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Gayathry Thampi
BS-MS Fourth Year, Physical Sciences
With advances in Synbio, a field that has received much attention is new systems of drug delivery. Optimising drug therapy by enhancing the specificity and efficiency of action of the drug and decreasing the side-effects on non-target tissues is the goal of this new technology.
So, without further ado, what is an Ideal Drug Delivery System?
This will deliver the drug only to the target tissue, after which it maintains a therapeutic concentration for a specific duration of time. From the recent advances in drug delivery systems it is can be seen that this technology has become a multidisciplinary science, in which a variety of approaches have been utilised in search of new systems.
Before discussing about drug delivery systems one should know the following :
The design of the system must take into consideration, the drug component, the carrier component and the desired route of administration.
The systems are specific, that is a system developed for one drug may not be usable for another drug with different physicochemical properties.
Here, the carrier component of the drug delivery systems, that is the drug delivery tools, is of importance to us.
Nanoscience has been pioneering the drug design market for quite some time now. The very first generation of nanoparticle-based therapy included lipid systems like liposomes and micelles that can contain inorganic nanoparticles like gold or magnetic nanoparticles. Nanotechnology bridges the barrier of biological and physical sciences by applying nanostructures at various fields of science, especially in nano based drug delivery systems, where such particles are of major interest. Being of the order of a few nanometres, these structures penetrate into the tissue system, facilitate easy uptake of the drug by cells, permit an efficient drug delivery, and ensure action at the targeted tissue or organ.
Graphene Structure
Soruce : Shutterstock
Liposomes for Drug Delivery
Source : Wikimedia CommonsHowever, the problems such as toxicity exhibited by nanoparticles cannot be ignored when considering the use of nanomedicine. More recently, nanoparticles have mostly been used in combination with natural products to lower the toxicity issues. The green chemistry route of designing nanoparticles loaded with drugs is widely encouraged in recent times as it minimises the hazardous constituents in the biosynthetic process. For example, alginate, which is a natural polymer derived from brown seaweed and has been expansively utilized for its potential uses in the biomedical field because of several favourable characteristics, such as low cost of manufacturing, harmonious nature and easy gelling. Perfluorohexane (PFH) nanodroplets stabilized with alginate was found to drive doxorubicin (chemotherapy drug that slows or stops the growth of cancer cells by blocking an enzyme called topoisomerase 2).
But, Synbio has started reaching new horizons in design of deliver systems in recent ears. You can simply pop a pill, which goes to your gut and dissolves to give way to the living strain of Clostridium it carries. While this bacteria is one of the natural residents of our guts, in this ingenious vehicle, it has been engineered to be laden with custom enzymes and molecules which could treat chronic diseases like Inflammatory Bowel Disease. Mimicking the vesicles and exosomes spouted out by living cells to deliver cargo into tissues is another promising approach being taken by synthetic biologists.
Humans and bacteria have a long history of parasitic and symbiotic relationships. In the body, some niches for bacteria, such as the anaerobic lumen of the intestines have low oxygen levels. Similar conditions are found in solid tumours because of increased oxygen demand. The hypoxic (oxygen deficient) areas in a tumour are relatively protected from attacks by the body's immune system, further facilitating bacterial colonization and growth. Bacteria can destroy diseased tissue by competing for nutrients and secreting toxins. They can also be genetically engineered to have extra anti-tumour activity and delivered to specific locations to act as therapeutics, nothing short of a magic bullet.
Yeast-based drug delivery has fuelled a promising development in the transport of drugs to various target sites. The yeast cells are attached to a solid surface with the aid of cross-linking agents like aminosilanes, glutaraldehyde and metal oxide. Detachment and delocation are possible as there is no physical barrier between cell and solution. Encapsulation of drugs in yeast microcapsule increases the bioavailability and protection of the drug from acidic conditions of the stomach. The yeast capsules have been successful in releasing the drug on contact with mucosal surfaces. Even the most promising nanoparticulate delivery systems suffer challenges from gastrointestinal barriers. Novel approaches using bio-inspired yeast microcapsule can help in the delivery of charged nanoparticles like quantum dots, iron oxide nanoparticle, and various fluorescent nanoparticles.
A general schematic for Yeast-based drug delivery
Newer drug delivery systems are more advantageous than the conventional therapies. These systems have better patient compliance, smooth plasma concentrations, ease of application, good delivery to the target tissues and less side effects. Liposomes, microspheres, nanoparticles, bacteria and yeast based drug delivery are a few of the carrier systems and are a part and parcel of newer drug delivery systems.
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