Tough Bioplastics from Babassu Oil-Based Acrylic Monomer, Hemicellulose Xylan, and Carnauba Wax.

We describe here the fabrication, characterization, and properties of tough bioplastics made of a babassu oil-based acrylic polymer (PBBM), hemicellulose xylan grafted with PBBM chains, and carnauba wax (CW). The plastic was primarily designed to obtain bioderived materials that can replace low-density polyethylene (LDPE) in certain food packaging applications. To obtain plastic, the radical polymerization of an original babassu oil-based acrylic monomer (BBM) in the presence of xylan macromolecules modified with maleic anhydride (X-MA) was conducted. The polymerization resulted in a material (PBBM-X) mostly consisting of highly branched PBBM/X-MA macromolecules. PBBM-X has a glass transition of 42 °C, a storage modulus of 130 MPa (at 25 °C, RT), and a Young's modulus of 30 MPa at RT. To increase the moduli, we blended PBBM-X with carnauba wax, a natural material with a high modulus and a melting temperature of ~80 °C. It was found that PBBM-X is compatible with the wax, as evidenced by the alternation of the material's thermal transitions and the co-crystallization of BBM side alkyl fragments with CW. As a result, the PBBM-X/CW blend containing 40% of the wax had a storage modulus of 475 MPa (RT) and a Young's modulus of 248 MPa (RT), which is close to that of LDPE. As polyethylene, the PBBM-X and PBBM-X/CW bioplastics have the typical stress-strain behavior demonstrated by ductile (tough) plastics. However, the bioplastic's yield strength and elongation-at-yield are considerably lower than those of LDPE. We evaluated the moisture barrier properties of the PBBM-X/(40%)CW material and found that the bioplastic's water vapor permeability (WVP) is quite close to that of LDPE. Our bioderived material demonstrates a WVP that is comparable to polyethylene terephthalate and lower than the WVP of nylon and polystyrene. Taking into account the obtained results, the fabricated materials can be considered as polyethylene alternatives to provide sustainability in plastics production in the packaging areas where LDPE currently dominates.

Factors associated with alveolar bone depth mesial to the mandibular third molars after orthodontic protraction.

INTRODUCTION: The objective of this research was to study the factors associated with the alveolar bone depth mesial to the mandibular third molars (M8) after the mandibular second (M7) and third molars were protracted into the space of the mandibular first molars (M6), which were newly extracted for orthodontic treatment or extracted more than 1 year before treatment. METHODS: This retrospective study included 57 adult patients (mean age 23.40 ± 4.40 years) in whom M6 were newly extracted for orthodontic treatment or extracted more than 1 year before treatment. The alveolar bone depth mesial to M8 was measured on posttreatment panoramic radiographs. The vertical, horizontal, and angular changes of M8 were measured on both pre- and posttreatment panoramic radiographs. Linear correlation and regression analyses were conducted to explore the factors associated with the alveolar bone depth mesial to M8. RESULTS: The alveolar bone conditions of M6 (R= -0.391, P <0.001) and the vertical movement directions of M8 (R= -0.433, P <0.001) were significant factors associated with the alveolar bone depth mesial to M8 after orthodontic protraction. CONCLUSIONS: Without considering the pretreatment periodontal status of M8, patients with M6 extracted exceeding 1 year before treatment and with M8 extruded after orthodontic protraction may exhibit deeper alveolar bone depth mesial to M8.

Potential Role of Integrin α5ß1/Focal Adhesion Kinase (FAK) and Actin Cytoskeleton in the Mechanotransduction and Response of Human Gingival Fibroblasts Cultured on a 3-Dimension Lactide-Co-Glycolide (3D PLGA) Scaffold.

BACKGROUND The stability of orthodontic treatment is thought to be significantly affected by the compression and retraction of gingival tissues, but the underlying molecular mechanism is not fully elucidated. The objectives of our study were to explore the effects of mechanical force on the ECM-integrin-cytoskeleton linkage response in human gingival fibroblasts (HGFs) cultured on 3-dimension (3D) lactide-co-glycolide (PLGA) biological scaffold and to further study the mechanotransduction pathways that could be involved. MATERIAL AND METHODS A compressive force of 25 g/m² was applied to the HGFs-PLGA 3D co-cultured model. Rhodamine-phalloidin staining was used to evaluate the filamentous actin (F-actin) cytoskeleton. The expression level of type I collagen (COL-1) and the activation of the integrin alpha5ß1/focal adhesion kinase (FAK) signaling pathway were determined by using real-time PCR and Western blotting analysis. The impacts of the applied force on the expression levels of FAK, phosphorylated focal adhesion kinase (p-FAK), and COL-1 were also measured in cells treated with integrin alpha5ß1 inhibitor (Ac-PHSCN-NH 2, ATN-161). RESULTS Mechanical force increased the expression of integrin alpha5ß1, FAK (p-FAK), and COL-1 in HGFs, and induced the formation of stress fibers. Blocking integrin alpha5ß1 reduced the expression of FAK (p-FAK), while the expression of COL-1 was not fully inhibited. CONCLUSIONS The integrin alpha5ß1/FAK signaling pathway and actin cytoskeleton appear to be involved in the mechanotransduction of HGFs. There could be other mechanisms involved in the promotion effect of mechanical force on collagen synthesis in addition to the integrin alpha5ß1 pathway.

Effects of Smad4 on the expression of caspase­3 and Bcl­2 in human gingival fibroblasts cultured on 3D PLGA scaffolds induced by compressive force.

