In physics and engineering, a phasor (a portmanteau of phase vector[1][2]), is a complex numberrepresenting a sinusoidal function whose amplitude (A), angular frequency (ω), and initial phase (θ) are time-invariant. It is related to a more general concept called analytic representation,[3] which decomposes a sinusoid into the product of a complex constant and a factor depending on time and frequency. The complex constant, which depends on amplitude and phase, is known as a phasor, or complex amplitude,[4][5] and (in older texts) sinor[6] or even complexor.[6]
A common situation in electrical networks is the existence of multiple sinusoids all with the same frequency, but different amplitudes and phases. The only difference in their analytic representations is the complex amplitude (phasor). A linear combination of such functions can be factored into the product of a linear combination of phasors (known as phasor arithmetic) and the time/frequency dependent factor that they all have in common.
The origin of the term phasor rightfully suggests that a (diagrammatic) calculus somewhat similar to that possible for vectors is possible for phasors as well.[6] An important additional feature of the phasor transform is that differentiation and integration of sinusoidal signals (having constant amplitude, period and phase) corresponds to simple algebraic operations on the phasors; the phasor transform thus allows the analysis (calculation) of the AC steady state of RLC circuits by solving simple algebraic equations (albeit with complex coefficients) in the phasor domain instead of solving differential equations (with real coefficients) in the time domain.[7][8] The originator of the phasor transform was Charles Proteus Steinmetz working at General Electric in the late 19th century.[9][10]
Glossing over some mathematical details, the phasor transform can also be seen as a particular case of the Laplace transform, which additionally can be used to (simultaneously) derive the transient response of an RLC circuit.[8][10] However, the Laplace transform is mathematically more difficult to apply and the effort may be unjustified if only steady state analysis is required.[10]
https://en.wikipedia.org/wiki/Phasor
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Decellularization is a pretty strange process. Using a special type of soap, it's possible to remove all the cellular material from a piece of tissue, leaving only the connective proteins and polymers behind that normally hold the cells in place. It leaves you with something that looks like the starting material, but is really just an empty sponge called a scaffold. Doctors and scientists have been exploring this technique for many years because those empty scaffolds are extremely useful for cell culture. By seeding them with cells taken from a patient, it's possible to grow a brand new organ or tissue able to be transplanted into a patient, potentially saving their life. The same technique could even be used to make lab grown meat. Today we explore this amazing process and turn an ordinary grape, into meat.
https://www.youtube.com/watch?v=FaVHTd9Ne_s
Decellularization (also spelled decellularisation in British English) is the process used in biomedical engineering to isolate the extracellular matrix (ECM) of a tissue from its inhabiting cells, leaving an ECM scaffold of the original tissue, which can be used in artificial organ and tissue regeneration. Organ and tissue transplantation treat a variety of medical problems, ranging from end organ failure to cosmetic surgery. One of the greatest limitations to organ transplantation derives from organ rejection caused by antibodies of the transplant recipient reacting to donorantigens on cell surfaces within the donor organ.[1] Because of unfavorable immune responses, transplant patients suffer a lifetime taking immunosuppressing medication. Stephen F. Badylak pioneered the process of decellularization at the McGowan Institute for Regenerative Medicine at the University of Pittsburgh.[2] This process creates a natural biomaterial to act as a scaffold for cell growth, differentiation and tissue development. By recellularizing an ECM scaffold with a patient’s own cells, the adverse immune response is eliminated. Nowadays, commercially available ECM scaffolds are available for a wide variety of tissue engineering. Using peracetic acid to decellularize ECM scaffolds have been found to be false and only disinfects the tissue.
