Vipul Bansal | RMIT University (original) (raw)
Papers by Vipul Bansal
![Research paper thumbnail of Self–Assembled Histidine Acid Phosphate Nanocapsules as Templates for Multifunctional Hollow Platinum Nanospheres in Ionic Liquid [BMIM][BF4] for Drug Delivery](https://attachments.academia-assets.com/53569181/thumbnails/1.jpg)
](During the past few decades, the design and fabrication of nano drug delivery vehicle has receive... more During the past few decades, the design and fabrication of nano drug delivery vehicle has received considerable attention for incorporating multi-functionality, emphasizing transportation of anticancer drugs to tumour sites. Protein-based nanoparticles hold significant promise in the development of anticancer drug delivery systems since they have remarkable superiority in biocompatibility, biodegradability and natural metabolism in physiologic systems. Ionic liquids (ILs) are a class of solvents that are composed solely of ions (ILs -commonly referred as room temperature molten salts or room temperature ionic liquids). They have recently emerged as green solvents or green reaction media, because of their reported unique physico-chemical properties. We report for the first time the controlled self-assembly of Histidine Acid phosphatase (HAP) enzyme in the IL 1butyl-3-methylimidazolium tetrafluoroborate [BMIM] [BF 4 ], leading to the formation of HAP nanocapsules as template for synthesis of platinum nanospheres. These HAP nanocontainers were loaded with an anticancer drug curcumin. We further demonstrated in vitro drug release and synergistic anticancer effect of these systems on three different cell lines viz. hepatocellular carcinoma (HepG2), breast cancer (MCF-7) and human acute monocytes (THP-1). The present work can extend our theoretical understanding on nanobio interfacial molecular self assembly and will facilitate the motivated insights of inorganic/organic hybrid nano-materials/ nano-particles/ nano-objects and ionic liquids based multi functional drug delivery vehicles with synergistic combination chemotherapy for potential application in tumor targeting.
Molecular pharmaceutics, 2016
Current cancer chemotherapies commonly suffer from non-specificity, drug resistance, poor bioavai... more Current cancer chemotherapies commonly suffer from non-specificity, drug resistance, poor bioavailability and narrow therapeutic indices. To achieve the optimum drug efficacy, we designed a polymeric drug delivery system for targeted intracellular delivery of a clinically-approved, water-soluble anticancer drug, gemcitabine hydrochloride (GEM). We utilised the unique ability of a cyclic pentapeptide cRGDfK to specifically target αvβ3 integrin receptors that are over-expressed on SKOV-3 human ovarian cancer cells. This significantly increased the effective intracellular drug concentration even at low doses, thereby remarkably improving the chemotherapeutic potential of GEM. cRGDfK-conjugated, GEM-loaded nanoparticles reduced the nonspecific hemolytic cytotoxicity of the drug, simultaneously influencing intracellular processes such as mitochondrial membrane potential (DΨm), reactive oxygen species (ROS) levels and apoptosis, thereby favourably influencing drug anti-proliferative effic...
Scientific reports, 2016
Approximately 20% of breast cancer cases are human epidermal growth factor receptor 2 (HER2)-posi... more Approximately 20% of breast cancer cases are human epidermal growth factor receptor 2 (HER2)-positive. This type of breast cancer is more aggressive and tends to reoccur more often than HER2-negative breast cancer. In this study, we synthesized trastuzumab (TZ)-grafted dendrimers to improve delivery of docetaxel (DTX) to HER2-positive breast cancer cells. Bioconjugation of TZ on the surface of dendrimers was performed using a heterocrosslinker, MAL-PEG-NHS. For imaging of cancer cells, dendrimers were also conjugated to fluorescein isothiocyanate. Comparative in vitro studies revealed that these targeted dendrimers were more selective, and had higher antiproliferation activity, towards HER2-positive MDA-MB-453 human breast cancer cells than HER2-negative MDA-MB-231 human breast cancer cells. When compared with unconjugated dendrimers, TZ-conjugated dendrimers also displayed higher cellular internalization and induction of apoptosis against MDA-MB-453 cells. Binding of TZ to the dend...
