Ultrasmall Polymer Research Articles

High-order Super-resolution Optical Fluctuation Imaging with Ultrasmall Polymer Dots

High-order Super-resolution Optical Fluctuation Imaging with Ultrasmall Polymer Dots

A biomimetic cuproptosis amplifier for targeted NIR-II fluorescence/photoacoustic imaging-guided synergistic NIR-II photothermal immunotherapy

The therapeutic efficacy of cuproptosis combined with phototheranostics is still hindered by easy copper efflux, nonspecific accumulation and limited light penetration depth. Here, a high-performance NIR-II semiconductor polymer was first synthesized through dual-donor engineering. Then a biomimetic cuproptosis amplifier (PCD@CM) was prepared by Cu(II)-mediated coordinative self-assembly of NIR-II ultrasmall polymer dots and the chemotherapeutic drug DOX, followed by camouflaging of tumor cell membranes. After homologous targeting delivery to tumor cells, overexpressed GSH in the tumor microenvironment (TME) triggers the disassembly of the amplifier and the release of therapeutic components through the reduction of Cu(II) to Cu(I), which enable NIR-II fluorescence/photoacoustic imaging-guided NIR-II photothermal therapy (PTT) and chemotherapy. The released Cu(I) induces the aggregation of lipoylated mitochondrial proteins accompanied by the loss of iron-sulfur proteins, leading to severe proteotoxic stress and eventually cuproptosis. NIR-II PTT and GSH depletion render tumor cells more sensitive to cuproptosis. The amplified cuproptosis sensitization provokes significant immune surveillance, triggering the immunogenic cell death (ICD) to promote cytotoxic T lymphocyte infiltration together with aPD-L1-mediated immune checkpoint blockade. This work proposes a new strategy to develop cuproptosis sensitization systems enhanced by NIR-II phototheranostics with homologous targeting and anti-tumor immune response capabilities.

Nanolayer Laser Absorber for Femtoliter Chemistry in Polymer Reactors.

Laser-induced forward transfer (LIFT) has the potential to be an alternative approach to atomic force microscopy based scanning probe lithography techniques, which have limitations in high-speed and large-scale patterning. However, traditional donor slides limit the resolution and chemical flexibility of LIFT. Here, a hematite nanolayer absorber for donor slides to achieve high-resolution transfers down to sub-femtoliters is proposed. Being wettable by both aqueous and organic solvents, this new donor significantly increases the chemical scope for the LIFT process. For parallel amino acid coupling reactions, the patterning resolution can now be increased more than five times (>111000 spotscm- 2 for hematite donor vs 20000 spotscm- 2 for standard polyimide donor) with even faster scanning (2vs 6ms per spot). Due to the increased chemical flexibility, other types of reactions inside ultrasmall polymer reactors: copper (I) catalyzed click chemistry and laser-driven oxidation of a tetrahydroisoquinoline derivative, suggesting the potential of LIFT for both deposition of chemicals, and laser-driven photochemical synthesis in femtoliters within milliseconds can be explored. Since the hematite shows no damage after typical laser transfer, donors can be regenerated by heat treatment. These findings will transform the LIFT process into an automatable, precise, and highly efficient technology for high-throughput femtoliter chemistry.

Ultrasmall Polymer Nanoparticles Formed by Instantaneous Nanosplitting of Surfactant-Free Emulsion.

Application of polymer nanoparticles has progressively broadened. There is now increasing interest in smaller polymer nanoparticles for use in organic solar cells and drug delivery systems. Unfortunately, it is difficult to control the particle size below 50 nm with conventional synthesis methods. Our previously proposed "two-step nanoprecipitation method" overcomes this problem. An oil-in-water emulsion is first formed from polymer solution and deionized water without using surfactant; it is then injected into ethanol to form particles. The particle formation mechanism in this method has now been investigated, and an interesting phenomenon was discovered: the injected droplets instantaneously split into nanosize droplets with a size of 100-150 nm. The splitting was very effective, and the formed nanosize droplets were virtually monodisperse. This occurred only for a mixture composition in which the surface tension of the poor solvent mixture (water and ethanol) equaled that of the good solvent. This composition also resulted in formation of the smallest particles. By adjusting the conditions, we were able to synthesize extremely small nanoparticles (∼5 nm) of poly(3-hexylthiophene). This method has the potential to synthesize nanoparticles composed of other types of materials, such as nonconductive polymers and small molecules.

Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy.

It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F- is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F--responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F− with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F− in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F−-sensitive red phosphorescence from iridium(III) complex to the F−-insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F− also changes its emission lifetime, and the lifetime-based detection of F− in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe’s concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications.

