BIOTECHNOLOGY AND MEDICINE

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There are so many benefits of biotechnology in the medical world. I'll be discussing some of them. One of which is the biosensor.

^{A device for measuring high blood pressure

Pixabay}

Biosensors are being developed for many applications in medicine. One device that is already available is the Glucowatch® Biographer. It is a device which measures blood glucose levels without puncturing the skin to take blood sample. The device looks like an ordinary watch; it is worn on the wrist and it has an LCD dial. However, people with diabetes use it to measure their blood glucose level, not the time.

How the glucose biosensor works

The back of the Glucowatch® Biographer that comes into contact with the skin has two circular flat plates. The two plates generate a low electric current that is directed into the skin. This causes positive and negative ions to move out of the skin, pulling glucose molecules from the blood with them. The glucose collects in gel discs that contain glucose oxidase. This enzyme catalyses a reaction that generates a small electric signal. The size of the signal is proportional to the glucose level in the blood. The Glucowatch® Biographer uses this signal to calculate a reading, which is then displayed.

^{A biosensor, an EEG integration

Pixabay}

How is the biosensor used?

Usually, people with diabetes who control their condition by insulin injections measure their blood glucose using the standard finger-prick method. They do this three or four times a day; before each meal and last thing at night.
The disadvantage of this is that the blood glucose level actually changes during a 12-hour period. This can be detected by the Glucowatch® Biographer because it takes readings every 20 minutes, rather than by much less frequent finger-prick tests. These show the glucose levels at points A, B and C, lulling the person into thinking their blood glucose is stable.

MONOCLONAL ANTIBODIES

Monoclonal antibodies are antibodies that can be produced in large amounts and that bind only to one, very specific target. This is usually part of a molecule, not even a whole molecule.

How are monoclonal antibodies produced?

The method used to create monoclonal antibodies is called hybridoma technology. It was first devised in the 1980s by Cesar Milstein, working in laboratories in Cambridge, UK. It basically involves fusing a cell that produces antibodies with one that is immortal. The figure below summarises the process of making a monoclonal antibody.

^{A general representation of the method used to produce monoclonal antibodies

Wikimedia, Adenosine • CC BY-SA 3.0}

The first step in the production of a mouse monoclonal antibody is to immunise a mouse with the molecule against which we want the monoclonal antibody to react. White blood cells in the mouse produce a range of different antibodies, directed against different parts of the molecule.

Cells called B lymphocytes that are responsible for making these antibodies are isolated from the mouse’s spleen. These cells are then fused with tumour cells that divide continuously and rapidly. This creates a single, large cell called a hybridoma. These hybridomas show properties of both ‘parent’ cells; they produce antibodies and they divide continuously.

854px-Monoclonal_antibodies.svg.png

^{Monoclonal antibodies for cancer. ADEPT, antibody directed enzyme prodrug therapy

Wikimedia, public domain}

One hybridoma can divide to produce a whole clone of identical hybridomas, all secreting the same antibody molecule. Once a clone has been established and is growing well in culture, the antibody produced by this collection of cells is called a monoclonal antibody.

Monoclonal antibodies used in diagnosis

Monoclonal antibodies can be linked to a radioactive isotope and, in this form, they have been used for diagnosing and monitoring disease since the early 1980s. Some forms of cancer can be diagnosed using monoclonal antibodies directed against molecules found only on the surface of cancer cells. When injected into patients, such a monoclonal antibody will carry its radioactive marker straight to the tumour, where it can be detected using CT (computerised tomography) scanning.

^{The preparation of slides of monoclonal antibodies for researchers. These highly specific cells shown are those labeling human breast cancer.

Wikimedia, public domain}

The pregnancy test

The time a pregnant woman would have been due for her next period, the embryo will have implanted and will be starting to secrete human chorionic gonadotrophin (hCG). Enough of this hormone passes into the urine for it to be detected by a modern pregnancy testing kit. This kit makes use of monoclonal antibodies that are specific for hCG and which are attached to a coloured chemical.