Analytical Chemistry, 2014
This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colo... more This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colorimetric biosensing assay. Our approach combines the inherent peroxidase-like nanozyme activity of gold nanoparticles (GNPs) with high affinity and specificity of an acetamiprid-specific S-18 aptamer to detect this neurotoxic pesticide in a highly rapid, specific, and sensitive manner. It is shown that the nanozyme activity of GNPs can be inhibited by its surface passivation with targetspecific aptamer molecules. Similar to an enzymatic competitive inhibition process, in the presence of a cognate target, these aptamer molecules leave the GNP surface in a target concentration-dependent manner, reactivating GNP nanozyme activity. This reversible inhibition of the GNP nanozyme activity can either be directly visualized in the form of color change of the peroxidase reaction product or can be quantified using UV−visible absorbance spectroscopy. This approach allowed detection of 0.1 ppm acetamiprid within an assay time of 10 min. This reversible nanozyme activation/inhibition strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.
Analytical Chemistry, 2014
This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colo... more This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colorimetric biosensing assay. Our approach combines the inherent peroxidase-like nanozyme activity of gold nanoparticles (GNPs) with high affinity and specificity of an acetamiprid-specific S-18 aptamer to detect this neurotoxic pesticide in a highly rapid, specific, and sensitive manner. It is shown that the nanozyme activity of GNPs can be inhibited by its surface passivation with targetspecific aptamer molecules. Similar to an enzymatic competitive inhibition process, in the presence of a cognate target, these aptamer molecules leave the GNP surface in a target concentration-dependent manner, reactivating GNP nanozyme activity. This reversible inhibition of the GNP nanozyme activity can either be directly visualized in the form of color change of the peroxidase reaction product or can be quantified using UV−visible absorbance spectroscopy. This approach allowed detection of 0.1 ppm acetamiprid within an assay time of 10 min. This reversible nanozyme activation/inhibition strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.
Langmuir, 2005
Macrophages are one of the principal immune effector cells that play essential roles as secretory... more Macrophages are one of the principal immune effector cells that play essential roles as secretory, phagocytic, and antigen-presenting cells in the immune system. In this study, we address the issue of cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. The cytotoxicity of gold nanoparticles has been correlated with a detailed study of their endocytotic uptake using various microscopy tools such as atomic force microscopy (AFM), confocal-laser-scanning microscopy (CFLSM), and transmission electron microscopy (TEM). Our findings suggest that Au(0) nanoparticles are not cytotoxic, reduce the production of reactive oxygen and nitrite species, and do not elicit secretion of proinflammatory cytokines TNF-alpha and IL1-beta, making them suitable candidates for nanomedicine. AFM measurements suggest that gold nanoparticles are internalized inside the cell via a mechanism involving pinocytosis, while CFLSM and TEM studies indicate their internalization in lysosomal bodies arranged in perinuclear fashion. Our studies thus underline the noncytotoxic, nonimmunogenic, and biocompatible properties of gold nanoparticles with the potential for application in nanoimmunology, nanomedicine, and nanobiotechnology.
Analytical Chemistry, 2012
We demonstrate an active microfluidic platform that integrates dielectrophoresis for the control ... more We demonstrate an active microfluidic platform that integrates dielectrophoresis for the control of silver nanoparticles spacing, as they flow in a liquid channel. By careful control of the nanoparticles spacing, we can effectively increase the surface-enhanced Raman scattering (SERS) signal intensity based on augmenting the number of SERS-active hot-spots, while avoiding irreversible aggregation of the particles. The system is benchmarked using dipicolinate (2,6pyridinedicarboxylic acid) (DPA), which is a biomarker of Bacillus anthracis. The validity of the results is discussed using several complementing characterization scenarios.
