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1.
Environ Sci Nano ; 11(2): 627-636, 2024 Feb 01.
Article in English | MEDLINE | ID: mdl-38881831

ABSTRACT

Semiconductor InSe 2D nanomaterials have emerged as potential photoresponsive materials for broadly distributed photodetectors and wearable electronics technologies due to their high photoresponsivity and thermal stability. This paper addresses an environmental concern about the fate of InSe 2D nanosheets when disposed and released into the environment after use. Semiconducting materials are potentially reactive and often form environmentally damaging species, for example reactive oxygen and nitrogen species, when degraded. InSe nanosheets are prepared using a semi bottom-up approach which involves a reaction between indium and selenium precursors at elevated temperature in an oxygen-free environment to prevent oxidation. InSe nanosheets are formed as a stable intermediate with micrometer-sized lateral dimensions and a few monolayer thickness. The InSe 2D nanosheets are obtained when the reaction is stopped after 30 minutes by cooling. Keeping the reaction at elevated temperature for a longer period, for example 60 minutes leads to the formation of InSe 3D nanoparticles of about 5 nm in diameter, a thermodynamically more stable form of InSe. The paper focuses on the colloidal stabilization of InSe nanosheets in an aqueous solution that contains epigallocatechin gallate (EGCG), a natural organic matter (NOM) simulant. We show that EGCG coats the surface of the hydrophobic, water-insoluble InSe nanosheets via physisorption. The formed EGCG-coated InSe nanosheets are colloidally stable in aqueous solution. While unmodified semiconducting InSe nanosheets could produce reactive oxygen species (ROS) when illuminated, our study shows low levels of ROS generation by EGCG-coated InSe nanosheets under ambient light, which might be attributed to ROS quenching by EGCG. Growth-based viability (GBV) assays show that the colloidally stable EGCG-coated InSe nanosheets adversely impact the bacterial growth of Shewanella oneidensis MR-1, an environmentally relevant Gram-negative bacterium in aqueous media. The impact on bacterial growth is driven by the EGCG coating of the nanosheets. In addition, live/dead assays show insignificant membrane damage of the Shewanella oneidensis MR-1 cells by InSe nanosheets, suggesting a weak association of EGCG-coated nanosheets with the cells. It is likely that the adverse impact of EGCG-coated nanosheets on bacterial growth is the result of increasing local concentration of EGCG either when adsorbed on the nanosheets when the nanosheets interact with the cells, or when desorbed from the EGCG-coated nanosheets to interact with the bacterial cells.

2.
Nanomedicine (Lond) ; 18(8): 659-666, 2023 04.
Article in English | MEDLINE | ID: mdl-37254845

ABSTRACT

Aim: Evaluation of lymphatic drainage can be challenging to differentiate between separate drainage basins because only one 'color' is typically employed in sentinel node studies. This study aimed to test the feasibility of multicolor in vivo lymphangiography using newly developed organic polymer dots. Materials & methods: Biocompatible, purely organic, hydroporphyrin-doped near-infrared-emitting polymer dots were developed and evaluated for in vivo multicolor imaging in mouse lymph nodes. Results & conclusion: The authors demonstrated successful multicolor in vivo fluorescence lymphangiography using polymer dots, each tuned to a different emission spectrum. This allows minimally invasive visualization of at least four separate lymphatic drainage basins using fluorescent nanoparticles, which have the potential for clinical translation.


Subject(s)
Quantum Dots , Sentinel Lymph Node Biopsy , Animals , Mice , Sentinel Lymph Node Biopsy/methods , Polymers , Lymph Nodes , Diagnostic Imaging/methods
3.
J Am Chem Soc ; 145(14): 7962-7973, 2023 04 12.
Article in English | MEDLINE | ID: mdl-37011179

