Novel pentablock copolymer (PLA–PCL–PEG–PCL–PLA)-based nanoparticles for controlled drug delivery: effect of copolymer compositions on the crystallinity of copolymers and in vitro drug release profile from nanoparticles

The purpose of this investigation was to design novel pentablock copolymers (polylactide–polycaprolactone–polyethylene glycol–polycaprolactone–polylactide) (PLA–PCL–PEG–PCL–PLA) to prepare nanoparticle formulations which provide continuous delivery of steroids over a longer duration with minimal burst effect. Another purpose was to evaluate the effect of poly(l-lactide) (PLLA) and poly(d,l-lactide) (PDLLA) incorporation on crystallinity of pentablock copolymers and in vitro release profile of triamcinolone acetonide (selected as model drug) from nanoparticles. PLA–PCL–PEG–PCL–PLA copolymers with different block ratio of PCL/PLA segment were synthesized. Release of triamcinolone acetonide from nanoparticles was significantly affected by crystallinity of the copolymers. Burst release of triamcinolone acetonide from nanoparticles was significantly minimized with incorporation of proper ratio of PDLLA in the existing triblock (PCL–PEG–PCL) copolymer. Moreover, pentablock copolymer-based nanoparticles exhibited continuous release of triamcinolone acetonide. Pentablock copolymer-based nanoparticles can be utilized to achieve continuous near–zero-order delivery of corticosteroids from nanoparticles without any burst effect.     

Germafluorene conjugated copolymer——synthesis and applications in blue-light-emitting diodes and host materials

A germafluorene-fluorene copolymer was successfully obtained via Suzuki polymerization. The germanium containing copolymer has an efficient blue light emission under the ultraviolet irradiation and its single layer EL device showed the highest brightness of 2630 cd/m² at 7.8 V and the highest efficiency of 0.301 lm/W at 6.2 V. The copolymer can also serve as the host material for phosphorescent metal complexes with the maximum brightness of 15600 cd/m² and the quantum efficiency of 8.5%. The results are quite promising and promise that as its analogs of fluorene and silafluorene, germafluorene is an excellent building block for blue light-emitting polymers and host materials. Supported by the National Natural Science Foundation of China (Grant Nos. 60325412, 90406021, and 50428303) and the Scientific Research Foundation of Nanjing University of Posts and Telecommunications (NUPT) (Grant No. NY206073)     

The “bottom-up” synthesis and applications of persistent luminescence nanoparticles

正Persistent luminescence refers to the phenomenon whereby luminescence remains after excitation ceases.In the past few decades,various kinds of persistent luminescent materials have been developed and widely employed in numerous applications,such as security signs,medical diagnostics and photocatalysis.Persistent luminescent materials offer distinctive advantages for biomedical applications,especially for bioimaging,as they can efficiently avoid autofluorescence and tissue-scattered light interference[1].Since     

Chiral helical polyacetylene�Cvinyl polymer core/shell nanoparticles: preparation and application to optically active composite films

Optically active core/shell nanoparticles (NPs) were prepared by combining aqueous catalytic microemulsion polymerization of a monosubstituted N-propargylsulfamide monomer and free-radical polymerization of two vinyl monomers (MMA and BA) in one specific system. In such novel NPs, poly(N-propargylsulfamide) forming the cores took helical conformations of a predominant handedness, endowing the NPs with interesting optical activities. The use of two vinyl monomers simultaneously in one system led to NPs with desirable dispersity and morphology. From the NP emulsions, optically active composite films were prepared with poly(vinyl alcohol) as supporting material, attesting to the potential applications of the optically active core/shell NPs. Following the strategy, other novel core/shell NPs and advanced materials can be anticipated. The current investigations provide large possibilities to realize practical applications of highly interesting helical polyacetylenes.     

Substituent effects in infrared spectroscopy—VII. Meta and para substituted methanesulphonanilides

Substituent effects on the NH frequencies of the conformers of methanesulphonanilides, their cyclic dimers and their hydrogen bonded complexes with acetonitrile have been analysed by means of the Hammet equation. An electron-withdrawing substituent may either increase or decrease ν(NH) in the XC₆H₄NHY series according to the electronic nature of the Y group. This can be explained by the non-monotonic dependence of the NH stretching frequency on the ionic character of the NH bond.     

