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Team:NJU China/Project
From 2013.igem.org
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Overview
Targeting medication has always been a challenge in gene therapy. It is urgently required to develop a new system to overcome the off-target effect, low efficiency and high toxicity of the currently available approaches. Using the principles of synthetic biology, we aimed at building up a new drug delivery system named Bio-missile. We wanted to encapsulate highly specific molecular medicine siRNA into targeting exosome for site-specific delivery. Exosomes are lipid bilayer vesicles, which are naturally secreted by almost all cell types, playing crucial roles in intercellular transport of bioactive molecules. Given their role as natural transporter, exosomes potentially represent a novel and exciting drug carrier for therapeutic purpose. Thus, modification of exosomes derived from cells may realize the goal of delivering drugs to local cellular environment. Outside modification: To endow the exosome with site-specific recognition ability, we designed a fusion proteins comprising of exosome surface protein lamp 2b, and receptor-binding peptides. The lamp 2b can bring the receptor-binding parts of the fusion protein onto the surface of the exosome. Thus the modified exosome will, in theory, has the ability to target specific tissues and organs. Nside modification: We have managed to encapsulate our ‘kill device’ siRNA into our exosomes. Recently, small interfering RNA (siRNA) is emerging as a promising therapeutic drug against a wide array of diseases and it functions to destroy viral gene through the RNA interference pathway. By designing siRNA against certain viral genes, we can use siRNA as molecular medicine for disease treatment. By transfecting our chassis, HEK 293T cells, with siRNA plasmids and collecting exosomes, we filled the exosomes with therapeutic siRNAs. And via the engineering of the target protein, we also endowed the exosome with the site-specific targeting ability. Our modified exosomes are just like the ‘biomissiles’, which can be delivered to specific cells and destroy target mRNAs, causing targeted destruction of diseases. Our project will open up avenues for therapeutic applications of exosomes as biomissile.
Chassis
Exosomes are lipid bilayer vesicles which are secreted by all cell types, and its diameter ranges from 30nm to 100nm. Given its role as a natural transporter of bioactive molecules, we want to utilize exosome as our drug carrier. The first problem we met is which chassis to choose to produce the exosomes we want. After screening through a large amount of different cell types, we choose to use HEK 293T cells as our chassis. HEK 293T cells is a subtype of human embryonic kidney cells and we choose this as our chassis for three main reasons. The first reason is that HEK 293T cells can secrete large amounts of exosomes so we can get enough exosomes by using HEK 293T cells as our chassis. The second reason is that HEK 293T cells are derived from human, so the exosome they secrete will be more human compatible and have little chance of inducing immune response compared to other non-human cells. The last reason is that HEK 293T cells are immortalized cells, which means that after genetically engineering them to produce the exosomes we want, we can simply subculture the cell line and keep them as cell factory to produce our desired exosomes massively.
Tranquillity
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Positivity
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Passion
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