2-Hydroxylethyl methacrylate (HEMA), a tooth restoration component, exerts its genotoxic effects in human gingival fibroblasts trough methacrylic acid, an immediate product of its degradation

HEMA (2-hydroxyethyl methacrylate), a methacrylate commonly used in dentistry, was reported to induce genotoxic effects, but their mechanism is not fully understood. HEMA may be degraded by the oral cavity esterases or through mechanical stress following the chewing process. Methacrylic acid (MAA) is the primary product of HEMA degradation. In the present work we compared cytotoxic and genotoxic effects induced by HEMA and MAA in human gingival fibroblasts (HGFs). A 6-h exposure to HEMA or MAA induced a weak decrease in the viability of HGFs. Neither HEMA nor MAA induced strand breaks in the isolated plasmid DNA, but both compounds evoked DNA damage in HGFs, as evaluated by the alkaline comet assay. Oxidative modifications to the DNA bases were monitored by the DNA repair enzymes Endo III and Fpg. DNA damage induced by HEMA and MAA was not persistent and was removed during a 120 min repair incubation. Results from the neutral comet assay indicated that both compounds induced DNA double strand breaks (DSBs) and they were confirmed by the γ-H2AX assay. Both compounds induced apoptosis and perturbed the cell cycle. Therefore, methacrylic acid, a product of HEMA degradation, may be involved in its cytotoxic and genotoxic action

Concomitant Control of Mechanical Properties and Degradation in Resorbable Elastomer-like Materials Using Stereochemistry and Stoichiometry for Soft Tissue Engineering

YesComplex biological tissues are highly viscoelastic and dynamic. Efforts to repair or replace cartilage, tendon, muscle, and vasculature using materials that facilitate repair and regeneration have been ongoing for decades. However, materials that possess the mechanical, chemical and resorption characteristics necessary to recapitulate these tissues have been difficult to mimic using synthetic resorbable biomaterials. Herein, we report a series of resorbable elastomer-like materials that are compositionally identical and possess varying ratios of cis:trans double bonds in the backbone. These features afford concomitant control over the mechanical and surface eroding degradation properties of these materials. We show the materials can be functionalized post-polymerization with bioactive species and enhance cell adhesion. Furthermore, an in vivo rat model demonstrates that degradation and resorption are dependent on succinate stoichiometry in the elastomers and the results show limited inflammation highlighting their potential for use in soft tissue regeneration and drug delivery

Synthesis of carboxylated derivatives of poly(isobutylene-co-isoprene) by azide–alkyne “click” chemistry

The final publication is available at Springer via https://dx.doi.org/10.1038/s41428-018-0130-yThe synthesis of carboxylated derivatives of poly(isobutylene-co-isoprene) (isobutylene–isoprene rubber, IIR) with substitution levels ranging from 1 to 4 mol% and different spacer lengths was accomplished through azide–alkyne Huisgen cycloaddition. Azido-functionalized IIR was first prepared by reacting brominated IIR with sodium azide to full conversion in a 90:10 tetrahydrofuran/N,N-dimethylacetamide mixture. The click reaction of azido-functionalized IIR with acetylenic acids, which was carried out using the copper(I) bromide/N,N,N′,N″,N″-pentamethyldiethylenetriamine catalyst system in tetrahydrofuran, yielded carboxylated IIRs. The products were characterized by 1H NMR and FT-IR spectroscopy, and their molecular weight was determined by size exclusion chromatography analysis. The conversion to carboxylated groups reached up to 100% as determined by NMR spectroscopy but was highly dependent on the type of solvent and the amounts of catalysts and reactants used in the procedures.ARLANXEO Canada Inc.Natural Sciences and Engineering Research Council (NSERC) of Canad

Morphological Evolution of Chloroaluminum Phthalocyanine Thin-films Followed In-situ By Atomic-force Microscopy

Chloroaluminum phthalocyanine (ClAlPc) thin films, vacuum sublimed on SnO2-covered glass substrates, were exposed to KCl solutions of various pH values (from 2.0 to 8.0) in the fluid cell of an atomic force microscope (AFM). The evolution of the surface morphology of the film was followed in situ. Complementary experiments on the film morphology were also performed by scanning electron microscopy. The chemical evolution of the film surface was obtained by time-of-flight secondary ion mass spectrometry. On the one hand, when ClAlPc is immersed in KCl solutions at pH = 2.0 or 3.0, a slow dissolution of the outermost surface of the film occurs. This is followed by the hydrolysis of ClAlPc in solution to form first the hydroxyaluminum phthalocyanine (HOAlPc) and then the mu-oxo-dimer, PcAlOAlPc. The latter recrystallizes as long needles on top of the initial film, thereby changing drastically its surface morphology. On the ether hand, when ClAlPc is immersed in KCl solutions at pH = 5.7 or 8.0, the hydrolysis of ClAlPc occurs at the surface of the film without noticeable morphological modifications. A subsequent immersion of the film in KCl at pH = 2.0 may have the same effect on the film morphology as the one previously described for pH = 2.0 or 3.0, as long as mechanical energy is provided to the film, either by ultrasound or by the cantilever tip of the AFM. When the latter is involved, the source of mechanical energy is localized in space and patterning of the surface morphology becomes possible