Nanotechnology, Nanomedicine and the Rational Design of New-Age Delivery Systems

by Professor Kostas Kostarelos

Our team at The Nanomedicine Lab within the Centre for Drug Delivery Research wants to generate and disseminate fundamental knowledge in the emerging field of nanomedicine by bringing together biomedical engineering, pharmacology and nanotechnology and their translation to advanced, clinically-relevant therapeutics and diagnostics.

Our aim is the development of novel, viable and effective therapeutics based on the transformation of nanotechnology tools and materials and their use as either the 'drug' or the 'delivery system'. Such components include DNA, RNA, viruses, stem cells, radionuclides, liposomes, carbon nanomaterials and other nanomaterials (quantum dots, fullerenes, carbon nanohorns).

The research efforts taking place within The Nanomedicine Lab are bridging the gap between fundamental nanomaterials engineering and pharmaceutical development towards the realisation of advanced therapeutic and imaging modalities. Our mission is to pioneer the cutting-edge and emerging discipline of nanomedicine. Some examples of what systems we have developed today:

Dendrimeric Nanocontainers that block Angiogenesis in Cancer

The Nanomedicine Lab recently demonstrated for the first time that poly-L-lysine (PLL) dendrimers can exhibit anti-angiogenic activity and block the formation of newly formed blood vessels in developing tumours. This has led to tumour growth delay of an aggressive murine melanoma model and significantly reduced tumour volume¹. Dendrimers are three dimensional nanometer scale hyper-branched polymers that have been described by Don Tomalia in the mid 1980's. Dendrimers have mainly been used as nanocontainers for small drugs, therapeutic macromolecules and MRI imaging agents.

PLL-dendrimer structure and tumor vasculature treated with control (left) and the PLL-dendrimer (right)1.

A number of dendrimers have been studied pre-clinically to show anti-angiogenic activity, but this inherent activity had not been shown previously in vivo or after systemic administration. In this study, the therapeutic activity was achieved after intravenous injection of the dendrimer without the need to include drugs or other therapeutic agents. Only two intravenous injections of the PLL dendrimer were sufficient to retard tumour growth with no systemic toxicity observed in the liver, spleen and kidneys. illustrates that new-generation nanocontainers may offer inherent biological activities whenever required and at the right location, such as in aggressive tumours that require high vascularisation for growth.

Nanotubes as Nanoneedles for Cells

Chemically modified carbon nanotubes with different functional groups were discovered to be able to internalise in a variety of cell types, including human cells. Carbon nanotubes have shown potential as new-age delivery systems and it is the chemical functionalisation that is critical in this transformation as it allows them to become water soluble, and therefore able to be used in biological fluids. Chemically functionalised nanotubes were able to easily cross cell barriers in mammalian, bacterial and fungal cells without causing cell death, and were even able to enter cells under conditions which would usually hinder this process². Nanotubes capable of acting as cell-penetrating materials will have tremendous advantages. The potential of functionalised carbon nanotubes to act as nanoneedles that pierce plasma membranes and translocate directly into cytoplasm without causing cell damage or death is significant for a variety of biomedical and biotechnology applications.

While the actual mechanism by which the functionalised nanotubes are taken up by cells is still unclear, the hypothesis that the team is working with is that they simply pierce the cell and move within. Some types of functionalisation prompted a greater uptake, but it was by no means a prerequisite. All functionalised nanotubes were taken up to a significant extent. The Nanomedicine Lab, in collaboration with the laboratories of Dr.A.Bianco at the CNRS in Strasbourg, France and Prof.M.Prato in Trieste, Italy, have experimented with attempts to intracellularly deliver small molecules, nucleic acids and imaging agents. If the research team's working hypothesis regarding the uptake of functionalised carbon nanotubes proves correct, the technique could offer significant advantages over current drug delivery technologies. Traditional delivery methods (using liposomes for example) usually exploit endocytosis, but stop before reaching the cytoplasm leaving other barriers for the drug to fight through. By piercing plasma membranes and heading straight to the cytoplasm, the functionalised carbon nanotube encounters fewer biological barriers and delivers the drug more directly.

