Targeted drug delivery (TDD) is a concept to deliver drug elements directly to intended action site. TDD makes a system to specify drug moiety straight to specific location. TDD systems suggest synthesis, techniques and mechanisms associated with loading, transporting, and unloading of drug compounds at exact positions in body to get desired therapeutic results. To overcome the toxic behavior of conventional drug delivery methods, TDD was proposed. Nanotechnology is a science that deals with engineering, modifying, and dealing with structures at nanoscale range. Recent advances in nanomedicine have led to invention of TDD systems. To successfully understand science behind TDD, it is necessary to combine many fields together involving polymer science, pharmacology, chemistry, physics, and biology of nano structures, bio conjunction of nanoforms with desired sites, and many more. This review discusses quantum nanoscience behind the scenes enabling TDD. This may further inspire researchers to expand their vision of TDD systems and enhance the goal of nanotechnology in clinical translations.
Top1. Introduction And Evolution Of Drug Delivery Systems
According to FDA, a drug is an active pharmaceutical ingredient (API) which is used in cure, treatment, diagnosis, mitigation and prevention of disease. A dosage form is the addition of drug (API) with non-drug components commonly called as additives or excipients (Langer, 1998). Drug delivery is an approach where the active ingredient of medication is delivered to patient in order to achieve some therapeutic approach in body by increasing the concentration of drug in some body parts (Benoit, 2020). Drug delivery system is highly integrated technique which requires integration of biologists, engineers, chemists and physicists to design proper dosage formation with suitable delivery mechanism (Mark SW, 2011).
1.1. Why We Need Drug Delivery Systems
Dosage form or unit doses are pharmaceutical formulations of drug product in specific mixture of API and inactive configuration. Direct clinical use of active drug substance “as it is” can be impractical and unfeasible as it is degraded by biological and chemical exposure to body’s digestive system. Also, API’s are sensitive to exposure to physical environmental factors such as pH, temperature, light, moisture etc. They have unpleasant organoleptic qualities such as taste, smell as well as potency and dosing handling issues which all leads to drug administration compliance (Langer, 1990). To overcome the difficulties of direct clinical use of API, role of excipients or additives come into play to provide organized structure, shaping formulation, enhancing bioavailability, masking bad taste, palatability and insuring safety during storage (Jain K, 2020) along with easing patient’s acceptability of drug. In a way the non-drug components, excipients or additives act as delivery systems for active drug components (Ku M.S, 2008).
Through the years, there have been remarkable advances in the drug delivery approaches due to increase in molecular complexity of diseases/viruses, leading to change in cultivating therapeutic modalities.
1.2. Conventional Drug Delivery Systems vs. Targeted Drug Delivery Systems
Conventional drug delivery methods distribute drug substance throughout the body whether or not there is requirement of drug delivery to unaffected cells/tissues. This also led to requirement of more drug dosage to patient so that after distribution all over body requisite amount must be delivered to affected cells/tissues for treatment purpose. This was the particular reason for repeated dosages which also initiated other side effects of that drug by affecting healthy cells. To deal with the downside of conventional drug delivery approaches, such as uncontrolled drug release, unorganized distribution, side effects and frequent dose administration, targeted drug delivery mechanisms were thinked up (Felicity Thomas, 2022).
Thusly, targeted drug delivery approaches were considered which administered drug molecules in body through drug delivery systems to ensure transport of active therapeutic substance across biological membranes of diseased site only. The interface between patient’s body and drug is managed by drug delivery systems. Thus, TDD also called “smart drug delivery“ is a method to deliver medication in such a manner that increase dosage of medicine in only some parts of the body rather than distributing it throughout the body through systematic blood circulation.