A drug can be defined as a medical compound used to treat a clinical condition or illness. Drug delivery is a branch of medicine dealing with procedures and mechanisms through which any kind of drug is passed into the human body without any adverse reactions or side-effects.
Drug delivery systems can be defined as mechanical components specifically designed to administer drugs into the patient’s body. These medical systems can vary in design depending upon the type and purpose of the drug delivered. A syringe with a needle is a basic example for an object used in drug delivery. Drug delivery systems may vary from objects made of plastic to electronic devices with advanced controls.
With advancements in the field of medicine and healthcare, design and usage of drug delivery systems undergo changes mainly to cater patient’s comfort and efficient drug delivery. Drug delivery systems are also aimed to provide better user control and high accuracy in drug measurement.
Few common types of drug delivery systems are nasal sprays, insulin pumps, patient controlled analgesics etc. Main factors considered in the design of drug delivery systems are the rate at which a measured amount of drug is delivered and the site of drug encounter.
Drug delivery mechanisms can be broadly classified under these types – mode of delivery, type of drug carrier etc. Most of the research in this field revolves around cancer treatments.
Mode of delivery
Oral drug delivery as a common mode of drug delivery at present
There are several ways by which a drug can be delivered into the body. Most common way is oral by which tablets, capsules or syrup are swallowed. When administered this way, common side effects occur such as an upset stomach. This is considered as one of the drawbacks existing in the present way of drug delivery. Most often, allergy medications can cause drowsiness though they deliver an efficient recovery.
Usage of microneedles as drug delivery systems in future
Microneedle patches are on the way to replace this system. In future they may provide an alternate method of drug delivery with minimal or zero side effects. Microneedle patches vary in design according to their usage. Generally they are an array of small needles with bio compatible materials containing a measured amount of medicine. They can be placed onto the patient’s skin and they penetrate. As the needle gets through only the surface skin, nerves are not disturbed and hence the patient may not feel any pain.
Some microneedle patches are completely dissolvable inside the body. As they are easy to use, they minimise the risk of damage and they do not produce any hazardous waste. Insulin and vaccines are common drugs that can be administered through microneedles.
Type of drug carrier
A drug carrier can be defined as an object carrying drug inside the body and delivering it at the needed location. For example, in a capsule tablet, the outer capsule acts as a drug carrier. Obviously the drug carrier should be able to dissolve by itself inside the body without any adverse reaction.
Current application of virus as drug carriers in cancer treatment
At present, certain types of cancer are being treated by using viruses. Engineered viruses are injected into the cancer patient’s body where the virus gets attached to the tumour cells. When the virus replicates itself, it breaks the tumour apart and destroys them. These viruses are called oncolytic viruses This concept of cancer treatment is currently under practice.
To enhance this therapy further, such oncolytic viruses are loaded with a gene producing molecule called ‘leptin’. In this case, leptin acts as a drug and the virus acts as a drug carrier. The purpose of using leptin in this treatment is – it triggers the arrival of the body’s natural immune response cells to the site of tumour. The body’s natural immune system recognizes the tumour when drawn into the site this way. Further it destroys the tumour even if it grows elsewhere inside the body.
Future advancements in the usage of engineered bacteria in cancer therapy
As a better alternative to the application of viruses in cancer therapy, bacteria are engineered to act as potential agents in killing cancer cells. Though the idea of using bacteria in cancer therapy is not new, application of specifically engineered bacteria is on the way towards advanced cancer therapy in future.
Engineered bacteria themselves act as drug delivery systems. They swiftly move to oxygen depleted areas where tumours thrive. This means they could specifically target tumour cells without affecting healthy cells. The attachment of bacteria with tumours can also be traced with an MRI which is an added advantage.
Bacteria can be engineered to completely destroy tumours by totally depleting oxygen. This kills the cancer cells by preventing growth. They can also be programmed to secrete toxins, which is an inherent property of bacteria. Such toxins have the potential to cause cell death and hence on successful attachment to a tumour, the bacteria can kill tumour cells effectively.
Introducing nanoparticles as drug carriers in future
As nanotechnology is emerging in all branches of engineering, the field of medicine also progresses to apply its benefits. In fact, application of nanotechnology in medicine is considered as one of the key areas that would bloom and thrive in future.
Geriatric studies show that most of the old age patients suffer from brain-related diseases for which no permanent cure could be formulated till now. Medications cannot be delivered directly to brain cells due to the ‘blood brain barrier’. With the usage of nanoparticles, it is promised that drugs can be applied to the brain directly with nanoparticles as carriers.
Thanks to the large surface area, nanoparticles are able to bind and carry drugs effectively. They can deliver drugs at the target site and decompose by themselves. Nanoparticles as drug carriers are mostly composed of lipids and polymers.
Drug delivery systems at present are undergoing transitions to evolve into more reliable, accurate and harmless medical systems to bring out safe and swift future drug delivery systems.