Mechanochromic Polymer Film with High Sensitivity toward Tensile Strain by the Post-Curing Ring-Closure Induced Pre-Stretching.

Mechanochromic materials have received broad research interests recently, owing to its ability to monitor the in situ stress/strain in polymer materials in a straightforward way. However, one major setback that hinders the practical application of these materials is their low sensitivity toward tensile strain. Here a new strategy for pre-stretching of the mechanochromic agent in a polymer film on the molecular scale, which can effectively enhance the mechanochromic sensitivity of a polymer film toward tensile strain, is shown. In situ fluorescent measurement during tensile test shows an early activation of the mechanochromic agent at tensile strain as low as 50%. The pre-stretching effect is realized by first inducing ring-opening of the mechanochromic agent by molecular functionalization, and then compelling the ring-closure process in the cured film by elevated temperature. This post-curing ring-closure process will result in pre-stretched mechanochromic agent in a crosslinked network. The mechanism for mechanochromic activation of polymer films with different composition is elaborated by visco-elastic measurements, and the effect of pre-stretching is further confirmed by films with other compositions. Combined with the simplicity of the method developed, this work could offer an alternative strategy to enhance the sensitivity of different mechanochromic agents toward tensile strain.

Acid-Labile Amphiphilic PEO-b-PPO-b-PEO Copolymers: Degradable Poloxamer Analogs.

Poly ((ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)) triblock copolymers commonly known as poloxamers or Pluronics constitute an important class of nonionic, biocompatible surfactants. Here, a method is reported to incorporate two acid-labile acetal moieties in the backbone of poloxamers to generate acid-cleavable nonionic surfactants. Poly(propylene oxide) is functionalized by means of an acetate-protected vinyl ether to introduce acetal units. Three cleavable PEO-PPO-PEO triblock copolymers (Mn,total = 6600, 8000, 9150 g·mol(-1) ; Mn,PEO = 2200, 3600, 4750 g·mol(-1) ) have been synthesized using anionic ring-opening polymerization. The amphiphilic copolymers exhibit narrow molecular weight distributions (Ð = 1.06-1.08). Surface tension measurements reveal surface-active behavior in aqueous solution comparable to established noncleavable poloxamers. Complete hydrolysis of the labile junctions after acidic treatment is verified by size exclusion chromatography. The block copolymers have been employed as surfactants in a miniemulsion polymerization to generate polystyrene (PS) nanoparticles with mean diameters of ≈200 nm and narrow size distribution, as determined by dynamic light scattering and scanning electron microscopy. Acid-triggered precipitation facilitates removal of surfactant fragments from the nanoparticles, which simplifies purification and enables nanoparticle precipitation "on demand."

Carbohydrate nanocarriers in biomedical applications: functionalization and construction.

The specific targeting of either tumor cells or immune cells in vivo by carefully designed and appropriately surface-functionalized nanocarriers may become an effective therapeutic treatment for a variety of diseases. Carbohydrates, which are prominent biomolecules, have shown their outstanding ability in balancing the biocompatibility, stability, biodegradability, and functionality of nanocarriers. The recent applications of sugar (mono/oligosaccharides and/or polysaccharides) for the development of nanomedicines are summarized in this review, including the application of carbohydrates for the surface-functionalization of various nanocarriers and for the construction of the nanocarrier itself. Current problems and challenges are also addressed.

Carbohydrate-Based Nanocarriers Exhibiting Specific Cell Targeting with Minimum Influence from the Protein Corona.

Whenever nanoparticles encounter biological fluids like blood, proteins adsorb on their surface and form a so-called protein corona. Although its importance is widely accepted, information on the influence of surface functionalization of nanocarriers on the protein corona is still sparse, especially concerning how the functionalization of PEGylated nanocarriers with targeting agents will affect protein corona formation and how the protein corona may in turn influence the targeting effect. Herein, hydroxyethyl starch nanocarriers (HES-NCs) were prepared, PEGylated, and modified on the outer PEG layer with mannose to target dendritic cells (DCs). Their interaction with human plasma was then studied. Low overall protein adsorption with a distinct protein pattern and high specific affinity for DC binding were observed, thus indicating an efficient combination of "stealth" and targeting behavior.

[Development of a visible light-curing calcium hydroxide cement].

A visible light-curing calcium hydroxide cement is presented here and the effects of its resin matrix on the Ca2+ releasing, compressive strength of set material and the pH value of water in which set materials immersed are evaluated. Experimental results show that the effects of the selected resin matrix on Ca2+ releasing, compressive strength and pH value are significant. The calcium hydroxide cement containing BEMA or EMA and HEMA as resin matrix has good properties. The pulp capping test showed that an excellent dentin bridge appeared in dogs capped teeth at 70 days. pulp, pulp capping, calcium hydroxide, visible light-curing, dental materials

Tailoring the stealth properties of biocompatible polysaccharide nanocontainers.

Fundamental development of a biocompatible and degradable nanocarrier platform based on hydroxyethyl starch (HES) is reported. HES is a derivative of starch and possesses both high biocompatibility and improved stability against enzymatic degradation; it is used to prepare nanocapsules via the polyaddition reaction at the interface of water nanodroplets dispersed in an organic miniemulsion. The synthesized hollow nanocapsules can be loaded with hydrophilic guests in its aqueous core, tuned in size, chemically functionalized in various pathways, and show high shelf life stability. The surface of the HES nanocapsules is further functionalized with poly(ethylene glycol) via different chemistries, which substantially enhanced blood half-life time. Importantly, methods for precise and reliable quantification of the degree of functionalization are also introduced, which enable the precise control of the chemistry on the capsules' surface. The stealth properties of these capsules is studied both in-vitro and in-vivo. The functionalized nanocapsules serve as a modular platform for specific cell targeting, as they show no unspecific up-taken by different cell types and show very long circulating time in blood (up to 72 h).