6-Thioguanine-loaded polymeric micelles deplete myeloid-derived suppressor cells and enhance the efficacy of T cell immunotherapy in tumor-bearing mice.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that suppress effector T cell responses and can reduce the efficacy of cancer immunotherapies. We previously showed that ultra-small polymer nanoparticles efficiently drain to the lymphatics after intradermal injection and target antigen-presenting cells, including Ly6chi Ly6g− monocytic MDSCs (Mo-MDSCs), in skin-draining lymph nodes (LNs) and spleen. Here, we developed ultra-small polymer micelles loaded with 6-thioguanine (MC-TG), a cytotoxic drug used in the treatment of myelogenous leukemia, with the aim of killing Mo-MDSCs in tumor-bearing mice and thus enhancing T cell-mediated anti-tumor responses. We found that 2 days post-injection in tumor-bearing mice (B16-F10 melanoma or E.G7-OVA thymoma), MC-TG depleted Mo-MDSCs in the spleen, Ly6clo Ly6g+ granulocytic MDSCs (G-MDSCs) in the draining LNs, and Gr1int Mo-MDSCs in the tumor. In both tumor models, MC-TG decreased the numbers of circulating Mo- and G-MDSCs, as well as of Ly6chi macrophages, for up to 7 days following a single administration. MDSC depletion was dose dependent and more effective with MC-TG than with equal doses of free TG. Finally, we tested whether this MDSC-depleting strategy might enhance cancer immunotherapies in the B16-F10 melanoma model. We found that MC-TG significantly improved the efficacy of adoptively transferred, OVA-specific CD8+ T cells in melanoma cells expressing OVA. These findings highlight the capacity of MC-TG in depleting MDSCs in the tumor microenvironment and show promise in promoting anti-tumor immunity when used in combination with T cell immunotherapies.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-015-1702-8) contains supplementary material, which is available to authorized users.

Charge-controlled nanoprecipitation as a modular approach to ultrasmall polymer nanocarriers: making bright and stable nanoparticles.

Ultrasmall polymer nanoparticles are rapidly gaining importance as nanocarriers for drugs and contrast agents. Here, a straightforward modular approach to efficiently loaded and stable sub-20-nm polymer particles is developed. In order to obtain ultrasmall polymer nanoparticles, we investigated the influence of one to two charged groups per polymer chain on the size of particles obtained by nanoprecipitation. Negatively charged carboxylate and sulfonate or positively charged trimethylammonium groups were introduced into the polymers poly(d,l-lactide-co-glycolide) (PLGA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA). According to dynamic light scattering, atomic force and electron microscopy, the presence of one to two charged groups per polymer chain can strongly reduce the size of polymer nanoparticles made by nanoprecipitation. The particle size can be further decreased to less than 15 nm by decreasing the concentration of polymer in the solvent used for nanoprecipitation. We then show that even very small nanocarriers of 15 nm size preserve the capacity to encapsulate large amounts of ionic dyes with bulky counterions at efficiencies >90%, which generates polymer nanoparticles 10-fold brighter than quantum dots of the same size. Postmodification of their surface with the PEG containing amphiphiles Tween 80 and pluronic F-127 led to particles that were stable under physiological conditions and in the presence of 10% fetal bovine serum. This modular route could become a general method for the preparation of ultrasmall polymer nanoparticles as nanocarriers of contrast agents and drugs.

Directional Crystallization of 20 nm Width Polymer Nanorods by the Inducement of Heterogeneous Nuclei at Their Tips

Crystallization of polymers under confinement has emerged as a new tool to fall into some of the classical problems of the crystallization of polymers. Furthermore, these investigations are essential to obtain nanostructures with a customized behavior, as the most important properties of such nanostructure (mechanical, optical, electrical, etc.) strongly depend on the crystalline features. Here we show a new crystallization strategy for achieving a completely oriented crystallization of ultrasmall polymer rods (20 nm in diameter) by inducing crystal nucleation centers exclusively at one of their tips. Such heterogeneous nucleation takes place at a temperature tens of degrees higher than the temperature at which the crystal nuclei would be spontaneously formed (via a homogeneous mechanism), so the formation of additional nuclei along the nanorods can be ruled out. Therefore, the confined polymer crystallizes unidirectionally along the nanorod axis just by the growth of already formed crystals. This strategy opens up the possibility of preparing polymer nanorods presenting considerably improved crystalline features. Thus, our nanorods show single-crystal orientation and high crystallinity. Interestingly, the new strategy also allows studying for the first time the kinetics of the unidirectional crystal growth under confinement. Thus, we show that the crystallization of the polymer nanorods shows the time dependency of a diffusion process, i.e., t0.5. Moreover, the linear crystallization rate value of the confined flat on lamellae is of 2.7 × 10–7 cm/s. Since the polymer nanorods crystallize exclusively through of the growth of crystals heterogeneously nucleated at one of their tips, and just a single flat on lamella can be accommodated in a 20 nm in diameter pores due to space reasons, what we present in this paper may be the study of the crystallization of a single lamella within each pore, which would mean that single-crystalline nanorods are obtained from the melt.