Biology for Engineers Study Material for B.TECH and other professional Courses. It includes ppts and pdf and lectures transcript
Course Syllabus and Suggestive Readings
Unit 3 Bio Medical Instrumentation
Electrical stimulus and biophysical activity: Patient, electrical shock and hazards, leakage current, Electrical activity of heart (ECG), Electrical activity of brain (EEG), Electrorentinogram (ERG), Electro-occologram (EOG), Electromyogram(EMG).
Biomedical recording systems: Basic Recording system , General consideration for signal conditioners Preamplifiers, Differential Amplifier , Isolation Amplifier, Vectorcardiograph, Phonocardiograph, Other biomedical records, , , Patient isolation and accident prevention.
Tissue Engineering:
Recombinant DNA technology, Stem cell biology & Tissue Engineering
The ECG is the most important test for interpretation of the cardiac rhythm, conduction system abnormalities, and the detection of myocardial ischemia. The ECG is also of great value in the evaluation of other types of cardiac abnormalities including valvular heart disease, cardiomyopathy, pericarditis, and hypertensive disease. Finally, the ECG can be used to monitor drug treatment (specifically antiarrhythmic therapy) and to detect metabolic disturbances.
An ECG can help detect:
arrhythmias – where the heart beats too slowly, too quickly, or irregularly
coronary heart disease – where the heart’s blood supply is blocked or interrupted by a build-up of fatty substances
heart attacks – where the supply of blood to the heart is suddenly blocked
cardiomyopathy – where the heart walls become thickened or enlarged
How an ECG is carried out
Small, sticky sensors called electrodes are attached to your arms, legs and chest. These are connected by wires to an ECG recording machine.
You do not need to do anything special to prepare for the test. You can eat and drink as normal beforehand.
Before the electrodes are attached, you’ll usually need to remove your upper clothing. Your chest may need to be shaved or cleaned. Once the electrodes are in place, you may be offered a hospital gown to cover yourself.
The test itself usually only lasts a few minutes. You should be able to go home soon afterwards or return to the ward if you’re already staying in hospital.
Types of ECG
There are 3 main types of ECG:
a resting ECG – carried out while you’re lying down in a comfortable position
a stress or exercise ECG – carried out while you’re using an exercise bike or treadmill
an ambulatory ECG – the electrodes are connected to a portable machine worn at your waist – your heart can be monitored at home for 1 or more days. This type of ECG is usually called a Holter monitor.
The type of ECG you have will depend on your symptoms and the heart problem suspected.
An exercise ECG may be recommended if your symptoms are triggered by physical activity. An ambulatory ECG may be more suitable if your symptoms are unpredictable and occur in random, short episodes.
Getting your results of your ECG
An ECG will show your heart rhythm and electrical activity as a graph displayed electronically or printed on paper.
For an ambulatory ECG, the ECG machine will store the information about your heart electronically. This can be checked by a doctor when the test is complete.
You may not be able to get the results of your ECG immediately. The recordings may need to be looked at by a specialist doctor to see if there are signs of a potential problem. Other tests may also be needed before it’s possible to tell you if there’s a problem.
You may need to visit the hospital, clinic or your GP a few days later to discuss your results with a doctor.
Risks and side effects of an ECG
An ECG is a quick, safe and painless test. No electricity is put into your body while it’s carried out.
There may be some slight discomfort when the electrodes are removed from your skin. It will be like removing a sticking plaster. Some people may develop a mild rash where the electrodes were attached.
An exercise ECG is performed under controlled conditions. The person carrying out the test will watch you. They’ll stop the test if you experience any symptoms or start to feel unwell.
Electromyography (EMG)
Electromyography (EMG) is a diagnostic procedure that evaluates the health condition of muscles and the nerve cells that control them. EMG results can help diagnose muscle disorders, nerve disorders, and disorders affecting the connection between nerves and muscles.
What is electromyography?