Human gingival fibroblasts (HGFs) are the main cells that comprise gingival tissue, where they transfer mechanical signals under physiological and pathological conditions. The exact mechanism underlying gingival tissue reconstruction under compressive forces remains unclear. The present study aimed to explore the effects of Smad4, caspase­3 and Bcl­2 on the proliferation of HGFs induced by compressive force. HGFs were cultured on poly(lactide­co­glycolide) (PLGA) scaffolds under an optimal compressive force of 25 g/cm2. Cell viability was determined via Cell Counting Kit­8 assays at 0, 12, 24, 48 and 72 h. The expression levels of Smad4, caspase­3 and Bcl­2 were measured via reverse transcription­quantitative PCR and western blotting. The application of compressive force on HGFs for 24 h resulted in a significant increase in cell proliferation and Bcl­2 expression, but a significant decrease in the expression of Smad4 and caspase­3; however, inverse trends were observed by 72 h. Subsequently, a lentivirus was used to overexpress Smad4 in HGFs, which attenuated the effects of compressive force on HGF proliferation and Bcl­2 expression, but enhanced caspase­3 expression, suggesting that Smad4 may regulate compressive force­induced apoptosis in HGFs. In conclusion, these findings increased understanding regarding the mechanisms of compressive force­induced HGF proliferation and apoptosis, which may provide further insight for improving the efficacy and stability of orthodontic treatment.

Synthesis, characterization and antibacterial properties of novel cellulose acetate sorbate.

In this paper, cellulose acetate (CA) with different degree of substitution (DS) of 2.17∼1.75 were obtained through hydrolysis of cellulose diacetate (CDA). Furthermore, novel cellulose acetate sorbate (CASA) were synthesized by esterification of CA and sorbic acid (SA). The DS of sorbyl groups varied within 0.12-1.20 by adjusting composition ratio, reaction time and temperature. Fourier transform infrared spectroscopy (FTIR), Nuclear magnetic resonance spectroscopy (NMR) and elemental analysis were used to determine the chemical structure. Scanning electron microscopy (SEM) indicated CASA showed denser surface morphology than CA. Thermal properties and crystallization of CASA were slightly decrease but did not affect their service performance. Specifically, all CASA showed excellent antibacterial ability, the maximum relative bactericidal rate reached 81.5 % for Escherichia coli (E. coli) and 95.4 % for Staphylococcus aureus (S. aureus), respectively. Moreover, the obtained CASA films using casting technique possessed good mechanical properties. These antibacterial CASA exhibited potential application in healthcare fields.

A Visiting Professorship in Undergraduate Medical Education at the University of Alberta: Reflections on possibilities for medical humanities in China, and elsewhere.

This article was migrated. The article was marked as recommended. Enhancing humanities in medical education is a pressing concern in China. Similar to other countries, medical education in China evolved over the past century to emphasize bioscience and technology in treating illness and disease. Increasing recognition of the limitations of biomedical technology led to emergence of the medical humanities in the West in the latter half of the 20 th century, an interdisciplinary area that has continued to expand and grow. In China and elsewhere, activity in this area developed somewhat later. Ongoing patient-doctor disputes and decline in public trust in the medical profession in China has led many to advocate for enhanced emphasis on humanism and medical humanities. In 2017, the Chinese government introduced new healthcare reforms which included an education and training plan that promotes medical humanities teaching. Global developments have led to a wide variety of models and approaches that may be considered in cultivating medical humanities and humanism in China. With the support of China Medical University in Shenyang, Liaoning Province, PRC, Professor Wei visited the Faculty of Medicine & Dentistry at the University of Alberta through the 2019/20 academic year. This article provides an overview of a wide array of medical humanities teaching and learning opportunities associated with the undergraduate medical education program at the University of Alberta. Professor Wei reflects on possibilities for medical humanities in medical education in China given all she learned and experienced as a visiting professor at the University of Alberta, which may be of interest to others who are also developing new approaches to introducing medical humanities as part of their health professions education program. Additional reflections regarding possibilities for global medical humanities are also offered.

Mechanical force promotes the proliferation and extracellular matrix synthesis of human gingival fibroblasts cultured on 3D PLGA scaffolds via TGF­ß expression.

Human gingival fibroblasts (HGFs) are responsible for connective tissue repair and scarring, and are exposed to mechanical forces under physiological and pathological conditions. The exact mechanisms underlying gingival tissue reconstruction under mechanical forces remain unclear. The present study aimfed to investigate the effects of mechanical forces on the proliferation and extracellular matrix synthesis in HGFs by establishing a 3­dimensional (3D) HGF culture model using poly(lactide­co­glycolide) (PLGA) scaffolds. HGFs were cultured in 3D PLGA scaffolds and a mechanical force of 0, 5, 15, 25 or 35 g/cm2 was applied to HGFs for 24 h. A mechanical force of 25 g/cm2 induced the highest proliferation rate, and thus was selected for subsequent experiments. Cell viability was determined using the MTT assay at 0, 24, 48 and 72 h. The expression levels of type I collagen (COL­1) and matrix metallopeptidase (MMP)­1 were examined by reverse transcription­quantitative polymerase chain reaction and ELISA, and transforming growth factor (TGF)­ß expression was evaluated by ELISA. The application of mechanical force on HGFs cultured on the 3D PLGA scaffolds resulted in a significant increase in cell proliferation and COL­1 expression, as well as a decrease in MMP­1 expression. A TGF­ß1 inhibitor was also applied, which attenuated the effects of mechanical force on HGF proliferation, and COL­1 and MMP­1 expression, thus suggesting that TGF­ß signaling pathways may mediate the mechanical force­induced alterations observed in HGFs. In conclusion, these findings helped to clarify the mechanisms underlying mechanical force­induced HGF proliferation and ECM synthesis, which may promote the development of targeted therapeutics to treat various diseases, including gingival atrophy caused by orthodontic treatment.