10 research outputs found
Detection of Bacteria Using Inkjet-Printed Enzymatic Test Strips
Low-cost diagnostics for drinking
water contamination have the
potential to save millions of lives. We report a method that uses
inkjet printing to copattern an enzyme–nanoparticle sensor
and substrate on a paper-based test strip for rapid detection of bacteria.
A colorimetric response is generated on the paper substrate that allows
visual detection of contamination without the need for expensive instrumentation.
These strips demonstrate a viable nanomanufacturing strategy for low-cost
bacterial detection
Probing the protein–nanoparticle interface: the role of aromatic substitution pattern on affinity
<div><p>A new class of cationic gold nanoparticles (NPs) has been synthesised bearing benzyl moieties featuring –NO<sub>2</sub> and –OMe groups to investigate the regioisomeric control of aromatic NP–protein recognition. In general, NPs bearing electron-withdrawing groups demonstrated higher binding affinities towards green fluorescent protein (GFP) than NPs bearing electron-donating groups. Significantly, a ∼7.5- and ∼4.3-fold increase in binding with GFP was observed for –NO<sub>2</sub> groups in <i>meta-</i>position and <i>para-</i>position, respectively, while <i>ortho</i>-substitution showed binding similar to the unsubstituted ring. These findings demonstrated that the NP–protein interaction can be controlled by tuning the spatial orientation and the relative electronic properties of the aromatic substituents. This improved biomolecular recognition provides opportunities for enhanced biosensing and functional protein delivery to the cells.</p></div
Control of Surface Tension at Liquid–Liquid Interfaces Using Nanoparticles and Nanoparticle–Protein Complexes
Subtle changes in the monolayer structure of nanoparticles
(NPs)
influence the interfacial behavior of both NPs and NP–protein
conjugates. In this study, we use a series of monolayer-protected
gold NPs to explore the role of particle hydrophobicity on their dynamic
behavior at the toluene–water interface. Using dynamic surface
tension measurements, we observed a linear decrease in the meso-equilibrium
surface tension (γ) and faster dynamics as the hydrophobicity
of the ligands increases. Further modulation of γ is observed
for the corresponding NP–protein complexes at the charge-neutralization
point
Ultrastable and Biofunctionalizable Gold Nanoparticles
Gold nanoparticles provide an excellent
platform for biological
and material applications due to their unique physical and chemical
properties. However, decreased
colloidal stability and formation of irreversible aggregates while
freeze-drying nanomaterials limit their use in real world applications.
Here, we report a new generation of surface ligands based on a combination
of short oligo (ethylene glycol) chains and zwitterions capable of
providing nonfouling characteristics while maintaining colloidal stability
and functionalization capabilities. Additionally, conjugation of these
gold nanoparticles with avidin can help the development of a universal
toolkit for further functionalization of nanomaterials
Enhanced Laser Desorption/Ionization Mass Spectrometric Detection of Gold Nanoparticles in Biological Samples Using the Synergy between Added Matrix and the Gold Core
Laser desorption/ionization mass
spectrometry (LDI-MS) has been
used to detect gold nanoparticles (AuNPs) in biological samples, such
as cells and tissues, by ionizing their attached monolayer ligands.
