20 research outputs found
Magnetic manipulation of superparamagnetic colloids in droplet-based optical devices
Magnetically assembled superparamagnetic colloids have been exploited as
fluid mixers, swimmers and delivery systems in several microscale applications.
The encapsulation of such colloids in droplets may open new opportunities to
build magnetically controlled displays and optical components. Here, we study
the assembly of superparamagnetic colloids inside droplets under rotating
magnetic fields and exploit this phenomenon to create functional optical
devices. Colloids are encapsulated in monodisperse droplets produced by
microfluidics and magnetically assembled into dynamic two-dimensional clusters.
Using an optical microscope equipped with a magnetic control setup, we
investigate the effect of the magnetic field strength and rotational frequency
on the size, stability and dynamics of 2D colloidal clusters inside droplets.
Our results show that cluster size and stability depend on the magnetic forces
acting on the structure under the externally imposed field. By rotating the
cluster in specific orientations, we illustrate how magnetic fields can be used
to control the effective refractive index and the transmission of light through
the colloid-laden droplets, thus demonstrating the potential of the
encapsulated colloids in optical applications
Synthetic and living micropropellers for convection-enhanced nanoparticle transport
Nanoparticles (NPs) have emerged as an advantageous drug delivery platform for the treatment of various ailments including cancer and cardiovascular and inflammatory diseases. However, their efficacy in shuttling materials to diseased tissue is hampered by a number of physiological barriers. One hurdle is transport out of the blood vessels, compounded by difficulties in subsequent penetration into the target tissue. Here, we report the use of two distinct micropropellers powered by rotating magnetic fields to increase diffusion-limited NP transport by enhancing local fluid convection. In the first approach, we used a single synthetic magnetic microrobot called an artificial bacterial flagellum (ABF), and in the second approach, we used swarms of magnetotactic bacteria (MTB) to create a directable âliving ferrofluidâ by exploiting ferrohydrodynamics. Both approaches enhance NP transport in a microfluidic model of blood extravasation and tissue penetration that consists of microchannels bordered by a collagen matrix.ISSN:2375-254
Renal clearable catalytic gold nanoclusters for in vivo disease monitoring
Ultra-small gold nanoclusters (AuNCs) have emerged as agile probes for in vivo imaging, as they exhibit exceptional tumour accumulation and efficient renal clearance properties. However, their intrinsic catalytic activity, which can enable increased detection sensitivity, has yet to be explored for in vivo sensing. By exploiting the peroxidase-mimicking activity of AuNCs and the precise nanometer size filtration of the kidney, we designed multifunctional protease nanosensors that respond to disease microenvironments to produce a direct colorimetric urinary readout of disease state in less than 1 h. We monitored the catalytic activity of AuNCs in collected urine of a mouse model of colorectal cancer where tumour-bearing mice showed a 13-fold increase in colorimetric signal compared to healthy mice. Nanosensors were eliminated completely through hepatic and renal excretion within 4 weeks after injection with no evidence of toxicity. We envision that this modular approach will enable rapid detection of a diverse range of diseases by exploiting their specific enzymatic signatures
Nanotechnology intervention of the microbiome for cancer therapy
The microbiome is emerging as a key player and driver of cancer. Traditional modalities to manipulate the microbiome (for example, antibiotics, probiotics and microbiota transplants) have been shown to improve efficacy of cancer therapies in some cases, but issues such as collateral damage to the commensal microbiota and consistency of these approaches motivates efforts towards developing new technologies specifically designed for the microbiomeâcancer interface. Considering the success of nanotechnology in transforming cancer diagnostics and treatment, nanotechnologies capable of manipulating interactions that occur across microscopic and molecular length scales in the microbiome and the tumour microenvironment have the potential to provide innovative strategies for cancer treatment. As such, opportunities at the intersection of nanotechnology, the microbiome and cancer are massive. In this Review, we highlight key opportunistic areas for applying nanotechnologies towards manipulating the microbiome for the treatment of cancer, give an overview of seminal work and discuss future challenges and our perspective on this emerging area
A Pulsatile Flow System to Engineer Aneurysm and Atherosclerosis Mimetic Extracellular Matrix
Alterations of blood flow patterns strongly correlate with arterial wall diseases such as atherosclerosis and aneurysm. Here, a simple, pumpless, close-loop, easy-to-replicate, and miniaturized flow device is introduced to concurrently expose 3D engineered vascular smooth muscle tissues to high-velocity pulsatile flow versus low-velocity disturbed flow conditions. Two flow regimes are distinguished, one that promotes elastin and impairs collagen I assembly, while the other impairs elastin and promotes collagen assembly. This latter extracellular matrix (ECM) composition shares characteristics with aneurysmal or atherosclerotic tissue phenotypes, thus recapitulating crucial hallmarks of flow-induced tissue morphogenesis in vessel walls. It is shown that the mRNA levels of ECM of collagens and elastin are not affected by the differential flow conditions. Instead, the differential gene expression of matrix metalloproteinase (MMP) and their inhibitors (TIMPs) is flow-dependent, and thus drives the alterations in ECM composition. In further support, treatment with doxycycline, an MMP inhibitor and a clinically used drug to treat vascular diseases, halts the effect of low-velocity flow on the ECM remodeling. This illustrates how the platform can be exploited for drug efficacy studies by providing crucial mechanistic insights into how different therapeutic interventions may affect tissue growth and ECM assembly
Magnetically Actuated Protease Sensors for in Vivo Tumor Profiling
Targeted
cancer therapies require a precise determination of the underlying
biological processes driving tumorigenesis within the complex tumor
microenvironment. Therefore, new diagnostic tools that capture the
molecular activity at the disease site in vivo are needed to better
understand tumor behavior and ultimately maximize therapeutic responses.
