Liposomes, the curious little spherical vesicles that closely resemble the structure of cell membranes, have been attracting a lot of attention in recent times. Known for their applications in the field of medical nanotechnology, these have been a subject of research since these were first discovered in the 1960s. Since then, scientists have found new ways to use these to develop robust and powerful drug delivery systems. The new mRNA-based COVID-19 vaccines are the fine examples of modern drug delivery systems that use lipid nanotechnology to reach their target cellular sites.
A subject of research for several years now, liposomal nanotechnology has been used to successfully develop stable and reliable novel drug delivery systems (NDDS). These NDDS have proved to be beneficial with applications across various medical therapies ranging from HIV to cancer to COVID-19 treatment.
Liposomes are very tiny nanoparticles that measure usually up to 100-300 nm in diameter. These are formed spontaneously when certain phospholipids are hydrated with water. Due to their nature, both water and fat-soluble active ingredients can be loaded onto these. These spherical liposome bubbles can be used to trap and stabilise a variety of compounds used in medications and ensure their safe passage through the body till these reach a specific target site. That’s how these become ideal transport vehicles for drugs in targeted therapies like cancer or HIV.
These structures can deliver both hydrophilic and hydrophobic compounds used in anti-bacterial, anti-fungal, immune-modulation, diagnostics, ophthalmic, vaccines, enzymes and genetic elements.
What makes these superior NDDS?
Liposomes are considered as one of the most efficient nanosystems with several approved formulations for disease treatment. The two important advantages of liposomes in drug delivery are biocompatibility and biodegradability, both of which are due to their lipid characteristics. These liposomal nanosystems also have other properties like smaller size, hydrophobic and hydrophilic character, low toxicity and immunogenicity, lower clearance rates and controlled release of drugs. Due to these properties, liposomes provide an established basis for the sustainable development of different products for the treatment of medical diseases by the smart delivery of drugs.
Today, liposomal nanosystems are being used in the medical industry as drug delivery vehicles in medicine, adjuvants in vaccination, signal enhancers/carriers in medical diagnostics and analytical biochemistry, solubilisers as well as support matrices for various ingredients.
Clinical usages of these systems cover diagnostic, therapeutic and vaccine improvement. Drug and gene delivery are two therapeutic aspects in which liposomes can be effective due to their specific properties. The involvement of liposomes in the treatment of various diseases like HIV, cancer, and in recent times, COVID-19, to name a few, has been investigated with satisfactory results.
Application in HIV therapy
Studies have shown that nanotechnology-based liposomal drug-delivery systems can improve anti-retroviral therapy (ARV) by controlling drug concentrations in target cells. As liposomes are naturally taken up by cells of the mononuclear phagocytic system (MPS), the therapy offers a convenient approach to improve the delivery of anti-HIV agents into infected cells. This can improve the efficacy of drugs and reduce their adverse side effects. HIV-infected cells could also be specifically targetted by using liposomes bearing surface-attached antibodies.
Tailor-made liposomes are biocompatible with the cell membrane and can also specifically target mononuclear phagocyte systems with a variety of drugs. These also help reduce the dose and frequency of dosing. Overall, the therapy offers a potential for improved quality of
life for HIV-positive patients.
Application in cancer therapy
Conventional treatment options for cancer, until recently, were not able to target cancerous cells without destroying healthy cells. Apart from this, the reduced drug dosage at the target cell also impedes the treatment. With liposomal nanotechnology, these challenges have been addressed.
Liposome-bound antibodies can be engineered to target tumour-specific antigens to ensure active targeting, and then transport drugs to the tumour. Once the nanoparticles bind with the receptor on the cancer cell, these are then taken up by the cell and the drug is released at the site. The drug is delivered to the target tumour site once it reaches the cancerous cell. This reduces the side effects on the healthy surrounding tissues. Liposomal Doxorubicin is a good example of a medication wrapped inside a liposome and delivered to the cancer site. It is useful in the treatment of ovarian cancer and multiple myeloma.
Application in anti-fungal therapy like mucormycosis (black fungus)
Liposomal amphotericin B is a formulation developed to improve the tolerability of intravenous amphotericin B, a gold standard for treating life-threatening invasive fungal infections like mucormycosis (black fungus). While the COVID-19 pandemic and the subsequent rise in mucormycosis cases brought the drug into the limelight, it has already been in clinical use for over two decades.
Application in COVID-19 vaccine development
While a lot of importance has been given to the bottling and distribution of the new mRNA-based vaccines, there is limited understanding of the science behind the formulation. These vaccines are based on lipid nanotechnology. Lipid nanoparticles or LNP technology is considered a medical breakthrough in vaccine-based delivery systems. It has enabled the development of stable mRNA-based COVID-19 vaccines at a blistering pace.
These LNPs effectively deliver the mRNA to the target cellular sites and help bind these to the relevant cells. Since mRNA, on its own, is too sensitive to degradation and rapid breakdowns, lipid nanoparticles (LNPs) ensure the protection of the mRNA until its uptake in cells. This results in a better cellular response and efficacy against virus replication, significantly enhancing the overall immunogenic response of vaccines.
The future of liposomal nanotechnology
One can say that liposomes have established their position in modern medicine as more and more applications emerge. One of the emerging technologies is the topical formulation of liposome active for the treatment of skin diseases. As the technology advances further, the field of liposomal nanotechnology will be a more reliable platform for the development of a range of bioproducts, especially in areas of medical diagnostics and public health.