical property of sub nano size glutathione stabilized gold cluster
    (Dalton Transactions, 2016-06) Nair, LV; Nair, RV; Jayasree, RS
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    Luminescent Gold Nanorod to enhance the NIR emission of Photosensitizer for Targeted Cancer Imaging and Dual therapy: Experimental and Theoretical Approach.
    (Chemistry:A European Journal., 2019-11) Nair, RV; Nair, LV; Govindachar, DM; Santhakumar, H; Nazeer, SS; Rekha, CR; Shenoy, SJ; Periyasamy, G; Jayasree, RS
    The strong plasmon absorption in the near‐infrared (NIR) region render gold nano rods (GNR) amenable for biomedical applications, particularly for photo‐thermal therapy. However, these nanostructures have not been explored for their imaging potential because of their weak emission profile. In this study, the weak fluorescence emission of GNR is tuned to match with the absorption of a photosensitizer molecule (PS), and the energy transfer from GNR to PS enhances emission profile of GNR‐PS combination. GNR complexes generally quench the fluorescence emission of nearby chromophores. However, in the present study, through a competition of energy transfer, the complex retains or rather enhances the fluorescence. The excitation dependent energy transfer has been explained experimentally and theoretically using DFT calculations and CIE chromaticity diagram and power spectrum. The final GNR‐PS complex modified for tumor specificity serves as an excellent organ specific theranostic probe for bioimaging and dual modal therapy, both in vitro and in vivo. Principal component analysis designates photodynamic therapy as a better candidate than the photothermal therapy for long term efficacy, in vivo.
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    A nanoarchitecture of a gold cluster conjugated gold nanorod hybrid system and its application in fluorescence imaging and plasmonic photothermal therapy
    (Nanoscale, 2022-08) Nair, RV; Puthiyaparambath, MF; Chatanathodi, R; Nair, LV; Jayasree, RS
    Engineering different nanomaterials into a single functional material can impart unique properties of the parental nanoparticles, especially in the field of bio imaging and therapy. Gold nanomaterials having different sizes, shapes and dimensionalities exhibit exceptional properties apart from their non-toxicity and hence are strong candidates in the biomedical field. Designing a hybrid nanomaterial of two gold nanostructures retaining the individual properties of the parental nanomaterials is challenging. Here, we demonstrate the synthesis of a hybrid nanomaterial (GQC@GNR), comprising an extremely small gold nanocluster and a representative of the asymmetric gold nanostructure, i.e., a gold nanorod, both having their own different exclusive optical properties like tuneable emission and NIR absorption characteristics, respectively. The hybrid system is designed to retain its emission and absorption in the NIR region to use it as an agent for simultaneous imaging and therapy. The formation of GQC@GNR and its architectonics heavily depend on the synthesis route and the parameters adopted which in turn have a direct influence on its properties. The architecture and its connection to the optical properties are explained using UV-Vis absorption and photoluminescence spectroscopy, zeta potential, transmission electron microscopy, etc. DFT-based computational modelling supports architectonics as explained by the experimental findings. The formation of the gold–gold hybrid system witnessed interesting science with a strong indication that materials with desired properties can be designed by appropriately modulating the architectonics of hybrid formation. Finally, folate conjugated GQC@GNR demonstrated its efficacy for targeted imaging and photothermal therapy in HeLa cells and tumor-bearing animal models. The detailed therapeutic efficacy of GQC@GNR is also explained based on Raman spectroscopy.
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    Real Time Imaging and Dynamics of Hippocampal Zn2+ under Epileptic Condition Using a Ratiometric Fluorescent Probe
    (Sci Rep. 2018, 2018-06) Santhakumar, H; Nair, RV; Philips, DS; Shenoy, SJ; Thekkuveettil, A; Ajayaghosh, A; Jayasree, RS
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    Vanadium pentoxide nanoplates: Synthesis, characterization and unveiling the intrinsic antibacterial activity
    (Materials Letters, 2020-06) Suma, PRP; Nair, RV; Paul, W; Jayasree, RS
    This study reports the synthesis and characterization of vanadium pentoxide nanoplates (VnNp) with the unique shape. Electron microscopy identified morphological alterations on the bacterial surface of representative Gram-positive, Staphylococcus aureus and Gram-negative, Escherichia coli upon VnNp treatment. In addition, Raman spectral mapping also elucidated changes in the bio-molecular signals from these bacteria. Further, the study proved reactive oxygen species (ROS) generation in E. coli biofilms. Overall, the results envision the possible use of VnNp as a potential surface coating agent to impart antibacterial activity.