ABSTRACT

Several classes of synthetic nanoparticles (NPs) induce rearrangements of cell membranes that can affect membrane function. This paper describes the investigation of the interactions between polystyrene nanoparticles and liposomes, which serve as model cell membranes, using a combination of laurdan fluorescence spectroscopy and coarse-grained molecular dynamics (MD) simulations. The relative intensities of the gel-like and fluid fluorescent peaks of laurdan, which is embedded in the liposome membranes, are quantified from the areas of deconvoluted lognormal laurdan fluorescence peaks. This provides significant advantages in understanding polymer-membrane interactions. Our study reveals that anionic polystyrene NPs, which are not cross-linked, induce significant membrane rearrangement compared to other cationic or anionic NPs. Coarse-grained MD simulations demonstrate that polymer chains from the anionic polystyrene NP penetrate the liposome membrane. The inner leaflet remains intact throughout this process, though both leaflets show a decrease in lipid packing that is indicative of significant local rearrangement of the liposome membrane. These results are attributed to the formation of a hybrid gel made up of a combination of polystyrene (PS) and lipids that forces water molecules away from laurdan. Our study concludes that a combination of negative surface charge to interact electrostatically with positive charges on the membrane, a hydrophobic core to provide a thermodynamic preference for membrane association, and the ability to extend non-cross linked polymer chains into the liposome membrane are necessary for NPs to cause a significant rearrangement in the liposomes.


Subject(s)
Liposomes , Nanoparticles , Liposomes/chemistry , Spectrometry, Fluorescence , Polystyrenes/chemistry , Laurates , Nanoparticles/chemistry
4.
Sensors (Basel) ; 22(19)2022 Sep 23.
Article in English | MEDLINE | ID: mdl-36236328

ABSTRACT

Semiconducting polymer dots (Pdots) are rapidly becoming one of the most studied nanoparticles in fluorescence bioimaging and sensing. Their small size, high brightness, and resistance to photobleaching make them one of the most attractive fluorophores for fluorescence imaging and sensing applications. This paper highlights our recent advances in fluorescence bioimaging and sensing with nanoscale luminescent Pdots, specifically the use of organic dyes as dopant molecules to modify the optical properties of Pdots to enable deep red and near infrared fluorescence bioimaging applications and to impart sensitivity of dye doped Pdots towards selected analytes. Building on our earlier work, we report the formation of secondary antibody-conjugated Pdots and provide Cryo-TEM evidence for their formation. We demonstrate the selective targeting of the antibody-conjugated Pdots to FLAG-tagged FLS2 membrane receptors in genetically engineered plant leaf cells. We also report the formation of a new class of luminescent Pdots with emission wavelengths of around 1000 nm. Finally, we demonstrate the formation and utility of oxygen sensing Pdots in aqueous media.


Subject(s)
Polymers , Quantum Dots , Fluorescent Dyes , Oxygen , Semiconductors
5.
ACS Appl Mater Interfaces ; 14(18): 20790-20801, 2022 May 11.
Article in English | MEDLINE | ID: mdl-35451825

ABSTRACT

Near-infrared (NIR) fluorescent semiconductor polymer dots (Pdots) have shown great potential for fluorescence imaging due to their exceptional chemical and photophysical properties. This paper describes the synthesis of NIR-emitting Pdots with great control and tunability of emission peak wavelength. The Pdots were prepared by doping poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1',3)-thiadiazole)] (PFBT), a semiconducting polymer commonly used as a host polymer in luminescent Pdots, with a series of chlorins and bacteriochlorins with varying functional groups. Chlorins and bacteriochlorins are ideal dopants due to their high hydrophobicity, which precludes their use as molecular probes in aqueous biological media but on the other hand prevents their leakage when doped into Pdots. Additionally, chlorins and bacteriochlorins have narrow deep red to NIR-emission bands and the wide array of synthetic modifications available for modifying their molecular structure enables tuning their emission predictably and systematically. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements show the chlorin- and bacteriochlorin-doped Pdots to be nearly spherical with an average diameter of 46 ± 12 nm. Efficient energy transfer between PFBT and the doped chlorins or bacteriochlorins decreases the PFBT donor emission to near baseline level and increases the emission of the doped dyes that serve as acceptors. The chlorin- and bacteriochlorin-doped Pdots show narrow emission bands ranging from 640 to 820 nm depending on the doped dye. The paper demonstrates the utility of the systematic chlorin and bacteriochlorin synthesis approach by preparing Pdots of varying emission peak wavelength, utilizing them to visualize multiple targets using wide-field fluorescence microscopy, binding them to secondary antibodies, and determining the binding of secondary antibody-conjugated Pdots to primary antibody-labeled receptors in plant cells. Additionally, the chlorin- and bacteriochlorin-doped Pdots show a blinking behavior that could enable their use in super-resolution imaging methods like STORM.


