115 research outputs found
Covalent immobilization: A review from an enzyme perspective
No full textEnzymes are indispensable in biotechnology, serving as biological catalysts in applications across various domains, including biosensors, fine chemicals production, pharmaceuticals, and drug development. In this context, enzyme immobilization is crucial for ensuring their retention on devices while preserving their activity over extended periods. Various immobilization methods, both physical (adsorption, affinity bonding, entrapment, encapsulation, and ionic bonding) and chemical (covalent bonding and crosslinking), have been explored, each exerting distinct impacts on enzyme stability and activity. Among these, chemical immobilization typically offers superior stability compared to physical methods due to the formation of stronger bonds between the enzyme and the support material. Covalent immobilization is commonly used due to its efficacy in enhancing enzyme stability. Carbodiimide chemistry and Schiff base reactions are the two most common covalent bond techniques used for immobilization, owing to the functional groups involved in the reaction (–NH2 and –COOH), which are commonly found on enzymes surface. This review provides a background on enzymes and the various methods for immobilizing them onto materials, before delving into carbodiimide and Shiff base reaction techniques. The characteristics, advantages, and disadvantages of both these techniques are discussed, including bond formation, reaction condition, and implications for application. Additionally, the review underscores the significance of enzyme orientation, structure, and conformational changes. Achieving optimal orientation and minimizing conformational alterations are critical factors in developing a stable, highly active, selective, scalable, and reproducible enzymatic biosensor
Cascading chemiresistive paper-based enzymatic biosensor for urea detection
No full textThe conventional approach for diagnosing high risk metabolic disorders, such as chronic kidney disease (CKD), involves drawing a blood sample, which necessitates access to a centralized facility, making it undesirable for frequent urea monitoring. Alternative biological fluids, such as saliva, have demonstrated potential as non-invasive mediums for CKD monitoring due to the strong correlation between blood urea and salivary urea levels, indicating their suitability for point-of-care test kits. In this study, we present an innovative chemiresistive paper-based enzymatic sensor that utilizes a combination of urease and polystyrene sulfonate (PSS) to measure urea. This sensor detects urea over a broad concentration range (10–110 mg/dl), encompassing the salivary urea levels found in both healthy (20±10 mg/dl) and diseased (100±10 mg/dl) individuals. Furthermore, the sensor’s response to urea remains unaffected by the presence of interfering molecules in saliva such as metabolites, proteins, sugars and acids. The stability and response time of the sensor were also assessed under various temperatures, as encountered during storage. Overall, the sensor developed in this study offers a promising solution for creating a rapid, scalable, cost-effective, and user-friendly point-of-care monitoring test kit for urea screening in resource-limited setting with restricted access to healthcare facilities
Why Go NANO on COVID-19 Pandemic?
No full textFunding: J.C. is funded by the European Research Council Starting Grant (ERCStG-2019- 848325).Although treating COVID-19 is shown to be challenging, NANOtechnology is around the corner to overcome potential drawbacks. The use of NANOtechnologies will definitely shape the worldwide approaches and tools to treat COVID-19. Here we highlight the importance of going NANO on the COVID-19 pandemic.publishersversionpublishe
Coaxial hydrogel structures for drug delivery to tumors
No full textBiopolymer-based hydrogels have emerged as promising platforms for drug delivery systems (DDSs) due to their inherent biocompatibility, tunable physical properties and controllable degradability. Yet, drug release in majority of these systems is solely contingent on diffusion of drug molecules through the hydrogel, which often leads to burst release of drugs from these systems. As a result, the main aim of this thesis was to develop suitable hydrogel platforms that allow sustained release of anti-cancer drugs, to be ultimately used as implants for local delivery of drugs to tumors. To this end, inspired by the chemistry of mussel adhesive proteins, a new generation of coaxial hydrogel structures were developed that could simultaneously exert both affinity and diffusion control over the release of chemotherapeutic drugs. Specifically, dopamine-modified hydrogel along with chemotherapeutic drugs was used as the main core component to confer affinity-controlled release, while a methacrylated hydrogel was used as the shell composition to provide the controlled diffusion barrier. Initially a well-recognized wet-spinning technique was employed to fabricate coaxial fibers with the given composition, mainly because this fabrication method allows high throughput and continuous production of coaxial structures. Accordingly, it was shown that the fabricated coaxial fibers were robust in both dry and wet conditions, and most importantly they were capable of exerting a controlled release of Doxorubicin (a chemotherapeutic drug) over a span of 3 weeks. Also, in vitro and in vivo evaluations showed that drug loaded coaxial fibers had optimal anticancer activity against pancreatic cancer cells..
