Liposomal Nanotechnology and its role in vaccine delivery systemsOctober 14, 2021
In the recent past, there have been many projects to develop sub-unit vaccines that are more effective and defined
Vaccination or immunization is the injection of small amounts of weakened or killed bacteria and viruses, or their parts, to trigger an immune response and produce antibodies against that particular pathogen. The vaccine prepares the body to fight against the infection causing organism when it actually enters the organism. This is classical vaccine development.
However, in more recent times, research has been focused on developing sub-unit vaccines that are more effective and defined. However, due to their synthetic nature, the immune response generated is weak. With the advent of COVID-19 and other complex pathogens like HIV and drug resistant tuberculosis, there has been an increase in the challenges posed to the development of efficacious vaccines. Antigens susceptible to genetic mutations are another source of concern. In today’s population where immunity is compromised due to poor lifestyle and habits, it is all the more challenging to develop vaccines that deliver best results.
In this complex and trying time, Liposomal Nanotechnology has been gaining a lot of attention, especially in the field of vaccine development. It has been the subject of research ever since 1960,and has since then proven to be a profound, robust and stable novel drug delivery platform. The new, mRNA based Covid 19 vaccine is a proven and strong example of a liposomal based drug delivery system (lipid nanotechnology) being used to reach target cellular sites.
Liposomes – Superior Drug Delivery Platforms
Liposomes are small spherical vessels that are composed of one or more phospholipid bilayers. The polar lipids are present in the outer and inner aqueous phase. Liposomes are formed spontaneously when phospholipids are hydrated with water. These liposomes closely resemble the structure of cell membranes. Due to this lipid bilayer structure, they can be encapsulated easily with hydrophilic, amphiphilic, and hydrophobic active molecules or drugs. The phospholipid protective shield entraps unstable molecules or substances and renders it resistant to enzymes, fluctuating pH levels and free radicals within the body, and delivers these to specific target sites. All of these unique properties, coupled with high biodegradability, biocompatibility and low toxicity, make them ideal as drug carriers. These liposomes range anywhere from 100 to 330 nm in diameter.
Liposome nanoparticles are used very widely as carriers in efficient drug delivery to target sites, as carriers for mRNA particles and adjuvants in vaccines, as signal enhancers in medical diagnostics and such other applications in modern medicines. Due to their specific property of biostability, they offer a sustained mechanism of delivering a variety of hydrophilic and hydrophobic compounds used in antibacterial, anti fungal, immunomodulation, vaccines and genetic elements.
Application of Liposomes in Vaccine Development
Ever since the Covid 19 pandemic set in, a lot has been written about the bottling and distribution of the mRNA-based vaccine. However, there is limited understanding of the actual science behind the development of the vaccine. The mechanism that has fortified these vaccines is lipid nanotechnology, which is a major breakthrough in vaccine delivery systems. It has played a crucial role in enabling the development of the Covid-19 mRNA-based vaccines.
Liposomes are ideal carriers for antigens and adjuvants (which stimulate the immune response and enhance antigen delivery) used in vaccines. The properties of the liposomes play a very important role in the local tissues distribution, retention, uptake and processing by the antigen presenting cells or APCs. In the case of the mRNA based Covid 19 vaccine, the mRNA strand is encapsulated within the stable structure or matrix of the nanoliposome. A key protein of the SARS COV 2 virus is encoded in the mRNA strand. Once injected into the body, this, along with the adjuvant encapsulated into the lipid nanoparticle, induces the production of the spike protein, which docks onto the human cell membrane. It acts as an antigen and triggers an immune response which primes the body for a defence against the real virus when there is an infection.
On its own, the mRNA strand is extremely sensitive to degradation. Hence, lipid nanoparticles or LNPs offer stability and protection during the delivery process of the mRNA strand until its uptake into the cell. This ensures an efficacious viral replication and a better cell response, thus enhancing the overall immunogenic response of the vaccine.
Bright Future for Liposomal Nanotechnology
With further research and newer applications emerging, liposomes offer great promise for future novel drug delivery systems. The versatile use of these liposomes makes them highly valuable carriers in vaccine delivery systems. They possess an innate ability to overcome biological barriers within the body and deliver stable state vaccine components (antigens) in a slow and sustained manner for optimum results and provide fundamental properties for the development of modern vaccines.
At the same time, the procedures involved in these novel drug delivery mechanisms are quite complex and involve considerable expenditure. Scale-up processes also seem to be too time-consuming for pharmaceutical applications. However, if given the right funding and opportunities, it can evolve as a more reliable platform for the development of a range of bioproducts with diverse medical applications.
The author is Managing Director of VAV Life Sciences