Medical Design Briefs - December 2021 - 14

High-Value Products
Although many are simple, inexpensive
consumables, an increasing
percentage are now being surface
treated using gas plasma or have
functional coatings specifically de -
signed to improve the quality of
research and increase the sophistication
of diagnostics. Among the goals
of surface modification is improved
adhesion and proliferation of antibodies,
proteins, cells, and tissue.
Most of the plasma applications
for plastic labware can be categorized
as simple treatments, such as
oxygen or argon plasma for cleaning
the substrate at the molecular level.
The use of plasma is also well established
for surface conditioning to
make polymers more hydrophobic
or hydro philic.
Potential plasma treatment applications
include coating polypropylene
or polystyrene plates with alcohol
or to facilitate protein binding to
the surface.
Gas plasma can provide surface
conditioning of in vitro diagnostic
platforms before the adsorption of
biological molecules (protein/antibody,
cells, carbohydrate, etc.) or biomimetic
polymers.
Multiple system configurations can offer flexibility, efficiency, repeatability, and throughput optimization.
(Credit: PVA TePla)
smooth, precise flow of liquids in the
narrow channels. This can be critical not
only for safety in medical procedures
but
also
processes.
Bonding Plastic with Dissimilar
Materials
When traditional chemical adhesives
fail to sufficiently bond dissimilar types
of materials, or if medical device companies
are looking to reduce the amount
of chemical waste produced, engineers
often turn to plasma treatments to solve
complex adhesion problems.
Plasma treatment can assist the bonding
of dissimilar materials. While treating
the plastic alone can improve its
binding, treating both materials en -
hances the binding of both by improving
adhesive wicking across the surface.
Whether bonding metal to plastic, silicon
to glass, polymers to other polymers
14
Cov
for
quality
for
industrial
[of different durometers], biological content
to [polymeric] microtiter plates, or
even bonding to PTFE, plasma can be
used to promote adhesion. Similar to
printing, adhesion promotion is achieved
by increasing the surface- free energy
through several mechanisms. This
includes precision cleaning, chemically
or physically modifying the surface,
increasing surface area by roughening,
and using primer coatings. The net effect
is a dramatic improvement in bonding.
In some cases, up to a 50x increase in
bond strength can be achieved.
Plasma Treatment of Plastic
Labware
Each year, billions of multi-well plates,
pipettes, bottles, flasks, vials, Eppendorf
tubes, culture plates, and other polymer
labware items are manufactured for
research, drug discovery, and diagnostics
testing.
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ToC
Multi-well, or microtiter, plates are
a standard tool in analytical research
and clinical diagnostic testing laboratories.
The most common material
used
to
manufacture
microtiter
plates is polystyrene, because it is biologically
inert, has excellent optical
clarity, and is tough enough to withstand
daily use.
Most disposable cell culture dishes
and plates are made of polystyrene.
Other polymers such as polypropylene
and polycarbonate are also used for
applications that must withstand a
broad range of temperatures, such as
for polymerase chain reaction (PCR)
for DNA amplification. However, un -
treated synthetic polymers are highly
hydrophobic and provide inadequate
binding sites for cells to anchor effectively
to their surfaces.
To improve biomolecule attachment,
survivability, and proliferation, the material
must be surface modified using plasma
to become more hydrophilic.
If polystyrene is treated with oxygen
plasma, it will become very hydrophilic,
so water spreads everywhere. This
allows aqueous solutions containing
biological content to spread and deliver
Medical Design Briefs, December 2021

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Medical Design Briefs - December 2021

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