Subject(s)
Polymers , Quantum Dots , Microscopy, Fluorescence , Optical Imaging/methods , Polymers/chemistry , Quantum Dots/chemistry , Semiconductors
6.
ACS Appl Mater Interfaces ; 14(11): 13858-13871, 2022 Mar 23.
Article in English | MEDLINE | ID: mdl-35258292

ABSTRACT

Humans have incorporated minerals in objects of cultural heritage importance for millennia. The surfaces of these objects, which often long outlast the humans that create them, are undeniably exposed to a diverse mixture of chemicals throughout their lifetimes. As of yet, the art conservation community lacks a nondestructive, accurate, and inexpensive flexible computational screening method to evaluate the potential impact of chemicals with art, as a complement to experimental studies. In this work, we propose periodic density functional theory (DFT) studies as a way to address this challenge, specifically for the aragonite phase of calcium carbonate, a mineral that has been used in pigments, marble statues, and limestone architecture since ancient times. Computational models allow art conservation scientists to better understand the atomistic impact of small-molecule adsorbates on common mineral surfaces across a wide variety of environmental conditions. To gain insight into the surface adsorption reactivity of aragonite, we use DFT to investigate the atomistic interactions present in small-molecule-surface interfaces. Our adsorbate set includes common solvents, atmospheric pollutants, and emerging contaminants. Chemicals that significantly disrupt the surface structure such as carboxylic acids and sulfur-containing molecules are highlighted. We also focus on comparing adsorption energies and changes in surface bonds, which allows for the identification of key features in the electronic structure presented in a projected-density-of-state analysis. The trends outlined here will guide future experiments and allow art conservators to gain a better understanding of how a wide range of molecules interact with an aragonite surface under variable conditions and in different environments.

7.
Langmuir ; 37(24): 7600-7610, 2021 06 22.
Article in English | MEDLINE | ID: mdl-34115507

ABSTRACT

Cationic nanoparticles are known to interact with biological membranes and often cause serious membrane damage. Therefore, it is important to understand the molecular mechanism for such interactions and the factors that impact the degree of membrane damage. Previously, we have demonstrated that spatial distribution of molecular charge at cationic nanoparticle surfaces plays an important role in determining the cellular uptake and membrane damage of these nanoparticles. In this work, using diamond nanoparticles (DNPs) functionalized with five different amine-based surface ligands and small phospholipid unilamellar vesicles (SUVs), we further investigate how chemical features and conformational flexibility of surface ligands impact nanoparticle/membrane interactions. 31P-NMR T2 relaxation measurements quantify the mobility changes in lipid dynamics upon exposing the SUVs to functional DNPs, and coarse-grained molecular dynamics simulations further elucidate molecular details for the different modes of DNP-SUV interactions depending on the surface ligands. Collectively, our results show that the length of the hydrophobic segment and conformational flexibility of surface ligands are two key factors that dictate the degree of membrane damage by the DNP, while the amount of surface charge alone is not predictive of the strength of interaction.


Subject(s)
Nanoparticles , Phospholipids , Cations , Ligands , Lipid Bilayers , Molecular Dynamics Simulation , Molecular Structure , Nanoparticles/toxicity
8.
NanoImpact ; 22: 100318, 2021 04.
Article in English | MEDLINE | ID: mdl-35559975