2011 International Conference on Nanoscience, Technology and Societal Implications, NSTSI11, 2011
Shape and size-controlled synthesis of metal and metal alloy nanoparticles have gained significan... more Shape and size-controlled synthesis of metal and metal alloy nanoparticles have gained significant attention due to their unique physico-chemical properties. Most of these synthesis routes have thus far explored use of toxic chemicals for metal nanoparticles synthesis, which limit their biological applications. With the increasing focus on eco-friendly routes towards nanomaterials synthesis and their biological applications, we show that metal (gold and silver) and their alloy nanoparticles with controlled composition can be synthesized using tyrosine amino acid. Antimicrobial activities of these nanoparticles were tested against model Gram positive bacteria Staphylococcus albus and Gram negative bacteria Escherichia coli. Irrespective of metal composition, tyrosine synthesized nanoparticles including AuNPs were found to be highly toxic towards S. albus, while antibacterial activity against E. coli was exhibited only by AgNPs and Ag containing alloys. The toxicity of tyrosine synthesized nanoparticles towards S. albus arises due to its ability to hydrolyze the peptidoglycan cell wall. In the case of E. coli, these nanoparticles showed toxicity due to the partial oxidation of Ag 0 into Ag + ions. The alloy nanoparticles toxicity depends on the silver fraction towards E. coli while all nanoparticles irrespective of composition have a similar effect on S. albus. UV-vis, TEM, AAS and zeta potential measurements were used to characterize these nanoparticles and their influence on the observed antimicrobial properties. SEM was used to study morphological changes and bactericidal action of these nanoparticles. The SEM results confirmed that treated E. coli and S. albus cells were damaged, showing formation of big holes and cell wall lysis.
PLoS ONE, 2013
Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size... more Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPs Tyr ) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona.
Polymer nanocapsules play an increasingly important role for drug delivery applications. Layer-by... more Polymer nanocapsules play an increasingly important role for drug delivery applications. Layer-by-layer (LbL) templated synthesis has received the widest attention to fabricate polymer nanocapsules. However, for drug delivery applications, the LbL approach may not necessarily offer the optimum nanocapsules. We make the first attempt to compare the LbL approach with a more recently developed solid core/mesoporous shell (SC/MS) templated approach in context of their suitability for construction of sub-500 nm sized capsules for drug delivery applications. The nanocapsules of chitosan, poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) are fabricated using LbL and SC/MS templating approaches and loaded with curcumin, a model lipophilic anticancer drug. The influence of the templating approach on capsule aggregation, polymer loading, drug loading, cellular uptake, and therapeutic efficacy against MCF-7 breast cancer cells is compared in an effort to identify the most suitable fabrication method and polymer material for drug delivery applications. In combination, among different tested nanocapsules, chitosan nanocapsules fabricated using the SC/MS approach are found to be the most promising candidate that demonstrates the optimum cytotoxic efficiency and significant potential for drug delivery.
Nanoscale, 2014
We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNP... more We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPs(Y)) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.
Physical Chemistry Chemical Physics, 2013
The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) mole... more The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed. ; Fax: +61 3 9925 2882; Tel: +61 3 9925 2882 † Electronic supplementary information (ESI) available: (S1) FT-Raman spectra of CV, CV bound gold and silver NP on a silicon substrate, (S2) K 2p core level spectra from tyrosine reduced AgNP and (S3) XPS core level spectra of tyrosine reduced AgNPs on a gold substrate. See
BioNanoScience, 2011
The focus of this research was the enhancement of radiation dose for microbeam radiotherapy (MRT)... more The focus of this research was the enhancement of radiation dose for microbeam radiotherapy (MRT) by the inclusion of gold nanoparticles (AuNPs) in the target. Microbeam radiotherapy is a technique that employs a very high dose rate of X-rays to kill highly resistant tumours such as glioma without jeopardizing the tolerance of normal tissue. The reduction of radiation dose rate used in this technique by using AuNPs may enhance the normal tissue tolerance while achieving better tumour control. In this study, microbeam kilovoltage X-ray of mean energy 125 keV from the SPring8 Synchrotron in Japan was used. The results show dose enhancement effects on endothelial cells by AuNPs which are consistent with previously documented results using broad beams of X-rays. It was also observed in this study that the inclusion of AuNPs accelerates cell migration towards the eradicated area which is important in normal tissue recovery. The phenomenon of cell migration is observed when cell fill depleted gaps that have been created by the microbeams or when such gaps are manually made by scratching the cell culture as a wound. The reason behind this acceleration of the rate of gap fillings is not well understood. However, it has been attributed to various biological processes and has also been thought of as being partially due to the effects of electrostatic charge of such particles. It could also be the combined effects of biological and electrostatic effects due to the charges of the particles inside the cells. Moreover, it is also observed that the cancerous glioma cell fills the gaps in much slower rates in comparison to the normal endothelial cells. This is consistent with the notion on which the MRT techniques are based.
