Effect of the Cross-Linking Density on the Swelling and Rheological Behavior of Ester-Bridged β-Cyclodextrin Nanosponges

The cross-linking density influences the physicochemical properties of cyclodextrin-based nanosponges (CD-NSs). Although the effect of the cross-linker type and content on the NSs performance has been investigated, a detailed study of the cross-linking density has never been performed. In this contribution, nine ester-bridged NSs based on β-cyclodextrin (β-CD) and different quantities of pyromellitic dianhydride (PMDA), used as a cross-linking agent in stoichiometric proportions of 2, 3, 4, 5, 6, 7, 8, 9, and 10 moles of PMDA for each mole of CD, were synthesized and characterized in terms of swelling and rheological properties. The results, from the swelling experiments, exploiting Flory–Rehner theory, and rheology, strongly showed a cross-linker content-dependent behavior. The study of cross-linking density allowed to shed light on the efficiency of the synthesis reaction methods. Overall, our study demonstrates that by varying the amount of cross-linking agent, the cross-linked structure of the NSs matrix can be controlled effectively. As PMDA βCD-NSs have emerged over the years as a highly versatile class of materials with potential applications in various fields, this study represents the first step towards a full understanding of the correlation between their structure and properties, which is a key requirement to effectively tune their synthesis reaction in view of any specific future application or industrial scale-up.

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Cross-linking of histones with dimethyl 3,3′-dithiobispropionimidate. Interference by a one-end reaction modifying histones at lysine amino groups

Biochemical Journal ◽

10.1042/bj2241019 ◽

1984 ◽

Vol 224 (3) ◽

pp. 1019-1022

Author(s):

E Kotthaus ◽

W H Strätling

Keyword(s):

Insoluble Fraction ◽

Cross Linking ◽

Amino Groups ◽

Large Excess ◽

Histone Dimers ◽

Acid Solubility ◽

Cross Linker ◽

The Cross ◽

Linker Molecules

We have studied the HClO4-solubility of histones H1 and H5 in hen erythrocyte nuclei after treatment with the cross-linker dimethyl 3,3′-dithiobispropionimidate (DTPI). The amount of acid-soluble, non-cross-linked, H1 and H5 histones was drastically decreased, and that of acid-soluble H1/H5 histone dimers went through an optimum as the DTPI concentration was raised. Incubation of the HClO4-insoluble fraction with 2-mercaptoethanol regenerated the acid-solubility of H1/H5 histones in this fraction. When purified H1/H5 histones were treated with increasing concentrations of DTPI under non-cross-linking conditions, the amount of HClO4-soluble histones also greatly decreased, but to a much lesser extent if the DTPI treatment was followed by reduction with 2-mercaptoethanol. This decrease was inversely correlated to the proportion of amino groups modified. It is concluded that, when the cross-linker was used in large excess, the cross-linking reaction competed with a one-end reaction modifying the histones at lysine amino groups by cross-linker molecules, of which the imidoester groups that had not reacted were hydrolysed. It is suggested that this modification produced the changes in acid-solubility.

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Study on Cross-Linking Degree of Polyethylene

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.658.56 ◽

2013 ◽

Vol 658 ◽

pp. 56-60

Author(s):

Li Qiu Zou ◽

Guang Feng Wu

Keyword(s):

Extraction Method ◽

Low Density Polyethylene ◽

Cross Linking ◽

Low Density ◽

Dicumyl Peroxide ◽

Linear Low Density Polyethylene ◽

Gel Content ◽

Complete Decomposition ◽

Cross Linker ◽

The Cross

In this paper, the linear low density polyethylene (LLDPE) was melted and cross-linked by dicumyl peroxide (DCP) used to prepare cross-linked polyethylene (XPE). The gel content was determined by extraction method. The effect of content of cross-linker, cross- linked time, cross-linked temperature and other factors on the gel content were studied. It was found that the extraction time should be 18h for XPE. The gel content increased with the increasing of cross-linked time. When the cross-linked time was 10-15min, DCP was almost complete decomposition. The gel content was basically stable when the cross-linked temperature was 170-175 oC. The maximum of gel fraction was about 90%.

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Denovo Identification of Cross-linked Peptides via Isotope Coded Linkage Tags

10.1101/2020.04.12.037614 ◽

2020 ◽

Author(s):

Harsha P. Gunawardena

Keyword(s):