Electromyography (EMG) is a diagnostic procedure that evaluates the health condition of muscles and the nerve cells that control them. These nerve cells are known as motor neurons. They transmit electrical signals that cause muscles to contract and relax. An EMG translates these signals into graphs or numbers, helping doctors to make a diagnosis.
A doctor will usually order an EMG when someone is showing symptoms of a muscle or nerve disorder. These symptoms may include tingling, numbness, or unexplained weakness in the limbs. EMG results can help the doctor diagnose muscle disorders, nerve disorders, and disorders affecting the connection between nerves and muscles.
Some doctors may refer to electromyography as an electrodiagnostic exam.
Why is electromyography performed?
Your doctor may perform an EMG if you’re experiencing symptoms that may indicate a muscle or nerve disorder. Some symptoms that may call for an EMG include:
Make sure to notify your doctor about any over-the-counter or prescription medications you may be taking. It’s also important to tell your doctor if you have a bleeding disorder, or if you have a pacemaker or implantable defibrillator. You may not be able to have an EMG if you have any of these medical conditions or devices.
If you’re able to have an EMG, you should do the following beforehand:
Avoid smoking for at least three hours before the procedure.
Bathe or take a shower to remove any oils from the skin. Don’t apply any lotions or creams after washing.
Wear comfortable clothing that doesn’t obstruct the area that your doctor will be evaluating. You may be asked to change into a hospital gown right before the procedure.
You will be asked to lie down on an examination table or to sit in a reclined chair. Your doctor may ask you to move into different positions during the procedure.There are two components to an EMG test: the nerve conduction study and needle EMG. The nerve conduction study is the first part of the procedure. It involves placing small sensors called surface electrodes on the skin to assess the ability of the motor neurons to send electrical signals. The second part of the EMG procedure, known as needle EMG, also uses sensors to evaluate electrical signals. The sensors are called needle electrodes, and they’re directly inserted into muscle tissue to evaluate muscle activity when at rest and when contracted.The nerve conduction study is performed first. During this portion of the procedure, your doctor will apply several electrodes to the surface of your skin, usually in the area where you’re experiencing symptoms. These electrodes will evaluate how well your motor neurons communicate with your muscles. Once the test is complete, the electrodes are removed from the skin.After the nerve conduction study, your doctor will perform the needle EMG. Your doctor will first clean the affected area with an antiseptic. Then, they will use a needle to insert electrodes into your muscle tissue. You may feel slight discomfort or pain while the needle is being inserted.The needle electrodes will evaluate the electrical activity of your muscles when contracted and when at rest. These electrodes will be removed after the test is over.During both parts of the EMG procedure, the electrodes will deliver tiny electrical signals to your nerves. A computer will translate these signals into graphs or numerical values that can be interpreted by your doctor. The entire procedure should take between 30 and 60 minutes.
Lecture Topic 3.1.2
Electroencephalogram (EEG)
What is an EEG?
An EEG is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto your scalp. The electrodes detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen, or as a recording that may be printed out on paper. Your healthcare provider then interprets the reading.
During an EEG, your healthcare provider typically evaluates about 100 pages, or computer screens, of activity. He or she pays special attention to the basic waveform, but also examines brief bursts of energy and responses to stimuli, such as flashing lights. Evoked potential studies are related procedures that also may be done. These studies measure electrical activity in your brain in response to stimulation of sight, sound, or touch.
The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG.
People with lesions of their brain, which can result from tumors or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion.
The test can also be used to diagnose other disorders that influence brain activity, such as Alzheimer’s disease, certain psychoses, and a sleep disorder called narcolepsy.
The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures.
There may be other reasons for your healthcare provider to recommend an EEG.
What are the risks of an EEG?
The EEG has been used for many years and is considered a safe procedure. The test causes no discomfort. The electrodes record activity. They do not produce any sensation. In addition, there is no risk of getting an electric shock.
