Electronic Supplementary Information (ESI)
Non-lithographic Patterning of Phage Displayed Peptides with
Wrinkled Elastomers
Swathi Swaminathan, Mitchell Bullough, Qifei Li, Anhong Zhou, Yue Cui*
Department of Biological Engineering, Utah State University, Logan, Utah 84322, USA
* Corresponding author, E-mail: yue.cui@usu.edu
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PHAGE DISPLAYED PEPTIDES ON ENTIRE PDMS WRINKLES
Figure S1. Fluorescent characterization of phage displayed peptides binding to the entire PDMS
wrinkles. Left: peptide-displaying phages. Right: bifunctional peptide. Scale bar: 10 µm.
DENSITOMETRIC FLUORESCENCE ANALYSIS OF THE PDMS WRINKLED
SURFACE
Table S1. Study of LSNNNLR-displaying phages with densitometric fluorescence analysis.
Peptide
LSNNNL
Rdisplaying
phages
Concentr
ation
(phage
particles/
µl)
Area Frame
(µm2)
Area
Perce
nt (%)
Densitomet
ric
maximum
value
Densitomet
ric mean
value
Densitom
etric
minimum
value
Exposure
time (ms)
5.6 x
1010
120366.2
97.3
658.75
535.40
475.20
3300
5.6 x 109
120366.2
75.2
452.25
328.65
395.35
3300
2
5.6 x 108
120366.2
59.35
280.90
205.30
215.90
3300
5.6 x 107
120366.2
42.25
150.65
112.75
182.45
3300
5.6 x 106
120366.2
24.15
97.65
65.25
51.80
3300
120366.2
0.87
-
-
-
3300
M13
(blank)
Table S2. Study of peptide (LSNNNLR-GGGG-HPQ) with densitometric fluorescence analysis.
Concent
ration
Densitomet
ric
maximum
value
Densitom
etric mean
value
Densitometri
c minimum
value
Exposure
time
94.6
585.62
540.41
495.20
4200
120366.2
81.27
472.25
448.8
425.35
4200
0.5
120366.2
67.75
320.90
293.275
265.65
4200
0.05
120366.2
54.62
234.65
213.57
192.48
4200
0.005
120366.2
35.88
105.63
83.985
62.34
4200
Area
Frame
µm2
Area
Percent
50
120366.2
5
Peptide
(µg/ml
of TBS)
LSNNNLRHPQ
3
ms
The fluorescent characterization of peptide density is shown in Table S2-S3. It can be
seen that the fluorescence signal increases as the concentration of peptide-displaying phages
increases or as the concentration of the bifunctional peptides increases. It was observed that the
fluorescent intensity decreased by ~88% when the concentration of phage displayed peptides
changed from 5.6×1010 phage particles/µl. Similarly, it was observed that the fluorescence
intensity decreases by ~85 % when the concentration of bifunctional peptide changed from 50
µg/ml to 0.005 µg/ml.
SIO2-BINDING PHAGE DISPLAYED PEPTIDES ON SIO2 AND PDMS
Figure S2. Fluorescent characterization of SiO2-binding phage displayed peptides binding to
SiO2 (left) and PDMS (right). Scale bar: 20 µm.
BLANK EXPERIMENT WITH NO DISPLAYED PEPTIDES ON PDMS SURFACE
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Figure S3: Fluorescent characterization of wrinkled PDMS with M13 phage (without displayed
peptides). Scale Bar: 20 µm.
CONTROL EXPERIMENTS ON ETCHED PDMS SURFACE USING SIO2 AND EPOXY
PHAGE DISPLAYED PEPTIDES
Figure S4. Fluorescent characterization of PDMS (plasma etched) with a SiO2 binding phage
displayed peptide, HKKPSKS (left) and an epoxy-binding phage displayed peptide, TLHPAAD
(Right). Scale Bar: 20 µm.
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FLOURESCENCE CHARACTERIZATION OF PDMS SURFACES WITH DIFFERENT
OXIDATION CONDITIONS
Figure S5. Fluorescence characterization of pure etched PDMS samples at (a) 15 W 30 s, (b) 80
W 10 min (c) 80 W 20 min, and (d) 80 W 30 min. All scale Bars: 20 µm.
FTIR FOR PDMS WITH OXIDATION AT 15 W 30 S AND 80 W 30 MIN
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Figure S6. FTIR experiments of PDMS etched at (a) 15 w 30 s and (b) 80 w 30 min.
The above FTIR spectra shows that there is not much difference in the two oxidation
conditions, 15 W 30 S and 80 W 30 mins. The 1296/cm wavenumber indicates the presence of
Si- CH3 band which is an indication that the surface is not an entire silica layer after plasma
oxidation. This is in accordance with the already published FMIR (frustrated multiple internal
reflection) analysis on poly(dimethylsiloxane) surfaces [1].
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INTERACTION BETWEEN THE LSNNLR PEPTIDE AND PDMS
During the biopanning, the phage displayed peptides may interact with the target surface
either by hydrophobic interaction or electrostatically. Hydrophobic interactions occur at very
high ionic concentrations while electrostatic interactions occur at low ionic strengths. Since the
panning was performed at a moderate ionic strength (0.05 M Tris-HCl, pH 7.5, 0.15 M NaCl),
the peptide selection appears to be based on the combination of both hydrophobic and
electrostatic interactions. In addition, research has shown that specific amino acid groups
(charged, hydrophobic and polar) at specific locations play a very important role in the binding
kinetics. The peptide sequence LSNNNLR contain the hydrophobic amino acids like leucine and
arginine and hydroxyl group containing amino acids like asparagine which indicate the
contribution of hydrophobic/hydrogen bonding interactions. Likewise, LSNNNLR is
hydrophobic peptides (pI 10.55) but with the presence of charged amino acids like arginine can
contribute to the ionic interactions with the target PDMS surface. Therefore, a combined effect
of both the electrostatic and hydrophobic forces account for the peptide-PDMS binding.
PHAGE DISPLAYED PEPTIDES FOR SIO2
Table S3. Summary of SiO2-binding phage displayed peptides.
Peptide Sequence
Frequency
Hydrophobicity
Isoelectric Point
HKKPSKS
5/12
14%
11.10
HSIHYRT
3/12
14%
9.36
HVSHSYR
2/12
14%
9.36
SHARTNK
2/12
14%
11.66
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REFERENCES
1.
R.Hollahan, J. & L.Carlson, G. 1970 Hydroxylation of Polydimethylsiloxane surfacres by
oxidixing
plasmas.
J.
Appl.
Polym.
Sci.
14,
2499-2508.
(doi:
10.1002/app.1970.070141006)
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