Database Search ◽

Cross Linking ◽

Interacting Proteins ◽

Accurate Identification ◽

Isotopic Signatures ◽

Fragment Ions ◽

Polypeptide Sequence ◽

Cross Linker ◽

The Cross ◽

Polypeptide Chains

ABSTRACTAn isotope labeled cross-linker (asymmetric d4-DTSSP) was developed to streamline the efforts required for the detection of cross-linked peptides. The cross-linking and mass spectrometry strategy we call Isotope Tagging of Interacting Proteins (iTIP) has improved the specificity of detecting cross-linked peptides and the accurate identification of the interacting peptide sequences via the incorporation of isotopic signatures that are readily observed in the MS/MS spectra. All tryptic peptides derived from the cross-linking reactions of a protein complex are first subjected to ETD-MS2 which results in the facile cleavage of the cross-linker at the disulfide bond and the release of inter-linked polypeptide chains that are detected as a pair of peaks (doublets) in the MS2 spectrum. The constituent peptide halves that are tagged by the heavy/light ends of the cross-linker are easily mass-selected from all other fragment ions, and each polypeptide half is then subjected to CID or HCD-MS3 for identification. The MS3 spectra are subjected to conventional database search strategies available for the sequencing of linear or non-cross-linked peptides. The confident identification of each polypeptide is further assisted by the presence of a stable isotope labeled fragment ions that localizes the cross-linked site on the polypeptide sequence.

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Influence of the chemical structure of cross-linking agents on properties of thermally reversible networks

Pure and Applied Chemistry ◽

10.1515/pac-2016-0804 ◽

2016 ◽

Vol 88 (12) ◽

pp. 1103-1116 ◽

Cited By ~ 5

Author(s):

Lorenzo Massimo Polgar ◽

Robin R.J. Cerpentier ◽

Gijs H. Vermeij ◽

Francesco Picchioni ◽

Martin van Duin

Keyword(s):

Chemical Structure ◽

Chemical Conversion ◽

Rubber Matrix ◽

Cross Linking ◽

Cross Link ◽

Molar Amount ◽

Link Density ◽

Cross Link Density ◽

Cross Linker ◽

The Cross

Abstract It is well-known that the properties of cross-linked rubbers are strongly affected by the cross-link density. In this work it is shown that for thermoreversibly cross-linked elastomers, the type and length of the cross-linker also have a significant effect. A homologous series of diamine and bismaleimide cross-linkers was used to cross-link maleic-anhydride-grafted EPM irreversibly and furan-modified EPM thermoreversibly, respectively. Bismaleimide cross-linkers with a polarity close to that of EPM and a relatively low melting point have a better solubility in the rubber matrix, which results in higher chemical conversion and, thus, higher cross-link densities at the same molar amount of cross-linker. Samples cross-linked with different spacers (aromatic and aliphatic spacers of different lengths) were compared at the same cross-link density to interpret the effects on the material properties. The rigid character of the short aliphatic and the aromatic cross-linkers accounts for the observed increase in hardness, Young´s modulus and tensile strength with respect to the longer, more flexible aliphatic cross-linkers. In conclusion, the structure of the cross-linking agent can be considered as an alternative variable in tuning the rubber properties, especially for thermoreversibly cross-linked rubber.

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Modulation of Entrapment Efficiency and In Vitro Release Properties of BSA-Loaded Chitosan Microparticles Cross-Linked with Citric Acid as a Potential Protein–Drug Delivery System

Materials ◽

10.3390/ma13081989 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1989 ◽

Cited By ~ 1

Author(s):

Natalia Sedyakina ◽

Andrey Kuskov ◽

Kelly Velonia ◽

Nataliya Feldman ◽

Sergey Lutsenko ◽

...

Keyword(s):

Drug Delivery ◽

Citric Acid ◽

In Vitro Release ◽

Entrapment Efficiency ◽

Cross Linking ◽

Release Mechanism ◽

Model Protein ◽

Cross Linker ◽

The Cross

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties was performed using different chitosan-to-cross-linker mass ratios and pH-values during fabrication of the microparticles. Non-cross-linked and cross-linked microparticles were studied in terms of size (4–12 μm), zeta potential (−15.7 to 12.8 mV), erosion (39.7–75.6%), a model protein encapsulation efficiency (bovine serum albumin) (6.8–27.6%), and loading capacity (10.4–40%). Fourier transform infrared spectroscopy and X-ray diffraction confirmed the ionic interaction between the protonated amine groups of chitosan and the carboxylate ions of the cross-linking agent. Scanning electron microscopy revealed that the non-cross-linked microparticles had an uneven shape with wrinkled surfaces, while the cross-linked formulations were spherical in shape with smooth surfaces. On the basis of these data, the role of the surfactant and microparticle structure on the release mechanism was proposed. Control of the microparticle shape and release mechanisms is expected to be crucial in developing carriers for the controlled delivery of proteins and peptides.

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Gelatin-Based Hydrogels through Homobifunctional Triazolinediones Targeting Tyrosine Residues

Molecules ◽

10.3390/molecules24030589 ◽

2019 ◽

Vol 24 (3) ◽

pp. 589 ◽

Cited By ~ 2

Author(s):

Roberto Guizzardi ◽

Luca Vaghi ◽

Marcello Marelli ◽

Antonino Natalello ◽

Ivan Andreosso ◽

...

