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Clinical & Experimental Optometry Jan 2020Ophthalmic lens design concerns the control of spectacle lens aberrations which occur when the eye rotates away from the optical centre of the lens. The most significant... (Review)
Review
Ophthalmic lens design concerns the control of spectacle lens aberrations which occur when the eye rotates away from the optical centre of the lens. The most significant aberrations are oblique astigmatism and mean oblique error (power error). A brief review of these aberrations is given, explaining how the lens designer can control them using just the bending of the lens, and what results can be achieved using simple spherical and toroidal surfaces. Before 1985, aspherical surfaces were used only for post-cataract spectacle lenses and high-power magnifiers. Today, aspherical surfaces are used by all major lens manufacturers to produce thinner, lighter and more attractive best-form lenses in the normal power range. Aspherical surfaces are employed because the surface itself is astigmatic and the surface astigmatism is used to combat aberrational astigmatism due to oblique incidence. The various types of aspherical surface and how the surface astigmatism arises is described, before considering how this feature is used to produce flatter, thinner lenses. In the case of astigmatic prescriptions, the surface requires different asphericities along its principal meridians and the geometry of these atoroidal surfaces is also described. The advent of free-form manufacturing techniques requires the lens designer to convert the surface description to the (x,y,z) co-ordinates needed to generate the surface. Examples of how these co-ordinates can be obtained from the equation to the surface are given for toroidal and aspherical surfaces. In the case of free-form progressive surfaces, the pre-determined z-co-ordinates must be added to the z-co-ordinates of the prescription surface to obtain the final free-form surface. In the case of optimised prescription surfaces, on-board software will analyse the result by ray tracing to obtain the final z-co-ordinates.
Topics: Equipment Design; Eyeglasses; Humans; Optics and Photonics; Refraction, Ocular; Visual Acuity
PubMed: 31222837
DOI: 10.1111/cxo.12930 -
Frontiers in Psychiatry 2022In 2021, the manufacturer of diamorphine reported a possible impending shortage for Switzerland and Germany. This led us to investigate this controlled medicine's... (Review)
Review
In 2021, the manufacturer of diamorphine reported a possible impending shortage for Switzerland and Germany. This led us to investigate this controlled medicine's manufacture, market, and regulatory constraints. Based on our analysis of legal texts and gray literature in the form of reports and documents, we propose recommendations to prevent and address diamorphine shortages in Switzerland. Diamorphine, also known as pharmaceutical "heroin," is used medically to treat persons with severe opioid use disorder in a handful of countries. The controlled medicine is manufactured from morphine, which, in turn, is extracted from opium poppies. Studying data from the International Narcotics Control Board for 2019, we find that Switzerland accounts for almost half of the worldwide medical consumption of diamorphine. It manufactures more than half of the worldwide total and keeps the largest stocks. Moreover, Switzerland is dependent on a sole supplier of diamorphine (monopoly). As a niche product, diamorphine has an increased risk of shortage. Such a shortage would immediately threaten a valuable public health program for around 1,660 Swiss patients. We believe it is urgent to curtail the monopoly and ensure a stable supply for the future.
PubMed: 35615450
DOI: 10.3389/fpsyt.2022.882299 -
Frontiers in Bioengineering and... 2021Current cutting-edge strategies in biomaterials science are focused on mimicking the design of natural systems which, over millions of years, have evolved to exhibit... (Review)
Review
Current cutting-edge strategies in biomaterials science are focused on mimicking the design of natural systems which, over millions of years, have evolved to exhibit extraordinary properties. Based on this premise, one of the most challenging tasks is to imitate the natural extracellular matrix (ECM), due to its ubiquitous character and its crucial role in tissue integrity. The anisotropic fibrillar architecture of the ECM has been reported to have a significant influence on cell behaviour and function. A new paradigm that pivots around the idea of incorporating biomechanical and biomolecular cues into the design of biomaterials and systems for biomedical applications has emerged in recent years. Indeed, current trends in materials science address the development of innovative biomaterials that include the dynamics, biochemistry and structural features of the native ECM. In this context, one of the most actively studied biomaterials for tissue engineering and regenerative medicine applications are nanofiber-based scaffolds. Herein we provide a broad overview of the current status, challenges, manufacturing methods and applications of nanofibers based on elastin-based materials. Starting from an introduction to elastin as an inspiring fibrous protein, as well as to the natural and synthetic elastin-based biomaterials employed to meet the challenge of developing ECM-mimicking nanofibrous-based scaffolds, this review will follow with a description of the leading strategies currently employed in nanofibrous systems production, which in the case of elastin-based materials are mainly focused on supramolecular self-assembly mechanisms and the use of advanced manufacturing technologies. Thus, we will explore the tendency of elastin-based materials to form intrinsic fibers, and the self-assembly mechanisms involved. We will describe the function and self-assembly mechanisms of silk-like motifs, antimicrobial peptides and leucine zippers when incorporated into the backbone of the elastin-based biomaterial. Advanced polymer-processing technologies, such as electrospinning and additive manufacturing, as well as their specific features, will be presented and reviewed for the specific case of elastin-based nanofiber manufacture. Finally, we will present our perspectives and outlook on the current challenges facing the development of nanofibrous ECM-mimicking scaffolds based on elastin and elastin-like biomaterials, as well as future trends in nanofabrication and applications.