In rare instances, an EEG can cause seizures in a person with a seizure disorder. This is due to the flashing lights or the deep breathing that may be involved during the test. If you do get a seizure, your healthcare provider will treat it immediately.
Other risks may be present, depending on your specific medical condition. Be sure to discuss any concerns with your healthcare provider before the procedure.
Certain factors or conditions may interfere with the reading of an EEG test. These include:
Low blood sugar (hypoglycemia) caused by fasting
Body or eye movement during the tests (but this will rarely, if ever, significantly interfere with the interpretation of the test)
Lights, especially bright or flashing ones
Certain medicines, such as sedatives
Drinks containing caffeine, such as coffee, cola, and tea (while these drinks can occasionally alter the EEG results, this almost never interferes significantly with the interpretation of the test)
Oily hair or the presence of hair spray
How do I get ready for an EEG?Ask your healthcare provider to tell you what you should do before your test. Below is a list of common steps that you may be asked to do.
Your healthcare provider will explain the procedure to you and you can ask questions.
You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
Wash your hair with shampoo, but do not use a conditioner the night before the test. Do not use any hair care products, such as hairspray or gels.
Tell your healthcare provider of all medicines (prescription and over-the-counter) and herbal supplements that you are taking.
Discontinue using medicines that may interfere with the test if your healthcare provider has directed you to do so. Do not stop using medicines without first consulting your healthcare provider.
Avoid consuming any food or drinks containing caffeine for 8 to 12 hours before the test.
Follow any directions your healthcare provider gives you about reducing your sleep the night before the test. Some EEG tests require that you sleep through the procedure, and some do not. If the EEG is to be done during sleep, adults may not be allowed to sleep more than 4 or 5 hours the night before the test. Children may not be allowed to sleep for more than 5 to 7 hours the night before.
What happens during an EEG?
You will be asked to relax in a reclining chair or lie on a bed.
Between 16 and 25 electrodes will be attached to your scalp with a special paste, or a cap containing the electrodes will be used.
You will be asked to close your eyes, relax, and be still.What happens after an EEG?
Skin irritation or redness may be present at the locations where the electrodes were placed, but this will wear off in a few hours.
Your healthcare provider will inform you when you may resume any medicines you stopped taking before the test.
Lecture Topic 3.1.3
Electroretinogram
The electroretinogram (ERG) is a diagnostic test that measures the electrical activity of the retina in response to a light stimulus. The ERG arises from currents generated directly by retinal neurons in combination with contributions from retinal glia. Importantly, the ERG is an objective measure of retinal function that can be recorded non-invasively under physiological conditions. The first known ERG was recorded from amphibian retina in 1865 by the Swedish physiologist Alarik Frithiof Holmgren. James Dewar of Scotland subsequently recorded the ERG in humans in 1877.
Preparation of the patient
According to ISCEV 2015 full-field ERG guidelines:
Avoid fundus phtography, fundus autofluorescence, fluorescein angiography, and other intense illumination before ERG recording. If this is unavoidable, allow at least 30 min recovery time in ordinary room illumination.
Maximally dilate the pupils (note pupil size before testing).
There is no need to correct refractive error.
Before dark-adapted protocols: 20 min of dark-adaptation.
Before light-adapted protocols: 10 min of light-adaptation.
If corneal contact lens electrodes are inserted after dark-adaptation, this should be performed under dim red light. Allow 5 min of extra dark adaptation after insertion of contact lens electrodes.
Present low strength flashes before stronger flashes to avoid partial light adaptation from strong flashes.
Request the patient to fixate steadily and not move his/her eyes. Ocular movements introduce large electrical artifacts, change electrode position, and may cause blockage of light by the eyelids/electrode.
Protect corneal surface with non-irritating ionic conductive solution (artificial tears or contact lens solutions containing sodium chloride and no more viscous than 0.5% methyl cellulose). Improper installation of contact lens electrodes can cause corneal abrasions.
