Supplementary Material
Key factors influencing the optical detection of
biomolecules by their evaporative assembly on
diatom frustules
Yu Wang, Deyuan Zhang*, Junfeng Pan, Jun Cai
Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, School of
Mechanical Engineering and Automation, Beihang University, XueYuan Road No.37,
HaiDian District, Beijing 100191, PR China
Tel.: +86 10 82339604;
fax: +86 10 82316603.
E-mal address: hutter2@163.com (Y. Wang), zhangdy@buaa.edu.cn (D. Zhang).
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Fig. S1. Evaporating assembly of FITC-protein brought about by diatom frustules: (a) Frustules
of diatom Coscinodiscus under a light microscope; the fluorescence distributions under a
fluorescence microscope after the FITC-protein added (b) at the beginning, (c) at 23 min, (d) at 35
min, (e) at 41 min, (f) at 47 min, and (g) at 55 min. (h) Fluorescence distribution of a single
diatom valve marked in g.
Whether the permeability of sieve pores affects the assembly of proteins
Figure S2a shows the SEM images of Coscinodiscus frustules. The diatom cell is ~80
μm in diameter, and has hexagon pore chambers arranged as honey comb. Figure S2b
shows the living diatom cells under a light microscope, which contain cytoplasm inside
their frustules. After added with FITC-protein solution, the fluorescence gradually
gathered to the diatom cells during evaporation. That means the assembly of protein is not
50 μm by the permeability of sieve pores.
affected
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Fig. S2. Images of seawater diatom Coscinodiscus. (a) SEM image of single diatom frustule, (b)
light microscopy image of living diatom cells, and (c) fluorescence distribution after FITC-protein
added and dried. After added with FITC-protein solution, the fluorescence gradually gathered to
the diatom cells during evaporation. That means the assembly of protein is not affected by the
permeability of sieve pores.
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Whether the surface area affects the assembly of proteins
The experiment focus on whether the surface area of frustules affects the assembly of
proteins. The Coscinodiscus frustules were coated with carbonyl iron, which cause their
surface area decrease from 27.9 m2/g (original frustules) to 0.57 m2/g. As Figure S3a
shows, the surface and pores of the frustules were covered with a uniform thin film (~200
nm in thickness). Figures S3b and S3c shows the microscopic images of the coated
frustules and clean frustules after added with FITC-protein solution and dried
respectively. For the coated frustules, the FITC-protein did not assemble on the frustules
but mainly distribute on the glass surface, indicating that the large surface area of the
frustules is the main reason for their ability to load large quantities of particles.
Fig. S3. Comparison of coated frustules and clean frustules. (a) SEM images of the carbonyl iron
coated frustules of Coscinodiscus diatomite. The surface and pores of the frustules were covered
with a uniform thin film (~200 nm in thickness). (b) Coated frustules and (c) clean frustules after
FITC-protein added and dried. For the coated frustules, the FITC-protein did not assemble on the
frustules but mainly distribute on the glass surface.
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Fig. S4. Evaporation assembly of particles brought about by glass powders. (a) Light microscopic
image of glass powders; (b) Distribution of FITC-proteins after the solution had dried; (c) Integral
optical density (IOD) of glass powder region; (d) IOD of control region. The AOI of selected
region can be calculated by equation: AOI=IODSum/AreaSum. The values of IODSum and AreaSum are
marked by green frames in c and d. The AOI of glass powders (AOIg) selected in c equals
403592/2724102= 0.1481, and the AOI of control region (AOIc) selected in d equals
141086/2629619=0.05365. Thus, AOIg/AOIc =0.1481/0.05365=2.76.
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Fig. S5. Evaporation assembly of particles brought about by (a, b) fumed silica, (c, d) powders of
silica-gel desiccant and (e, f ) silica sand. (a, c, e) are light microscopic images and (b, d, f) are
fluorescence microscopic images showing distribution of FITC-proteins after the solution had
dried.
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Fig. S6. Evaporation assembly of particles brought about by (a, b) sand, (c, d) powders of plastic
and (e, f) powders of PMMA after the solution had dried. (a, c, e) are light microscopic images
and (b, d, e) are fluorescence microscopic images showing distribution of FITC-proteins after the
solution had dried. Powders of plastic and PMMA were obtained from plastic cup and PMMA
plate respectively using sand papers.
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Fig. S7. Schematic illustration of distribution of FITC-proteins on (a) transparent particle and (b)
non-transparent particle. For non-transparent particle, the fluorescence on the back side of particle
can not be detected.
Fig. S8. Images of the diatom substrates: (a) glass slide adhered with Coscinodiscus frustules, (b)
PDMS substrate bonded with arrayed Navicula frustules, and (c) SEM image of the arrayed
Navicula frustules in b. Figure a and b were taken under a light microscope.
Fig. S9. Distribution of FITC-proteins after washing for 30 s: (a) diatom-glass substrate after
washed, and (b) Diatom-PDMS substrate. The images were taken under a fluorescence
microscope.
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Fig. S10. Microscopic images of the arrayed Nitzschia frustules in the partially arrayed
diatom substrate: (a) array of Nitzschia frustules, and (b) Nitzschia frustules in a single
array dot.
Table S1 Signal intensity scanned at each printed dot
Dot 1
Dot 2
Dot 3
Dot 4
Dot 5
Dot 6
Dot 7
Dot 8
Average
Diatom_Cy3-BSA
11506
9361
8856
9711
7503
6870
5439
4822
8008.5
Diatom_NC
-37.5
-23.5
226
198
156.5
-91.5
-202.5
210
143.3
Diatom_H IgG
34251
31005
23394
28029
17130
25612
20340
14082
24230.3
Glass_ Cy3-BSA
4846
3849
5336
4152
2882
2471
1869
1657
3382.8
Glass_NC
0
0
0
0
0
0
0
0
0
Glass_H IgG
16933
13050
10423
10161
7464
7653
6108
4937
9591.1
Fig. S11. SEM images of Nitzschia frustules, the size is ~12×7×3 μm3.
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