Search results for "polymers"

Statistical Analysis of a Method to Predict Drug–Polymer Miscibility

2015

In this study, a method proposed to predict drug-polymer miscibility from differential scanning calorimetry measurements was subjected to statistical analysis. The method is relatively fast and inexpensive and has gained popularity as a result of the increasing interest in the formulation of drugs as amorphous solid dispersions. However, it does not include a standard statistical assessment of the experimental uncertainty by means of a confidence interval. In addition, it applies a routine mathematical operation known as "transformation to linearity," which previously has been shown to be subject to a substantial bias. The statistical analysis performed in this present study revealed that t…

Torsional effects on the molecular polarizabilities of the benzothiazole (A)-benzobisthiazole (B) oligomer A-B13-A

1996

Abstract We outline a method for the calculation of multipole moments and molecular dipole-dipole ( ), dipole-quadrupole ( ), and quadrupole-quadrupole ( ) polarizabilities, which we have successfully applied to benzothiazole (A)-benzobisthiazole (B) oligomer A-B13-A. Three model rotational isomers have been characterized: (1) the fully planar (000) rotational isomer; (2) a conformation with each unit rotated 10° in the alternate direction (+−+), and (3) a rotational isomer with each unit rotated 10° in the same direction (+++). The dipole moment, μ , is smaller for isomers 000 and +−+ than for isomer +++. The calculation of , , and has been performed by use of the interacting induced dipol…

A bioinspired metal–organic approach to cross-linked functional 3D nanofibrous hydro- and aero-gels with effective mixture separation of nucleobases …

2020

The direct reaction between Cu(CH3COO)2 and uracil-1-acetic acid in water gives rise to the formation of a hydrogel consisting of entangled nanometric ribbons of a crystalline antiferromagnetic 1D Cu(ii) coordination polymer (CP) decorated with biocompatible uracil nucleobases. This hydrogel is the precursor for the preparation of a meso/macroporous ultralight aerogel that shows a remarkable Young's modulus. As a proof-of-concept of the molecular recognition capability of the terminal uracil moieties anchored at Cu(ii) CP chains, this material has been tested as the selective stationary phase for the separation of nucleobase derivatives in HPLC columns.

Oxidative Addition of Halogens on Open Metal Sites in a Microporous Spin-Crossover Coordination Polymer

2009

Conformations, Transverse Fluctuations and Crossover Dynamics of a Semi-Flexible Chain in Two Dimensions

2014

We present a unified scaling description for the dynamics of monomers of a semiflexible chain under good solvent condition in the free draining limit. We consider both the cases where the contour length $L$ is comparable to the persistence length $\ell_p$ and the case $L\gg \ell_p$. Our theory captures the early time monomer dynamics of a stiff chain characterized by $t^{3/4}$ dependence for the mean square displacement(MSD) of the monomers, but predicts a first crossover to the Rouse regime of $t^{2\nu/{1+2\nu}}$ for $\tau_1 \sim \ell_p^3$, and a second crossover to the purely diffusive dynamics for the entire chain at $\tau_2 \sim L^{5/2}$. We confirm the predictions of this scaling descr…

Temperature-controlled poly(propylene) glycol hydrophobicity on the formation of inclusion complexes with modified cyclodextrins. A DSC and ITC study.

2011

The study highlighted the main forces driving the formation of hydroxypropyl-cyclodextrins (HP-CDs) + poly(propylene) glycol 725 g mol(-1) inclusion complexes. The temperature parameter was chosen as the variable to modulate the hydrophobicity of the polymer, and consequently ITC experiments as functions of temperature as well as DSC measurements were done in a systematic way. The polymer is not included into HP-α-CD, it is strongly bound to HP-β-CD and it is floating in HP-γ-CD. The stability of the inclusion complexes is entropy controlled. The gain of the entropy is a unique result compared to the opposite literature findings for inclusion complexes based on polymers and CDs. This peculi…

Uptake of polymeric nanoparticles in a human induced pluripotent stem cell-based blood-brain barrier model: Impact of size, material, and protein cor…

2021

The blood–brain barrier (BBB) maintains the homeostasis of the central nervous system, which is one of the reasons for the treatments of brain disorders being challenging in nature. Nanoparticles (NPs) have been seen as potential drug delivery systems to the brain overcoming the tight barrier of endothelial cells. Using a BBB model system based on human induced pluripotent stem cells (iPSCs), the impact of polymeric nanoparticles has been studied in relation to nanoparticle size, material, and protein corona. PLGA [poly(lactic-co-glycolic acid)] and PLLA [poly(d,l-lactide)] nanoparticles stabilized with Tween® 80 were synthesized (50 and 100 nm). iPSCs were differentiated into human brain m…

Core Cross-Linked Polymeric Micelles for Specific Iron Delivery: Inducing Sterile Inflammation in Macrophages.

2021

Iron is an essential co-factor for cellular processes. In the immune system, it can activate macrophages and represents a potential therapeutic for various diseases. To specifically deliver iron to macrophages, iron oxide nanoparticles are embedded in polymeric micelles of reactive polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine). Upon surface functionalization via dihydrolipoic acid, iron oxide cores act as crosslinker themselves and undergo chemoselective disulfide bond formation with the surrounding poly(S-ethylsulfonyl-l-cysteine) block, yielding glutathione-responsive core cross-linked polymeric micelles (CCPMs). When applied to primary murine and human macrophages, these nanoparti…

α-Chymotrypsin-Catalyzed Reaction Confined in Block-Copolymer Vesicles

2010

Herein the reactivity of the enzyme α-chymotrypsin in the confinement of polystyrene-block-poly(acrylic acid) (PS-b-PAA) vesicles was investigated. Enzyme and substrate molecules were encapsulated in PS-b-PAA vesicles with internal diameters ranging from 26 nm to 165 nm during the formation of the vesicles. While the loading efficiencies of enzyme and substrate molecules were practically identical for vesicles of identical size, they were found to increase with decreasing vesicle size. The kinetics of the α-chymotrypsin catalyzed hydrolysis of N-succinyl-Ala-Ala-Phe-7-amido-4-methylcoumarin (AMC) was evaluated following the increase of the absorption of the product 7-amino-4-methylcoumarin …

A Monte Carlo Study of Knots in Long Double-Stranded DNA Chains.

2016

We determine knotting probabilities and typical sizes of knots in double-stranded DNA for chains of up to half a million base pairs with computer simulations of a coarse-grained bead-stick model: Single trefoil knots and composite knots which include at least one trefoil as a prime factor are shown to be common in DNA chains exceeding 250,000 base pairs, assuming physiologically relevant salt conditions. The analysis is motivated by the emergence of DNA nanopore sequencing technology, as knots are a potential cause of erroneous nucleotide reads in nanopore sequencing devices and may severely limit read lengths in the foreseeable future. Even though our coarse-grained model is only based on …