Synergistic mechanical effects of calcite micro- and nanoparticles and β-nucleation in polypropylene copolymers

For improving the understanding of mechanical effects in micro- and nanocomposites based on polypropylene (PP) copolymers and precipitated or ground calcium carbonate (PCC or GCC), especially in the presence of significant portions of the β-modification, a set of compounds based on different PP grades and fillers with optional β-nucleation prepared by melt compounding was studied. A synergistic improvement of mechanical properties by a combination of calcite particles and β-nucleation was found for two of the investigated high-impact base polymers up to 20 wt.% of nanofiller. While in the past research positive toughness effects were always limited to PP homopolymers with a moderate original impact strength and to particles of less than 100 nm average diameter, the toughness of high impact ethylene–propylene impact copolymers could be increased by more than 150% even at sub-zero temperatures where the failure behaviour is determined by the disperse elastomer phase.     

The σ− selection rule in electron attachment and autoionization of diatomic molecules

It is shown theoretically that Σ⁺ ⇐ Σ⁻ transitions in electron attachment and autionization of diatomic molecules are forbidden. For the verification of this selection rule, two experimental examples are given.     

Substituent effects in infrared spectroscopy—carbonyl stretching frequency in substituted acetonaphthones,acetylfluorenes and acetylbiphenyls

The carbonyl stretching frequencies of several ring substituted acetonaphthones, acetylfluorenes and acetylbiphenyls have been measured in CCl₄/CHCl₃ solvent and correlated with the substituent constants. The data are also analysed by DSP equation to evaluate ϱ_I and ϱ_R. Compared to acetylfluorenes, acetylbiphenyls transmit substituent effects to a lesser extent, which is explained in terms of the noncoplanarity of the two phenyl rings in the later system.     

Microstructure evolution in Stöber-type silica nanoparticles and their in vitro apatite deposition

Prepared via Stöber-type sol–gel routes were three types of silica particles of <1 μm in size: pure silica, Ca-involving silica, and chitosan/alginate-coated silica with a polymershell-silica core structure. Calcium ions were impregnated in the organic layers of the polymer-coated silica particle. The sol–gel procedure was applied to tetraethoxysilane dissolved in an ethanol/water mixture, while Ca–silica was derived from CaCl₂-containing ethanol/water solutions. Scanning and transmission electron micrograph analyses indicated that those silica particles consisted of ~10 nm primary particles, the Ca–silica particles (~500 nm) were larger than the Ca-free ones (~200 nm) and that their size increased with the Ca concentration in the precursor solutions. From ¹H- and ²⁹Si- magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra and ²⁹Si cross-polarization NMR spectra, the mechanism of primary particle agglomeration and degradation of the secondary particles in saline were discussed in terms of the content of H₂O molecules and >Si–OH as well as hydrogen bonding interactions among them. In addition, the Ca–silica and core-shell silica deposited apatite in Kokubo’s simulated body fluid. Thus, the present Ca–silica and polymer-coated silica particles were suggested to be applicable to injectable bone fillers for bone generation.     

Au nanoparticles based ultra-fast “Turn-On” fluorescent sensor for detection of biothiols and its application in living cell imaging

Au or other metal nanostructures have the ability to strongly quench the fluorescence of fluorophores.This feature has made AuNP-conjugates attractive for the construction of platforms for various bioanalytes to overcome the limitations of small molecule fluorophores(poor solubility,long reaction time).In this paper,an ultrafast "Turn-On" fluo rescent sensor for biothiols was constructed.The sensor is based on the fluorescent resonance energy transfer(FRET) effect between the fluorophore(PN) and AuNPs,which effectively quenches the fluorescence of the fluorophore.In the presence of thiols,PN is displaced and released from AuNP surfaces,and thus,the fluorescence is rapidly restored.The sensor features appreciable water solubility and ultrafast response time(a few seconds for Cys).In addition,it exhibits high selectivity and a detection limit as low as 12 nmol/L for Hcy.Moreover,the sensor presents good biocompatibility and has been successfully applied for imaging biothiols in living cells.     

Environment- and sequence-dependence of helical type in membrane-spanning peptides composed of β3-amino acids

Transmembrane (TM) β-peptides comprised of acyclic β(3)-amino acids demonstrate equilibrium between 12- and 14-helical structures in an environment- and sequence-dependent manner. Circular dichroism (CD) spectra of TM β(3)-peptides may be described as linear combinations of the 12- and 14-helical CD spectra. The apparent malleability of β(3)-substituted acyclic β-peptides has practical implications for foldamer design, as it suggests that both the 14-helix and 12-helix might be reasonable platforms for molecular recognition.     