Keyword(s):

Thermal Stability ◽

Drug Delivery Systems ◽

Chemical Nature ◽

Mechanical Stability ◽

Cross Linking ◽

Swelling Properties ◽

Tyrosine Residues ◽

Cross Linker ◽

The Cross ◽

Chemical Cross Linking

Gelatin is a biopolymer with interesting properties that can be useful for biomaterial design for different applications such as drug delivery systems, or 3D scaffolds for tissue engineering. However, gelatin suffers from poor mechanical stability at physiological temperature, hence methods for improving its properties are highly desirable. In the present work, a new chemical cross-linking strategy based on triazolinedione ene-type chemistry towards stable hydrogel is proposed. Two different homobifunctional 1,2,4-triazoline-3,5(4H)-diones, namely 4,4′-hexane-1,6-diylbis(3H-1,2,4-triazoline-3,5(4H)-dione) 1 and 4,4′-[methylenebis(4,1-phenylene)]bis(3H-1,2,4-triazoline-3,5(4H)-dione) 2 were used as cross-linkers in different ratio to tyrosine residues in gelatin. The reaction was proved effective in all experimented conditions and hydrogels featured with different thermal stability were obtained. In general, the higher the cross-linker/tyrosine ratio, the more thermostable the hydrogel. The swelling properties are strictly dependent upon the chemical nature of the cross-linker.

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In Situ Cross-linking Polymerization-Induced Self-Assembly: Not Only Generates Cross-linked Structures But Also Promotes Morphology Transition by the Cross-linker

Polymer Chemistry ◽

10.1039/d1py00046b ◽

2021 ◽

Author(s):

Jamshid Kadirkhanov ◽

Cheng-Lin Yang ◽

Zi-Xuan Chang ◽

Ren-Man Zhu ◽

Cai-Yuan Pan ◽

...

Keyword(s):

Self Assembly ◽

Cross Linking ◽

Morphology Transition ◽

Convenient Approach ◽

Cross Linker ◽

The Cross

Compared with the post-polymerization cross-linking strategy, in situ cross-linking by divinyl comonomers in polymerization-induced self-assembly (PISA) is a more straightforward and convenient approach to produce structurally stabilized nano-objects. However, cross-linking...

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Photoinduced DNA Interstrand Cross-Linking by Benzene Derivatives: Leaving Groups Determine the Efficiency of the Cross-Linker

The Journal of Organic Chemistry ◽

10.1021/acs.joc.0c02234 ◽

2020 ◽

Vol 86 (1) ◽

pp. 493-506

Author(s):

Heli Fan ◽

Xiaohua Peng

Keyword(s):

Cross Linking ◽

Benzene Derivatives ◽

Cross Linker ◽

The Cross ◽

Leaving Groups

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Cranberry Juice Extract Rapidly Protects Demineralized Dentin against Digestion and Inhibits Its Gelatinolytic Activity

Materials ◽

10.3390/ma14133637 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3637

Author(s):

Yong Wang ◽

Austin Green ◽

Xiaomei Yao ◽

Hang Liu ◽

Saleha Nisar ◽

...

Keyword(s):

Grape Seed ◽

Dental Composite ◽

Cross Linking ◽

Cranberry Juice ◽

Composite Restorations ◽

Dentin Collagen ◽

Cross Linker ◽

The Cross ◽

Demineralized Dentin

Improving the longevity of composite restorations has proven to be difficult when they are bonded to dentin. Dentin demineralization leaves collagen fibrils susceptible to enzymatic digestion, which causes breakdown of the resin–dentin interface. Therefore, measures for counteracting the enzymatic environment by enhancing dentin collagen’s resistance to degradation have the potential to improve the durability of dental composite restorations. This study aimed to evaluate the effects of polyphenol-rich extracts and a chemical cross-linker on the cross-linking interaction, resistance to digestion, and endogenous matrix metalloproteinase (MMP) activities of dentin collagen under clinically relevant conditions. Ten-µm-thick films were cut from dentin slabs of non-carious extracted human third molars. Following demineralization, polyphenol-rich extracts—including grape seed (GSE), green tea (GTE), and cranberry juice (CJE)—or chemical cross-linker carbodiimide with n-hydroxysuccinimide (EDC/NHS) were applied to the demineralized dentin surfaces for 30 s. The collagen cross-linking, bio-stabilization, and gelatinolytic activities of MMPs 2 and 9 were studied by using Fourier-transform infrared spectroscopy, weight loss, hydroxyproline release, scanning/transmission electron microscopy, and in situ zymography. All treatments significantly increased resistance to collagenase degradation and reduced the gelatinolytic MMP activity of dentin collagen compared to the untreated control. The CJE- and GSE-treated groups were more resistant to digestion than the GTE- or EDC/NHS-treated ones (p < 0.05), which was consistent with the cross-linking interaction found with FTIR and the in situ performance on the acid-etched dentin surface found with SEM/TEM. The collagen films treated with CJE showed the lowest MMP activity, followed by GSE, GTE, and, finally, EDC/NHS. The CJE-treated dentin collagen rapidly increased its resistance to digestion and MMP inhibition. An application of CJE as short as 30 s may be a clinically feasible approach to improving the longevity of dentin bonding in composite restorations.

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