ABSTRACT

Surface properties of engineered nanomaterials (ENMs) have been shown to influence their interaction with biological systems. However, studies to date have largely focused on hydrophilic materials, likely due to biocompatibility concerns and aqueous exposure conditions necessary for many model systems. Therefore, a knowledge gap exists in nanotoxicity literature for impacts of hydrophobic ENMs, with studies of hydrophobic materials largely limited to carbon ENMs. Here we demonstrate testing of hydrophobic quantum dots (QDs) using the nematode C. elegans, a model soil organism cultured on solid media and amenable to hydrophobic exposures. To evaluate the influence of hydrophobicity, we compared CdSe/ZnS QDs functionalized with hydrophobic trioctylphosphine oxide (TOPO) to identical QDs functionalized with hydrophilic dihydrolipoic acid-polyethylene glycol (DHLA-PEG) and alternative hydrophobic CdSe/ZnS QDs functionalized with oleic acid (OA). Results show that hydrophobic TOPO QDs are significantly more toxic than hydrophilic DHLA-PEG QDs, and substitution of TOPO with OA yields relatively non-toxic hydrophobic QDs. Fluorescence microscopy shows TOPO QDs loosely associated with the organism's cuticle, but atomic force microscopy shows no difference in cuticle structure from exposure. Importantly, TOPO ligand alone is as toxic as TOPO QDs, and our data suggests that TOPO may impact neuromuscular function, perhaps upon displacement from the QD surface. This study demonstrates the importance of examining ligand-specific impacts of hydrophobic ENMs and indicates OA-functionalized QDs as a potential alternative to TOPO QDs for reduced toxicity.


Subject(s)
Quantum Dots , Animals , Caenorhabditis elegans , Hydrophobic and Hydrophilic Interactions , Ligands , Quantum Dots/toxicity , Surface Properties
9.
ACS Appl Bio Mater ; 3(2): 1097-1104, 2020 Feb 17.
Article in English | MEDLINE | ID: mdl-33215080

ABSTRACT

In this study, synthetic mimics of antimicrobial peptides based on poly(oxanorbornene) molecules (or PONs) were used to coat CdTe quantum dots (QDs). These PONs-CdTe QDs were investigated for their activity against Escherichia coli, a bacterium with antibiotic resistant strains. At the same time, the antibacterial activity of the PONs-CdTe QDs was compared to the antibacterial activity of free PONs and free CdTe QDs. The observed antibacterial activity of the PONs-CdTe QDs was additive and concentration dependent. The conjugates had a significantly lower minimum inhibitory concentration (MIC) than the free PONs and QDs, particularly for PONs-CdTe QDs which contained PONs of high amine density. The maximum activity of PONs-CdTe QDs was not realized by conjugating PONs with the highest intrinsic antibacterial activity (i.e., the lowest MIC in solution as free PONs), indicating that the mechanism of action for free PONs and PONs-CdTe QDs is different. Equally important, conjugating PONs to CdTe QDs decreased their hemolytic activity against red blood cells compared to free PONs, lending to higher therapeutic indices against E. coli. This could potentially enable the use of higher, and therefore more effective, PONs-QDs concentrations when addressing bacterial contamination, without concerns of adverse impacts on mammalian cells and organisms.

10.
Langmuir ; 36(35): 10412-10420, 2020 09 08.
Article in English | MEDLINE | ID: mdl-32787039

ABSTRACT

Cationic amphiphilic polymers are often used to coat nanoparticles as they increase chemical stability in solution and exhibit membrane disruption activities. Among these, poly(oxonorbornenes) (PONs) are tunable membrane disruptors. They can be constructed with either one amine-terminated side chain and one hydrophobic alkyl side chain (PON-50) or two amine-terminated side chains (PON-100) on each repeat unit and can then be conjugated to gold nanoparticles using O-(2-carboxyethyl)-O'-(2-mercaptoethyl) heptaethylene glycol (HEG) spacers. While the amine content and membrane disruption activity of PONs can be controlled, the detailed structural properties of PONs conjugated to gold nanoparticles remain less understood. To address this, we performed molecular dynamics simulations of PON-50 and PON-100 to determine the nonbonded energies of PON structures as a function of amine composition. We found increasing energetic stabilization with decreasing amine composition. These results were consistent with experimental observations obtained with X-ray photoelectron spectroscopy (XPS) in which PON-100 was found to have the lowest conjugation efficiency to gold surfaces out of a range of PON amination ratios. Computationally obtained energetics suggest that replacing the aliphatic amine groups with aromatic amine groups can reverse this behavior and lead to more stable PON structures with increasing amine content. We also found that the curvature of the gold nanoparticle surface affects interactions between the surface and the amine groups of PON-50. Increasing curvature decreased these interactions, resulting in a smaller effective footprint of the HEG-PON-50 structure.