Thermodynamics of alternating copolymer of styrene and CO in the 0—600 K region

The temperature dependence of heat capacity and the temperatures and enthalpies of physical transitions of the alternating copolymer of styrene and CO were studied in the 5—600 K region by the adiabatic vacuum and dynamic calorimetric techniques. The heat of combustion of the copolymer was measured at 298.15 K in a calorimeter with a static bomb and an isothermal shield. The thermodynamic parameters of glass transition and fusion were determined. The thermodynamic functions in the 0—550 K region and thermodynamic characteristics of the formation of the copolymer from simple substances at T = 298.15 K and p = 101.325 kPa were calculated. The thermodynamic parameters of alternating copolymerization in the bulk of styrene and CO were calculated in the 0—350 K region at a standard pressure.     

Correlation between glass transition and crystallization phenomena in context of Meyer–Neldel rule

The physical origin of the glass transition and its possible connection with crystallization is still an unresolved problem of glass science. Recent publications demonstrate the strong evidence of intrinsic relation between glass transition and crystallization phenomena. Here, we study this problem by using Meyer–Neldel rule (MNR) as a tool. The observation of MNR in thermally activated non-isothermal crystallization was verified by us in past. The objective of the present work is to check the applicability of MNR for thermally activated non-isothermal glass transition and crystallization in some chalcogenide glasses. We found that like crystallization, the glass transition phenomenon also obeys the MNR.     

Thermodynamics of alternating copolymer of propylene and CO in the 0–550 K region

The temperature dependences of the heat capacity and the temperatures and enthalpies of physical transitions of the alternating copolymer of propylene and CO were studied in the 5–550 K region by adiabatic vacuum and dynamic calorimetry techniques. The heat of combustion of the copolymer was measured at 298.15 K in a calorimeter with a static bomb and an isothermal shield. The thermodynamic parameters of glass transition and fusing were estimated. The thermodynamic functions in the 0–450 K region and the thermodynamic characteristics of the formation of the copolymer from simple substances atT=298.15 K andp=101.325 kPa were calculated. The thermodynamic parameters of the alternating copolymerization of bulk propylene and CO were calculated in the 0–450 K region at standard pressure.     

Structures of an infinite helical water chain and discrete lattice water in metal–organic framework structures

Two supramolecular complexes Ni[(Py)₂C(OH)₂]₂·(CH₃COO)₂·4H₂O 1 and Co[(Py)₂C(OH)₂]₂·(CH₃COO)₂·2H₂O 2 have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. The X-ray diffraction analysis indicates that the center metal (Ni²⁺ and Co²⁺) ions having the same coordination environments are chelated by two pyridyl N atoms and a hydroxyl O atom of the gem-diol ligand in an octahedral geometry. In 1, the lattice water molecules form infinite single helical chains, while in 2, two lattice water molecules are discrete. In their crystal structures, intermolecular O–H···O and C–H···O hydrogen bonds form an extensive three-dimensional network, which consolidates the crystal packing.     

ESI-TEM imaging of surfactants and ions sorbed in Stöber silica nanoparticles

The sorption of surfactants and NaCl in silica nanosized particles creates unexpected spatial distributions of solutes that were evidenced by electron spectroscopy imaging in the transmission electron microscope (ESI/TEM). The spectral images show that simple ions (Na(+), Cl(-), Br(-)) are actually absorbed within the particles irrespective of their charges, while surfactant chains are adsorbed at the particle surfaces. The expected effect of the surfactants on particle aggregation is also observed in the micrographs. In the case of salt, close-packed silica particle arrays are formed at low ionic strength, but only coarse aggregates form at higher salt concentrations. The particles absorb both Na(+) and Cl(-) ions in similar amounts, from 0.5 mol L(-)(1) NaCl, but Na(+) ions are depleted from the particles' immediate outer vicinity, where Cl(-) ions are in turn accumulated. These results confirm that St?ber silica nanoparticles are highly porous and reveal their potential usefulness as carriers of small molecules and ions, due to the small particle size, exceptional colloidal stability, and this newly found sorption behavior.     

Cyclization and halogenation of substituted o-allylphenols with diacetoxyiodobenzene in the presence of iodine or bromine

Substituted 2-halomethyl-2,3-dihydrobenzofurans were synthesized in one pot and in mild yield from substituted o-allylphenols with diacetoxyiodobenzene in the presence of 12 or Br2 in dry CH2Cl2 under reflux.