This is the illustration of my 5 projects related to Biomedical Engineering.

1. Tingting Xu
Research Experience
2 papers submitted
Skills involved:
Biomedical Experiments, Computer
Image Processing, Matlab programming

2. Project 1:
Using Cellulose Acetate Membrance
Electrophoresis to Separate Serum
Proteins

3. • Introduction
Before the summer holiday of my second year in
university, I was selected as student leader for the
biomedical experiment teaching assistant.
In the summer vacation, we, the TAs did not have a
holiday. Instead, we did basic teaching experiments
that using cellulose acetate membrance
electrophoresis to seperate serum proteins.
After that, we taught the BME department students
(150 people) how to conduct this experiment and
marked their homework.

4. Instruments & Materials
• Instruments: 220V DC electrical source,
Electrophoresis tank

5. Acetate film, Glass capillary, Filter paper
Reagent: Serum, electrophoretic buffer, dyeing liquor,
rinsing water

6. Methods
1. Preparation work
We first connect the DC electrical source and
the Electrophoresis tank. After that, we cut
the filter paper into double deck banded
paper and Fill the tank with electrophoretic
buffer.

7. 2. Point sample
At this section, we use the glass capillary to absorb
the serum and uniformly sample the serum on the
Acetate film by the sheet glass.

8. 3. Electrophoresis
After the investigation on the influence of
several factors to the result of electrophoresis,
we find the best condition for electrophoresis.
110 Voltage Direct Current, 1 Hour
Electrophoresis

9. 4. Dye and Rinse
Prepared dyeing liquor
and rinsing water are
applied in this section.
After the rinsing is
done, we can see the
separated five
components of serum
protein.

10. Results

11. Conclusion
From this experience I learned the importance of team
cooperation. Without the hard working of all the members
in our group, we can not make it such a success.
What is more, I learned how to do academic research
myself. Suitable design and planning is the prerequisite of a
good experiment. This includes taking consideration of the
variables, like the voltage magnitude, electrophoresis time
and so on.
All in all, the results demonstrate that we successfully
separate the serum protein by using the Cellulose Acetate
Membrance Electrophoresis.

12. Project2:
Preparation and Transformation of
E.coli Competence
Purpose
1. Learn and acquire the steps to prepare the
E.coli Competence
2. Understand the theory of how to transform
E.coli into competence phase and combine it
with plasmid DNA.

13. Theory for Preparation and
transformation
This figure shows the main steps for transform E.coli into intergrated
E.coli and Plasmid DNA phase. Firstly, it is essential to prepare the
E.coli inot competence E.coli phase by controlling temperature and
mixture. Then, after the preparation, plasmid DNA and E.coli can be
combined easily since the E.coli is in the competence phase.

14. Detailed Steps and Condition for
transformation
1. Cultivation of the E.coli
Take one pure colony from the E.coli into 2ml LB culture medium.
Shake overnight at 37℃ until it comes into the exponential phase.
2. Prepare the competence phase E.coli
Put the LB medium in a centrifugal tube on the ice for 10 minutes.
Then centrifugate it under 4 ℃ at a speed of 3000 revolutions per
minute.
Use CaCl2 solution to increase the permeability of E.coli to make it a
competence phase.
3. Transformation
Mix the competence phase E.coli and PBS plasmid DNA solution in
water bath for 90 seconds under 42℃ or 5 minutes under 37℃.

15. Reselts
We have done several control experiments to
see wether the E.coli have transformed and
successfully combined the plasmid DNA by
cultivating them with the ampicillin medium.
This medium would kil the E.coli without PBS
plasmid DNA, while the transformed E.coli can
prosper.

16. These two figures are the well grown sample of E.coli (right one) and
killed E.coli (left one) when put into ampicillin medium.

17. This is the table
illustrates the result of
our comparison
experiments. We have
made eight experiments
group numbered. The
variables are the E.coli,
Amp condition and
Plasmid DNA. + stands
for adding this variable
in the group, - stands for
none.
From the growing
condition of the E.coli we
can see the
transformation condition
and wether E.coli has
inserted plasmid DNA
into its own.

18. Teaching the students
Since I have been the teaching assistant once, I am more familiar with the
things that a TA should do. Our job not only contains preparing
teaching for classes, but also the enhancement of the quality of teaching.
We arrange some students to do the experiment earlier than others to
guarantee a time difference to improve the efficiency for using the
centrifuge.
Being the TA, I can also feel the hard work of the teachers. We have to
prepare early in the morning before the students arrived. This includes the
reaction solution and equipment such as centrifuge and centrifuge tube.
I want to thank Miss Jin Xiao for giving me this chance to be the Teaching
Assistant. I leant to do academic experiments and to lead a group to work
actively and creatively.
Thank you for your attention!

19. Project3:
Combination and property
investigation of conA and nano
fluorescent probe

20. I just illustrate the concept and outline of our
project since the detailed preparing process is
a little complicated and unimportant
compared to the innovative idea.
Purpose
Preparation of conA-linked, high-performance
quantum dot.

21. Methods
• Because the conA
can not be linked BS
to quantum dots conA BS
A
BS
directly, we used A A
Bovine serum
albumin (BSA) as a
bridge to combine conA
them together.
BS BS
• Firstly, we A A
linked conA and BSA BS
BSA as a whole, as A
shown in the
following figure.

22. Secondly, BSA and QD are linked up.

23. Detection of the conjuction of QD and
conA
• This section is mainly designed to test the
conjunction of QD and conA, which also is my
main job.
• The method we utilized is sodium dodecyl
sulfate polyacrylamide gel electrophoresis
(SDS-PAGE).

24. • Here is the
instrument
for the
electrophor
esis.

25. Above is one of the results for the electrophoresis. The first one from the right is made
of conA, the second one is conA and QD, the third one is conA linked QD by
Glutaraldehyde, the last one is QD and Glutaraldehyde
From the third one from the right we can see that QD and conA are successfully
linked together. If they are separated, there would be a band in the down area like
all the three other groups.

26. Project 4:
A two dimensional visualization
of the propagating speed of cortical
spreading depression in rat cortex

27. Introduction
Characterized by EEG depression, temporary disruption of ion
homeostasis, DC potential shift and the change of optical
intrinsic signals, CSD is a transient suppression of neuronal
activity and spreads like a wave from a focal point toward the
periphery at a speed of 2–5 mm/min.
Previous studies have focused on the propagation speed of
CSD by only manually choosing several points in the CSD-
invaded cortex to estimate its average speed.
We aim to visualize propagation speed of CSD with two
dimensions over the imaged cortex.

28. Materials and Methods
A. Origin site estimation of CSD
Temporal clustering analysis (TCA) and least
square estimation (LSE) are combined to
determine the pixel location of the pinprick point
according to our previous works.
B. Coordinate transformation
The coordinate (x1,y1) of Pixel 1 can be
converted to polar coordinate (R，θ) as following
equation:

29. Fig. 1: Coordinate transformation is illustrated in a raw optical image of
the rat cortex.

30. C. Temporal lag Recognition
Fig. 2: Using OISI signal to estimate the time lag for CSD propagation. (A)
Normalized intensity of light signal for Pixel1 and Pixel2. The black squares are the
points which have the highest intensity. (B) Using the correlation coeffient for time
interval calculation. The red line shows the template part from Pixel1, stepping
along the Pixel2, which is the target.

31. Results
For one representative CSD imaging trial, we used
our method for propagating speed calculation (Fig. 3).
Fig. 3 Spatiotemporal evolution of a typical CSD wave.

32. Basing on this dataset, we obtained two images (120×160 pixels)
represent the diffusion velocity of CSD at each pixel. The picture
was visualized based on the propagation speed of CSD at every
pixel in the image. It had been smoothed by using a sliding 3 by
3 window.
Fig. 4 The two dimensional visualization of the spreading speed of CSD on the
imaged cortex are presented. The left figure is obtained using the second method
described above, while the right figure was calculated by applying the first
approach.

33. From the time course of light reflectance variance
in ROI 1, 2 and 3, we knew that CSD had the
fastest speed in ROI 1 and the speed in ROI 3 was
the slowest, which is consistent with the
visualization level in these two figures (Fig. 4).
Fig. 5: The normalized
optical reflectance during the
time course of Pixel1 and
Pixel2 in ROI 1, ROI 2 and
ROI 3 region. The right down
figure is the raw picture of
the imaged cortex with a
scale of 0 to 4. The black box
with white number shows the
region it represents and two
white dots are the Pixel1 and
Pixel2. The white dot which
is nearer to the pinprick is
Pixel1 and the other is Pixel2.

34. DISCUSSION
In conventional method, randomly chosen
points in the areas of the cortex could only
represent the velocity in limited region and
neglect the heterogeneous pattern of the speed
of CSD over the whole cortex. This two
dimensional visualization of CSD propagating
speed can help us map the abnormal regions and
understand the propagation mechanism of CSD
better.

35. Project 5:Image registration
The purpose of this project is to investigate
the principle and theory for communication
between rat olfactory bulb and the brain. Two
sourses of lights, the fluorescence and
reflection light are used to illuminate the open
brain. The two kinds of light resources may
provide individual information about
the physiological reacion.

36. • My job is to do image registration because
there are difference between the two imaging
camera, such as size and magnification times.
This work is a little like image processing.
I first did some simple tests like using
magzines for image registration and the
results turned well.

38. Then, I registered
the images
obtained in the
experiment.