Aggregation Behavior of Polyether Block Copolymers with Dendritic Structure in Aqueous Solutions

Two dendritic block copolymers with the same contents of PPO and PEO but different branches and blocks were synthesized by anion polymerization. Their aggregation behavior and aggregation morphology were investigated by steady-state fluorescence and transmission electron microscopy. For SD64 copolymer with PPO-PEO diblock branch, it can be proved that only intermolecular aggregates are formed, the aggregation number and aggregation diameter are increased with concentration. Whereas for SD343 dendritic copolymer with PPO-PEO-PPO triblock branch, hydrophobic PPO chains located on the edge of SD343 copolymers can associate within the same polymer chain and also between different polymer chains, so the aggregates were inclined to change from intramolecular micelles to intermolecular clusters with concentration increasing.     

The Synthesis of Amide Dendritic Gelators and its Self-assembly Behavior in MMA

Three kinds of amide dendritic gelators, G₁-C₁₂-G₁, G₂-C₁₂-G₂ and gelator-1, were synthesized, and their self-assemble behavior in methyl methacrylate (MMA) was firstly investigated. The structures of the amide dendritic gelators were confirmed by ¹H-NMR and Mass spectra (MS). The gelation ability of the amide dendritic gelators was researched through tube inversion experiment, the results of which showed that different structures led to quite different gelation ability, including gel-sol temperature and critical concentration to form a stable gel. SEM experiments showed that three kinds of gelator formed different gel morphologies in MMA, all of which were nanoscale gel. All the three amide dendritic gelators could not only form stable gel network at certain temperature with different concentrations in MMA, but also in each case, an optically transparent gel was formed, which indicated dendrimers in the MMA had a good compatibility.     

Responsive Linear‐Dendritic Block Copolymers

The combination of dendritic and linear polymeric structures in the same macromolecule opens up new possibilities for the design of block copolymers and for applications of functional polymers that have self‐assembly properties. There are three main strategies for the synthesis of linear‐dendritic block copolymers (LDBCs) and, in particular, the emergence of click chemistry has made the coupling of preformed blocks one of the most efficient ways of obtaining libraries of LDBCs. In these materials, the periphery of the dendron can be precisely functionalised to obtain functional LDBCs with self‐assembly properties of interest in different technological areas. The incorporation of stimuli‐responsive moieties gives rise to smart materials that are generally processed as self‐assemblies of amphiphilic LDBCs with a morphology that can be controlled by an external stimulus. Particular emphasis is placed on light‐responsive LDBCs. Furthermore, a brief review of the biomedical or materials science applications of LDBCs is presented.

     

Fabrication of PDMS microlens array by digital maskless grayscale lithography and replica molding technique

This paper presents a facile and effective method to fabricate microlens array in polydimethylsiloxane (PDMS). The microlens array model is fabricated in photoresist via digital maskless grayscale lithography technique and the replica molding technique is used to fabricate PDMS microlens array. A convex PDMS microlens array with rectangular aperture and concave PDMS microlens array with hexagonal aperture are fabricated. The morphological characteristics of the microlens arrays are measured by microscope and 3D profiler. The results indicate that the profiles of the PDMS microlens arrays are clear and distinct. This method provides a simple and low-cost approach to prepare large area, concave or convex with arbitrary shape microlens array, which has potential application in many optoelectronic devices.     

光波段柔性基超材料制备及光学性质

采用化学电沉积方法,通过控制沉积电压,电沉积时间等实验参量,确定出最优实验条件,在冰浴条件下,实验温度范围为0~2 ℃之间,在氧化铟锡导电薄膜表面沉积二维结构随机排列的纳米银树枝,并在银树枝表面涂覆一定厚度的绝缘薄膜聚乙烯醇后,与另外一层银树枝组装制作成银树枝/聚乙烯醇/银树枝复合结构.实验表明,参比样品在可见光波段400～750 nm处没有透射峰的出现,而银树枝/聚乙烯醇/银树枝复合结构在此波段有多个透射通带峰,且在相应波长表现出了聚焦效应.     

铝纳米粉末活化树突状细胞的作用

采用电爆炸法制备金属铝纳米粉末(ALEX),验证了其免疫增强效应及肿瘤预防效果.首先,利用铝金属丝电爆炸法,并应用羧基端基聚合物配体反应的方法合成了分散性良好的ALEX.利用静电物理吸附将抗原卵清蛋白(OVA)、抗原多肽(Peptide)接枝于ALEX表面,傅里叶变换红外光谱检测证明抗原与ALEX成功覆合.其次,验证了ALEX增强特异性免疫反应的效果.通过体外实验证明, ALEX可提高树突状细胞(DCs)的抗原提呈效果;同时,对免疫后小鼠血清抗体进行了定量检测,结果表明ALEX可显著提高小鼠体内抗原特异性抗体的水平.最后,利用小鼠黑色素瘤模型,验证了含有ALEX的肿瘤疫苗能够有效预防肿瘤的发生.     

