Insurance of Biosafety

As iGEM committee emphasized, we have paid great attention to the possible risks of MagHER2some during our entire process of iGEM. And we have complied with relevant regulations and completed the filling of safety forms and animal use form carfully a month earlier.

In this page, the main safety issues of our project design are discussed below.

Cell-free system

The production and release of genetically modified organisms (GMOs) are controversial topics within present scientific community^[1], thus we also considered about the possibility risks may cause by two chassis organisms >Magnetospirillum gryphiswaldense and SHuffle^® E.coli and other organisms used in MagHER2some. In accordance with iGEM’s safety rules and standards, we do not plan to release any GMOs actively in any cases to strictly aviod possible ecological disorders happening. Moreover, in accordance with iGEM’s safety rules and standards, our final product is based on native magnetosome and created a cell-free system instead of live bacteria. This design not only meets “no-release” principle perfectly, but also minimizes possible cytotoxicity and immunotoxicity caused by bacteria when our novel MRI contrast agent is injected into our users. What needs to be added here is the biotools we implemented on MagHER2some are all protein and without any nucleic acid, which means MagHER2some is totally nonhazardous and unable to express any gene in all circumstances, especially when it is released into environment by accdient or injected into patients' circulatory system.

BioBricks

A. Magnetosome

The main reason why we chose magnetosome as the most basic BioBricks is that it have been proven to be highly biocompatible^[2]. It has been reported that chemical toxicity of magnetosome from iron ions is negligible negligible^[3][4] due to the insolubility of Fe3O4. Therefore, the primary safety issues of magnetosome may be relevant to (a) their nanoscale size, which leads to embolism, blockage, and deposition in the body and (b) impurities, particularly proteins, nucleic acids, and polysaccharides associated with magnetosome extracted from bacterial cells, resulting in immunotoxicity.

As we had a further understanding of those studies related to the biocompatibility of magnetosome, we found out that existing studies have shown the body tissue distribution and host tissue elimination following administration of magnetosome into the vascular system ^[5] and in vitro cytotoxicity for mouse fibroblasts^[6].

It has been observed that magnetosome displayed targeted distribution in Sprague DawleySD rat liver except other organs, suggesting that magnetosome may avoid incurring organ congestion or infarction in vivo rely on the lower likelihood of congregation than other nanoparticles.

Purified and sterilized magnetosomes were found to be nontoxic to mouse fibroblasts in vitro. Moreover, another research shows that the injection of 1 mg magnetosome did not increase body temperature of rabbits during the pyrogen test, which showed antigens or pyrogens free with magnetosome administration ^[7].

B. ZZ domain

ZZ domain is a homologous immunoglobulin (Ig)-binding domain which belongs to Staphy- lococcus aureus protein A (SpA). According to our biological engineering, we created a recombinant protein mamC-ZZ which is able to bind to the fragment crystallizable (Fc) region of single chain antibody fragment (scFv) tightly. ZZ domain is a reactive antibody-binding BioBricks, and SpA which ZZ domain belongs to is widely used in clinical application^[8][9], refers to a conclusion that ZZ domain is safe enough to be used as a BioBricks.

C. single chain antibody fragment (scFv)

Single chain antibody fragment (scFv) is the most significant important part of our biological engineering design that determines diagnostic efficiency and imaging results of Mag-HER2-someMagHER2some. Accordingly, we chose a certain kind of scFv called modified from a widely use breast cancer medicine Trastuzumab, which has the ability to that binds with high affinity to the extracellular domain of HER2 in a high affinity way. Trastuzumab is a relatively safe and usually well-tolerated drug^[10]. As a monoclonaln antibody, trastuzumab is not modulate by the classic routes of drug elimination^[11]. Its clearance does not appear to occur by excretion and liver metabolism as in conventional drugs, but rather by an analogue mechanism relating to the homeostatic regulation of endogenous immunoglobulin G^[12]. Thus, problems such as drug-drug interactions and interference with unwanted targets (frequently one of the main causes of drugs’ ‘adverse effects’) are unlikely.

Final Product: reflects biosafety as a whole
Those studies that mentioned above are all strong evidence which ensure all BioBricks of MagHER2some to be safe enough. However, there is still a long term exploration for us to implement our biological engineering into a reliable final product.

Interacrtion between BioBricks:We carried out a series of protein three-dimensional structure prediction about the result of the interaction between recombinant protein mamC-ZZ and Trastuzumab. No evidence shows that any effective domain has been changed or blocked because of interaction, refered MagHER2some to a therapeutic beneficial product.

Suitable Nanoscale: We decided to control the size of MagHER2some into a appopriate range (15~35 nm), which not only prevents that MagHER2some would be removed by reticuloendothelial system, but also ensure that MagHER2some can be excreted into urine and feces ^[13][14].

Further Clinical Trials: What needed to be mentioned again is we still need a long term exploration on biosafety. We will conduct further clinical trials of MagHER2some, and launch the corresponding drug instruction.You can see more clinical trials design here at Link.

Finally, we planning to optimize the producing procedure of the final products, which is designed with nonhazardous materials and harmless reagents.