The diagram below shows how a home pregnancy test kit works for a pregnant woman (a, b, and c) and for a woman who is not pregnant (d)

^{How a home pregnancy test kit works||an image drawn by me}

As we can see that there are four levels (taking the lowest point of the strip as the first level) in each of the pregnancy test strip in the diagrams a to d.

So, starting with diagram a, The urine is drawn up the test strip by capillary action.

The first level has the urine sample of pregnant woman containing hCG molecules. The second level is where the mobile anti-hCG antibodies complexed with coloured granules. The third level is that of immobilised anti-hCG antibodies. The fourth level is the zone of immobilised antibodies which react with the anti-hCG antibody colour complex.

In the diagram b, the hCG attached to the colour/antibody complex moves up the test strip. This happens in the level two of the test strip.

In the diagram c, hCG attached to the colour/antibody complexes moves up to dock with the immobilised (fixed) hCG antibodies in the test window. All the complexes are stopped at one place, forming a visible coloured band and confirming pregnancy. Colour/antibody complexes without hCG attached move on to the control window.

At the third level, immobilised hCG antibodies trap the coloured complexes/hCG while the antibody complexes trapped by anti-antibodies occurs at the fourth level.

In the diagram d, with the urine of a non-pregnant woman, the colour/antibody complexes have no attached hCG, all the complexes move past the immobilised hCG antibodies in the test window and attach to the anti-antibodies in the control window, showing that the test has worked.

A coloured band always appears in the control window, showing the test has run correctly. A coloured band in this window confirms pregnancy while no coloured band indicates no pregnancy

Treating disease with monoclonal antibodies

The use of monoclonal antibodies in the treatment of different diseases has really expanded over the past 15 years. Most monoclonal antibodies are used for cancer treatment.

Normally, antibodies are produced in the body by B cells when into contact with an antigen – such as a surface molecule on a bacterium. Researchers have developed techniques to take one of these B cells, which is making an antibody they are interested in, and fuse it with an immortal cancer cell. The resulting cells divide again and again but never die and they all make exactly the same sort of antibody. These become manufacturing centres for that type of antibody – which is then called a monoclonal antibody

Monoclonal antibodies can be made to directly attack specific molecules on cancer cells – they kill only the cancer cells and no other body cells. They do a lot of damage in this way. Monoclonal antibodies can also be attached to radioactive molecules or to toxins, and can act as ‘guided missiles to target cancer cells.

^{Monoclonal antibodies for cancer. ADEPT, antibody directed enzyme prodrug therapy.

Wikimedia, public domain}

Developing new drugs and treatments

Developing any new therapy is a time-consuming and expensive process, and developing new drugs and monoclonal antibody therapies takes several years

The process starts in a laboratory with researchers who are carrying out fundamental research into how the body works or what goes wrong in a particular disease. When they identify the mechanism of a disease at the molecular level, it often suggests how pathways can be altered or blocked – by a potential treatment for that disease.

This is often a natural molecule, perhaps a substrate for an enzyme in a biochemical pathway. This natural molecule can then be modified using chemical techniques to create a library of thousands of potential compounds that could one day become drugs. These molecules are screened using automated high-throughput methods and those that seem to have the desired activity are chosen for further testing. These are usually called lead compounds.

^Pixabay

Lead compounds are then tested in cell systems in culture to see if they show activity in living cells. If they show promise, they can be further modified to try to create a molecule with the highest activity. This then goes on to the next round of testing – in small animals like mice and rats.

There is a lot of opposition to animal testing, but there is no other way to see how a potential treatment behaves in a living cell in a living system. Although mice are not the same as people, testing how a drug affects a mouse can provide a great deal of useful information that helps refine the drug further. This can take several more years. Eventually, when researchers are confident that a drug is looking very hopeful, it then enters a new type of testing in people. These tests are called clinical trials.

There are three main phases of clinical trial and a drug must pass through all of them before it can be approved for use in patients.

Drug_discovery_cycle.svg.png

^{Schematic diagram of drug discovery cycle.

Wikimedia, CC BY-SA 4.0}

Phase I trials

Phase I studies are mainly concerned with the drug’s safety and are generally done in a small number of people, usually less than a hundred. Researchers look for possible side-effects, how well the drug is tolerated and how the drug passes through the body.