Electrooculogram
The electroocoulogram (EOG) is an elecrophysiologic test that measures the existing resting electrical potential between the cornea and Bruch’s membrane. The mean transepithelial voltage of bovine Retinal pigment epithelium is 6 millivolts (mV). The EOG was described and named by Elwin Marg in 1951. Clinical applications were described first by Geoffrey Arden in 1962, who realized that the most valuable information was the comparison of the amplitudes under light and dark-adapted states (the Arden ratio).
The patient should be in stable indoor lighting for at least 30 min before the test. Strong retinal illumination including retinal imaging (fluorescein angiogram, fundus photography and others) and indirect ophthalmoscopy should be avoided during this period.
The patient is told to remain still other than moving his/her eyes back and forth. Four recording skin electrodes (silver-silver chloride or gold-disk) are placed at the medial and lateral canthi of both eyes, and the grounding electrode is placed on the forehead. The difference of electrical potential of the anterior and posterior part of the eyeball is called the standing potential.[2] Standing potential indirectly measures the transepithelial potential (TEP) of the retinal pigment epithelium (RPE). TEP is the difference of membrane potential of basolateral and apical membranes of RPE.
Components of the EOG
The light-insensitive component accounts for the dark trough and is dependent on the integrity of the retinal pigment epithelium (RPE) as well as the cornea, lens, and ciliary body. The light-sensitive component is the slow light rise of the EOG and is generated by the depolarization of the basal membrane of the RPE.
The EOG is abnormal in:
Best vitelliform macular dystrophy (early stage) and in carriers
Stargardt macular dystrophy (advanced stage)
Pattern dystrophies (normal or modestly subnormal)
Membranoproliferative glomerulonephritis with electron dense material deposition in the choriocapillaris (normal or subnormal)
Ectodermal dysplasia, ectrodactyly, and macular dystrophy, EEM syndrome (markedly reduced)
Retinitis pigmentosa and rod-cone dystrophies
Acquired cone and cone-rod dystrophies
Oguchi disease
Fundus Albipunctatus (no notable light rise with dark adaptation of 15 minutes)
Recorders provide permanent visual trace or record of an applied electrical signal. The most basic electronic recording system consists of 3 important components:
The electrode picks up the bioelectric potentials whereas the transducer converts the physiological signal to be measured into a usable electrical output.
The signal conditioner converts the output of the electrode/transducer into an electrical quantity suitable for operating the writing system.
The writing system provides a visible graphic representation of the quantity of the physiological variable of interest.
To make the signal from any transducer compatible with the input signal required for the driver amplifier of the display or recording system, it is usual to arrange to normalize the electrical signals produced by each transducer. This is done in the signal conditioner which adjusts its output to a common signal level e.g. one volt. The necessary adjustments of gain and frequency response are provided by the signal conditioners.
A vectorcardiogram is a graphic recording of electric forces of the heart. it is a noninvasive procedure that graphically records the direction and magnitude of the heart’s electric forces by means of a continuous series of vector loops. Three planes of the heart are recorded (frontal, sagittal and horizontal)A vectorcardiogram is used to assess ischemia, conduction defects and chamber enlargement (hypertrophy or dilation)
PROCEDURE
Establish a relaxed environment
Place the client in a supine position
Conduction jelly is placed on the electrodes and the electrodes are applied and recording is made
Phonocardiography
diagnostic technique that creates a graphic record, or phonocardiogram, of the sounds and murmurs produced by the contracting heart, including its valves and associated great vessels.The phonocardiogram is obtained either with a chest microphone or with a miniature sensor in the tip of a small tubular instrument that is introduced via the blood vessels into one of the heart chambers.
Lecture Topic 3.2.2
Electrical Safety
Electrically powered equipment can pose a significant hazard to workers, particularly when mishandled or not maintained. Many electrical devices have high voltage or high power requirements, carrying even more risk.