During the past few decades, the design and fabrication of nano drug delivery vehicle has receive... more During the past few decades, the design and fabrication of nano drug delivery vehicle has received considerable attention for incorporating multi-functionality, emphasizing transportation of anticancer drugs to tumour sites. Protein-based nanoparticles hold significant promise in the development of anticancer drug delivery systems since they have remarkable superiority in biocompatibility, biodegradability and natural metabolism in physiologic systems. Ionic liquids (ILs) are a class of solvents that are composed solely of ions (ILs -commonly referred as room temperature molten salts or room temperature ionic liquids). They have recently emerged as green solvents or green reaction media, because of their reported unique physico-chemical properties. We report for the first time the controlled self-assembly of Histidine Acid phosphatase (HAP) enzyme in the IL 1butyl-3-methylimidazolium tetrafluoroborate [BMIM] [BF 4 ], leading to the formation of HAP nanocapsules as template for synthesis of platinum nanospheres. These HAP nanocontainers were loaded with an anticancer drug curcumin. We further demonstrated in vitro drug release and synergistic anticancer effect of these systems on three different cell lines viz. hepatocellular carcinoma (HepG2), breast cancer (MCF-7) and human acute monocytes (THP-1). The present work can extend our theoretical understanding on nanobio interfacial molecular self assembly and will facilitate the motivated insights of inorganic/organic hybrid nano-materials/ nano-particles/ nano-objects and ionic liquids based multi functional drug delivery vehicles with synergistic combination chemotherapy for potential application in tumor targeting.
Molecular pharmaceutics, 2016
Current cancer chemotherapies commonly suffer from non-specificity, drug resistance, poor bioavai... more Current cancer chemotherapies commonly suffer from non-specificity, drug resistance, poor bioavailability and narrow therapeutic indices. To achieve the optimum drug efficacy, we designed a polymeric drug delivery system for targeted intracellular delivery of a clinically-approved, water-soluble anticancer drug, gemcitabine hydrochloride (GEM). We utilised the unique ability of a cyclic pentapeptide cRGDfK to specifically target αvβ3 integrin receptors that are over-expressed on SKOV-3 human ovarian cancer cells. This significantly increased the effective intracellular drug concentration even at low doses, thereby remarkably improving the chemotherapeutic potential of GEM. cRGDfK-conjugated, GEM-loaded nanoparticles reduced the nonspecific hemolytic cytotoxicity of the drug, simultaneously influencing intracellular processes such as mitochondrial membrane potential (DΨm), reactive oxygen species (ROS) levels and apoptosis, thereby favourably influencing drug anti-proliferative effic...
Scientific reports, 2016
Approximately 20% of breast cancer cases are human epidermal growth factor receptor 2 (HER2)-posi... more Approximately 20% of breast cancer cases are human epidermal growth factor receptor 2 (HER2)-positive. This type of breast cancer is more aggressive and tends to reoccur more often than HER2-negative breast cancer. In this study, we synthesized trastuzumab (TZ)-grafted dendrimers to improve delivery of docetaxel (DTX) to HER2-positive breast cancer cells. Bioconjugation of TZ on the surface of dendrimers was performed using a heterocrosslinker, MAL-PEG-NHS. For imaging of cancer cells, dendrimers were also conjugated to fluorescein isothiocyanate. Comparative in vitro studies revealed that these targeted dendrimers were more selective, and had higher antiproliferation activity, towards HER2-positive MDA-MB-453 human breast cancer cells than HER2-negative MDA-MB-231 human breast cancer cells. When compared with unconjugated dendrimers, TZ-conjugated dendrimers also displayed higher cellular internalization and induction of apoptosis against MDA-MB-453 cells. Binding of TZ to the dend...