Matrix metalloproteinases (MMPs) drive multiple aspects of tumorigenesis,
and their activity can be monitored using engineered peptide substrates
as protease-specific probes. To identify tumor specific activity profiles,
local sampling of the tumor microenvironment is necessary, such as
through remote control of probes, which are only activated at the
tumor site. Alternating magnetic fields (AMFs) provide an attractive
option to remotely apply local triggering signals because they penetrate
deep into the body and are not likely to interfere with biological
processes due to the weak magnetic properties of tissue. Here, we
report the design and evaluation of a protease-activity nanosensor
that can be remotely activated at the site of disease via an AMF at
515 kHz and 15 kA/m. Our nanosensor was composed of thermosensitive
liposomes containing functionalized protease substrates that were
unveiled at the target site by remotely triggered heat dissipation
of coencapsulated magnetic nanoparticles (MNPs). This nanosensor was
combined with a unique detection assay to quantify the amount of cleaved
substrates in the urine. We applied this spatiotemporally controlled
system to determine tumor protease activity in vivo and identified
differences in substrate cleavage profiles between two mouse models
of human colorectal cancer
Synthetic and living micropropellers for convection-enhanced nanoparticle transport
Nanoparticles (NPs) have emerged as an advantageous drug delivery platform for the treatment of various ailments including cancer and cardiovascular and inflammatory diseases. However, their efficacy in shuttling materials to diseased tissue is hampered by a number of physiological barriers. One hurdle is transport out of the blood vessels, compounded by difficulties in subsequent penetration into the target tissue. Here, we report the use of two distinct micropropellers powered by rotating magnetic fields to increase diffusion-limited NP transport by enhancing local fluid convection. In the first approach, we used a single synthetic magnetic microrobot called an artificial bacterial flagellum(ABF), and in the second approach,we used swarms of magnetotactic bacteria (MTB) to create a directable "living ferrofluid" by exploiting ferrohydrodynamics. Both approaches enhance NP transport in a microfluidicmodel of blood extravasation and tissue penetration that consists of microchannels bordered by a collagen matrix.National Cancer Institute (Grant P30-CA1405
A Pulsatile Flow System to Engineer Aneurysm and Atherosclerosis Mimetic Extracellular Matrix
Alterations of blood flow patterns strongly correlate with arterial wall diseases such as atherosclerosis and aneurysm. Here, a simple, pumpless, closeâloop, easyâtoâreplicate, and miniaturized flow device is introduced to concurrently expose 3D engineered vascular smooth muscle tissues to highâvelocity pulsatile flow versus lowâvelocity disturbed flow conditions. Two flow regimes are distinguished, one that promotes elastin and impairs collagen I assembly, while the other impairs elastin and promotes collagen assembly. This latter extracellular matrix (ECM) composition shares characteristics with aneurysmal or atherosclerotic tissue phenotypes, thus recapitulating crucial hallmarks of flowâinduced tissue morphogenesis in vessel walls. It is shown that the mRNA levels of ECM of collagens and elastin are not affected by the differential flow conditions. Instead, the differential gene expression of matrix metalloproteinase (MMP) and their inhibitors (TIMPs) is flowâdependent, and thus drives the alterations in ECM composition. In further support, treatment with doxycycline, an MMP inhibitor and a clinically used drug to treat vascular diseases, halts the effect of lowâvelocity flow on the ECM remodeling. This illustrates how the platform can be exploited for drug efficacy studies by providing crucial mechanistic insights into how different therapeutic interventions may affect tissue growth and ECM assembly.ISSN:2198-384