Electrical Shock Hazards
The major hazards associated with electricity are electrical shock, fire and arc flash. Electrical shock occurs when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.
The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry. Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin.
The effect of the shock may range from a slight tingle to severe burns to cardiac arrest. The chart below shows the general relationship between the degree of injury and amount of current for a 60-cycle hand-to-foot path of one second’s duration of shock. While reading this chart, keep in mind that most electrical circuits can provide, under normal conditions, up to 20,000 milliamperes of current flow.
A hazardous arc flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. Potential places where this can happen include:
Panel boards and switchboards
Motor control centers
Metal clad switch gear
Transformers
Motor starters and drive cabinets
Fused disconnects
Any place that can have equipment failure
only qualified workers who have been trained in the avoidance of electrical hazards are permitted to work on or near exposed energized parts. Safety related work practices are employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contact when work is performed near or on equipment or circuits which are or may be energized. The specific safety-related work practices must be consistent with the nature and extent of the associated electrical hazards.
Use of Protective Equipment
Employees working in areas where there are potential electrical hazards must be provided with and use electrical protective equipment appropriate for the parts of the body to be protected and the work performed. Protective equipment must be maintained in a safe, reliable condition and be periodically inspected or tested as required by 29 CFR 1910.137, Electrical Protective Devices.
General Protective Equipment and Tools
Insulated tools and handling equipment must be used by employees working near exposed energized conductors or circuit parts if the tools and/or equipment may make contact with the conductors or parts. The insulating material of tools and equipment must be protected where it is subject to damage.
Working Outdoors
Electrical hazards on construction or renovation sites or work performed outdoors must be controlled through the use of Ground Fault Circuit Interrupters (GFCIs).
Extension Cords
Workers must visually inspect extension cords and cord and plug connected equipment daily before use. Damaged extension cords must be removed from service and destroyed. Damaged or defective equipment must be removed from service and destroyed or repaired by a qualified electrician.
Lecture Topic 3.2.3
Preamplifier
A preamplifier (preamp) is a device that converts a weak electrical signal into a noise-tolerant audible output signal, while an amplifier (power amp) is a device that can increase the power of the output level of any signal, albeit with some added noise.
What’s the exact difference between preamps and power amps?
Preamps are necessary for powering quiet sounds without increasing their noise floor, whereas power amps are necessary for powering sounds that are too loud to be processed by a preamp. Both are used to convert small signals into bigger signals, but what is it exactly that makes them different?
In technical terms, it all has to do with the impedance level. Defined as the opposition to current flow, impedance is used to hold back (i.e., impede) the level of noise and power of an output signal. High impedance means less power and less noise, while low impedance means more noise and more power.
Preamps have high impedance, meaning they can power weak signals into line-level signals without adding too much noise. For this reason, preamps are favored by audiophiles and are commonly used to process microphone recordings. However, they’re virtually useless in dealing with speaker-level signals: since the level of impedance in the preamp is very high, they do not have the required wattage to drive a loud signal.
Preamps are used to power microphone signals instead of power amps due to their ability to contain noise-floor levels. If you use a power amp to boost a mic input, you’ll notice the recording will sound very noisy, causing a significant reduction in sound quality. On the other hand, preamps will increase the level of the mic input without sacrificing its sound quality.
CHAPTER 3
Lecture Topic 3.3.1
Recombinant DNA Technology
In the past century, the recombinant DNA technology was just an imagination that desirable characteristics can be improved in the living bodies by controlling the expressions of target genes. However, in recent era, this field has demonstrated unique impacts in bringing advancement in human life. By virtue of this technology, crucial proteins required for health problems and dietary purposes can be produced safely, affordably, and sufficiently. This technology has multidisciplinary applications and potential to deal with important aspects of life, for instance, improving health, enhancing food resources, and resistance to divergent adverse environmental effects. Recombinant DNA technology is playing a vital role in improving health conditions by developing new vaccines and pharmaceuticals. The treatment strategies are also improved by developing diagnostic kits, monitoring devices, and new therapeutic approaches. Synthesis of synthetic human insulin and erythropoietin by genetically modified bacteria.The advent of recombinant DNA technology revolutionized the development in biology and led to a series of dramatic changes. It offered new opportunities for innovations to produce a wide range of therapeutic products with immediate effect in the medical genetics and biomedicine by modifying microorganisms, animals, and plants to yield medically useful substances.