11.
Int J Pharm ; 564: 281-292, 2019 Jun 10.
Article in English | MEDLINE | ID: mdl-30999048

ABSTRACT

HSP90 inhibitors have the potential to treat many types of cancer due to the dependence of tumor cells on HSP90 for cell growth and proliferation. The Cullin-5 (Cul5) E3 ubiquitin ligase is required for HSP90 inhibitors to induce client protein degradation and subsequent cell death. Cul5 is expressed at low levels in breast cancer cells compared to patient matched controls. This observed low Cul5 expression may play a role in the reported decreased efficacy of 17-AAG and related HSP90 inhibitors as a monotherapy. We have developed a method for delivery of 17-AAG plus Cul5 DNA to cells via gold nanoparticles (AuNPs). Delivery of AuNPs containing Cul5 DNA increases the sensitivity of Cul5 deficient AU565 cells to 17-AAG. Characterization of AuNPs by UV-vis spectrum, TEM, gel electrophoresis assay and 1H NMR indicate attachment of both 17-AAG and DNA payload as well as AuNP stability. Studies in Cul5 deficient AU565 cells reveal that delivery of Cul5 and 17-AAG together increase cytotoxicity. Our results provide evidence that delivery of DNA with drug may serve as a method to sensitize drug resistant tumor cells.


Subject(s)
Benzoquinones/pharmacology , Breast Neoplasms/therapy , Cullin Proteins/genetics , DNA/administration & dosage , Gold/administration & dosage , Lactams, Macrocyclic/pharmacology , Metal Nanoparticles/administration & dosage , Cell Line , HSP90 Heat-Shock Proteins/antagonists & inhibitors , Humans
12.
Langmuir ; 34(46): 13924-13934, 2018 11 20.
Article in English | MEDLINE | ID: mdl-30351964

ABSTRACT

This study advances the chemical research community toward the goal of replacing toxic cadmium-containing quantum dots (QDs) with environmentally benign InP QDs. The InP QD synthesis uniquely combines the previously reported use of InP magic-sized clusters (MSCs) as a single-source precursor for indium and phosphorus to form InP QDs, with zinc incorporation and subsequent ZnS shelling, to form InPZn/ZnS QDs with luminescence properties comparable to those of commonly used cadmium-containing luminescent QDs. The resulting InPZn/ZnS QDs have an emission quantum yield of about 50% across a broad range of emission peak wavelengths and emission peaks averaging 50 nm fwhm. The emission peak wavelength can be easily tuned by varying the Zn/In ratio in the reaction mixture. The strategy of using zinc stearate to tune the emission properties is advantageous as it does not lead to a loss of emission quantum yield or emission peak broadening. Although the initial optical properties of InP and InPZn/ZnS QDs are promising, thermal stability measurements of InPZn QDs show significant degradation in the absence of a shell compared to the CdSe QDs particularly at increased temperature in the presence of oxygen, which is indicative of thermal oxidation. There is no significant difference in the degradation rate of InP QDs made from molecular precursors and from MSCs. Additionally, the emission intensity and quantum yield of InPZn/ZnS QDs when purified and diluted in organic solvents under ambient conditions decrease significantly compared to those of CdSe/ZnS QDs. This indicates instability of the ZnS shell when prepared by common literature methods. This must be improved to realize high-quality, robust Cd-free QDs with the capability of replacing CdSe QDs in QD technologies.


