Self-Healing Tile Sets

Biology provides the synthetic chemist with a tantalizing and frustrating challenge: to create complex objects, defined from the molecular scale up to meters, that construct themselves from elementary components, and perhaps even reproduce themselves. This is the challenge of bottom-up fabrication. The most compelling answer to this challenge was formulated in the early 1980s by Ned Seeman, who realized that the information carried by DNA strands provides a means to program molecular self-assembly, with potential applications including DNA scaffolds for crystallography [19] or for molecular electronic circuits [15]. This insight opened the doors to engineering with the rich set of phenomena available in nucleic acid chemistry [20]

Proofreading tile sets: Error correction for algorithmic self-assembly

For robust molecular implementation of tile-based algorithmic self-assembly, methods for reducing errors must be developed. Previous studies suggested that by control of physical conditions, such as temperature and the concentration of tiles, errors (ε) can be reduced to an arbitrarily low rate - but at the cost of reduced speed (r) for the self-assembly process. For tile sets directly implementing blocked cellular automata, it was shown that r ≈ βε^2 was optimal. Here, we show that an improved construction, which we refer to as proofreading tile sets, can in principle exploit the cooperativity of tile assembly reactions to dramatically improve the scaling behavior to r ≈ βε and better. This suggests that existing DNA-based molecular tile approaches may be improved to produce macroscopic algorithmic crystals with few errors. Generalizations and limitations of the proofreading tile set construction are discussed

NASA Tech Briefs, January 2012

Contents of this issue are: (1) Energy-Based Tetrahedron Sensor for High-Temperature, High-Pressure Environments (2) Handheld Universal Diagnostic Sensor (3) Large-Area Vacuum Ultraviolet Sensors (4) Fiber Bragg Grating Sensor System for Monitoring Smart Composite Aerospace Structures (5) Health-Enabled Smart Sensor Fusion Technology (6) Extended-Range Passive RFID and Sensor Tags (7) Hybrid Collaborative Learning for Classification and Clustering in Sensor Networks (8) Self-Healing, Inflatable, Rigidizable Shelter (9) Improvements in Cold-Plate Fabrication (10) Technique for Radiometer and Antenna Array Calibration - TRAAC (11) Real-Time Cognitive Computing Architecture for Data Fusion in a Dynamic Environment (12) Programmable Digital Controller (13) Use of CCSDS Packets Over SpaceWire to Control Hardware (14) Key Decision Record Creation and Approval Module (15) Enhanced Graphics for Extended Scale Range (16) Debris Examination Using Ballistic and Radar Integrated Software (17) Data Distribution System (DDS) and Solar Dynamic Observatory Ground Station (SDOGS) (18) Integration Manager (19) Eclipse-Free-Time Assessment Tool for IRIS (20) Automated and Manual Rocket Crater Measurement Software (21) MATLAB Stability and Control Toolbox Trim and Static Stability Module (22) Patched Conic Trajectory Code (23) Ring Image Analyzer (24) SureTrak Probability of Impact Display (25) Implementation of a Non-Metallic Barrier in an Electric Motor (26) Multi-Mission Radioisotope Thermoelectric Generator Heat Exchangers for the Mars Science Laboratory Rover (27) Uniform Dust Distributor for Testing Radiative Emittance of Dust-Coated Surfaces (28) MicroProbe Small Unmanned Aerial System (29) Highly Stable and Active Catalyst for Sabatier Reactions (30) Better Proton-Conducting Polymers for Fuel-Cell Membranes (31) CCD Camera Lens Interface for Real-Time Theodolite Alignment (32) Peregrine 100-km Sounding Rocket Project (33) SOFIA Closed- and Open-Door Aerodynamic Analyses (34) Sonic Thermometer for High-Altitude Balloons (35) Near-Infrared Photon-Counting Camera for High-Sensitivity Observations (36) Integrated Optics Achromatic Nuller for Stellar Interferometry (37) High-Speed Digital Interferometry (38) Ultra-Miniature Lidar Scanner for Launch Range Data Collection (39) Shape and Color Features for Object Recognition Search (40) Explanation Capabilities for Behavior-Based Robot Control (41) A DNA-Inspired Encryption Methodology for Secure, Mobile Ad Hoc Networks (42) Quality Control Method for a Micro-Nano-Channel Microfabricated Device (43) Corner-Cube Retroreflector Instrument for Advanced Lunar Laser Ranging (44) Electrospray Collection of Lunar Dust (45) Fabrication of a Kilopixel Array of Superconducting Microcalorimeters with Microstripline Wiring Spacecraft Attitude Tracking and Maneuver Using Combined Magnetic Actuators (46) Coherent Detector for Near-Angle Scattering and Polarization Characterization of Telescope Mirror Coating