Tools Of Recombinant DNA Technology
he restriction enzymes used in recombinant DNA technology play a major role in determining the location at which the desired gene is inserted into the vector genome. They are two types, namely Endonucleases and Exonucleases.The Endonucleases cut within the DNA strand whereas the Exonucleases remove the nucleotides from the ends of the strands. The restriction endonucleases are sequence-specific which are usually palindrome sequences and cut the DNA at specific points.
The vectors – help in carrying and integrating the desired gene. These form a very important part of the tools of recombinant DNA technology as they are the ultimate vehicles that carry forward the desired gene into the host organism. Plasmids and bacteriophages are the most common vectors in recombinant DNA technology that are used as they have a very high copy number. Host organism – into which the recombinant DNA is introduced. The host is the ultimate tool of recombinant DNA technology which takes in the vector engineered with the desired DNA with the help of the enzymes.
Process of Recombinant DNA Technology
The complete process of recombinant DNA technology includes multiple steps, maintained in a specific sequence to generate the desired product.
Step-1. Isolation of Genetic Material.
The first and the initial step in Recombinant DNA technology is to isolate the desired DNA in its pure form i.e. free from other macromolecules.
Step-2.Cutting the gene at the recognition sites.
The restriction enzymes play a major role in determining the location at which the desired gene is inserted into the vector genome. These reactions are called ‘restriction enzyme digestions’.
Step-3. Amplifying the gene copies through Polymerase chain reaction (PCR).
It is a process to amplify a single copy of DNA into thousands to millions of copies once the proper gene of interest has been cut using restriction enzymes.
Step-4. Ligation of DNA Molecules.
In this step of Ligation, the joining of the two pieces – a cut fragment of DNA and the vector together with the help of the enzyme DNA ligase.
Step-5. Insertion of Recombinant DNA Into Host.
In this step, the recombinant DNA is introduced into a recipient host cell. This process is termed as Transformation. Once the recombinant DNA is inserted into the host cell, it gets multiplied and is expressed in the form of the manufactured protein under optimal conditions.
Application of Recombinant DNA Technology
DNA technology is also used to detect the presence of HIV in a person.
Gene Therapy – It is used as an attempt to correct the gene defects which give rise to heredity diseases.
Clinical diagnosis – ELISA is an example where the application of recombinant
Lecture Topic 3.3.2
stem cell
stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells and some cells that are destined to differentiate (become specialized). Stem cells are an ongoing source of the differentiated cells that make up the tissues and organs of animals and plants. There is great interest in stem cells because they have potential in the development of therapies for replacing defective or damaged cells resulting from a variety of disorders and injuries, such as Parkinson disease, heart disease, and diabetes. Embryonic stem cells (often referred to as ES cells) are stem cells that are derived from the inner cell mass of a mammalian embryo at a very early stage of development, when it is composed of a hollow sphere of dividing cells (a blastocyst).
Types of Stem Cells
Totipotent Stem Cell: Totipotent stem cells have the capacity to divide and give rise to all types of cells in an organism. Totipotency, which enables cells to create both extra-embryonic and embryonic structures, has the highest differentiation potential.
Pluripotent Stem Cell: Unlike extraembryonic structures like the placenta, pluripotent stem cells (PSCs) can create cells from all germ layers. One illustration is embryonic stem cells (ESCs).
