Physiological features of periodontal regeneration and approaches for periodontal tissue engineering utilizing periodontal ligament cells

Experimental studies have shown that the potential of periodontal regeneration seems to be limited by the regenerative capacity of the cells involved. The regeneration of damaged periodontal tissues is mediated by various periodontal cells and is regulated by a vast array of extracellular matrix informational molecules that induce both selective and nonselective responses in different cell lineages and their precursors. In this paper, we first review periodontal ligament tissue and its different cell subpopulations including fibroblasts and paravascular stem cells, and their functions during the development and homeostasis of periodontal tissues. Because conventional periodontal regeneration methods remain insufficient to obtain a complete and reliable periodontal regeneration, the concept of periodontal tissue engineering has been based on the generation of the conditions necessary to improve the healing of periodontal tissues. Additionally, the potential of periodontal ligament cells for use in periodontal tissue engineering to overcome the limitations of conventional periodontal regenerative therapies is discussed, followed by an update of the recent progress and future directions of research utilizing periodontal ligament cells for predictable periodontal regeneration.     

Engineering an allosteric binding site for aminoglycosides into TEM1-β-Lactamase

Allosteric regulation of enzyme activity is a remarkable property of many biological catalysts. Up till now, engineering an allosteric regulation into native, unregulated enzymes has been achieved by the creation of hybrid proteins in which a natural receptor, whose conformation is controlled by ligand binding, is inserted into an enzyme structure. Here, we describe a monomeric enzyme, TEM1-β-lactamase, that features an allosteric aminoglycoside binding site created de novo by directed-evolution methods. β-Lactamases are highly efficient enzymes involved in the resistance of bacteria against β-lactam antibiotics, such as penicillin. Aminoglycosides constitute another class of antibiotics that prevent bacterial protein synthesis, and are neither substrates nor ligands of the native β-lactamases. Here we show that the engineered enzyme is regulated by the binding of kanamycin and other aminoglycosides. Kinetic and structural analyses indicate that the activation mechanism involves expulsion of an inhibitor that binds to an additional, fortuitous site on the engineered protein. These analyses also led to the defining of conditions that allowed an aminoglycoside to be detected at low concentration.     

Structural and optical properties of chlorinated plasma polymers

Amorphous hydrogenated chlorinated carbon (a-C:H:Cl) films were produced by the plasma polymerization of chloroform–acetylene–argon mixtures in a radiofrequency plasma enhanced chemical vapor deposition system. The main parameter of interest was the proportion of chloroform in the feed, R_C, which was varied from 0 to 80%. Deposition rates of 80 nm min^? 1 were typical for the chlorinated films. Infrared reflection–absorption spectroscopy revealed the presence of C–Cl groups in all the films produced with chloroform in the feed. X-ray photoelectron spectroscopy confirmed this finding, and revealed a saturation of the chlorine content at ~ 47 at.% for R_C ≥ 40%. The refractive index and optical gap, E₀₄, of the films were roughly in the 1.6 to 1.7, and the 2.8 to 3.7 eV range. These values were calculated from transmission ultraviolet–visible-near infrared spectra. Chlorination leads to an increase in the water surface contact angle from ~ 40° to ~ 77°.     

Samarium‐Promoted Asymmetric Aldol–Tishchenko Reaction: Synthesis of Amino Acid‐Derived 4‐Amino‐1,3‐diols

A samarium‐mediated novel synthesis of enantiopure 4‐amino‐1,3‐diols is carried out through a samarium‐promoted aldol–Tishchenko reaction starting from chiral α′‐amino‐α‐chloro ketones (derived from natural α‐amino acids) and aldehydes. The process takes place with moderate levels of stereoselectivity and in high yields. A mechanism is proposed to explain these results while the absolute configuration and structure of the aldol–Tishchenko adducts were established by X‐ray analysis. This method has also been utilized for the synthesis of enigmols, 1‐deoxysphingoid base analogues.     

A Theory of Vulnerability of Water Pipe Network (TVWPN)

The main objective of this paper is to introduce the proposed theory of vulnerability of water pipe network (TVWPN) and, in particular, its theoretical concepts. These concepts have a basis in the structural vulnerability theory (Agarwal et al., Civ Eng Environ Syst 18(2):141–165, 2001a, J Struct Saf 23(3):203–220, 2001b; Lu et al., Struct Eng 77(18):17–23, 1999; Lu 1998; Pinto 2002; Pinto et al., J Struct Saf 24:107–122, 2002; Yu 1997). The fundamental contribution of this theory is to help design water pipe networks (WPN) more robust against damage to the pipelines. This is achieved through an analysis of the form of the network. The application of the TVWPN is presented through an example of a water pipe network.     

An Efficient Catalytic Chromium‐Mediated Iodocyclopropanation Reaction: Stereoselective Synthesis of Iodocyclopropanecarboxamides

A catalytic chromium‐mediated novel synthesis of iodocyclopropanecarboxamides is reported. This reaction can be carried out on aromatic (E)‐ or (Z)‐α,β‐unsaturated amides in which the CC double bond is di‐ or trisubstituted. This process takes place with total stereospecificity and the new C I stereogenic center is generated with high stereoselectivity. Some synthetic applications of the obtained iodocyclopropanecarboxamides are also reported. The structures of the iodocyclopropanes and derivatives were established by X‐ray analysis.     

Effect of graphene oxide on the pH-responsive drug release from supramolecular hydrogels

Polypseudorotaxane (PPR) hydrogels formed by inclusion complexes between poly(ethylene glycol) (PEG) and α-cyclodextrin (α-CD) are highlighted as promising biomaterial for drug delivery. Here, we report a novel injectable PPR hydrogel containing graphene oxide (GO) for pH-responsive controlled release of doxorubicin hydrochloride (DOX). Our results showed that the gelation rates of the PEG/α-CD supramolecular structures could be tailored depending on the reagent concentrations. The formation of PEG/α-CD inclusion complexes was confirmed by TEM and XRD, the latter further confirming that GO restricts their formation. The supramolecular hydrogels were easily loaded with DOX by simple addition into the PEG solution before the complex formation with the α-CD solution. Noteworthy, disruption of ionic interactions between DOX and GO in the nanocomposite at pH = 5.5 resulted in higher DOX release than under physiological conditions (pH = 7.4). This pH dependence was barely observed in pure PPR hydrogel. These findings introduce DOX-loaded supramolecular hydrogels nanocomposites as promising carriers for pH-responsive and therefore localized, drug delivery systems.