PubMed: 34336798
DOI: 10.3389/fbioe.2021.652384 -
Pharmaceutics Sep 2022Nanoparticulate technologies have revolutionized drug delivery allowing for passive and active targeting, altered biodistribution, controlled drug release... (Review)
Review
Nanoparticulate technologies have revolutionized drug delivery allowing for passive and active targeting, altered biodistribution, controlled drug release (temporospatial or triggered), enhanced stability, improved solubilization capacity, and a reduction in dose and adverse effects. However, their manufacture remains immature, and challenges exist on an industrial scale due to high batch-to-batch variability hindering their clinical translation. Lipid-based nanomedicines remain the most widely approved nanomedicines, and their current manufacturing methods remain discontinuous and face several problems such as high batch-to-batch variability affecting the critical quality attributes (CQAs) of the product, laborious multistep processes, need for an expert workforce, and not being easily amenable to industrial scale-up involving typically a complex process control. Several techniques have emerged in recent years for nanomedicine manufacture, but a paradigm shift occurred when microfluidic strategies able to mix fluids in channels with dimensions of tens of micrometers and small volumes of liquid reagents in a highly controlled manner to form nanoparticles with tunable and reproducible structure were employed. In this review, we summarize the recent advancements in the manufacturing of lipid-based nanomedicines using microfluidics with particular emphasis on the parameters that govern the control of CQAs of final nanomedicines. The impact of microfluidic environments on formation dynamics of nanomaterials, and the application of microdevices as platforms for nanomaterial screening are also discussed.
PubMed: 36145688
DOI: 10.3390/pharmaceutics14091940 -
Micromachines Mar 2022Electropolishing (EP) is most widely used as a metal finishing process. It is a non-contact electrochemical process that can clean, passivate, deburr, brighten, and... (Review)
Review
Electropolishing (EP) is most widely used as a metal finishing process. It is a non-contact electrochemical process that can clean, passivate, deburr, brighten, and improve the biocompatibility of surfaces. However, there is clear potential for it to be used to shape and form the topology of micro-scale surface features, such as those found on the micro-applications of additively manufactured (AM) parts, transmission electron microscopy (TEM) samples, micro-electromechanical systems (MEMs), biomedical stents, and artificial implants. This review focuses on the fundamental principles of electrochemical polishing, the associated process parameters (voltage, current density, electrolytes, electrode gap, and time), and the increasing demand for using environmentally sustainable electrolytes and micro-scale applications. A summary of other micro-fabrication processes, including micro-milling, micro-electric discharge machining (EDM), laser polishing/ablation, lithography (LIGA), electrochemical etching (MacEtch), and reactive ion etching (RIE), are discussed and compared with EP. However, those processes have tool size, stress, wear, and structural integrity limitations for micro-structures. Hence, electropolishing offers two-fold benefits of material removal from the metal, resulting in a smooth and bright surface, along with the ability to shape/form micro-scale features, which makes the process particularly attractive for precision engineering applications.zx3.
PubMed: 35334760
DOI: 10.3390/mi13030468 -
Annual Review of Biomedical Engineering Jul 2021Additive manufacturing's attributes include print customization, low per-unit cost for small- to mid-batch production, seamless interfacing with mainstream medical 3D... (Review)
Review
Additive manufacturing's attributes include print customization, low per-unit cost for small- to mid-batch production, seamless interfacing with mainstream medical 3D imaging techniques, and feasibility to create free-form objects in materials that are biocompatible and biodegradable. Consequently, additive manufacturing is apposite for a wide range of biomedical applications including custom biocompatible implants that mimic the mechanical response of bone, biodegradable scaffolds with engineered degradation rate, medical surgical tools, and biomedical instrumentation. This review surveys the materials, 3D printing methods and technologies, and biomedical applications of metal 3D printing, providing a historical perspective while focusing on the state of the art. It then identifies a number of exciting directions of future growth: () the improvement of mainstream additive manufacturing methods and associated feedstock; () the exploration of mature, less utilized metal 3D printing techniques; () the optimization of additively manufactured load-bearing structures via artificial intelligence; and () the creation of monolithic, multimaterial, finely featured, multifunctional implants.
