The conductivity of a poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film can be enhanced by more than two orders of magnitude by adding a compound with two or more polar ...groups, such as ethylene glycol, meso‐erythritol (1,2,3,4‐tetrahydroxybutane), or 2‐nitroenthanol, to an aqueous solution of PEDOT:PSS. The mechanism for this conductivity enhancement is studied, and a new mechanism proposed. Raman spectroscopy indicates an effect of the liquid additive on the chemical structure of the PEDOT chains, which suggests a conformational change of PEDOT chains in the film. Both coil and linear conformations or an expanded‐coil conformation of the PEDOT chains may be present in the untreated PEDOT:PSS film, and the linear or expanded‐coil conformations may become dominant in the treated PEDOT:PSS film. This conformational change results in the enhancement of charge‐carrier mobility in the film and leads to an enhanced conductivity. The high‐conductivity PEDOT:PSS film is ideal as an electrode for polymer optoelectronic devices. Polymer light‐emitting diodes and photovoltaic cells fabricated using such high‐conductivity PEDOT:PSS films as the anode exhibit a high performance, close to that obtained using indium tin oxide as the anode.
The conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is enhanced by the addition of ethylene glycol, meso‐erythritol, or 2‐nitroethanol, which change the conformation of the PEDOT chains. High‐performance polymer light‐emitting diodes (see Figure) and solar cells using enhanced PEDOT:PSS films as the anode are demonstrated.
The delivery of medical agents to a specific diseased tissue or cell is critical for diagnosing and treating patients. Nanomaterials are promising vehicles to transport agents that include drugs, ...contrast agents, immunotherapies and gene editors. They can be engineered to have different physical and chemical properties that influence their interactions with their biological environments and delivery destinations. In this Review Article, we discuss nanoparticle delivery systems and how the biology of disease should inform their design. We propose developing a framework for building optimal delivery systems that uses nanoparticle-biological interaction data and computational analyses to guide future nanomaterial designs and delivery strategies.
Recently, films created by incorporating metallic nanoparticles into organic or polymeric materials have demonstrated electrical bistability, as well as the memory effect, when subjected to an ...electrical bias. Organic and polymeric digital memory devices based on this bistable electronic behavior have emerged as a viable technology in the field of organic electronics. These devices exhibit fast response speeds and can form multiple‐layer stacking structures, demonstrating that organic memory devices possess a high potential to become flexible, ultrafast, and ultrahigh‐density memory devices. This behavior is believed to be related to charge storage in the organic or polymer film, where devices are able to exhibit two different states of conductivity often separated by several orders of magnitude. By defining the two states as “1” and “0”, it is now possible to create digital memory devices with this technology. This article reviews electrically bistable devices developed in our laboratory. Our research has stimulated strong interest in this area worldwide. The research by other laboratories is reviewed as well.
Research on electrically bistable devices using organic or polymer thin films is reviewed. These bistable devices have high potential for application in nonvolatile digital memory. The figure shows an organic/polymeric memory device that has been developed at the University of California, Los Angeles. The devices can be switched on a nanosecond time scale, and the data can be stored for a long period of time.
A recent metaanalysis shows that 0.7% of nanoparticles are delivered to solid tumors. This low delivery efficiency has major implications in the translation of cancer nanomedicines, as most of the ...nanomedicines are sequestered by nontumor cells. To improve the delivery efficiency, there is a need to investigate the quantitative contribution of each organ in blocking the transport of nanoparticles to solid tumors. Here, we hypothesize that the removal of the liver macrophages, cells that have been reported to take up the largest amount of circulating nanoparticles, would lead to a significant increase in the nanoparticle delivery efficiency to solid tumors. We were surprised to discover that the maximum achievable delivery efficiency was only 2%. In our analysis, there was a clear correlation between particle design, chemical composition, macrophage depletion, tumor pathophysiology, and tumor delivery efficiency. In many cases, we observed an 18–150 times greater delivery efficiency, but we were not able to achieve a delivery efficiency higher than 2%. The results suggest the need to look deeper at other organs such as the spleen, lymph nodes, and tumor in mediating the delivery process. Systematically mapping the contribution of each organ quantitatively will allow us to pinpoint the cause of the low tumor delivery efficiency. This, in effect, enables the generation of a rational strategy to improve the delivery efficiency of nanoparticles to solid tumors either through the engineering of multifunctional nanosystems or through manipulation of biological barriers.
The liver and spleen are major biological barriers to translating nanomedicines because they sequester the majority of administered nanomaterials and prevent delivery to diseased tissue. Here we ...examined the blood clearance mechanism of administered hard nanomaterials in relation to blood flow dynamics, organ microarchitecture and cellular phenotype. We found that nanomaterial velocity reduces 1,000-fold as they enter and traverse the liver, leading to 7.5 times more nanomaterial interaction with hepatic cells relative to peripheral cells. In the liver, Kupffer cells (84.8 ± 6.4%), hepatic B cells (81.5 ± 9.3%) and liver sinusoidal endothelial cells (64.6 ± 13.7%) interacted with administered PEGylated quantum dots, but splenic macrophages took up less material (25.4 ± 10.1%) due to differences in phenotype. The uptake patterns were similar for two other nanomaterial types and five different surface chemistries. Potential new strategies to overcome off-target nanomaterial accumulation may involve manipulating intra-organ flow dynamics and modulating the cellular phenotype to alter hepatic cell interactions.
