Dataset Information

Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

ABSTRACT: Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked ?-d-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The copolymers were characterized by ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and used in the formation of supramolecular hydrogels through the addition of ?-cyclodextrin (?-CD) to induce crosslinking. These hydrogels possessed thixotropic properties; shear-thinning to liquid upon agitation but settling into gels at rest. In contrast to most of the other hydrogels produced through the use of poly(ethylene glycol) (PEG)-grafted polymers, the pectin-PEGMA/?-CD hydrogels were unaffected by temperature changes.

SUBMITTER: Chan SY

PROVIDER: S-EPMC6432130 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

Chan Siew Yin SY Choo Wee Sim WS Young David James DJ Loh Xian Jun XJ

Polymers 20161118 11

Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-d-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The cop ...[more]

PMID: 30974681

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Project description:Growth factors have been shown to be potent mediators of osteogenesis. However, their use in tissue-engineered scaffolds not only can be costly but also can induce undesired responses in surrounding tissues. Thus, the ability to specifically induce osteogenic differentiation in the absence of exogenous growth factors through manipulation of scaffold material properties would be desirable for bone regeneration. Previous research indicates that addition of inorganic or hydrophobic components to organic, hydrophilic scaffolds can enhance multipotent stem cell (MSC) osteogenesis. However, the combined impact of scaffold inorganic content and hydrophobicity on MSC behavior has not been systematically explored, particularly in three-dimensional (3D) culture systems. The aim of the present study was therefore to examine the effects of simultaneous increases in scaffold hydrophobicity and inorganic content on MSC osteogenic fate decisions in a 3D culture environment toward the development of intrinsically osteoinductive scaffolds. Mouse 10T½ MSCs were encapsulated in a series of novel scaffolds composed of varying levels of hydrophobic, inorganic poly(dimethylsiloxane) (PDMS) and hydrophilic, organic poly(ethylene glycol) (PEG). After 21 days of culture, increased levels of osteoblast markers, runx2 and osteocalcin, were observed in scaffolds with increased PDMS content. Bone extracellular matrix (ECM) molecules, collagen I and calcium phosphate, were also elevated in formulations with higher PDMS:PEG ratios. Importantly, this osteogenic response appeared to be specific in that markers for chondrocytic, smooth muscle cell, and adipocytic lineages were not similarly affected by variations in scaffold PDMS content. As anticipated, the increase in scaffold hydrophobicity accompanying increasing PDMS levels was associated with elevated scaffold serum protein adsorption. Thus, scaffold inorganic content combined with alterations in adsorbed serum proteins may underlie the observed cell behavior.

Project description:In this work we present a fundamental analysis based on small-angle scattering, linear rheology and differential scanning calorimetry (DSC) experiments of the role of different hydrogen bonding (H-bonding) types on the structure and dynamics of chain-end modified poly(ethylene glycol) (PEG) in bulk. As such bifunctional PEG with a molar mass below the entanglement mass Me is symmetrically end-functionalized with three different hydrogen bonding (H-bonding) groups: thymine-1-acetic acid (thy), diamino-triazine (dat) and 2-ureido-4[1H]-pyrimidinone (upy). A linear block copolymer structure and a Newtonian-like dynamics is observed for PEG-thy/dat while results for PEG-upy structure and dynamics reveal a sphere and a network-like behavior, respectively. These observations are concomitant with an increase of the Flory-Huggins interaction parameter from PEG-thy/dat to PEG-upy that is used to quantify the difference between the H-bonding types. The upy association into spherical clusters is established by the Percus-Yevick approximation that models the inter-particle structure factor for PEG-upy. Moreover, the viscosity study reveals for PEG-upy a shear thickening behavior interpreted in terms of the free path model and related to the time for PEG-upy to dissociate from the upy clusters, seen as virtual crosslinks of the formed network. Moreover, a second relaxation time of different nature is also obtained from the complex shear modulus measurements of PEG-upy by the inverse of the angular frequency where G' and G'' crosses from the network-like to glass-like transition relaxation time, which is related to the segmental friction of PEG-upy polymeric network strands. In fact, not only do PEG-thy/dat and PEG-upy have different viscoelastic properties, but the relaxation times found for PEG-upy are much slower than the ones for PEG-thy/dat. However, the activation energy related to the association dynamics is very similar for both PEG-thy/dat and PEG-upy. Concerning the segmental dynamics, the glass transition temperature obtained from both rheological and calorimetric analysis is similar and increases for PEG-upy while for PEG-thy/dat is almost independent of association behavior. Our results show how supramolecular PEG properties vary by modifying the H-bonding association type and changing the molecular Flory-Huggins interaction parameter, which can be further explored for possible applications.

Dataset Information

Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

Publications

Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

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