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WHITE CELLS AS ANTICANCER DRUG CARRIERS Advanced ovarian carcinoma is associated with extremely poor outcomes; fewer than 30% of patients survive past 10 years, largely due to the fact that the majority of patients present with widely metastatic disease within the peritoneal cavity. Controlling such disease with chemotherapy remains challenging due to the inability to target disseminated tumors and severe toxicity to healthy organs. Since M1 macrophages and tumor cells are mutually attracted to each other in vivo, and elicit significant antitumor responses, these cells are promising as drug-delivery agents. Guo et al. (DOI: 10.1021/acsnano.8b08872) tested this strategy using M1 macrophages as ferriers for doxoyrubicin (M1-Dox), a common chemotherapeutic agent for ovarian carcinoma. The researchers loaded this drug into the murine macrophage RAW264.7 line through a facile co-incubation method. In vitro experiments showed that these M1-Dox cells had more potent antitumor effects against ovarian cancer cells than other commercial doxoyrubicin carriers at the same drug concentration. Their antitumor efficacy was also significantly higher in a three-dimensional tumor model. In a mouse model of peritoneal metastasis, M1-Dox dramatically shrank tumors and significantly increased survival without adverse effects to healthy tissue. Further investigation showed that these cells delivered their doxorubicin cargo through the formation of a network of tunneling nanotubes, forming up to 43 of these nanotubes per cell to connect with neighboring cells and beyond. Although these drug carriers have significant challenges to clinical translation, the authors suggest that M1 macrophages could offer a safe and effective platform for treating ovarian and other cancers.
have notable drawbacks, such as significant amounts of moisture remaining in the fabrics due to limited water-transport capacities and relatively slow evaporation rates and moisture-wicking from the environment to the skin in high humidity conditions, leaving wearers feeling hot and sticky. To improve the performance of moisture-wicking technologies, Wang et al. (DOI: 10.1021/acsnano.8b08242) created fabrics that achieve directional water transport and ultrafast evaporation using multibranching porous networks that obey Murray’s law, much like the networks that vascular plants use to achieve transpiration. The researchers accomplished this improved moisture-wicking by creating bilayers of TF-629C dip-coated polylactic acid and cellulose acetate with multiscale pores from macro to micro levels. These bilayers were then dipcoated in a solution that contained well-dispersed microfibrillated cellulose fibers, then electrosprayed with C6FPU on the polylactic acid layer to create a hydrophobic-to-hydrophilic gradient. Experiments showed that these materials evinced an ultrafast water evaporation that was nearly six times faster than that of cotton fabric and more than two times faster than Coolmax. The authors suggest that these materials could form the basis for the next generation of moisture-wicking fabrics.
A COCKTAIL FOR MEDIUM-TERM MALE CONTRACEPTION An estimated 85 million unintended pregnancies occur annually worldwide. Although women have traditionally carried the majority of the burden of contraception, long-term pharmaceutical contraceptives have the risk of serious side effects, such as venous thromboembolism and abnormal endometrial angiogenesis. Male contraceptives include short-term methods, such as condoms, and long-term ones, such as vasectomy; however, medium-term contraceptive methods with flexible reversibility are not currently available. Toward this end, Bao et al. (DOI: 10.1021/acsnano.8b06683) designed a cocktail-like strategy that involves injecting the vas deferens, the duct that conveys sperm from the testicles to the urethra, with agents that both physically clog this region while also chemically inhibiting sperm motility. Their method involves sequentially injecting poly(ethylene glycol) mixed with gold
MOISTURE-WICKING FABRIC THAT MIMICS VASCULAR PLANTS Moisture-wicking fabrics have been a boon for athletes, soldiers, and industrial workers, creating drier and cooler microclimates for increased personal comfort in extreme environmental conditions. These materials rely on capillary force to drive sweat through small capillary pores in the fabric through chemical forces or surface tension, then guiding it to the outer surface for fast evaporation. Although Coolmax and other technologies have achieved commercial success, these fabrics © 2019 American Chemical Society
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DOI: 10.1021/acsnano.9b01193 ACS Nano 2019, 13, 935−938
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Cite This: ACS Nano 2019, 13, 935−938
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nanoparticles as a temperature-increasing agent and switchable physical barrier, ethylenediaminetetraacetic acid (EDTA) as a sperm chemical inhibitor and hydrogel solvent, another layer of poly(ethylene glycol) mixed with gold nanoparticles, and calcium alginate as a long-term physical barrier. By adjusting the doses of these materials, the researchers achieved male contraception in mice from periods lasting between 2 and 20 weeks, all without changing the normal sexual behavior of the animals. Radiating the vas deferens with near-infrared light reversed these effects, restoring fertility within a week. Although this method still needs significant refinement before clinical translation, the authors suggest that it offers a promising starting point for reversible, medium-term contraception for men.