Analytical Chemistry, 2014
This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colo... more This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colorimetric biosensing assay. Our approach combines the inherent peroxidase-like nanozyme activity of gold nanoparticles (GNPs) with high affinity and specificity of an acetamiprid-specific S-18 aptamer to detect this neurotoxic pesticide in a highly rapid, specific, and sensitive manner. It is shown that the nanozyme activity of GNPs can be inhibited by its surface passivation with targetspecific aptamer molecules. Similar to an enzymatic competitive inhibition process, in the presence of a cognate target, these aptamer molecules leave the GNP surface in a target concentration-dependent manner, reactivating GNP nanozyme activity. This reversible inhibition of the GNP nanozyme activity can either be directly visualized in the form of color change of the peroxidase reaction product or can be quantified using UV−visible absorbance spectroscopy. This approach allowed detection of 0.1 ppm acetamiprid within an assay time of 10 min. This reversible nanozyme activation/inhibition strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.
Analytical Chemistry, 2014
This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colo... more This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colorimetric biosensing assay. Our approach combines the inherent peroxidase-like nanozyme activity of gold nanoparticles (GNPs) with high affinity and specificity of an acetamiprid-specific S-18 aptamer to detect this neurotoxic pesticide in a highly rapid, specific, and sensitive manner. It is shown that the nanozyme activity of GNPs can be inhibited by its surface passivation with targetspecific aptamer molecules. Similar to an enzymatic competitive inhibition process, in the presence of a cognate target, these aptamer molecules leave the GNP surface in a target concentration-dependent manner, reactivating GNP nanozyme activity. This reversible inhibition of the GNP nanozyme activity can either be directly visualized in the form of color change of the peroxidase reaction product or can be quantified using UV−visible absorbance spectroscopy. This approach allowed detection of 0.1 ppm acetamiprid within an assay time of 10 min. This reversible nanozyme activation/inhibition strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.
Langmuir, 2005
Macrophages are one of the principal immune effector cells that play essential roles as secretory... more Macrophages are one of the principal immune effector cells that play essential roles as secretory, phagocytic, and antigen-presenting cells in the immune system. In this study, we address the issue of cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. The cytotoxicity of gold nanoparticles has been correlated with a detailed study of their endocytotic uptake using various microscopy tools such as atomic force microscopy (AFM), confocal-laser-scanning microscopy (CFLSM), and transmission electron microscopy (TEM). Our findings suggest that Au(0) nanoparticles are not cytotoxic, reduce the production of reactive oxygen and nitrite species, and do not elicit secretion of proinflammatory cytokines TNF-alpha and IL1-beta, making them suitable candidates for nanomedicine. AFM measurements suggest that gold nanoparticles are internalized inside the cell via a mechanism involving pinocytosis, while CFLSM and TEM studies indicate their internalization in lysosomal bodies arranged in perinuclear fashion. Our studies thus underline the noncytotoxic, nonimmunogenic, and biocompatible properties of gold nanoparticles with the potential for application in nanoimmunology, nanomedicine, and nanobiotechnology.
Analytical Chemistry, 2012
We demonstrate an active microfluidic platform that integrates dielectrophoresis for the control ... more We demonstrate an active microfluidic platform that integrates dielectrophoresis for the control of silver nanoparticles spacing, as they flow in a liquid channel. By careful control of the nanoparticles spacing, we can effectively increase the surface-enhanced Raman scattering (SERS) signal intensity based on augmenting the number of SERS-active hot-spots, while avoiding irreversible aggregation of the particles. The system is benchmarked using dipicolinate (2,6pyridinedicarboxylic acid) (DPA), which is a biomarker of Bacillus anthracis. The validity of the results is discussed using several complementing characterization scenarios.
