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Polymer micelles are one of the most investigated nanocarriers for drug delivery; many have entered clinical trials and some are in clinic use, but their delivery systems have not yet shown the expected high therapeutic efficacy in clinics. Further understanding their in vivo behaviors, particularly how quickly and by what mechanism polymer micelles are cleared ( i. e., via micelles or unimers) once injected, is key to solving this dilemma. Herein, we hope to answer these questions for the clinically relevant polyethylene glycol- block-poly(ε-caprolactone) (PEG-PCL) and PEG- block-poly(d,l-lactide) (PEG-PDLLA) micelles. A small fraction of the hydrophobic chain ends was conjugated with a pair of fluorescence resonance energy transfer (FRET) dyes, Cy5 and Cy5.5, and used to fabricate FRET micelles whose FRET efficiency was correlated to the percentage of polymer chains in the micelles, the micelle degree. In vitro, serum proteins induced PEG-PCL micelle dissociation to some extent; mouse serum or blood surprisingly did not induce micelle dissociation but once with shear applied by a microfluidic channel caused most PEG-PCL micelles dissociated. After intravenous administration in mice, the PEG-PCL or PEG-PDLLA micelles were quickly sequestered into the liver as unimers, and the micelle degree in the blood quickly decreased to about 20%. The FRET-imaging experiments showed that in blood vessels the micelles quickly dissociated into unimers, which were found associated with albumin in blood and in liver. Thus, it is concluded that, upon intravenous injection, the shear and the bloodborne proteins (particularly albumin) induced the most (∼80%) PEG-PCL and PEG-PDLLA micelles to quickly dissociate into unimers, which were sequestered by Kupffer cells, while intact micelles were difficult to clear. These micelles were able to penetrate tumors and were very stable with cell membranes, but dissociated gradually inside cells. These findings on in vivo micelle fate and the clearance mechanism are directional for the rational design of polymer micelles for improved therapeutics; particularly, improving micelle stability in blood is the prerequisite for surface functionalizations such as introducing targeting ligands.

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In this study, a muti-benzaldehyde functionalized poly(ethylene glycol) analogue, poly(ethylene oxide-co-glycidol)-CHO (poly(EO-co-Gly)-CHO), was designed and synthesized for the first time, and applied as a cross-linker to develop an injectable hydrogel system. Simply mixing two aqueous precursor solutions of glycol chitosan (GC) and poly(EO-co-Gly)-CHO led to the in situ formation of chemically cross-linked hydrogels under physiological conditions. The cross-linking was attributed to a Schiff's base reaction between amino groups of GC and aldehyde groups of poly(EO-co-Gly)-CHO. The gelation time, water uptake, mechanical properties and network morphology of the GC/poly(EO-co-Gly) hydrogels were well modulated by varying the concentration of poly(EO-co-Gly)-CHO. Degradation of the in situ formed hydrogels was confirmed both in vitro and in vivo. The integrity of the GC/poly(EO-co-Gly) hydrogels was maintained for up to 12 weeks subcutaneously in ICR mice. The feasibility of encapsulating chondrocytes in the GC/poly(EO-co-Gly) hydrogels was assessed. Live/Dead staining assay demonstrated that the chondrocytes were highly viable in the hydrogels, and no dedifferentiation of chondrocytes was observed after 2 weeks of in vitro culture. Cell counting kit-8 assay gave evidence of the remarkably sustained proliferation of the encapsulated chondrocytes. Maintenance of the chondrocyte phenotype was also confirmed with an examination of characteristic gene expression. These features suggest that GC/poly(EO-co-Gly) hydrogels hold potential as an artificial extracellular matrix for cartilage tissue engineering.

Polymerization-induced self-assembly (PISA) was achieved by conducting an initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) at low ppm of copper catalyst concentration. A poly(oligo(ethylene oxide) methyl ether methacrylate) 50 (POEOMA 50 ) macroinitiator and stabilizer was synthesized by an aqueous ICAR ATRP using Cu II Cl 2 /tris(pyridin-2-ylmethyl)amine (TPMA) complex. Subsequently, the dispersion polymerization of benzyl methacrylate (BnMA) in ethanol was realized with a Cu II Br 2 /TPMA complex either at room temperature or at 65 °C using V-70 or AIBN as radical initiators, respectively. The effect of catalyst concentration, radical initiators, targeted degree of polymerization (DP) of PBnMA, solids content, and temperature on the molecular characteristics and self-assembly behavior of block copolymers POEOMA−PBnMA was evaluated by gel permeation chromatography (GPC), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Block copolymers assembled into spheres, wormlike aggregates, and vesicles with diameters ranging from 100 to 600 nm, depending on the temperature, solids content, and the DP of PBnMA. The effect of the temperature on the polymerization behavior and morphological evolution was attributed to the temperature-dependent plasticization of the core-forming PBnMA block above and below its glass transition temperature (T g = 54 °C).

This review summarizes recent progress in the catalysts and reactors for light alkane dehydrogenation, providing new directions for dehydrogenation technologies.

Metal sulfide catalysts were highly efficient in the activation of C−H bond for isobutane dehydrogenation, and the dehydrogenation performance was better than that of the commercial catalysts Cr 2 O 3 /Al 2 O 3 and Pt−Sn/Al 2 O 3 , providing a class of environmentally friendly and economical alternative catalysts for industrial application.

Glaser coupling reaction of alkynyl groups was used as a new ring-closure technique to synthesize monocyclic poly(ethylene oxide) (PEO) and polystyrene (PS) successfully. The linear PEO with hydroxyl groups at both ends was prepared by ring-opening polymerization (ROP) of ethylene oxide (EO) using 2,2-dimethyl-1,3-propanediol and diphenylmethylpotassium (DPMK) as co-initiators, terminated by anhydrous methanol. The linear PS with hydroxyl groups at both ends was prepared by anionic polymerization using lithium naphthalenide as initiator and terminated by EO. The propargyl-telechelic precursors (l-PEO and l-PS) were then obtained by the reaction between hydroxyl-telechelic polymers (HO-PEO-OH and HO-PS-OH) and propargyl bromide in the presence of sodium hydride. The intramolecular cyclizations of the latter were carried out in the presence of Cu(I)Br/N,N,N 0 ,N 00 ,N 00 -pentamethyldiethylenetriamine (PMDETA) under mild conditions with oxygen in the air as oxidant and the efficiency was as high as nearly 100%. The cyclic PEO and PS (c-PEO and c-PS) were characterized by GPC, 1 H NMR, FTIR, and MALDI-TOF MS. G factors (ratio of the apparent peak molar masses of cyclic product to their linear precursor) derived from GPC profiles were in the range 0.63-0.80. The highly efficient Glaser coupling took place at ambient temperature and did not need oxygen removal procedures, so it was a convenient approach for nearly quantitative preparation of cyclic polymers.