Functionalisable cyclopolymers by ring-closing metathesis

Post‐polymerisation modification of polymers is extremely beneficial in terms of designing brand new synthetic pathways toward functional complex polymers. While many chemical groups could provide a platform for chemical functionalisation, arguably one of the most versatile groups is the olefin functionality. This could be significant as the olefins do not readily interfere with common polymerisation techniques such as ring-opening polymerisation (ROP) but can be transformed into a broad range of functional groups. Ring-Closing Metathesis (RCM) is a powerful method for the preparation of cyclic compounds by the formation of new carbon-carbon double bonds. The aim of this project is utilising RCM as a post-polymerisation modification tool for preparing novel functionalisable cyclopolymers. This work includes monomer synthesis, ring-opening polymerisation and post-polymerisation modification. Whereas aliphatic polyethers are highly established polymers and used for an immense variety of applications, stereoregular cyclic architectures of polyethers mimic natural polymers remain rare in synthetic polymer chemistry. Herein we disclosed the formation of a stereocontrolled 1,4-linked six-membered functionalisable cyclopolyether (FCPE) prepared by RCM. Further post-polymerisation modification by diastereoselective dihydroxylation (DH) afforded a novel polymer family encompassing a poly(ethylene glycol) backbone and sugar-like functionalities “PEGose”. The high stereoregularity of FCPE and PEGose produced helical conformation structures. In particular, (R,R) cis PEGose structure has an extended pseudohelical structure similar to amylose. Different ring sizes of cyclopolyethers were sought from two other different starting polymers; poly(epoxy-hexene) (PEH) and poly(divinyl-oxirane) (PDVO). While divinyl oxirane (DVO) and epoxy hexene (EH) were successfully polymerised by ROP, the RCM of PEH gave mainly a cross-linked polymer. The project also attempted to expand the principle to polyesters to afford 1,4-linked six-membered functionalisable cyclopolyesters. To have the desired structure, a novel polymer of poly(vinyl glycolic acid) (PVGA) was made by ROP of a new monomer, 5-vinyl-1,3-dioxolan-4-ones (vinyl-Dox), using an aluminium salen catalyst system. However, the RCM of the last polymer was not completed even after two days of the reaction and gave mainly a cross-linked polymer. Finally, in a collaborative project, ROP of L-thionolactide was reported for the first time using aluminium salen catalysts. The polymerisation was controlled, regioselective and completed within a few hours

Evaluation the effect of high and low viscosity Nano-hydroxylapatite gel in repairing of an induced critical-size tibial bone defect in dogs: Radiolographical study

Many types of bioactive materials are categorized as bone tissue substitutes for reconstruction and regeneration of bone defects, such as nano-hydroxyapatite. The objective of the present study was to radiologically evaluate the bone healing process in experimentally induced tibial defects in dogs treated with two different viscosity concentrations of nano-hydroxyapatite gel. Twelve adult, healthy Mongrel dogs were included. A critical size bone defect of 3–0.7 cm was induced surgically in the lateral border of the tibial bone of the right limb of all dogs enrolled in this study. The dogs were then categorized into two treatment groups: Group 1 (6 dogs): The defect was filled with prepared hydroxyapatite nanogel at a concentration of 33%, and Group 2 (6 dogs) hydroxyapatite nanogel at a concentration of 24% was used as a filling material. The healing process of the tibial defect and associated clinical and radiolographical findings were recorded in all studied groups at 30 and 60 days postoperatively. The results of the current study showed complete healing of the induced defect in the absence of any signs of pain or discomfort. Radiographically, there was an increase in radiographic density in the first group at 60 days. There is continuing healing in the late stage of the bone segment with the surrounding area and a crossing callus with cortical irregularities, denoting a chronic periosteal reaction and a good healing process. In the second group, the defect was completely filled with cortical thickening, which appears denser, denoting a periosteal reaction. In conclusion, using hydroxyapatite nanogel with high viscosity as a bone substitute contributed to progressing bone tissue regeneration with good callus formation and giving perfect mechanical support to defective bone