2011 International Conference on Nanoscience, Technology and Societal Implications, NSTSI11, 2011
Shape and size-controlled synthesis of metal and metal alloy nanoparticles have gained significan... more Shape and size-controlled synthesis of metal and metal alloy nanoparticles have gained significant attention due to their unique physico-chemical properties. Most of these synthesis routes have thus far explored use of toxic chemicals for metal nanoparticles synthesis, which limit their biological applications. With the increasing focus on eco-friendly routes towards nanomaterials synthesis and their biological applications, we show that metal (gold and silver) and their alloy nanoparticles with controlled composition can be synthesized using tyrosine amino acid. Antimicrobial activities of these nanoparticles were tested against model Gram positive bacteria Staphylococcus albus and Gram negative bacteria Escherichia coli. Irrespective of metal composition, tyrosine synthesized nanoparticles including AuNPs were found to be highly toxic towards S. albus, while antibacterial activity against E. coli was exhibited only by AgNPs and Ag containing alloys. The toxicity of tyrosine synthesized nanoparticles towards S. albus arises due to its ability to hydrolyze the peptidoglycan cell wall. In the case of E. coli, these nanoparticles showed toxicity due to the partial oxidation of Ag 0 into Ag + ions. The alloy nanoparticles toxicity depends on the silver fraction towards E. coli while all nanoparticles irrespective of composition have a similar effect on S. albus. UV-vis, TEM, AAS and zeta potential measurements were used to characterize these nanoparticles and their influence on the observed antimicrobial properties. SEM was used to study morphological changes and bactericidal action of these nanoparticles. The SEM results confirmed that treated E. coli and S. albus cells were damaged, showing formation of big holes and cell wall lysis.
PLoS ONE, 2013
Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size... more Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPs Tyr ) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona.
Polymer nanocapsules play an increasingly important role for drug delivery applications. Layer-by... more Polymer nanocapsules play an increasingly important role for drug delivery applications. Layer-by-layer (LbL) templated synthesis has received the widest attention to fabricate polymer nanocapsules. However, for drug delivery applications, the LbL approach may not necessarily offer the optimum nanocapsules. We make the first attempt to compare the LbL approach with a more recently developed solid core/mesoporous shell (SC/MS) templated approach in context of their suitability for construction of sub-500 nm sized capsules for drug delivery applications. The nanocapsules of chitosan, poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) are fabricated using LbL and SC/MS templating approaches and loaded with curcumin, a model lipophilic anticancer drug. The influence of the templating approach on capsule aggregation, polymer loading, drug loading, cellular uptake, and therapeutic efficacy against MCF-7 breast cancer cells is compared in an effort to identify the most suitable fabrication method and polymer material for drug delivery applications. In combination, among different tested nanocapsules, chitosan nanocapsules fabricated using the SC/MS approach are found to be the most promising candidate that demonstrates the optimum cytotoxic efficiency and significant potential for drug delivery.
Nanoscale, 2014
We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNP... more We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPs(Y)) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.
Physical Chemistry Chemical Physics, 2013
The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) mole... more The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed. ; Fax: +61 3 9925 2882; Tel: +61 3 9925 2882 † Electronic supplementary information (ESI) available: (S1) FT-Raman spectra of CV, CV bound gold and silver NP on a silicon substrate, (S2) K 2p core level spectra from tyrosine reduced AgNP and (S3) XPS core level spectra of tyrosine reduced AgNPs on a gold substrate. See
BioNanoScience, 2011
The focus of this research was the enhancement of radiation dose for microbeam radiotherapy (MRT)... more The focus of this research was the enhancement of radiation dose for microbeam radiotherapy (MRT) by the inclusion of gold nanoparticles (AuNPs) in the target. Microbeam radiotherapy is a technique that employs a very high dose rate of X-rays to kill highly resistant tumours such as glioma without jeopardizing the tolerance of normal tissue. The reduction of radiation dose rate used in this technique by using AuNPs may enhance the normal tissue tolerance while achieving better tumour control. In this study, microbeam kilovoltage X-ray of mean energy 125 keV from the SPring8 Synchrotron in Japan was used. The results show dose enhancement effects on endothelial cells by AuNPs which are consistent with previously documented results using broad beams of X-rays. It was also observed in this study that the inclusion of AuNPs accelerates cell migration towards the eradicated area which is important in normal tissue recovery. The phenomenon of cell migration is observed when cell fill depleted gaps that have been created by the microbeams or when such gaps are manually made by scratching the cell culture as a wound. The reason behind this acceleration of the rate of gap fillings is not well understood. However, it has been attributed to various biological processes and has also been thought of as being partially due to the effects of electrostatic charge of such particles. It could also be the combined effects of biological and electrostatic effects due to the charges of the particles inside the cells. Moreover, it is also observed that the cancerous glioma cell fills the gaps in much slower rates in comparison to the normal endothelial cells. This is consistent with the notion on which the MRT techniques are based.