Advances in liquid phase transmission electron microscopy (LP-TEM) have enabled the monitoring of polymer dynamics in solution at the nanoscale, but radiolytic damage during LP-TEM imaging challenges its routine use in polymer science. Here, we focus on understanding, mimicking and mitigating radiolytic damage observed in functional polymers in LP-TEM. Using polymer vesicles in aqueous solutions as a model system, we quantitatively show how polymer damage occurs in all conceivable (LP-)TEM environments to which polymers might be exposed. It is found that radiolytic damage to polymers is negligible in vacuum but becomes substantial in water-containing environments. We elucidate the primary characteristics of polymer damage in water vapor and liquid water, addressing the observed differences. Furthermore, we introduce ultraviolet light irradiation in the presence of hydrogen peroxide to replicate the observed polymer damage and morphological changes on lab scale, allowing the use of bulk techniques to probe damage at the polymer chain level. Finally, we compare the protective effects of commonly used hydroxyl radical scavengers and reveal that the effectiveness of graphene's protection is distance dependent. We anticipate that our work will help to guide the design of LP-TEM experiments for polymers in a rational and informed manner.
Abstract The electron‐deficient ester group substitution in the sidechain of the commonly used electron‐withdrawing quinoxaline (Qx) unit is seldom studied, while ester‐substituted Qx units possess easy syntheses and facile modulation of the polymer solubility, and the enhanced electron‐withdrawing property of ester substituted Qx unit can theoretically broaden the optical absorption of the resulting polymers and improve the open circuit voltage in the corresponding organic solar cells (OSCs). In this work, a novel ester‐substituted Qx‐based narrow bandgap polymer (NBG) donor material PBDTT‐EFQx, which exhibits an absorption edge of 790 nm (bandgap < 1.6 eV), is designed and synthesized. Results show that the OSCs composed of PBDTT‐EFQx and PC 71 BM present the highest power conversion efficiency (PCE) of 6.8%, compared to PCEs of 5.0% for PBDTT‐EFQx:ITIC based devices and 4.1% for PBDTT‐EFQx:N2200 based devices, respectively. Characterizations and analyses indicate that the PC 71 BM‐based OSCs have well‐matched energy levels, better complementary light absorption, the highest and most balanced carrier mobilities, as well as the lowest degree of recombination losses, and therefore, leading to the highest PCE among the three types of OSCs. This work reveals that the ester‐substituted quinoxaline unit is one of the potential building blocks for NBG polymer donors.
Conjugated polymers have been proven to be full of promising application in photoacoustic (PA) imaging. Generally, the absorption spectra of PA contrast agents lying in the near-infrared (NIR) II window are requisite to eliminate the light absorption and scattering of tissue, skin, and blood. In this concise study, strong acceptor acrylate-substituted thiadiazoloquinoxaline (ATQ) was developed and used to copolymerize with different donors, yielding three NIR II polymers. Results show that (i) ATQ-based polymers can reach an ultralow optical band gap of 0.56 eV; (ii) the ATQ-based polymer nanoparticles have good biocompatibility and high PA signal intensity with a tissue penetration depth up to 10 mm; and (iii) under NIR II laser irradiation, the signal-to-noise ratio of mouse cerebrovascular during in vivo PA imaging enhanced by 10 times after injecting ATQ-based nanoparticles. This work reveals that acrylate-substituted ATQ-based polymers, which can be easily synthesized and functionalized, extend the absorption spectra to longer wavelengths, and decrease the radiative decay rate (kr), are a promising class of NIR polymers for developing efficient PA contrast agents.
Polymer vesicles and lipid nanoparticles are supramolecular structures with similar physicochemical properties that are self-assembled from different amphiphilic molecules. Because of their efficient drug encapsulation capability, they are good candidates for drug delivery systems. In recent years, nanoparticles with different compositions, sizes, and morphologies have been applied to the delivery of a wide variety of different therapeutic molecules, such as nucleic acids, proteins, and enzymes; their remarkable chemical versatility allows for customization to specific biological applications. In this review, design approaches for polymer vesicles and lipid nanoparticles are summarized with representative examples in terms of their physicochemical properties (size, shape, and mechanical features), preparation strategies (film rehydration, solvent switch, and nanoprecipitation), and applications (with a focus on diagnosis, imaging, and RNA-based therapy). Finally, the challenges limiting the transition from laboratory to clinical application and future perspectives are discussed.
