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Team:UCSF/lily
From 2013.igem.org
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- Idea
- The switch
- Overview
- Designed TAL regulators
- Mutual repressor switch
Positive feedback loop switch 
Controls
- Safety mechanisms
- Overview
- Escape tag
- Termination
Microcapsule degradation
- Implementation
- Modeling
- Overview
Pharmacokinetics - Modeling methods
- Mutual repressor switch
- Positive feedback loop switch
Experimental model Interactive simulations
- Parts
- Notebook
- Experimental methods
Lablog - Lab safety
- Society
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The Challenge Biological drugs such as hormones, enzymes, cytokines or antibodies are increasingly used to treat different diseases. Due to systemic administration, these drugs often have adverse effects. Additionally, the high cost of biopharmaceuticals imposes a heavy burden on health systems. We aimed to use the principles of synthetic biology to develop an advanced and safe method of in situ production of biological drugs to increase the quality of patients' lives. This system should increase compliance to therapy, decreas the number of required invasive drug administrations and enable advanced multistage therapy while local administration could reduce the side effects. We addressed this challenge by implementing microencapsulated engineered mammalian cells that can be regulated from the outside to produce different therapeutics. This system should be effective, reliable, safe and potentially more cost-effective. |
The switch
Switches are the basic regulatory elements through which the state of cells can be controlled. We designed a new type of a universal bistable toggle switch for mammalian cells based on designed DNA-binding proteins. Its properties enable simultaneous introduction of several orthogonal switches and construction of complex logic devices. We found that a classic toggle switch topology is ineffective if based on TAL effectors. Our modeling explaines that the reason for this is noncooperative binding of monomeric TAL effectors to DNA. We solved this problem by introducing nonlinearity through the addition of the addition of positive feedback loops consisting of pairs of TAL activators and repressors competing for binding. This arrangement resulted, both theoretically and experimentally in mammalian cells, in functional switch that can be regulated by small molecule inducers. Read more... |
Safety
In order to enable safe application of engineered cells in the microencapsulation based therapy we designed three safety mechanisms to degrade the alginate capsules at the end of the therapy, terminate the therapeutic cells by induction of apoptosis and to tag any escaped cells for elimination by the host's natural killer cells. Read more... |
Implementation
In consultations with medical experts we tailored our therapeutic devices based on implanted microencapsulated engineered cells to the treatments of hepatitis C and ischaemic heart disease by in situ production of therapeutic protein effectors whose efficiency has already been demonstrated. In agreement with our pharmacokinetic models, this strategy could reduce side effects and improve efficiency of these therapies. Switching between production of effectors with antiviral or anti-inflammatory and tissue regenerative effect could be regulated by administrating a small molecule inducer. Read more... |
Modeling
Modeling was used to simulate and improve the properties of the switch and the pharmacokinetic distribution of drugs in the tissue, which is required for an effective therapy and decreased side effects. We introduced improved methods of switch simulations such as a quantitative parameter derivation and algorithmic/mixed simulation that can capture mixed regulator binding to operators. We also included into the wiki a server for online switch simulation. A pharmacokinetic model of the local delivery of therapeutics by microencapsulated cells predicted that this type of drug delivery should have reduced systemic side effects. Exhaustive modeling of the switch demonstrated that the classic genetic toggle switch arrangement is not stable without cooperativity, but it confirmed functionality and improved robustness of the our switch design with two positive feedback loops. This topology does not require cooperativity since nonlinearity is introduced by the positive feedback loop. Read more... |
Society
Different aspects of general medical applications of synthetic biology and our project specifically were discussed with a wide range of stakeholders, including medical professionals, patients, experts on the law and ethics of GMO use and release, scientists, the media and the general public that will all have to participate in a successful introduction of synthetic biology applications to clinical use. We attempted to organize a network of Slovenian high schools to share the excitement of synthetic biology with younger generations and to demonstrate its application in medicine and other fields. Read more... |
Perspectives
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Abstract in plain english Biological drugs are being used ever more often as advanced drugs for the treatment of numerous diseases, due to their more specific mode of action. In current therapies the biological drugs are usually distributed more or less throughout the whole body, although each function should often be restricted to a specific organ or tissue. This can cause serious side effects, requires larger dosages and consequently raises the price of therapy. Our solution to this problem was to implant cells producing biological drugs inside the very tissue where the drug is required. The drug producing cells are safely sealed inside microcapsules that prevent cells from spreading throughout the body and protect them from destruction by cells of the host immune system. We constructed a device that allows implanted cells to produce different types of drugs while switching between those production states can be controlled from the outside by a physician, depending on the stage of the disease. We designed our device specifically for the therapy of hepatitis C or heart attack. Against hepatitis C the engineered cells produce a protein with antiviral activity, whose biological activity we have tested and confirmed. After the state of the cells is switched, a protein that improves liver regeneration would be produced. For the therapy after a heart attack we designed cells to suppress local inflammation and promote formation of new blood vessels only around the affected tissue. A physician may initiate self-destruction of the therapeutic cells and capsules by an outside stimulus when the therapy is complete or at any other given time. We believe our system to be safe, effective and applicable in the real world for the therapy of different types of diseases. |
Achievements in technical details
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Project sponsors
     
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