An all‐organic electrically bistable device and its application in non‐volatile memory is reported (see Figure). The switching mechanism is attributed to electric‐field‐induced charge transfer from ...an organic electron donor to an acceptor, so that the device switches from a low‐ to a high‐conductivity state. This device provides a new direction for data‐storage technology based on organic composites.
Understanding how nanoparticles are eliminated from the body is required for their successful clinical translation. Many promising nanoparticle formulations for in vivo medical applications are large ...(>5.5 nm) and nonbiodegradable, so they cannot be eliminated renally. A proposed pathway for these nanoparticles is hepatobiliary elimination, but their transport has not been well-studied. Here, we explored the barriers that determined the elimination of nanoparticles through the hepatobiliary route. The route of hepatobiliary elimination is usually through the following pathway: (1) liver sinusoid, (2) space of Disse, (3) hepatocytes, (4) bile ducts, (5) intestines, and (6) out of the body. We discovered that the interaction of nanoparticles with liver nonparenchymal cells (e.g., Kupffer cells and liver sinusoidal endothelial cells) determines the elimination fate. Each step in the route contains cells that can sequester and chemically or physically alter the nanoparticles, which influences their fecal elimination. We showed that the removal of Kupffer cells increased fecal elimination by >10 times. Combining our results with those of prior studies, we can start to build a systematic view of nanoparticle elimination pathways as it relates to particle size and other design parameters. This is critical to engineering medically useful and translatable nanotechnologies.
The concept of nanoparticle transport through gaps between endothelial cells (inter-endothelial gaps) in the tumour blood vessel is a central paradigm in cancer nanomedicine. The size of these gaps ...was found to be up to 2,000 nm. This justified the development of nanoparticles to treat solid tumours as their size is small enough to extravasate and access the tumour microenvironment. Here we show that these inter-endothelial gaps are not responsible for the transport of nanoparticles into solid tumours. Instead, we found that up to 97% of nanoparticles enter tumours using an active process through endothelial cells. This result is derived from analysis of four different mouse models, three different types of human tumours, mathematical simulation and modelling, and two different types of imaging techniques. These results challenge our current rationale for developing cancer nanomedicine and suggest that understanding these active pathways will unlock strategies to enhance tumour accumulation.
Thallium (Tl) pollution caused by mining and processing of Tl-enriched ores has become an increasing concern. This study explored the geochemical fractionation and vertical transfer of Tl in a soil ...profile (200 cm) from a representative Tl-As mineralized area, Southwest China. The results showed that the soils were heavily enriched by Tl and As, with concentration ranging from 3.91–17.3 and 1830–8840 mg/kg (6.79 and 2973 mg/kg in average), respectively. Approximately 50% of Tl occurred in geochemically mobile fractions in the topsoil, wherein the reducible fraction was the most enriched fraction. Further characterization using LA-ICP-MS and TEM revealed that enriched Tl and As in soils were mainly inherited from the weathering of mine tailing piles upstream. XPS characterization indicated that Fe oxides herein may play a critical role in the oxidation of Tl(I) to Tl(III) which provoked further adsorption of Tl onto Fe oxides, thereby facilitating Tl enrichment in the reducible fraction. The findings highlight that the pivotal role of Fe oxides from mineralized area in the co-mobility and migration of Tl and As in the depth profile.
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•Half of geochemically mobile fraction of thallium (Tl) was observed in the topsoils.•Dominant portion (29%) of mobile Tl was enriched in the reducible fraction.•Participation of Fe oxides plays a critical role in generating highly elevated mobile Tl.•LA-ICP-MS and TEM revealed Tl translocation pathway from tailings to soil profile.
Nanoparticle delivery to solid tumours over the past ten years has stagnated at a median of 0.7% of the injected dose. Varying nanoparticle designs and strategies have yielded only minor ...improvements. Here we discovered a dose threshold for improving nanoparticle tumour delivery: 1 trillion nanoparticles in mice. Doses above this threshold overwhelmed Kupffer cell uptake rates, nonlinearly decreased liver clearance, prolonged circulation and increased nanoparticle tumour delivery. This enabled up to 12% tumour delivery efficiency and delivery to 93% of cells in tumours, and also improved the therapeutic efficacy of Caelyx/Doxil. This threshold was robust across different nanoparticle types, tumour models and studies across ten years of the literature. Our results have implications for human translation and highlight a simple, but powerful, principle for designing nanoparticle cancer treatments.
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