Layer-by-Layer Assembly of Supported Lipid Bilayer Poly-l-Lysine Multilayers.

Multilayer lipid membranes perform many important functions in biology, such as electrical isolation (myelination of axons), increased surface area for biocatalytic purposes (thylakoid grana and mitochondrial cristae), and sequential processing (golgi cisternae). Here we develop a simple layer-by-layer methodology to form lipid multilayers via vesicle rupture onto existing supported lipid bilayers (SLBs) using poly l-lysine (PLL) as an electrostatic polymer linker. The assembly process was monitored at the macroscale by quartz crystal microbalance with dissipation (QCM-D) and the nanoscale by atomic force microscopy (AFM) for up to six lipid bilayers. By varying buffer pH and PLL chain length, we show that longer chains (≥300 kDa) at pH 9.0 form thicker polymer supported multilayers, while at low pH and shorter length PLL, we create close packed layers (average lipid bilayers separations of 2.8 and 0.8 nm, respectively). Fluorescence recovery after photobleaching (FRAP) and AFM were used to show that the diffusion of lipid and three different membrane proteins in the multilayered membranes has little dependence on lipid stack number or separation between membranes. These approaches provide a straightforward route to creating the complex membrane structures that are found throughout nature, allowing possible applications in areas such as energy production and biosensing while developing our understanding of the biological processes at play

Desenvolvimento de uma nova membrana bioativa para o tratamento de lesões da pele

Skin and soft tissue infections (SSTIs) have high rates of morbidity and mortality associated. Despite the successful treatment of some SSTIs, those affecting the subcutaneous tissue, fascia, or muscle delay the healing process and can lead to life-threatening conditions. Therefore, it is fundamental to develop antimicrobial wound dressings to deal with such pathological situations. Recently, wound dressings loaded with antimicrobial agents emerged as viable options to reduce wound bacterial colonization and infection, in order to improve the healing process. In this thesis, a new antimicrobial wound dressing was produced and characterized. In this context, polycaprolactone (PCL) nanofibrous membranes functionalized with biosynthesized maillard reaction products (MRPs) were produced using an electrospinning apparatus. The functionalization of PCL nanofibers with MRPs allowed the production of membranes with the mechanical, wettability and porosity features required for wound exudate absorption as well as nutrients and gas exchange. Furthermore, MRPs-modified PCL membranes were also able to inhibit Staphylococcus aureus and Pseudomonas aeruginosa growth, without inducing any cytotoxic effect to human fibroblast cells. These findings support the potential use of the produced membranes in the healing process.As infeções da pele e dos tecidos moles (IPTMs) têm sido associadas a altas taxas de morbidade e mortalidade. Apesar do sucesso alcançado no tratamento de algumas IPTMs, aquelas que afetam o tecido subcutâneo, a fáscia ou o músculo retardam o processo de cicatrização e podem conduzir a situações que comprometem a vida do paciente. No sentido de contornar/evitar estas condições patológicas, torna-se fundamental desenvolver revestimentos com propriedades antimicrobianas. Recentemente, o desenvolvimento de pensos que incorporam agentes antimicrobianos surgiu como uma alternativa inovadora na redução da colonização bacteriana e infeção da ferida, com o intuito de melhorar o processo de cicatrização. Nesta tese, foi produzido e caracterizado um novo revestimento de pele com atividade bactericida. Neste contexto, foram produzidas membranas de policaprolactona (PCL) funcionalizadas com produtos resultantes da reação de maillard (PRM), recorrendo à técnica de eletrofiação. A funcionalização de nanofibras de PCL com PRM permitiu a produção de membranas com propriedades mecânicas, caráter hidrofílico e porosidade adequadas que permitem uma boa absorção do exsudado da ferida, assim como a troca de nutrientes e gases. Além disso, as membranas de PCL modificadas por PRM foram capazes de inibir o crescimento de Staphylococcus aureus e Pseudomonas aeruginosa, sem induzir qualquer efeito citotóxico em células de fibroblastos humanos. Estes resultados sugerem que as membranas em estudo têm um elevado potencial para serem aplicadas no processo de cicatrização

