Recent Advances in Synthetic Bioelastomers

This article reviews the degradability of chemically synthesized bioelastomers, mainly designed for soft tissue repair. These bioelastomers involve biodegradable polyurethanes, polyphosphazenes, linear and crosslinked poly(ether/ester)s, poly(ε-caprolactone) copolymers, poly(1,3-trimethylene carbonate) and their copolymers, poly(polyol sebacate)s, poly(diol-citrates) and poly(ester amide)s. The in vitro and in vivo degradation mechanisms and impact factors influencing degradation behaviors are discussed. In addition, the molecular designs, synthesis methods, structure properties, mechanical properties, biocompatibility and potential applications of these bioelastomers were also presented

Photonic molecules and spectral engineering

This chapter reviews the fundamental optical properties and applications of pho-tonic molecules (PMs) - photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and en-hanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically-induced transparency, and enhancing sensitivity of microcavity-based bio-, stress- and rotation-sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally-tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.Comment: A review book chapter: 29 pages, 19 figure

Triple-A syndrome with prominent ophthalmic features and a novel mutation in the AAAS gene: a case report.

Triple-A syndrome (Allgrove syndrome) is an autosomal recessive disorder characterized by adrenal insufficiency, alacrima, achalasia, and - occasionally - autonomic instability. Mutations have been found in the AAAS gene on 12q13

The development and characterization of degradable, segmented polyurethanes containing amino acid-based chain extenders

grantor: University of TorontoDegradable segmented polyurethanes were attained through the incorporation of experimental amino acid-based (L-phenylalanine and L-lysine), ester containing chain extenders. The phenylalanine-based chain extender was synthesized and purified to a good final yield (~45%). A protected form of L-lysine (N-[epsilon]-carbobenzoxy-L-lysine) was used to avoid unwanted crosslinking reactions during polymerization. Difficulties with low yield (~1%) and incomplete diesterification of the lysine-based chain extender were mitigated by alteration of the linking diol chemistry. A low toxicity L-lysine-based diisocyanate (2,6-diisocyanato methyl caproate, LDI) was used to synthesize the degradable polyurethanes. The effect of soft segment type (polycaprolactone diol, PCL and polyethylene oxide, PEO) and chain extender type and content on physicochemical properties was evaluated. The polymers ranged from completely amorphous to semicrystalline. Tensile strengths varied from 1.0 to 30.8 MPa. Bulk hydrophilicity ranged from water soluble to 1.3% water uptake, depending primarily on soft segment chemistry and content. Generally, the PEO-containing polyurethanes were weak, hydrophilic materials while the PCL polyurethanes were strong, hydrophobic elastomers. The carbobenzoxy (CBZ) protecting group of the L-lysine ester chain extended polyurethane was removed by hydrogenolysis. Nuclear magnetic resonance spectroscopic analysis indicated that deprotection resulted in a 37 mol% reduction in CBZ content. However, deprotection resulted in backbone urethane cleavage leading to reduced molecular weight and loss of hard segment. The 'in vitro' degradation properties of the polyurethanes were studied in buffer and enzyme solutions to evaluate the susceptibility to passive and enzymatic hydrolysis, respectively. Inclusion of amino acid-based chain extenders conferred enhanced susceptibility towards enzymatic attack by two model enzymes (chymotrypsin and trypsin) and increasing chain extender content led to increasing enzymatic erosion. Enzymatic degradation and erosion proceeded via a surface-limited mechanism, causing little change in bulk properties. The magnitude of erosion was enzyme-dependent, making it possible to tune erosion based on the enzyme profile at the application site. Lastly, the 'in vitro' cytocompatibility of the polyurethane degradation products generated during buffer incubation was evaluated by MTT assay. The polyurethane degradation products were not found to elicit a significant cytotoxic response (<75% cell viability) for any exposure time suggesting that the polyurethanes may be useful for biomedical applications.Ph.D