Multipotent Stem Cell: PSCs have a wider range of differentiation than multipotent stem cells, yet multipotent stem cells can specialise in discrete cells from particular cell lineages. A haematopoietic stem cell, which may give rise to various blood cell types, is one illustration.
Oligopotent Stem Cell: Multiple cell types can be created by differentiating oligopotent stem cells. One type of stem cell can divide into white blood cells but not red blood cells in the myeloid stem cell.
Unipotent Stem Cell: These are solely capable of producing cells of the same kind. They can regenerate themselves, which means they still stem cells. Adult muscle stem cells are one example of that
Stem Cell TherapyStem cell therapy commonly referred to as regenerative medicine uses stem cells or their byproducts to encourage the repair response of sick, malfunctioning or wounded tissue. It is the next step in the transplantation of organs, replacing donor organs which are scarce with cells.
Stem cell therapy, like any other treatment, carries with it the possibility that the patient’s immune system will reject the cells that are employed in the treatment. The enormous promise that stem cells have is that they are able to divide an infinite number of times and differentiate into a wide variety of cell types. We can receive stem cells from our bodies, from foetal amniotic fluid, from pluripotent cells, and the stem cells of other people. The bone marrow, brain, blood vessels, skin, teeth, and several other tissues all contain stem cells.
Lecture Topic 3.3.3
Tissue engineering
Tissue engineering, scientific field concerned with the development of biological substitutes capable of replacing diseased or damaged tissue in humans. The term tissue engineering was introduced in the late 1980s.Tissue engineering integrates biological components, such as cells and growth factors, with engineering principles and synthetic materials. Examples of tissues that are candidates for tissue engineering include skin, cartilage, heart, and bone. The production of skin substitutes has played an important role in improving the success of skin graft surgeries,especially for complex wounds such as burns.Substitute tissues of the renal system, including urinary bladders and urethras, have also been engineered and transplanted successfully, thereby broadening therapeutic opportunities for complicated renal disorders. The terms “tissue engineering” and “regenerative medicine” have become largely interchangeable, as the field hopes to focus on cures instead of treatments for complex, often chronic, diseases.
Scaffolds– Scaffolds are materials engineered for the formation of new functional tissues and used for medical purposes. Scaffolds recreate the in-vivo environment that is provided by the extracellular matrix. Depending on its origin, Scaffolds are classified into two types. Natural scaffolds take part in the process of morphogenesis and function acquisition of different cell types in the in-vivo environment
Uses of scaffolds include-
cell attachment and migration
retention of cells and biochemical factors
allowance for the diffusion of vital cell products and expressed products
The three types of biomaterials that are used for fabrication of scaffolds are:Ceramics– They have excellent biocompatibility because of their chemical and structural similarity. They constitute high mechanical stiffness and very low elasticity. Examples include- hydroxyapatite (HA) and tri-calcium phosphate (TCP), for bone regeneration applications.Synthetic polymers– They exhibit controlled degradation characteristics and are easy to be fabricated with a tailored architecture. Examples include- polystyrene, poly-l-lactic acid (PLLA), polyglycolic acid (PGA) and poly-dl-lactic-co-glycolic acid (PLGA).Natural polymers– They are biologically active and allow host cells to produce their own extracellular matrix and replace the degraded scaffold.Application of Tissue Engineeringrepair damaged tissues and organs. They stimulate the body’s own repair mechanisms to heal previously irreparable tissues or organs. If the body cannot heal itself, the tissues or organs can be grown in the laboratory and then implanted.
Some key research areas include-
Implantation of human liver in mice: The implantation of the engineered human liver into the mice can make the drug interactions similar to that happens in the human system. The test of toxicity, species-specific responses can be easily understood by the researchers.Regeneration of a new kidney: The kidney scaffolds seeded with epithelial and endothelial cells developed in organ tissue. The tissue produced urine both in-vitro and in-vivo in rats. The ability to regenerate a new kidney is a leap forward in overcoming the problems of donor organ shortages.