A Phase I clinical trial of Trabio, a fully human monoclonal antibody, was designed to prevent scarring in patients having surgery for glaucoma. The trial was a double-blind randomised trial, with Trabio versus placebo (an injection of saline).

As this was a Phase I trial, its main aim was to establish if Trabio was safe and if it caused swelling or other problems when injected at or near the site of operation. Trabio was shown to be safe and well tolerated in this group of patients: there were no serious local injection site reactions and no serious adverse events were reported. There were also some signs that scarring was reduced, but it was difficult to see any significant difference in the small number of patients in the trial (24). A follow up Phase II study was then planned.

Phase II trials

Phase II studies are designed to test out how well the drug can treat a particular disease. The second phase of testing may last from several months to a few years and involve up to several hundred patients. Most Phase II studies are placebo-controlled, double-blind randomised trials.

Tefibazumab, a humanised monoclonal antibody, was tested for its ability to treat Staphylococcus aureus infections. This monoclonal antibody binds to a protein that is expressed in the body in infected cells, called adhesion protein clumping factor A.

A total of 60 patients took part in the trial; 30 were given the monoclonal antibody and the other 30 a placebo. People were randomly assigned to the two groups. The results showed that there was no difference in the two groups with respect to adverse reactions to the treatment, which told the researchers that the monoclonal antibody was safe. Fewer patients in the tefibazumab group died and fewer got worse, so the study concluded that this monoclonal antibody would be worth investigating further for treating this type of bacterial infection.

Phase III trials

In a Phase III study, an experimental drug is tested in several hundred to several thousand patients with the disease.

Most phase III studies are also double-blind, randomised trials. Phase III studies can last years. Once a drug or treatment has passed through Phase II trials for one type of disease, it may well then go on to Phase III trials for other, related diseases such as a different type of cancer.

Panitumumab is a fully human monoclonal antibody directed against the epidermal growth factor receptor (EGFR). In a Phase III trial, researchers compared two groups of people with advanced colon cancer, who had not responded to chemotherapy: 232 of them were given supportive care and the other 231 were given supportive care and panitumumab. They then measured the time that each patient remained at the same level of health without their symptoms getting any worse.

Patients who received the monoclonal antibody remained the same for 14 weeks but patients in the other group started to get worse after only 8 weeks. Analysing the data showed that this result was statistically significant. Although 6 weeks doesn’t seem a long time, for these seriously ill patients it did make a big difference and panitumumab therapy has since been approved for use in advanced colon cancer.

^{Graph showing the various approval tracks and research phases

Kernsters • CC-BY-SA-3.0}

In developing new drugs and treatments, some terms are commonly used and are very important. Some of those terms are placebo, control group, double-blind, randomized testing, etc.

So, what is a placebo?

Placebo is something that mimics a drug to 'fool’ people into thinking they are taking a real drug. It has been known for a long time that many people who feel ill start to feel better if they are given something like a sugar pill. This has no physiological effect but they feel better because of the psychological effect of believing the pill will do them good.

In clinical trials, experimental drugs are tested in comparison with placebos to assess the actual impact of the drug, to make sure they are not just measuring this psychological ‘placebo effect’. Testing a drug against a placebo nullifies this effect and makes the trial results more reliable.

Some other important terms

The point of control groups, double-blinding and randomised testing is to reduce error, self-deception and bias on the part of the people who are running the trial and the people taking part in the trial. For example, although they might not mean to, if someone knew they were taking the drug they might exaggerate how much better they feel, which would distort the results.

Control group

A control group is a group of people who are identical in every way to an experimental group in a clinical trial.

The two groups contain the same numbers of people and are usually matched for age, sex, ethnic grouping and lifestyle (all non-smokers, etc.). This is done to reduce the number of variables in the experiment.

Double-blind

A double-blind test is a control group test where neither the person running the trial nor the people in the trial know who is receiving the experimental drug and who is receiving the placebo. The drug and the placebo look identical and they are prepared and labelled by someone who doesn't interact with the people in the trial.

Randomised

A randomised trial is one in which people are randomly assigned to either the control or the experimental group. Neither the people in the trial nor the people running the trial pick who goes in which group.