Topics: Artificial Intelligence; Humans; Printing, Three-Dimensional; Prostheses and Implants
PubMed: 34255995
DOI: 10.1146/annurev-bioeng-082020-032402 -
Stem Cell Research & Therapy Jul 2012Aastrom Biosciences has developed a proprietary cell-processing technology that enables the manufacture of ixmyelocel-T, a patient-specific multicellular therapy... (Review)
Review
Aastrom Biosciences has developed a proprietary cell-processing technology that enables the manufacture of ixmyelocel-T, a patient-specific multicellular therapy expanded from a small sample of a patient's own bone marrow. Ixmyelocel-T is produced under current good manufacturing practices (cGMP) in a fully closed, automated system that expands mesenchymal stem cells (MSCs) and macrophages. While the cell types in ixmyelocel-T are the same as those found in the bone marrow, the numbers of MSCs and alternative macrophages are greater in ixmyelocel-T. We propose that the mixture of expanded MSCs and alternatively activated macrophages promote long-term tissue repair of ischemic tissue. The multiple cell types in ixmyelocel-T have a range of biological activities that are likely to contribute to a complex mechanism of action. Clinical trial data collected to date support the potential for ixmyelocel-T as an efficacious and safe treatment for ischemic cardiovascular indications, including critical limb ischemia (CLI) and a severe form of heart failure, dilated cardiomyopathy (DCM). The CLI clinical program has completed phase 2 and has reached concurrence with the Food and Drug Administration (FDA) on a phase 3 study (REVIVE) through the Special Protocol Assessment (SPA) process. The phase 3 study began screening patients in February 2012. The DCM clinical program will initiate phase 2b in 2012.
Topics: Antigens, CD; Cardiovascular Diseases; Clinical Trials as Topic; Drug Industry; Humans; Kaplan-Meier Estimate; Macrophages; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Phenotype
PubMed: 22776246
DOI: 10.1186/scrt117 -
Materials (Basel, Switzerland) Aug 2021Nickel-titanium alloys have been widely used in biomedical, aerospace and other fields due to their shape memory effect, superelastic effect, as well as biocompatible... (Review)
Review
Nickel-titanium alloys have been widely used in biomedical, aerospace and other fields due to their shape memory effect, superelastic effect, as well as biocompatible and elasto-thermal properties. Additive manufacturing (AM) technology can form complex and fine structures, which greatly expands the application range of Ni-Ti alloy. In this study, the development trend of additive manufactured Ni-Ti alloy was analyzed. Subsequently, the most widely used selective laser melting (SLM) process for forming Ni-Ti alloy was summarized. Especially, the relationship between Ni-Ti alloy materials, SLM processing parameters, microstructure and properties of Ni-Ti alloy formed by SLM was revealed. The research status of Ni-Ti alloy formed by wire arc additive manufacturing (WAAM), electron beam melting (EBM), directional energy dedication (DED), selective laser sintering (SLS) and other AM processes was briefly described, and its mechanical properties were emphatically expounded. Finally, several suggestions concerning Ni-Ti alloy material preparation, structure design, forming technology and forming equipment in the future were put forward in order to accelerate the engineering application process of additive manufactured Ni-Ti alloy. This study provides a useful reference for scientific research and engineering application of additive manufactured Ni-Ti alloys.
PubMed: 34443019
DOI: 10.3390/ma14164496 -
Blood Purification 2016The manufacture and sale of natural products constitute a multi-billion dollar industry. Nearly a third of the American population admit to using some form of... (Review)
Review
BACKGROUND
The manufacture and sale of natural products constitute a multi-billion dollar industry. Nearly a third of the American population admit to using some form of complementary or alternative medicine, with many using them in addition to prescription medications. Most patients fail to inform their healthcare providers of their natural product use and physicians rarely inquire. Annually, thousands of natural product-induced adverse events are reported to Poison Control Centers nationwide. Natural product manufacturers are not responsible for proving safety and efficacy, as the FDA does not regulate them. However, concerns exist surrounding the safety of natural products.
SUMMARY
This review provides details on natural products that have been associated with renal dysfunction. We have focused on products that have been associated with direct renal injury, immune-mediated nephrotoxicity, nephrolithiasis, rhabdomyolysis with acute renal injury, hepatorenal syndrome, and common adulterants or contaminants that are associated with renal dysfunction.
KEY MESSAGES
The potential for natural products to cause renal dysfunction is justifiable. It is imperative that natural product use be monitored closely in all patients. Healthcare practitioners must play an active role in identifying patients using natural products and provide appropriate patient education.
Topics: Acute Kidney Injury; Biological Products; Health Knowledge, Attitudes, Practice; Hepatorenal Syndrome; Humans; Kidney; Nephrolithiasis; Quality Control; Renal Insufficiency, Chronic; Rhabdomyolysis
PubMed: 26766569
DOI: 10.1159/000441268