A BETTER WAY TO SCAVENGE MONOCLONAL ANTIBODIES HOMOGENEOUSLY pH-responsive polymers, with pH-titratable functional groups, have found uses in many biotechnological applications from biosensing to purification. They have also been used as building blocks in nanoscale therapeutic systems, including bioconjugates and polymer micelles. In addition, studies have shown that pH-responsive polymers can act as “micro-buffering” agents that can locally control the bulk pH of small compartments, a phenomenon that has been exploited to control the pH of subcellular components such as endosomes and lysosomes. Thus, these materials may also be able to buffer the local pH around the nanoscale systems of which they are composed. Anees et al. (DOI: 10.1021/acsnano.8b07202) take advantage of this “nanobuffering” concept to manipulate the binding affinity of a protein toward antibodies, a phenomenon that is pH dependent. The researchers developed a scavenger by attaching a pH-responsive (co)polymer to Protein-A, a protein that binds to antibodies in the immunoglobulin G family at near-neutral pH. However, experiments showed that at more acidic pH, the antibodies remained attached to the protein, despite the normally detrimental effect this would typically have on binding. These findings suggest that the pH-responsive polymer made Protein-A relatively insensitive to the bulk pH while modifying the local pH. The researchers used the same phenomenon to trigger precipitation at basic pH of the protein−antibody complexes, which remained bound despite unfavorable pH conditions. Adding strong ion-pairing salts caused the complex to separate, enabling the researchers to recover the antibodies and recycle the scavenger. The authors suggest that this system could be used to manipulate other protein complexes.
SEEING WHERE NANOPARTICLES LAND IN THE LUNGS WITHOUT DISSECTION Nanomaterials are increasingly being used in medicine and industry. However, when inhaled, these materials can cause dose-dependent oxidative stress and inflammation not only to the lungs but to secondary organs they reach through the circulatory system. To study these effects, researchers have used a variety of imaging modalities, including X-ray computed tomography, magnetic resonance imaging, and positron emission tomography. However, these methods often cannot resolve biological interactions of nanoparticles with tissue nor visualize nanoparticle localization at cellular resolution. Other methods, such as transmission electron microscopy and twodimensional stereological techniques, can examine and quantify nanoparticle localization and distribution at the cellular level, but destroy three-dimensional tissue architecture. Currently, no technique can both visualize the spatial distribution of nanoparticles while quantifying their accumulated dose in whole organs with cellular resolution. Yang et al. (DOI: 10.1021/acsnano.8b07524) report a method that combines light sheet fluorescence with optical tissue clearing to accomplish this feat. They used this technique to examine lung morphology and distribution of three different types of nanoparticles with cellular resolution in nondissected ex vivo murine lungs after two different types of nanoparticle application. Their findings show that ventilator-assisted aerosol inhalation exhibited more homogeneous distributions in conducting airways and acini, compared to enhanced central deposition for intratracheal instillation. At cellular resolution, the researchers noted that nanoparticle deposition was patchy in the bronchioles and acini and more pronounced for instillation. The authors suggest that this technique could help accelerate studies of nanoparticle biokinetics and bioactivity within intact tissues for toxicology and nanomedical applications. 936
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STOP-AND-GO IMAGING OF DNA ORIGAMI ON MEMBRANES The technique known as DNA origami has given rise to a multitude of DNA-based nanostructures. For example, researchers have developed DNA structures that mimic the shape and functionality of membrane nanopores and interfaced them with lipid membranes. Due to the membranes’ inherent fluidity and the mobility of associated molecules, imaging these dynamic systems has been challenging. Although the movement of the DNA structures is slow enough to be traceable in a conventional fluorescence microscope, diffraction-limited microscopes do not reveal the structural organization of these complexes. Conversely, diffusing objects are much too fast to image with super-resolution techniques that provide access to structural details. To overcome these hurdles, Kempter et al. (DOI: 10.1021/ acsnano.8b04631) developed a method to control the diffusional behavior of DNA nanostructures so that they can be monitored with super-resolution imaging. Using three-legged triskelion DNA origami, the researchers placed these nanostructures on lipid bilayers. By changing the concentrations of MgCl2 and NaCl in the buffer, the researchers were able to manipulate the movement of the triskelions in a stop-and-go manner. The immobilized structures could be resolved with DNA points accumulation for imaging in nanoscale topography (DNA-PAINT) super-resolution imaging, which could also be used to track structures while in motion. DNA-PAINT also enabled the researchers to follow and to image the triskelions as they assembled into a hexagonal two-dimensional lattice after the addition of a set of oligonucleotides. The authors suggest that this control over diffusional behavior could help researchers manipulate the motion of membrane-associated cargoes for a variety of applications.