Subject(s)
Indium/chemistry , Phosphines/chemistry , Quantum Dots/chemistry , Sulfides/chemistry , Zinc Compounds/chemistry , Cadmium/chemistry , Chemistry Techniques, Synthetic , Luminescence , Models, Molecular , Molecular Conformation , Nanotechnology , Solutions , Stearic Acids/chemistry
13.
ACS Nano ; 12(6): 5741-5752, 2018 06 26.
Article in English | MEDLINE | ID: mdl-29883099

ABSTRACT

As-synthesized malic acid carbon dots are found to possess photoblinking properties that are outstanding and superior compared to those of conventional dyes. Considering their excellent biocompatibility, malic acid carbon dots are suitable for super-resolution fluorescence localization microscopy under a variety of conditions, as we demonstrate in fixed and live trout gill epithelial cells. In addition, during imaging experiments, the so-called "excitation wavelength-dependent" emission was not observed for individual as-made malic acid carbon dots, which motivated us to develop a time-saving and high-throughput separation technique to isolate malic acid carbon dots into fractions of different particle size distributions using C18 reversed-phase silica gel column chromatography. This post-treatment allowed us to determine how particle size distribution influences the optical properties of malic acid carbon dot fractions, that is, optical band gap energies and photoluminescence behaviors.

14.
Langmuir ; 34(15): 4614-4625, 2018 04 17.
Article in English | MEDLINE | ID: mdl-29558808

ABSTRACT

The article describes the interactions between poly (oxonorbornenes) (PONs)-coated gold nanoparticles (AuNPs) with phospholipid vesicles and shows that the strength of these interactions strongly depends on the molecular structure of PONs, specifically their amine/alkyl side chain ratio. PONs, which are a recently introduced class of cationic polyelectrolytes, can be systematically varied to control the amine/alkyl ratio and to explore how the chemical character of cationic polyelectrolytes affects their interactions and the interactions of their nanoparticle conjugates with model membranes. Our study shows that increasing the amine/alkyl ratio by copolymerization of diamine and 1:1 amine/butyl oxonorbornene monomers impacts the availability of PONs amine/ammonium functional groups to interact with phospholipid membranes, the PONs surface coverage on AuNPs, and the membrane disruption activity of free PONs and PONs-AuNPs. The study makes use of transmission electron microscopy, UV-vis spectroscopy, dynamic light scattering, thermogravimetric analysis, fluorescamine assay, ζ-potential measurements, and X-ray photoelectron spectroscopy measurements to characterize the PONs-AuNPs' size, size distribution, aggregation state, surface charge, and PONs surface coverage. The study also makes use of real-time fluorescence measurements of fluorescent liposomes before and during exposure to free PONs and PONs-AuNPs to determine the membrane disruption activity of free PONs and PONs-AuNPs. As commonly observed with cationic polyelectrolytes, both free PONs and PONs-AuNPs display significant membrane disruption activity. Under conditions where the amine/alkyl ratio in PONs maximizes PONs surface coverage, the membrane disruption activity of PONs-AuNPs is about 10-fold higher than the membrane disruption activity of the same free PONs. This is attributed to the increased local concentration of ammonium ions when PONs-AuNPs interact with the liposome membranes. In contrast, the hydrophobicity of amine-rich PONs, which are made for example from diamine oxonorbornene monomers, is significantly reduced. This leads to a significant reduction of PON surface coverage on AuNPs and in turn to a significant decrease in membrane disruption.


Subject(s)
Amines/chemistry , Gold/chemistry , Metal Nanoparticles/chemistry , Dynamic Light Scattering , Microscopy, Electron, Transmission , Norbornanes/chemistry , Structure-Activity Relationship
15.
ACS Appl Nano Mater ; 1(9): 4788-4800, 2018 Sep 28.
Article in English | MEDLINE | ID: mdl-30931431

ABSTRACT

Cadmium-containing luminescent quantum dots (QD) are increasingly used in display, bioimaging, and energy technologies; however, significant concerns have been raised about their potentially adverse impact on human health and the environment. This study makes use of a broad toolkit of analytical methods to investigate and increase our understanding of the interactions of luminescent cadmium-containing (CdSe) and cadmium-free (ZnSe) QD, with and without a passivating higher bandgap energy ZnS shell, with phospholipid vesicles (liposomes), which model bacterial membranes, and with Shewanella oneidensis MR-1, an environmentally relevant bacteria. A unique feature of this study is that all QD types have the same surface chemistry, being capped with uncharged poly(ethylene glycol) ligands. This enables focusing the study on the impact of the QD core on liposomes and bacterial cells. The study reveals that QD association with liposome and bacterial cell membranes is imperative for their adverse impact on liposomes and bacterial cells. The QD' concentration-dependent association with liposomes and bacterial cells destabilizes the membranes mechanically, which leads to membrane disruption and lysis in liposomes and to bacterial cell death. The study also shows that cadmium-containing QD exhibit a higher level of membrane disruption in bacterial cells than cadmium-free QD. ZnSe QD have low membrane impact, and coating them with a ZnS shell decreases their membrane disruption activity. In contrast, CdSe QD exhibit a high level of membrane impact, and coating them with a ZnS shell does not decrease, but in fact further increases, their membrane disruption activity. This behavior might be attributed to higher affinity and association of CdSe/ZnS QD with liposomes and bacterial cells and to a contribution of dissolved zinc ions from the ZnS shell to increased membrane disruption activity.