Nanoengineering Artificial Viral Envelopes

Gene therapy involves the delivery of a functional gene by a vector into target cells, resulting in a desired therapeutic effect. Adenovirus (Ad) has shown great promise in gene therapy, however clinical and in vivo studies have reported severe immunogenic responses and an overwhelming accumulation and gene expression in the liver resulting in significant hepatotoxicity. We are attempting to overcome these limitations by engineering artificial envelopes around non-enveloped viruses by allowing the self-assembly of a variety of lipid molecules (zwitterionic, anionic, cationic, responsive) around viral capsids^3,4.

Such exercises in nanoscale engineering of viral gene therapy vectors are thought to offer significant improvements in their safety profile by allowing also re-targeting and tissue-specific gene transfer. New generation vectors for genetic therapies and vaccines are currently under development.

Liposome-Quantum Dot Hybrids for Combinatory Therapeutic & Diagnostic Applications

Quantum dots (QD) are being explored in biomedicine as fluorescent probes of intracellular compartments and for cell labelling and tracking in vivo.

Our Nanomedicine Lab has developed two novel types of lipid-quantum dot hybrid vesicle systems to achieve improved biocompatibility and the opportunity to develop nanoparticles for combinatory imaging (quantum dot component) and therapeutic (vesicle component) capabilities. The first liposome-QD hybrid system was engineered by allowing small (less than 5nm in diameter), hydrophobic CdSe/ZnS core/shell QD to be embedded within the vesicle lipid bilayers (L-QD)⁵. The second type consists of larger (20-40nm in diameter), hydrophilic, surface functionalized QD encapsulated at the inner liposome aqueous phase (f-QD-L)⁶. Both types of lipid-quantum dot hybrids were shown to successfully label tumor cells in vitro and in vivo. We believe that liposome-nanoparticle hybrids of this type using a variety of nanoparticles (gold, silver, iron, gadolinium) can provide a wide range of new-age liposome-based delivery systems for therapeutic or diagnostic purposes.

References

1. Al-Jamal KT, Al-Jamal WT, Akerman S, Podesta JE, Yilmazer A, Turton JA, Bianco A, Vargesson N, Kanthou C, Florence AT, Tozer GM, Kostarelos K., Systemic antiangiogenic activity of cationic poly-L-lysine dendrimer delays tumor growth. Proc Natl Acad Sci U S A. 2010, 107(9):3966-71.
2. Kostarelos K, Lacerda L, Pastorin G, Wu W, Wieckowski S, Luangsivilay J, Godefroy S, Pantarotto D, Briand JP, Muller S, Prato M, Bianco A., Cellular uptake of functionalized carbon nanotubes is independent of functional group and cell type. Nature Nanotechnology 2007, 2(2):108-13.
3. Singh R, Al-Jamal KT, Lacerda L, Kostarelos K., Nanoengineering artificial lipid envelopes around adenovirus by self-assembly. ACS Nano 2008, 2(5):1040-50.
4. Singh R, Tian B, Kostarelos K., Artificial envelopment of nonenveloped viruses: enhancing adenovirus tumor targeting in vivo. FASEB J. 2008, 22(9):3389-402
5. Al-Jamal WT, Al-Jamal KT, Tian B, Lacerda L, Bomans PH, Frederik PM, Kostarelos K., Lipid-quantum dot bilayer vesicles enhance tumor cell uptake and retention in vitro and in vivo. ACS Nano, 2008, 2(3):408-18
6. Al-Jamal WT, Al-Jamal KT, Bomans PH, Frederik PM, Kostarelos K., Functionalized-quantum-dot-liposome hybrids as multimodal nanoparticles for cancer. Small 2008, 4(9):1406-15.

Copyright AZoNano.com, Professor Kostas Kostarelos (University of London)