With a wide variety of decellularization-inducing treatments available, combinations of physical, chemical, and enzymatic treatments are carefully monitored to ensure that the ECM scaffold maintains the structural and chemical integrity of the original tissue.[2] Scientists can use the acquired ECM scaffold to reproduce a functional organ by introducing progenitor cells, or adult stem cells (ASCs), and allowing them to differentiate within the scaffold to develop into the desired tissue. The produced organ or tissue can be transplanted into a patient. In contrast to cell surface antibodies, the biochemical components of the ECM are conserved between hosts, so the risk of a hostile immune response is minimized.[3][4] Proper conservation of ECM fibers, growth factors, and other proteins is imperative to the progenitor cells differentiating into the proper adult cells. The success of decellularization varies based on the components and density of the applied tissue and its origin.[5] The applications to the decellularizing method of producing a biomaterial scaffold for tissue regeneration are present in cardiac, dermal, pulmonary, renal, and other types of tissues. Complete organ reconstruction is still in the early levels of development.[6]
https://en.wikipedia.org/wiki/Decellularization
Decellularization of porcine heart valves is the removal of cells along with antigenic cellular elements[1] by either physical or chemical decellularization of the tissue.[2] This decellularized valve tissue provides a scaffold with the remaining extracellular matrix (ECM) that can then be used for tissue engineering and valve replacement in humans inflicted with valvular disease.[3] Decellularized biological valves have potential benefit over conventional valves through decreased calcification which is thought to be an immuno-inflammatory response initiated by the recipient.[4]
https://en.wikipedia.org/wiki/Decellularization_of_porcine_heart_valve
A bioartificial heart is an engineered heart that contains the extracellular structure of a decellularized heart and cellular components from a different source. Such hearts are of particular interest for therapy as well as research into heart disease. The first bioartificial hearts were created in 2008 using cadaveric rat hearts.[1][2][3] In 2014, human-sized bioartificial pig hearts were constructed.[4] Bioartificial hearts have not been developed yet for clinical use, although the recellularization of porcine hearts with human cells opens the door to xenotransplantation.[4][5]
Background[edit]
Heart failure is one of the leading causes of death. In 2013, an estimate of 17.3 million deaths per year out of the 54 million total deaths was caused by cardiovascular diseases, meaning that 31.5% of the world's total death was caused by this.[6] Often, the only viable treatment for end-stage heart failure is organ transplantation.[5] Currently organ supply is insufficient to meet the demand, which presents a large limitation in an end-stage treatment plan.[2][5] A theoretical alternative to traditional transplantation processes is the engineering of personalized bioartificial hearts. Researchers have had many successful advances in the engineering of cardiovascular tissue and have looked towards using decellularized and recellularized cadaveric hearts in order to create a functional organ.[5] Decellularization-recellularization involves using a cadaveric heart, removing the cellular contents while maintaining the protein matrix (decellularization), and subsequently facilitating growth of appropriate cardiovascular tissue inside the remaining matrix (recellularization).[5]
Over the past years, researchers have identified populations of cardiac stem cells that reside in the adult human heart. This discovery sparked the idea of regenerating the heart cells by taking the stem cells inside the heart and reprogramming them into cardiac tissues.[7] The importance of these stem cells are self-renewal, the ability to differentiate into cardiomyocytes, endothelial cells and smooth vascular muscle cells, and clonogenicity. These stem cells are capable of becoming myocytes, which are for stabilizing the topography of the intercellular components, as well as to help control the size and shape of the heart, as well as vascular cells, which serve as a cell reservoir for the turnover and the maintenance of the mesenchymal tissues.[7] However, in vivo studies have demonstrated that the regenerative ability of implanted cardiac stem cells lies in the associated macrophage-mediated immune response and concomitant fibroblast-mediated wound healing and not in their functionality, since these effects were observed for both live and dead stem cells.[8]
Methodology[edit]
The preferred method to remove all cellular components from a heart is perfusion decellularization. This technique involves perfusing the heart with detergents such as SDS and Triton X-100 dissolved in distilled water.[1]
The remaining ECM is composed of structural elements such as collagen, laminin, elastin and fibronectin. The ECM scaffold promotes proper cellular proliferation and differentiation, vascular development, as well as providing mechanical support for cellular growth.[5] Because minimal DNA material remains after the decellularization process, the engineered organ is biocompatible with the transplant recipient, regardless of species. Unlike traditional transplant options, recellularized hearts are less immunogenic and have a decreased risk of rejection.[2][9]
Once the decellularized heart has been sterilized to remove any pathogens, the recellularization process can occur.[2] Multipotent cardiovascular progenitors are then added to the decellularized heart and with additional exogenous growth factors, are stimulated to differentiate into cardiomyocytes, smooth muscle cells and endothelial cells.[10]
Recellularized heart functionality[edit]
The most promising results come from recellularized rat hearts. After only 8 days of maturation, the heart models were stimulated with an electrical signal to provide pacing. The heart models showed a unified contraction with a force equivalent to ~2% of a normal rat heart or ~25% of that of a 16-week-old human heart.[1][5]
Although far from use in a clinical setting, there have been great advances in the field of bioartificial heart generation.[2][5][10] The use of decellularization and recellularization processes, has led to the production of a three dimensional matrix that promotes cellular growth; the repopulation of the matrix containing appropriate cell composition; and the bioengineering of organs demonstrating functionality (limited) and responsiveness to stimuli.[2][5] This area shows immense promise and with future research may redefine treatment of end stage heart failure.
https://en.wikipedia.org/wiki/Bioartificial_heart
Decellularized ECM[edit]
Decellularized extracellular matrix based bioinks can be derived from nearly any mammalian tissue. However, often organs such as heart, muscle, cartilage, bone, and fat are decellularized, lyophilized, and pulverized, to created a soluble matrix that can then be formed into gels.[13] These bioinks possess several advantages over other materials due to their derivation from mature tissue. These materials consist of a complex mixture of ECM structural and decorating proteins specific to their tissue origin. Therefore, dECM-derived bioinks are particularly tailored to provide tissue-specific cues to cells. Often these bioinks are cross-linked through thermal gelation or chemical cross-linking such as through the use of riboflavin.[14]
See also[edit]
- 3D printing
- 3D bioprinting
- List of 3D printer manufacturers
- List of common 3D test models
- List of emerging technologies
- List of notable 3D printed weapons and parts
- Organ-on-a-chip
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