Browsing by Author "Nair, LV"

Now showing 1 - 11 of 11
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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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    Cadmium selenium quantum dot based nanosensor with femto molar level sensitivity for the detection of the pesticide endosulfan
    (Journal of Polymer Science and Engineering., 2024-01) Nair, LV; Nair. RV; Jayasree, RS
    Endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) is an off-patent insecticide used in agricultural farms. Its usage as a pesticide has become highly controversial during the last decades. This is due to its reported hazardous nature to the health and side effects like growth retardation, hydrocephalus, and undesired changes in the male and female hormones leading to complications in sexual maturity. Endosulfan is the main culprit among all pesticide poisoning incidents around the world. Though the usage of this dreaded pesticide is banned by most countries, the high stability of this molecule to withstand degradation for a long period poses a threat to mankind even today. So, it has become highly essential to detect the presence of this poisonous pesticide in the drinking water and milk around these places. It is also advisable to check the presence of this toxic material in the blood of the population living in and around these places so that an early and appropriate management strategy can be adopted. With this aim, we have developed a sensor for endosulfan that displayed high selectivity and sensitivity among all other common analytes in water and biological samples, with a wide linear concentration range (2 fM to 2 mM), a low detection limit (2 fM), and rapid response. A citrate functionalized cadmium selenium quantum dot was used for this purpose, which showed a concentration-dependent fluorescence enhancement, enabling easy and sensitive sensing. This sensor was utilized to detect endosulfan in different sources of water, human blood serum and milk samples with good recoveries. It is also noted that the quantum dot forms a stable complex with endosulfan and is easy to separate it from the contaminated source, paving a solution for purifying the contaminated water. More detailed tests and validation of the sensor is needed to confirm these observations.
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    Fluorescence Imaging Assisted Photo dynamic Therapy Using Photosensitizer-Linked Gold Quantum Clusters
    (ACS NANO, 2015) Nair, LV; Nazeer, SS; Jayasree, RS; Ajayaghosh, A
    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 mu g (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.
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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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    Investigation of apoptotic events at molecular level induced by SERS guided targeted theranostic nanoprobe
    (NANOSCALE, 2016) Narayanan, N; Nair, LV; Karunakaran, V; Joseph, MM; Nair, JB; Ramya, AN; Jayasree, RS; Maiti, KK
    Herein, we have examined distinctive structural and functional variations of cellular components during apoptotic cell death induced by a targeted theranostic nanoprobe, MMP-SQ@GNR@LAH-DOX, which acted as a SERS "on/off" probe in the presence of a MMP protease and executed synergistic photothermal chemotherapy, as reflected by the SERS fingerprinting, corresponding to the phosphodiester backbone of DNA.
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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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    A Near-Infrared Fluorescent Nanosensor (AuC@Urease) for the Selective Detection of Blood Urea
    (Small, 2013-04) Nair, LV; Philips, DS; Jayasree, RS; Ajayaghosh, A
    The use of a nanosensor (AuC@Urease) based on an NIR-emitting gold cluster and urease enzyme selectively detects urea in whole blood. The detection is based on an enzyme-specific conversion of urea to ammonium ions which facilitates pH-induced aggregation of AuC, leading to fluorescence quenching. This method does not interfere with urease inactive analytes or the autofluorescence of blood as confirmed by comparable urea levels obtained by AuC@Urease and standard clinical methods within an error limit of ±3%
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    nvestigation of apoptotic events at molecular level induced by SERS guided targeted theranostic nanoprobe
    (Nanoscale, 2016-05) Nisha, N; Nair, LV; Karunakaran, V; Joseph, MM; Nair, JB; Ramya, AN; Jayasree, RS; Maiti, K
    Herein we have distinctively examined structural and functional variations of cellular components during apoptotic cell death induced by targeted theranostic nanoprobe MMP-SQ@GNR@LAHDOX which acted as SERS “on/off” probe in peace with the vicinity of MMP protease and excuted synergistic photothermal chemotherapy reflected by SERS fingerprinting corresponding to phosphodiester backbone of DNA.
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    Porphyrin and doxorubicin mediated nanoarchitectonics of copper clusters: a bimodal theranostics for cancer diagnosis and treatment in vitro
    (J Mater Chem B., 2024-01) Joseph, M; Rahman Pathiripparambath, MS; Thomas, V; Tharayil, H; Jayasree, RS; Nair, LV
    Nanoarchitectonics, an emerging strategy, presents a promising alternative for developing highly efficient next-generation functional materials. Multifunctional materials developed using nanoarchitectonics help to mimic biological molecules. Porphyrin-based molecules can be effectively utilized to design such assemblies. Metal nanocluster is one of the functional materials that can shed more insight into developing nanoarchitectonic materials. Herein, an inherently near-infrared (NIR) fluorescing copper nanocluster (CuC)-mediated structural assembly via protoporphyrin IX (PPIX) and doxorubicin (Dox) is demonstrated as the functional material. Dox-loaded porphyrin-mediated CuC assembly shows singlet oxygen generation and 66% drug release at 15 min. Furthermore, the efficacy of this material is tested for cancer diagnosis and bimodal therapeutic strategy due to the fluorescing ability of the cluster and loading of PPIX as well as the drug, respectively. The nanoarchitecture exhibits targeted imaging and 83% cell death in HeLa cells upon laser irradiation with 10 nmoles and 20 nmoles of PPIX and Dox, respectively.