Delivering nano-cargo to the right cell address
Gene therapy relies on inserting functional genes into a host cell. The process requires a vector to carry the cargo that normally consists of gene(s) and possibly other requisite molecules. Most research has focused on using viruses as vectors. Hijacking a cell with their genetic material is part of a virus's survival in the host. A heat-loving bacterium, Aquifex aeolicus (AaLS) was the subject of research by the EU-funded 'Protein engineering for encapsulation and intracellular transport' (Protengenctrans) project. A thermophilic bacterium, its protein capsule or coat is stable at over 700 ˚C so inserting multiple mutations does not usually affect its structure. Protengenctrans scientists lined the inner surface of the AaLS capsule with negatively charged amino acid residues to create a container for cargo molecules. Cargo included a variety of molecules such as plasmids (rings of bacterial DNA) and DNA ladders of different lengths. Gold nanoparticles, in the forefront of news at the moment for breast cancer diagnosis, were also successfully delivered. To enhance cellular uptake of drugs, protein transduction domain (PTD) peptides can be used. Protengenctrans scientists aimed to make the most of this facility and as a first step developed a method to decorate the AaLS capsid with genetically encoded tissue-selective PTDs. The team worked on loading PTD-AaLS with guest molecules, monitoring uptake of the complexes and then inducing intracellular release of the molecular guests. Tags such as fluorophores for tracking molecules, used in many genetic therapies, were also included in the cargo. Applications for this research are very wide-ranging. Exciting new gene therapies are the obvious targets and include gene delivery to replace malfunctioning genetic material and modulation of hyperactive or hypoactive genes. Other uses are tissue-specific delivery, fluorophores for imaging and cytotoxic molecules to target tumours.