16.
Langmuir ; 33(12): 3018-3027, 2017 03 28.
Article in English | MEDLINE | ID: mdl-28245133

ABSTRACT

The increasing commercialization of consumer electronic products that make use of II-VI semiconductor quantum dots (QDs) has raised significant concerns about their impact on natural systems and human health once they are released into the environment at the end of the product's lifetime. In this paper, we demonstrate the addition of fluorescence lifetime spectroscopy to the existing tool kit of spectroscopic techniques to quantitatively monitor changes in QD properties as they form and degrade in solution. Our study reveals that because of its rich information content, fluorescence lifetime spectroscopy has a limited utility as a stand-alone technique in the study of QD formation and degradation. However, combining fluorescence lifetime spectroscopy with the commonly used emission quantum yield and peak width measurements along with other analytical methods, including ultraviolet-visible spectroscopy, transmission electron microscopy, and inductively coupled plasma mass spectrometry measurements, significantly enhances the existing analytical tool kit and provides the capability to monitor in real time, the formation and degradation of luminescent QDs in organic and aqueous solutions under environmentally relevant conditions.

17.
ACS Cent Sci ; 1(3): 117-23, 2015 Jun 24.
Article in English | MEDLINE | ID: mdl-27162961

ABSTRACT

The interaction of nanomaterials with biomolecules, cells, and organisms is an enormously vital area of current research, with applications in nanoenabled diagnostics, imaging agents, therapeutics, and contaminant removal technologies. Yet the potential for adverse biological and environmental impacts of nanomaterial exposure is considerable and needs to be addressed to ensure sustainable development of nanomaterials. In this Outlook four research needs for the next decade are outlined: (i) measurement of the chemical nature of nanomaterials in dynamic, complex aqueous environments; (ii) real-time measurements of nanomaterial-biological interactions with chemical specificity; (iii) delineation of molecular modes of action for nanomaterial effects on living systems as functions of nanomaterial properties; and (iv) an integrated systems approach that includes computation and simulation across orders of magnitude in time and space.

18.
Anal Bioanal Chem ; 405(30): 9729-37, 2013 Dec.
Article in English | MEDLINE | ID: mdl-24173659

ABSTRACT

In this paper we describe the fabrication and characterization of new liposome encapsulated quantum dot-fluorescence resonance energy transfer (FRET)-based probes for monitoring the enzymatic activity of phospholipase A2. To fabricate the probes, luminescent CdSe/ZnS quantum dots capped with trioctylphosphine oxide (TOPO) ligands were incorporated into the lipid bilayer of unilamellar liposomes with an average diameter of approximately 100 nm. Incorporating TOPO capped quantum dots in liposomes enabled their use in aqueous solution while maintaining their hydrophobicity and excellent photophysical properties. The phospholipid bilayer was labeled with the fluorophore NBD C6-HPC (2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexa decanoyl-sn-glycero-3-phosphocholine). The luminescent quantum dots acted as FRET donors and the NBD dye molecules acted as FRET acceptors. The probe response was based on FRET interactions between the quantum dots and the NBD dye molecules. The NBD dye molecules were cleaved and released to the solution in the presence of the enzyme phospholipase A2. This led to an increase of the luminescence of the quantum dots and to a corresponding decrease in the fluorescence of the NBD molecules, because of a decrease in FRET efficiency between the quantum dots and the NBD dye molecules. Because the quantum dots were not attached covalently to the phospholipids, they did not hinder the enzyme activity as a result of steric effects. The probes were able to detect amounts of phospholipase A2 as low as 0.0075 U mL(-1) and to monitor enzyme activity in real time. The probes were also used to screen phospholipase A2 inhibitors. For example, we found that the inhibition efficiency of MJ33 (1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol) was higher than that of OBAA (3-(4-octadecyl)benzoylacrylic acid).