Abstract Polymeric nanoarchitectures are crafted from amphiphilic block copolymers through a meticulous self‐assembly process. The composition of these block copolymers is finely adjustable, bestowing precise control over the characteristics and properties of the resultant polymeric assemblies. These nanoparticles have garnered significant attention, particularly in the realm of biological sciences, owing to their biocompatibility, favorable pharmacokinetics, and facile chemically modifiable nature. Among the myriad of polymeric nanoarchitectures, micelles and polymersomes stand out as frontrunners, exhibiting much potential as cargo carrier systems for diverse bio‐applications. This review elucidates the design strategies employed for amphiphilic block copolymers and their resultant assemblies, specifically focusing on micelles and polymersomes. Subsequently, it discusses their wide‐ranging bio‐applications, spanning from drug delivery and diagnostics to bioimaging and artificial cell applications. Finally, a reflective analysis will be provided, highlighting the current landscape of polymeric cargo carriers, and discussing the opportunities and challenges that lie ahead. With this review, it is aimed to summarize the recent advances in polymeric assemblies and their applications in the biomedical field.
Abstract Advances in liquid phase transmission electron microscopy (LP‐TEM) have enabled the monitoring of polymer dynamics in solution at the nanoscale, but radiolytic damage during LP‐TEM imaging limits its routine use in polymer science. This study focuses on understanding, mimicking, and mitigating radiolytic damage observed in functional polymers in LP‐TEM. It is quantitatively demonstrated how polymer damage occurs across all conceivable (LP‐)TEM environments, and the key characteristics and differences between polymer degradation in water vapor and liquid water are elucidated. Importantly, it is shown that the hydroxyl radical‐rich environment in LP‐TEM can be approximated by UV light irradiation in the presence of hydrogen peroxide, allowing the use of bulk techniques to probe damage at the polymer chain level. Finally, the protective effects of commonly used hydroxyl radical scavengers are compared, revealing that the effectiveness of graphene's protection is distance‐dependent. The work provides detailed methodological guidance and establishes a baseline for polymer degradation in LP‐TEM, paving the way for future research on nanoscale tracking of shape transitions and drug encapsulation of polymer assemblies in solution.
Abstract Synthetic micro/nanomotors have been extensively exploited over the past decade to achieve active transportation. This interest is a result of their broad range of potential applications, from environmental remediation to nanomedicine. Nevertheless, it still remains a challenge to build a fast-moving biodegradable polymeric nanomotor. Here we present a light-propelled nanomotor by introducing gold nanoparticles (Au NP) onto biodegradable bowl-shaped polymersomes (stomatocytes) via electrostatic and hydrogen bond interactions. These biodegradable nanomotors show controllable motion and remarkable velocities of up to 125 μm s −1 . This unique behavior is explained via a thorough three-dimensional characterization of the nanomotor, particularly the size and the spatial distribution of Au NP, with cryogenic transmission electron microscopy (cryo-TEM) and cryo-electron tomography (cryo-ET). Our in-depth quantitative 3D analysis reveals that the motile features of these nanomotors are caused by the nonuniform distribution of Au NPs on the outer surface of the stomatocyte along the z-axial direction. Their excellent motile features are exploited for active cargo delivery into living cells. This study provides a new approach to develop robust, biodegradable soft nanomotors with application potential in biomedicine.
Polymersomes, nanosized polymeric vesicles, have attracted significant interest in the areas of artificial cells and nanomedicine. Given their size, their visualization via confocal microscopy techniques is often achieved through the physical incorporation of fluorescent dyes, which however present challenges due to potential leaching. A promising alternative is the incorporation of molecules with aggregation-induced emission (AIE) behavior that are capable of fluorescing exclusively in their assembled state. Here, we report on the use of AIE polymersomes as artificial organelles, which are capable of undertaking enzymatic reactions in vitro. The ability of our polymersome-based artificial organelles to provide additional functionality to living cells was evaluated by encapsulating catalytic enzymes such as a combination of glucose oxidase/horseradish peroxidase (GO
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