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A Universal Surface Coating for Lab-On-A-Chip and Biosensor Applications
Baumgartner T, Jennins D, Huang C, Carroll M, Chung E, Cooper S, de las Heras R, Gao Y, Hodyl J, Ling T, Maeji N, McElnea C,
Munian C, Ohse BT, Vukovic P, Wong A, Yang L
Anteo Technologies Pty Ltd | Eight Mile Plains, Brisbane, Australia | www.anteotech.com
Introduction
Attaching biomolecules onto solid supports is a necessary step in developing and manufacturing most in vitro diagnostics and point-ofcare products. However, direct immobilisation of antibodies to synthetic surfaces, e.g. silicon wafers, glass, ceramics, or plastics can
damage proteins and adversely impact both their structure and function. The conventional methods, for example passive adsorption and
covalent binding, are continually challenged by new generation materials, miniaturisation, and increasingly complex assay platforms.
Anteo Technologies has developed an alternative approach, Mix&Go™, that utilises a metal polymer surface chemistry. The polymeric
metal ions of Mix&Go, chelate and bind by avidity to both the surface and to biomolecules, acting as a molecular velcro (Figure 1). On
hydrophobic sufaces where there are no electron donating groups available, half of the Mix&Go can be substituted with hydrophobic
moieties and form hydrophobic interactions to activate the surface. The remaining chelation potential of Mix&Go is then available to
couple proteins.
Various formulations of Mix&Go have been developed that can change the surface characteristics of the base material, modifying the
strength of binding, wettability and surface charge. This is important to control protein binding and the stability of bound biomolecules on
a broad range of surfaces used in biosensors. Presented is the experimental data generated using this approach on surfaces commonly
used in Lab-on-A-Chip and Point-of-Care devices. Figure 1. Mix&Go, a molecular glue comprised of polymeric
metal ions that chelate to available electron donating groups
on synthetic surfaces and proteins. Aim
During biosensor development the material chosen for the binding surface must be carefully selected for both biomolecule coupling
and for the detection method chosen. In some cases it may be diﬃcult to optimise for both. The aim is to modify surfaces used in
biosensor applications, no matter the material, using Mix&Go technology to;
1.  attach biomolecules without aﬀecting their function,
2.  create a uniform coating and
3.  improve binding eﬃciency.
Methods
The surface was incubated with Mix&Go Reagent for 1 hour and then washed. The antibody was then added in coupling buﬀer and
incubated for 1 hour. The surface was then washed and was ready for use. This is shown in figure 2. Modified surfaces include: gold
colloids, polystyrene (PS), cyclic olefin copolymer (COC), polycarbonate (PC), polyethylene terephthalate glycol (PETG) and glass.
Figure 2. The process of activation and coupling using Mix&Go
Results
Mix&Go has been applied to a range of surfaces. The images and table below show the results from contact angle, electron microscopy (SEM and TEM), Atomic Force Microscopy (AFM), light
microscopy and fluorescence read outs.
A
B
Contact Angle
Contact Angle
%CV
Untreated
Mix&Go Activated
15%
25º
47º ± 7º
Material
Glass
Figure 3. Scanning Electron Microscopy (SEM) images. Image A shows the Mix&Go film
with a thickness of ~2 nm. Image B shows the antibody coupled Mix&Go surface with a
thickness of ~10 nm.
Polystyrene (PS)
91º
53º ± 5º
9%
Cyclic Olefin (COC)
96º
50º ± 5º
11%
Polycarbonate (PC)
82º
58º ± 5º
8%
Polyethylene
terephthalate glycol
(PETG)
72º
54º ± 2º
8%
Table 1. The measured contact angle (water) on diﬀerent surfaces before and after activation
with Mix&Go. After Mix&Go activation the contact angle of the materials are all around 50º
which is optimal for biomolecule binding.
5
A
5
B
4
8
4
6
6
4
3
4
3
2
m
µ
0
2
m
n
2
m
µ
0
2
m
n
-2
-2
-4
-4
1
1
-6
-6
-8
0
Figure 4. Contact angles on an untreated polystyrene (PS) surface compared to contact
angles (water) on PS surfaces treated with two diﬀerent Mix&Go formulations designated Hx
and Hy. These images show how the diﬀerent Mix&Go formulations reduce contact angle,
allowing control of wettability.
0
1
2
B.
5570
6000
Qdots in Decane
40,000
4000
35,000
MFI
Qdots in dH2O
30,000
Qdots with Mix&Go in
Isopropanol
25,000
20,000
2000
Qdots with Mix&Go in Water
1000
15,000
Mix&Go in Water
10,000
5,000
36
2
3000
200 nm
magnetic
particles
Qdot linked
Mix&Go 200 nm
magnetic particles
Figure 5. Fluorescence data showing transfer of Mix&Go activated quantum dots from the
organic phase (Decane) to the aqueous phase. These activated quantum dots may then be
used to tag biomolecules. They can also be bound to magnetic nanoparticles as shown in
the TEM image (indicated by arrows). 1
Mix&Go Streptavidin
Microarray Slide
Commercial Streptavidin
Microarray Slide
0
200nm Mix&Go activated
magnetic beads
Qdot linked Mix&Go
magnetic beads
Untreated 45,412
0
1
2
3
4
5
µm
5000
46,676
44,513
Fluorescence
5
Qdot 800 (Life Technologies) linked Mix&Go beads
Background vs Signal
50,000
0
4
Figure 6. AFM of untreated (A) and Mix&Go activated (B) COC surfaces. The untreated
roughness is 4.7 ± 0.5 nm and the Mix&Go activated roughness is 4.5 ± 1 nm. Overall the
Mix&Go activated COC surface appears to be more homogeneous. This enables better
uniformity of biomolecule binding.
Activation and Transfer of Organic Qdots to
Aqueous Phase using Mix&Go
45,000
3
µm
Figure 7. Biotin-RPE binding on
Streptavidin Mix&Go microarray slides
vs commercial standard (3D Type). Top
images show signal from an untreated
slide. The bottom images show signal
from slides treated with biotin to block
active streptavidin. The same amount of
signal is still seen on the commercial
slide after blocking showing that all
binding is non-specific. The Mix&Go
slide only shows signal for the top slide
suggesting that the binding is specific to
the streptavidin.
Pre-treated with
biotin to block
A.
0
Conclusion
The results show that the benefits of Mix&Go translate across surfaces. The data shows thin films of Mix&Go (Figure 3A) activate the surface and allow coupling of monolayers of antibody (Figure
3B). Also shown is the ability for Mix&Go to alter the wettability of the surface for enhanced flow and biomolecule binding (Figure 4). The ability to adjust the wettability of a surface has been used
to transfer organic quantum dots to a water based solution and then using them to coat another surface (Figure 5). Coating uniformity and biomolecule function is also improved using Mix&Go
(Figure 6 and 7). Overall Mix&Go technology allows flexibility in material choice for biosensor development without compromising on the fuction of the biomolecule.