REPAIRING OF TRANSVERSELY CUTTING ACHILLES TENDONWITH AUTOGENOUSSMALL INTESTINAL SUBMUCOSAL LAYER IN DOGS

The current trail designed toevaluate the effectivenessofusing small intestinalsubmucosa ( SIS ) to accelerate healing of Achilles tendon in thestray local breeddog .Ten healthy dogs of both sexeswere usedin thepresent studywhich randomly divided into two equal groups. Thefirstgroup;Achilles tendon acutetransversely transectedand sutured via cross mattress technique with silk suture materialwith supporting ofgypsona.The second groupacute transected tendon sutured andtreated with thesmall intestinal submucosal patch .All operative dogs inspected clinically,grossly as well ashistopathologically during different periods. Results obtained in the first group showed no contamination, no complicationsand there was no anatomical distortions were detectedat operative site except there is adhesion between tendon and neighboring tissues in the first group healing was uncompleted, suture material still presence up to 90 day.At treatment groupclinically animals lame and sign of mild stiffness appeared for three days, no serious complications, grossly was no adhesion detected, the submucosa subsided completely and complete healing occurs at 90 days postoperatively.Histologicallyatcontrol group 30 days post operativelyuncompleted healing, moderate fibroblast proliferation and inflammatory cells were presence, but at 90 dayspresence of dense connective at the site of operation. In treatmentgroup healing progress, autograft is mostly atrophied and organized with granulation at 90 days,hence healing completed perfectly at this period. In conclusion The repairing of acute transverse cutting of Achilles tendon was significantly accelerated with small intestinal submucosal layer which was absorbed andimproves the tissue quality render the native one

Cerebrospinal fluid microRNAs as potential biomarkers in Alzheimer’s disease

Alzheimer’s disease (AD) is the leading form of dementia worldwide, but its early detection and diagnosis remain a challenge. MicroRNAs (miRNAs) are a group of small endogenous RNA molecules that regulate mRNA expression. Recent evidence suggests miRNAs play an important role in the five major hallmarks of AD pathophysiology: amyloidogenesis, tauopathy, neuroinflammation, synaptic dysfunction, and neuronal death. Compared to traditional biomarkers of AD, miRNAs display a greater degree of stability in cerebrospinal fluid. Moreover, aberrant changes in miRNA expression can be measured over time to monitor and guide patient treatment. Specific miRNA profiles and combinations may also be used to distinguish AD subjects from normal controls and other causes of dementia. Because of these properties, miRNAs are now being considered as promising and potential biomarkers of AD. This review comprehensively summarizes the diagnostic potential and regulatory roles miRNAs play in AD

Olefin cross metathesis and ring-closing metathesis in polymer chemistry

The use of olefin cross metathesis in preparing functional polymers, through either pre-functionalisation of monomers or post-polymerisation functionalisation is growing in both scope and breadth. The broad functional group tolerance of olefin metathesis offers a wealth of opportunities for introducing a broad range of functional groups into the polymer backbone, tuning polymer properties and expanding potential applications. Similarly, ring-closing metathesis offers the ability to tune the polymer macrostructure and microstructure to similar effect. In this review, we explore the importance of understanding selectivity in olefin cross metathesis in designing functional polymers, the manipulation of this reactivity to prepare (multi)functional polymers, and show how polymer systems can be constructed to favour ring closing and change backbone structure and properties

Patterns of diagnostic procedures for lung cancer pathology in the Middle East and North Africa

Background: Accurate pathological diagnosis is the first critical step in the management of lung cancer. This step is important to determine the histological subtype of the cancer and to identify any actionable targets. Our study aimed at evaluating the patterns of procedures used to obtain pathological diagnosis of lung cancer in the Middle East and North Africa (MENA) Region. Methods: Data of consecutive patients with the diagnosis of non-small cell lung cancer (NSCLC) were collected from participating centers from different countries in the MENA Region. Methods of obtaining tissue diagnosis and workup were analyzed to determine the practice patterns of obtaining tissue diagnosis of lung cancer. Results: A total of 566 patients were recruited from 10 centers in 5 countries including Saudi Arabia, United Arab Emirates (UAE), Qatar, Lebanon and Algeria. Majority of patients were males (78.1%) with a median age of 61 years (range, 22-89 years). Obtaining tissue diagnosis was successful in the first attempt in 72.3% of patients, while 16.4% and 6.3% of patients required 2nd and 3rd attempt, respectively. The success in first attempt was as follows: image guided biopsy (91%), surgical biopsy (88%), endobronchial biopsy (79%) and cytology (30%). The success in the second attempt was as follows; surgical biopsy (100%), image guided biopsy (95%), endobronchial biopsy (65%), cytology (25%). Conclusions: More than quarter of the patients required repeated biopsy in the MENA Region. Image guided biopsy has the highest initial yield. Implementing clear process and multidisciplinary guidelines about the selection of diagnostic procedures is needed. © 2019 Journal of Thoracic Disease. All rights reserved