Antibacterial Broad-Spectrum Dendritic/Gellan Gum Hybrid Hydrogels with Rapid Shape-Forming and Self-Healing for Wound Healing Application

Treating wound infections is a difficult task ever since pathogenic bacteria started to develop resistance to common antibiotics. The present study develops hybrid hydrogels based on the formation of a polyelectrolyte complex between the anionic charges of dopamine-functionalized Gellan Gum (GG-DA) and the cationic moieties of the TMP-G2-alanine dendrimer. The hydrogels thus obtained can be doubly crosslinked with CaCl₂, obtaining solid hydrogels. Or, by oxidizing dopamine to GG-DA, possibly causing further interactions such as Schiff Base and Michael addition to take place, hydrogels called injectables can be obtained. The latter have shear-thinning and self-healing properties (efficiency up to 100%). Human dermal fibroblasts (HDF), human epidermal keratinocytes (HaCaT), and mouse monocyte cells (RAW 264.7), after incubation with hydrogels, in most cases show cell viability up to 100%. Hydrogels exhibit adhesive behavior on various substrates, including porcine skin. At the same time, the dendrimer serves to crosslink the hydrogels and endows them with excellent broad-spectrum microbial eradication activity within four hours, evaluated using Staphylococcus aureus 2569 and Escherichia coli 178. Using the same GG-DA/TMP-G2-alanine ratios hybrid hydrogels with tunable properties and potential for wound dressing applications can be produced.     

Crosslinked Redox‐Responsive Micelles Based on Lipoic Acid‐Derived Amphiphiles for Enhanced siRNA Delivery

Successful application of gene silencing approaches critically depends on systems that are able to safely and efficiently deliver genetic material such as small interfering RNA (siRNA). Due to their beneficial well‐defined dendritic nanostructure, self‐assembling dendrimers are emerging as promising nanovectors for siRNA delivery. However, these kinds of vectors are plagued with stability issues, especially when considered for in vivo applications. Therefore, in the present study, disulfide‐based temporarily fixed micelles are developed that can degrade upon reductive conditions, and thus lead to efficient cargo release. In detail, lipoic acid‐derived crosslinked micelles are synthesized based on small polymerizable dendritic amphiphiles. Particularly, one candidate out of this series is able to efficiently release siRNA due to its redox‐responsive biodegradable profile when exposed to simulated intracellular environments. As a result, the reduction‐triggered disassembly leads to potent gene silencing. In contrast, noncrosslinkable, structurally related constructs fails under the tested assay conditions, thereby confirming the applied rational design approach and demonstrating its large potential for future in vivo applications.

     

Pt-Cu and Pt-Pd-Cu concave nanocubes with high-index facets and superior electrocatalytic activity

Pt-Cu nanostructures: Pt-Cu nanocubes (NCs), concave nanocubes (CNCs), and Pt-Pd-Cu CNCs with high-index facets (HIFs) were prepared through progressive galvanic replacements in a one-pot hydrothermal approach. The HIF-enclosed CNCs showed superior activities to (100)-enclosed NC catalysts for methanol oxidations owing to the modification of both the surface electronic structures and the surface atomic arrangements (see figure).     

Functionalized Polystyrene Nanoparticles Trigger Human Dendritic Cell Maturation Resulting in Enhanced CD4+ T Cell Activation

Nanoparticles (NP) represent a promising tool for biomedical applications. Here, sulfonate‐ and phosphonate‐functionalized polystyrene NP are analyzed for their interaction with human monocyte‐derived dendritic cells (DC). Immature dendritic cells (iDC) display a higher time‐ and dose‐dependent uptake of functionalized polystyrene NP compared to mature dendritic cells (mDC). Notably, NP induce an enhanced maturation of iDC but not of mDC (upregulation of stimulatory molecules and cytokines). NP‐triggered maturation results in a significantly enhanced T cell stimulatory capacity (increased CD4⁺ T cell proliferation and IFN‐γ production), indicating a shift to a pronounced Th1 response. Immunomodulatory properties of NP may be a useful strategy for strengthening the efficacy of NP‐based approaches in immunotherapy.