Doctor of Philosophy

dissertationInspired by the Sandcastle Worm, biomimetic of the water-borne adhesive was developed by complex coacervation of the synthetic copolyelectrolytes, mimicking the chemistries of the worm glue. The developed underwater adhesive was designed for sealing fetal membranes after fetoscopic surgery in twin-to-twin transfusion syndrome (TTTS) and sealing neural tissue of a fetus in aminiotic sac for spina bifida condition. Complex coacervate with increased bond strength was created by entrapping polyethylene glycol diacrylate (PEG-dA) monomer within the cross-linked coacervate network. Maximum shear bond strength of ~ 1.2 MPa on aluminum substrates was reached. The monomer-filled coacervate had complex flow behavior, thickening at low shear rates and then thinning suddenly with a 16-fold drop in viscosity at shear rates near 6 s-1. The microscale structure of the complex coacervates resembled a three-dimensional porous network of interconnected tubules. This complex coacervate adhesive was used in vitro studies to mimic the uterine wall-fetal membrane interface using a water column with one end and sealed with human fetal membranes and poultry breast, and a defect was created with an 11 French trocar. The coacervate adhesive in conjunction with the multiphase adhesive was used to seal the defect. The sealant withstood an additional traction of 12 g for 30-60 minutes and turbulence of the water column without leakage of fluid or slippage. The adhesive is nontoxic when in direct contact with human fetal membranes in an organ culture setting

How do factors known to cause preterm premature rupture of the membranes affect the ultrastructure and integrity of the amnion?

Introduction: Preterm premature rupture of the fetal amniotic membrane (PPROM) is a cause of preterm birth and affects 2% of women worldwide. Causative factors such as uterine contractions and inflammatory mediators such as PGE2 weaken the fetal membrane due to a loss in biomechanical properties. This study investigated the influence of fibre orientation on the mechanical properties of the amniotic membrane (AM) and the effect of cyclical tensile strain (CTS) regimens on the fibre network within the AM as well as on PGE2 production. Methods: AM were collected from women undergoing term elective Caesarean Section at University College Hospital. AM from the cervix and placental regions were stained to identify fibre orientation. Specimens of AM were then subjected to a strain to failure regimen (Bionix 100, MTS). AM were also subjected to CTS using the Bose bioreactor (Bose Enduratec, UK). Assays for GAG, DNA, collagen, elastin and PGE2 were performed and compared to unstrained membrane. Results: The mechanical properties of the AM were dependent on fibre orientation with samples where fibres were strained in parallel being stronger than those strained perpendicular (p=0.0002 comparing the placental region using Student t test). Histological examination of the fibres revealed an abundance of elastin rather than collagen fibres within the AM. CTS reduced collagen and elastin synthesis within the AM, which was most marked in the cervical region (p=0.002, for elastin and p=0.02 for collagen, both in the cervical region). PGE2 production increased in strained specimens, again, most marked in the cervical region (p=0.00001). Conclusion: This study shows that fibre orientation is an important factor which influences the mechanical properties of the AM. Furthermore, elastin may have a larger contribution to membrane integrity than previously thought. CTS influenced the AM to cause weakening by decreasing the collagen and elastin content and increasing PGE2 production

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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Advances in Electronic-Nose Technologies Developed for Biomedical Applications

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry