Team:ShanghaiTech China/Nanoparticles

ShanghaiTech iGEM

Background

In our system, blue light is used as a signal for the excitation of the pDawn NAS gene expression. Since blue light may be harmful to the human body and cannot go through tissues to reach the gut, we decided to treat our patients with NIR(Near-Infrared Light) in vitro, and convert it to blue light in vivo using a kind of upconversion nanoparticles[1]. NIR has been widely accepted as a tool of medical examination for its high security, and the nanoparticles we used are also harmless to human body. Besides, nanoparticles’ nontoxic composition, agarose microcapsules are included to guarantee unnecessary contents will not be released into the intestinal system easily. Combining these components, we can construct a safe NIR-excited gene expression system.

Nanoparticles

The nanoparticles (i.e., 38 ± 2 nm b-NaYF4:20%Yb, 2% Er@b-NaYF4) exhibit an excitation spectrum peak at 980 nm and emission peak at 440-483 nm upon 980-nm light irradiation. [2] (figure1.1&1.2)

Figure 1.1(left) Excitation properties of nanoparticles[2]

Figure 1.2(right) Appearance of nanoparticles

The poly acrylic acids coat of the nanoparticles allow them binding to the sugar residue in the glycoproteins on the E. coli membranes. In that case, when NIR is beamed to the bacteria, it is immediately converted to blue light on the cell membranes and further activate the gene expression of N-palmitoyl serinol.

Feasibility of penetration of NIR through human abdominal wall

About 30 nW/cm2 470nm blue light is able to induct adequate gene expression of NAS[3] . We suppose a 10-3 transmittance of NIR from the belt to the intestine tract [4], and a 10-6 upconversion efficiency of the nanoparticles according to experiment data. So by using a 30W/cm2 (30nW/cm2*103*106) NIR belt, whose light as strong as a single filament lamp, we can realize portable and comfortable blood sugar control.

Experiment

To prove the upconversion features of the nanoparticles, we used Zeiss LSM 710 fluorescence microscope to give out 980nm laser with the intensity of 5%, 10%, 15%, 20%, 25%, 30%. The emission wavelength was set to be 520 nm and detection wavelength 440-483 nm. Photographs were taken as the nanoparticles were excited by every grade of the NIR laser (Figure 1.5). The fluorescence intensity was presented by IntDen/area upon image J analysis. Curves of fluorescence intensity at different NIR grade is shown as below (Figure 1.6).

Figure 1.6 Curves of fluorescence intensity at different NIR grades




References

[1] Ma, Y.et al. Mammalian Near-Infrared Image Vision through Injectable and Self-Powered Retinal Nanoantennae. Cell 177, 243-255 e215, doi:10.1016/j.cell.2019.01.038 (2019).

[2] Mai, H. X.et al. High-quality sodium rare-earth fluoride nanocrystals: controlled synthesis and optical properties. J Am Chem Soc 128, 6426-6436, doi:10.1021/ja060212h (2006).

[3] Ohlendorf, R., Vidavski, R. R., Eldar, A., Moffat, K. & Moglich, A. From dusk till dawn: one-plasmid systems for light-regulated gene expression. J Mol Biol 416, 534-542, doi:10.1016/j.jmb.2012.01.001 (2012).

[4] Wan, S., Parrish, J. A., Anderson, R. R. & Madden, M. Transmittance of nonionizing radiation in human tissues. Photochem Photobiol 34, 679-681, doi:10.1111/j.1751-1097.1981.tb09063.x (1981).


ShanghaiTech China iGEM @ 2019