A systematic study of maghemite/PMMA nano-fibrous composite via an electrospinning process: synthesis and characterization
No full textAbstract not availableHossein Mohammad Khanloua, Bee Chin Anga, Sepehr Talebiana, Mohsen Marani Barzanib, Mahyar Silakhorib, Hadi Fauzi
Electrically Conducting Hydrogel Graphene Nanocomposite Biofibers for Biomedical Applications
No full text© Copyright © 2020 Talebian, Mehrali, Raad, Safaei, Xi, Liu and Foroughi. Conductive biomaterials have recently gained much attention, specifically owing to their application for electrical stimulation of electrically excitable cells. Herein, flexible, electrically conducting, robust fibers composed of both an alginate biopolymer and graphene components have been produced using a wet-spinning process. These nanocomposite fibers showed better mechanical, electrical, and electrochemical properties than did single fibers that were made solely from alginate. Furthermore, with the aim of evaluating the response of biological entities to these novel nanocomposite biofibers, in vitro studies were carried out using C2C12 myoblast cell lines. The obtained results from in vitro studies indicated that the developed electrically conducting biofibers are biocompatible to living cells. The developed hybrid conductive biofibers are likely to find applications as 3D scaffolding materials for tissue engineering applications
Prediction and characterization of surface roughness using sandblasting and acid etching process on new non-toxic titanium biomaterial: adaptive-network-based fuzzy inference System
No full textAn adaptive neuro-fuzzy system (ANFIS) model was employed to predict the surface roughness. Surface roughening of titanium biomaterials has a crucial effect on increasing the biocompatibility. For this purpose, sandblasted, large-grit, acid-etched (SLA) has been introduced as an effective method to change the surface texturing and roughness. Subsequent processes—polishing, sandblasting and acid etching or SLA—were employed to modify the surface. Alumina particles for surface blasting and Kroll’s etchant (3 ml HF + 6 ml HNO₃ + 100 ml H₂O) for acid etching were utilized in this experiment. This was performed for three different periods of time (10, 20 and 30 s) and temperatures (25, 45 and 60 centigrade). Correspondingly, the Ti-13Zr-13Nb surfaces were evaluated using a field emission scanning electron microscope for texturing, contact mode profile meter for the average surface roughness (Ra) (nm) and atomic force microscopy for surface texturing at the nano-scale. In addition, the surface roughness was reduced in each condition, particularly in extremely high conditions. Significantly, the ANFIS model predicted the Ra amount of textured surface with an error band of 10 %. This research presents an idea to use the ANFIS model to obtain proper biological signs on the roughened surface in terms of surface roughness.Hossein Mohammad Khanlou, Bee Chin Ang, Mohsen Marani Barzani, Mahyar Silakhori, Sepehr Talebia
Gazing Station: Hierarchy and Surveillance in Amsterdam’s Former Post Office
No full textAR2A011Architectural History ThesisArchitecture, Urbanism and Building Science
Variation of fatigue strength of parts manufactured by laser powder bed fusion
No full textThis study reports the variability of the fatigue strength of specimens manufactured by the laser powder bed fusion process with respect to their location on the build plate. Specimens from the right-hand and left-hand halves of the build plate were tested under high cycle fatigue. Comparison of the fatigue data suggests that the specimens manufactured on the right-hand half of the build plate have a higher fatigue strength than those manufactured on the left-hand half. One reason for the observed discrepancy in fatigue strength was the higher accumulation of spattered powder particles on the left-hand side as compared to the right-hand side of the build plate. These spattered particles are oxidised, and form defects such as inclusions within the specimen. © 2021 The Author(s
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