China
Africa
Explore chapters and articles related to this topic
In Situ Sensors for Monitoring the Marine Environment
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Graham A. Mills, Gary R. Fones, Silke Kröger
Biofouling of optical and sensor surfaces remains to be solved and is often a neglected area of research by instrument manufacturers, as recognized in the recent EU FP7 call for the development of new antifouling materials. This is a particular challenge in nutrient-rich coastal waters where true operational lifetime can be only 1–2 weeks. Fouling can in some instances have a significant impact on the data obtained from in situ sensors, for example, some organisms can alter the local oxygen concentration near a sensing head, and some can exhibit natural fluorescence. The environmental situation in respect of biofouling is complex, and a number of different approaches have been suggested. These include mechanical scrapers or wipers, use of nontoxic (e.g., silicone greases) chemicals, the “uncontrolled” release of a biocide (e.g., leaching of tributyl tin and the use of copper coatings, meshes, and shutters), and “controlled” release methods based on localized seawater electrochlorination devices or automatic acid-dispensing systems (Delauney et al. 2010). Other solutions are being sought in the use of coatings and nanocoatings and those that peel away over a deployment period and biomimetic surfaces (e.g., peptide–peptoid conjugates and phosphorylcholine-based polymers) that were initially developed for medical applications. The use of natural occurring antifouling products from marine species has also been suggested.
Recent advances in stent-assisted coiling of cerebral aneurysms
Published in Expert Review of Medical Devices, 2020
Soliman Oushy, Lorenzo Rinaldo, Waleed Brinjikji, Harry Cloft, Giuseppe Lanzino
The key limitations of SAC (i.e. thromboembolic events and need for dual antiplatelet agents (DAPT)) may be addressed by ongoing studies of two IVDF with antithrombogenic coating: the Pipeline Shield (Medtronic, Irvine, California,USA) and p48_HPC (Phenox, Bochum, Germany). Pipeline Shield uses a phosphorylcholine coating shown to reduce platelet adhesion and activation [121,122]. On the other hand, the p48_HPC uses a glycan-based multilayer hydrophilic polymer coating with significant reduction in thrombogenicity compared to the uncoated p48 flow diverter [123]. Although currently limited to IVFD, surface coating technology may be adopted in future intracranial stents. Future developments in surface-coating technology may reduce the need for DAPT to a single agent or eliminate it altogether only if the safety and efficacy has been demonstrated in prospective comparative trials. Alternatively, the application of IVFD may exp for treatment, further replacing SAC as the first-line treatment option in ruptured aneurysms cases if DAPT is no longer required.
In Vitro models for thrombogenicity testing of blood-recirculating medical devices
Published in Expert Review of Medical Devices, 2019
Surface wettability, described as ‘hydrophobicity’ or ‘hydrophilicity,’ is generally measured by the contact angle a sessile drop makes when placed on the surface. A basic definition of hydrophobic (contact angle >90 degrees) and hydrophilic (contact angle <90 degrees) is generally accepted in the scientific community [27]. Studies have focused on the influence of wettability on the protein deposition phase of the coagulation response because these interactions are defined by van der Waals and electrostatic forces [28]. Plasma proteins generally have hydrophobic patches buried in their core and hydrophilic amino acids on their surface. It has been suggested that hydrophobic surfaces adsorb more proteins because the association of hydrophobic patches and the biomaterial surface is thermodynamically favorable and readily displaces water molecules. Hydrophilic surfaces generally adsorb less protein because they have strong polar interactions with the immediately contacting water layer, making it thermodynamically less favorable for proteins to displace these bonds [29]. Upon adsorption, these proteins do not denature [30,31], so biological activity is generally preserved [32]. Fibrinogen is able to bind in similar concentrations on hydrophilic and hydrophobic surfaces [33] and elicits a platelet-mediated thrombosis when bound to a surface [34]. In a study to assess protein adhesion on a potentially biocompatible coating, 2-methacryloyloxyethyl phosphorylcholine (MPC), the hydration layer created by the phosphorylcholine and water interaction was thought to be responsible for decreased protein adhesion [35].
Impact of spontaneous liposome modification with phospholipid polymer-lipid conjugates on protein interactions
Published in Science and Technology of Advanced Materials, 2022
Haruna Suzuki, Anna Adler, Tianwei Huang, Akiko Kuramochi, Yoshiro Ohba, Yuya Sato, Naoko Nakamura, Vivek Anand Manivel, Kristina N Ekdahl, Bo Nilsson, Kazuhiko Ishihara, Yuji Teramura
Enhancing the systemic circulation time of liposomes is key to obtaining a successful liposome-based drug delivery system that can deliver encapsulated drugs to the site of interest, for example, to facilitate the accumulation of liposomes in tumors via the enhanced permeability and retention effect [10]. However, in vivo liposomes interact with biological surroundings, leading to non-specific adsorption of plasma proteins and rapid clearance of liposomes from the circulation, which is generally detected for nanoparticles [11–13]. Therefore, the surface modification of liposomes with poly(ethylene glycol) (PEG), a synthetic, flexible, uncharged, and water-soluble polymer, is the gold standard to reduce liposome – protein interactions [14]. Bound water molecules generate a hydration layer around the PEG chains, thus suppressing the non-specific protein adsorption on liposomes [15]. However, PEGylated liposomes are rapidly cleared from the circulation upon repeated injections due to the formation of anti-PEG antibodies via the accelerated blood clearance effect (ABC effect) [16], which was first described by Dams et al. [17]. Additionally, there have been reports on the generation of anti-PEG antibodies in healthy individuals, who have not previously been administered any PEGylated therapeutics, which may also contribute to the reduced circulation time of PEGylated liposomes [18]. Therefore, it is essential to develop effective alternatives to PEGylated liposomes. Our group has focused on poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) (PMPC), which is used for coating clinical biomedical devices [19], and PMPC-conjugated lipids have been studied as alternative liposome coatings [20–23].