Novel acrylic formulations incorporating an amphiphilic macromonomer, Triton methacrylate MT, have been prepared to be applied in intervertebral disks (IVD) restoration processes. The solid phase of the formulations is composed of poly (methyl methacrylate), PMMA, incorporating in some cases chondroitin sulfate, CS, as a regenerative bioactive molecule, whereas the liquid phase is constituted by MT and 2-hydroxyethyl methacrylate, HEMA, and in some formulations acrylic acid, AA, was also added. These are prepared similarly to acrylic bone cement formulations. The obtained curing parameters, with maximum temperatures in the range of 41-72 degrees C, make them suitable to be applied as injectable systems. Glass transition temperatures and swelling degree have also been determined. Mechanical properties such as compressive, stress relaxation, and shear tests have been analyzed for all of the prepared IVD formulations exhibiting shape memory characteristics and a pronounced elastic behavior that make them as excellent candidates for the intervertebral application.
This article explores the synthesis of a novel methacrylic macromonomer with an amphiphilic character derived from poly(ethylene glycol) tert-octylphenyl ether (MT) and its respective homopolymer. To know their reactivity in radical copolymerization reactions with methyl methacrylate (MMA), a model monomer (MTm) was synthesized to determine the reactivity ratios and compare them with the low molar fractions of copolymers of MT with MMA because they were difficult to isolate. They were r MTm ϭ 0.97 and r MMA ϭ 0.95. The compositional diagrams when representing the weight fraction of MT and MTm in the feed and the copolymer suggested that a clear correlation exists between the experimental points of the model monomer MTm and the macromonomer MT ones, suggesting that the length of the side poly(ethylene oxide) chain does not affect the reactivity of the methacrylic double bond in the prepared monomers for this type of polymerization reaction. The reactivity ratios of the copolymers have a tendency for the formation of random or Bernoullian copolymers. The glass-transition temperatures (T g 's) of the prepared copolymers were determined by differential scanning calorimetry, deviated from the Fox equation, and discussed on the basis of treatments that consider the influence of the monomeric units along the copolymer chains, determining the T g of the corresponding alternating dyads.
New injectable acrylic formulations have been prepared to be applied in restoration processes for intervertebral disks (IVDs). The solid phase of the formulations is composed of poly(methyl methacrylate) (PMMA), incorporating in some cases chondroitin sulphate (CS) as a regenerative bioactive molecule, whereas the liquid phase is constituted by an amphiphilic macromonomer (MT), 2-hydroxyethyl methacrylate (HEMA) and, in some formulations, acrylic acid (AA). The curing parameters and the mechanical properties of the IVD formulations make them excellent candidates for intervertebral application. In vitro and in vivo evaluation of the prepared IVD formulations is described in terms of CS release, surface analysis after immersion in SBF solutions, and biocompatibility studies based on MTT assay and Alamar blue test, as well as in vivo implantation in female Wistar rats, by injection of the IVD formulations followed by histological evaluations to assess tissue response.
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