Many NP-attached ligands, however, are difficult to ionize by LDI,
making it impossible to track these NPs in biological samples. In
this work, we demonstrate that concentrations of matrix-assisted LDI
(MALDI) matrices an order of magnitude below the values typically
used in MALDI can facilitate the selective detection of AuNPs with
these ligands, even in samples as complex as cell lysate. This enhanced
sensitivity arises from a synergistic relationship between the gold
core and the matrix that helps to selectively ionize ligands attached
to the AuNPs
Functional Gold Nanoparticles as Potent Antimicrobial Agents against Multi-Drug-Resistant Bacteria
We present the use of functionalized gold nanoparticles (AuNPs) to combat multi-drug-resistant pathogenic bacteria. Tuning of the functional groups on the nanoparticle surface provided gold nanoparticles that were effective against both Gram-negative and Gram-positive uropathogens, including multi-drug-resistant pathogens. These AuNPs exhibited low toxicity to mammalian cells, and bacterial resistance was not observed after 20 generations. A strong structure–activity relationship was observed as a function of AuNP functionality, providing guidance to activity prediction and rational design of effective antimicrobial nanoparticles
The Interplay of Size and Surface Functionality on the Cellular Uptake of Sub-10 nm Gold Nanoparticles
Correlation of the surface physicochemical properties of nanoparticles with their interactions with biosystems provides key foundational data for nanomedicine. We report here the systematic synthesis of 2, 4, and 6 nm core gold nanoparticles (AuNP) featuring neutral (zwitterionic), anionic, and cationic headgroups. The cellular internalization of these AuNPs was quantified, providing a parametric evaluation of charge and size effects. Contrasting behavior was observed with these systems: with zwitterionic and anionic particles, uptake <i>decreased</i> with increasing AuNP size, whereas with cationic particles, uptake <i>increased</i> with increasing particle size. Through mechanistic studies of the uptake process, we can attribute these opposing trends to a surface-dictated shift in uptake pathways. Zwitterionic NPs are primarily internalized through passive diffusion, while the internalization of cationic and anionic NPs is dominated by multiple endocytic pathways. Our study demonstrates that size and surface charge interact in an interrelated fashion to modulate nanoparticle uptake into cells, providing an engineering tool for designing nanomaterials for specific biological applications
Rapid Identification of Bacterial Biofilms and Biofilm Wound Models Using a Multichannel Nanosensor
Identification of infectious bacteria responsible for biofilm-associated infections is challenging due to the complex and heterogeneous biofilm matrix. To address this issue and minimize the impact of heterogeneity on biofilm identification, we developed a gold nanoparticle (AuNP)-based multichannel sensor to detect and identify biofilms based on their physicochemical properties. Our results showed that the sensor can discriminate six bacterial biofilms including two composed of uropathogenic bacteria. The capability of the sensor was further demonstrated through discrimination of biofilms in a mixed bacteria/mammalian cell <i>in vitro</i> wound model
Multiplexed Imaging of Nanoparticles in Tissues Using Laser Desorption/Ionization Mass Spectrometry
Imaging
of nanomaterials in biological tissues provides vital information
for the development of nanotherapeutics and diagnostics. Multiplexed
imaging of different nanoparticles (NPs) greatly reduces costs, the
need to use multiple animals, and increases the biodistribution information
that can enhance diagnostic applications and accelerate the screening
of potential therapeutics. Various approaches have been developed
for imaging NPs; however, the readout of existing imaging techniques
relies on specific properties of the core material or surface ligands,
and these techniques are limited because of the relatively small number
of NPs that can be simultaneously measured in a single experiment.
Here, we demonstrate the use of laser desorption/ionization mass spectrometry
(LDI-MS) in an imaging format to investigate surface chemistry dictated
intraorgan distribution of NPs. This new LDI-MS imaging method enables
multiplexed imaging of NPs with potentially unlimited readouts and
without additional labeling of the NPs. It provides the capability
to detect and image attomole levels of NPs with almost no interferences
from biomolecules. Using this new imaging approach, we find that the
intraorgan distributions of same-sized NPs are directly linked to
their surface chemistry
Dual-Mode Mass Spectrometric Imaging for Determination of <i>in Vivo</i> Stability of Nanoparticle Monolayers
Effective correlation of the <i>in vitro</i> and <i>in vivo</i> stability of nanoparticle-based
platforms is a key challenge in their translation into the clinic.
Here, we describe a dual imaging method that site-specifically reports
the stability of monolayer-functionalized nanoparticles <i>in
vivo</i>. This approach uses laser ablation inductively coupled
plasma mass spectrometry (LA-ICP-MS) imaging to monitor the distributions
of the nanoparticle core material and laser desorption/ionization
mass spectrometry (LDI-MS) imaging to report on the monolayers on
the nanoparticles. Quantitative comparison of the images reveals nanoparticle
stability at the organ and suborgan level. The stability of particles
observed in the spleen was location-dependent and qualitatively similar
to <i>in vitro</i> studies. In contrast, <i>in vivo</i> stability of the nanoparticles in the liver differed dramatically
from <i>in vitro</i> studies, demonstrating the importance
of <i>in vivo</i> assessment of nanoparticle stability