Targeted delivery of macromolecules using a novel virus-mimicking liposomal system

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering

Abstract

The efficient intracellular delivery of therapeutic molecules using liposomal systems has been of interest for many years. However, issues remain with regards to the successful delivery of macromolecules using liposomes, which cause quick elimination of the delivery system from the bloodstream or induction of an immune response, affecting the efficacy of the payload. The use of non-viral vectors can address this issue as they have the ability to mimic viruses, hence allowing evasion of the mononuclear phagocyte system (MPS), which in turn allows circulation times of up to one week as well as enhanced treatment of the targeted tumour (Geng et al., 2007; Niu et al., 2013). Chen et al. have developed polymers that mimic the activity of viral fusogenic peptides with the novelty of being pH-responsive (Chen et al., 2017). Preliminary work carried out by the group shows promising results with regards to the successful intracellular delivery of macromolecules such as nucleic acids and proteins. This could be beneficial for more targeted delivery of drugs and therapeutic molecules to treat diseases such as cancer. Another area of interest is to prolong the shelf life, enhance targeting capacity and improve controlled release of such liposomal drug delivery systems (Payton et al., 2014). The ability to store these delivery systems for a longer amount of time, without the loss of stability and functionality, would be very beneficial not only to protect the payload, but also economically, to commercialize these systems within industry.
The aim of this project is to synthesise a novel virus-mimicking liposomal delivery system using pH-responsive polymers developed by Chen et al. as the surface coating (Chen et al., 2017). The system will be optimised for more controllable and targeted intracellular delivery of macromolecules such as proteins and nucleic acids into a range of different cell types, including cancer cell lines. The ability for the system to cross the cell membrane, successfully release the payload, and ultimately trigger apoptosis will be assessed. Moreover, the storage method of these delivery systems will be optimised to allow for longer storage at room temperature without compromising the integrity of the system.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509486/1 01/10/2016 31/03/2022
1966268 Studentship EP/N509486/1 01/10/2017 30/09/2021 Apanpreet Kaur Bhamra
 
Description A novel virus-mimicking liposomal system (VMLS) was successfully optimized using the surface modification of conventional liposomes with a multifunctional, pH-responsive polymer developed in-house. Controlled release of various macromolecular payloads such as nucleic acids, as well as small molecule drugs was successfully achieved by varying the cholesterol content in the liposomes and optimizing the coating density of the polymer on the surface. The objectives achieved thus far are as follows:

Firstly, self-amplifying RNA (sa-RNA), a very large, highly negatively charged macromolecule, was successfully encapsulated into the VMLS with encapsulation efficiencies of ~80%. These encapsulated delivery systems were then delivered into human embryonic kidney (HEK) cells with transfection efficiencies 1.5 orders of magnitude higher than the gold standard, poly(ethylenimine) (PEI), which is commonly used for the delivery of nucleic acids. The membrane-disruptive activity of the delivery systems after surface modification with the polymer was also investigated. It was found that at physiological pH (pH 7.4) the delivery systems were not membrane-lytic regardless of polymer concentration on the surface of the liposomes. However, at endosomal pH (pH 6.5), as the polymer concentration increased the membrane disruption increased. This shows that the polymer plays a desirable role in allowing liposomes to carry macromolecules such as nucleic acids, which are otherwise susceptible to enzyme degradation. In-vivo protein expression in mice showed that, as the polymer concentration of the system increased, the protein expression was more prevalent. This means that the polymer influences protein expression in-vivo. In addition, in-vitro and in-vivo immunogenicity studies showed that these systems have minimal toxicity, akin to the commercially available PEI.

Secondly, delivery of small molecule, hydrophobic drugs can be a challenge due to the aqueous environment they are expected to be delivered in. To address this issue, liposomal systems can be used to protect the payload. The VMLS is advantageous because it has shown high transfection efficiencies of hydrophobic, small molecule drugs such as Ruxolitinib and Tofacitinib into Hela cells, compared to using liposomes alone.

Moreover, the co-delivery of sa-RNA with Ruxolitinib was investigated to explore the effect of introducing small molecule drugs on the cell transfection efficiency of macromolecules such as nucleic acids. It was found that using VMLS as the delivery system allowed maximum transfection efficiency of sa-RNA, ~2 orders of magnitude higher than commercially used PEI. This shows that, introducing Ruxolitinib to the system enhances the transfection efficiency of sa-RNA.

More recently, room temperature storage of the VMLS was looked at by encapsulating cryoprotectants with payloads, followed by freeze-drying. At this stage, it has been found that it is possible to successfully encapsulate cryoprotectants such as sugars, into the VMLS and freeze dry without compromising the structure or integrity of the VMLS membrane.
Exploitation Route In terms of academic routes, to further progress the work done so far, in-vivo studies would be helpful to take the co-delivery of small molecules drugs with macromolecules further. Studies such as protein expression, immunogenicity and cytotoxicity would be helpful data for future PhD students to attain in order to be one step closer to commercialise this novel delivery system. Furthermore, it would be interesting to see future PhD students use the VMLS to deliver payloads into more tougher environments, such as immune cells, which tend to be quite sensitive to foreign bodies. Moreover, it would be useful to take the work done on the room temperature storage of the VMLS further by looking at long-term storage, to see the effect of a long shelf-life on the efficacy of the payloads as well as the stability of the VMLS membrane.

Considering non-academic routes, all the outcomes thus far can be used to obtain a patent for the VMLS and commercialise this delivery system to benefit the pharmaceutical and healthcare sectors. Depending on the drug encapsulated, the system can be used by the pharmaceutical industry to improve the controlled and targeted delivery of specific drugs to the target site. The method used to synthesise the VMLS is mass producible; this, paired with the room temperature storage stability, makes this delivery system suitable to compete with current, commercially available products. This system would be easy for clinicians to use, as simple hydration activates the freeze-dried delivery system, making it ready to inject into patients within minutes.
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description The novel pH responsive polymer developed by the research group has proven to be a promising candidate for intracellular therapeutic delivery of both macromolecules and small molecule drugs, therefore addressing the treatment of multiple disease models. The application can range from cancer therapy to vaccine delivery. The work undertaken using this funding has enhanced the design, optimisation and development of the VMLS, as well as allowing a better understanding of intracellular delivery mechanisms of the VMLS. The work contributes to the design of more efficient macromolecular drug carriers, tailoring delivery to target specific applications. This could have a global impact in the pharmaceutical and healthcare sectors. The VMLS is a delivery system, which can be easily and cost effectively prepared, making it suitable for mass production. The significantly enhanced cell transfection of the VMLS, relative to the commercially available gold standard, would give this delivery system a competitive edge when it reaches the market. The work has been taken further into a collaborative nature, through working with the Future Vaccine Manufacturing Research (FVMR) Hub for vaccine delivery using functional nucleic acids. This drives the progression and understanding of the VMLS development pipeline, from the lab bench, to the clinic.
First Year Of Impact 2018
Sector Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Societal,Economic