of architecture: 5-faced square pyramids, 6-faced cubes, and cylindrical tubes. The researchers found that each of these architectures demonstrates an exponential increase in enhancements with varying plasmon wavelengths, influenced by the size of the structures. However, each shape had its own distinct 3D plasmon hybridization modes. The strong point-based enhancement in tubular graphene extends over the entire cross-sectional edge at the openings of the tubes. The pyramids exhibited a lower edge-based enhancement that created a strong field at the base but not at the apex. The cubes did not have strong point and edge-based enhancements, but rather had uniformly strong fields of enhancement over large areas. The authors suggest that the plasmonic field enhancement of these shapes could open pathways for applications of 3D graphene in previously unrealized domains.
FIELD OF DREAMS: IMAGING CARBON NANOTUBES’ ELECTRONIC STATES WITH QUANTUM DOTS Applications including catalysis, spectroscopy, plasmonics, and electronics all rely on localization of charge carriers. To improve the design and performance of these applications, charge localization must be better understood at the sub-nanometer scale. Charge localization has been well studied in carbon nanotube field effect transistors, in which a voltage applied across the nanotube changes its conductivity to turn the current on and off. But whereas much is known about charge localization in the longitudinal direction, much less is known about the lateral localization, nor has it been directly visualized. Nguyen et al. (DOI: 10.1021/acsnano.8b06806) used singlemolecule absorption scanning tunneling microscopy (SMASTM) to image the transverse localization of carbon nanotube electronic states induced by the electrostatic field of a nearby excited quantum dot. Using a PbS quantum dot stimulated by laser light, the researchers nudged the quantum dot closer in some experiments and rotated it in others. Their results show that the quantum dot can be used as a switch to turn transverse polarization on and off. They found a strongly localized SMASTM signal on the carbon nanotube when the quantum dot is close. In addition, the polarization of the electronic states, particularly LUMO to LUMO+3, strongly depends on the state, separation, and orientation of the nanotube and quantum dot. This trend in polarization occurs both on metallic and nonmetallic surfaces. These results, the authors say, can be explained by a simple tight binding model. They suggest that their findings highlight the possibility of optically gating carbon nanotubes using quantum dots as switches.
ENHANCING PLASMONIC FIELDS WITH PYRAMIDS, CUBES, AND TUBES Two-dimensional graphene plasmons enhance the electric field around the graphene surface by confining light, making the nearfield intensity several orders of magnitude higher than the incident wave. The long lifetime of this tunable plasmon resonance, along with superior mechanical properties, make graphene a natural choice for applications such as reconfigurable metamaterials and optoelectronic devices for photodetection, vibrational spectroscopy techniques, and solar cells. However, exponential decay of the enhanced field just a few nanometers away from the surface severely degrades the performance of these devices. A high spatial coverage for the plasmonic nearfield is necessary to overcome surface and edge-limited efficiencies in these devices. Agarwal et al. (DOI: 10.1021/acsnano.8b08145) formed patterned graphene into hollow three-dimensional (3D) nanoarchitectures to achieve nonspatially constrained nearfield enhancement. Their study focused on three distinct types 937
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SPLITTING SUNLIGHT FOR PHOTOVOLTAICS AND PHOTOSYNTHESIS About 47% of the energy in the solar spectrum is visible light, and about 51% is infrared radiation. Over the past several years, researchers have made significant headway in developing organic semiconductors that specifically absorb infrared light. By optimizing their chemical structure, these materials can localize absorption in a narrow region, enabling the transmittance of visible light. Because such light is key for photosynthesis, it may be possible to harvest infrared energy for power while still utilizing visible light to grow plants. Liu et al. (DOI: 10.1021/acsnano.8b08577) tested this idea by creating flexible transparent organic photovoltaic devices that collect energy from infrared light while using visible light to grow plants underneath. For each device, the researchers used one of three different infrared-absorbing organic semiconductors as the acceptor, mixed with a different polymer as a donor. They created flexible photovoltaics by using poly(ethylene terephthalate) as the substrate with silver mesh with a spin-coated conducting polymer as a transparent electrode. Tests showed that each of these devices had excellent photovoltaic properties, with power-conversion efficiency (PCE) values of up to 10%. Bending only decreased the PCE of these devices by about 10%. In addition, the transparency of these devices allowed enough visible light to pass through to grow plants. Using mung beans as a model system, the researchers show that although the growing speed was slightly slower under the photovoltaic devices, they grew just as much after 13 days compared to plants in unobstructed sunlight. The authors suggest that transparent semiconductors that absorb infrared light hold considerable potential beyond simple photovoltaic applications.
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