Subject(s)
Azoles/chemistry , Fluorescent Dyes , Liposomes/chemistry , Luminescent Measurements , Nitrobenzenes/chemistry , Phospholipases A2/analysis , Phospholipases A2/metabolism , Quantum Dots , Cadmium Compounds/chemistry , Fluorescence Resonance Energy Transfer , Humans , Nanotechnology , Organophosphorus Compounds/chemistry , Selenium Compounds/chemistry , Sulfides/chemistry , Zinc Compounds/chemistry
19.
J Am Chem Soc ; 133(7): 2028-30, 2011 Feb 23.
Article in English | MEDLINE | ID: mdl-21280652

ABSTRACT

The paper describes the development of highly sensitive particle-based fluorescence resonance energy transfer (FRET) probes that do not use molecular fluorophores as donors and acceptors. In these probes, CdSe/ZnS luminescent quantum dots (QDs) were capped with multiple histidine-containing peptides to increase their aqueous solubility while maintaining their high emission quantum yield and spectral properties. The peptide-modified QDs (QD-His) were covalently attached to carboxyl-modified polystyrene (PS) microspheres to form highly emitting PS microspheres (QD-PS). Gold nanoparticles (AuNPs) were then covalently attached to the QD-PS surface to form AuNP-QD-PS composite microspheres that were used as FRET probes. Attachment of AuNPs to QD-PS completely quenched the QD emission through FRET interactions. The emission of QD-PS was restored when the AuNPs were removed from the surface by thiol ligand displacement. The new AuNP-QD-PS FRET platform is simple to prepare and highly stable, and it opens many new possibilities for carrying out FRET assays on microparticle-based platforms and in microarrays. The versatility of these assays could be greatly increased by replacing the linkers between the QDs and AuNPs with ones that selectively respond to specific cleaving agents or enzymes.


Subject(s)
Fluorescent Dyes/chemistry , Gold/chemistry , Metal Nanoparticles/chemistry , Microspheres , Polystyrenes/chemistry , Quantum Dots , Biological Assay/methods , Fluorescence Resonance Energy Transfer , Molecular Structure
20.
J Am Chem Soc ; 132(5): 1460-1, 2010 Feb 10.
Article in English | MEDLINE | ID: mdl-20073459

ABSTRACT

This paper describes the development of new fluorescence resonance energy transfer (FRET)-based quantum dot probes for proteolytic activity. The CdSe/ZnS quantum dots are incorporated into a thin polymeric film, which is prepared by layer-by-layer deposition of alternately charged polyelectrolytes. The quantum dots, which serve as fluorescent donors, are separated from rhodamine acceptor molecules, which are covalently attached to the film surface by a varying number of polyelectrolyte layers. When excited with visible light, the emission color of the polyelectrolyte multilayer film appears orange due to FRET between the quantum dots and molecular acceptors. The emission color changes to green when the rhodamine molecules are removed from the surface by enzymatic cleavage. The new probe design enables the use of quantum dots in bioassays, in this study for real-time monitoring of trypsin activity, while alleviating concerns about their potential toxicity. Application of these quantum dot FRET-based probes in microfluidic channels enables bioanalysis of volume-limited samples and single-cell studies in an in vivo-like environment.


Subject(s)
Fluorescence Resonance Energy Transfer/methods , Microfluidic Analytical Techniques/methods , Quantum Dots , Trypsin/metabolism , Cadmium Compounds/chemistry , Fluorescence Resonance Energy Transfer/instrumentation , Fluorescent Dyes/chemistry , Microfluidic Analytical Techniques/instrumentation , Rhodamines/chemistry , Selenium Compounds/chemistry , Sulfides/chemistry , Trypsin/analysis , Zinc Compounds/chemistry
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