Medical Design Briefs - December 2022 - 14

Plasma Treatment
lymerized onto the plastic by plasmaenhanced
chemical vapor deposition.
The resulting coating can be a very thin
(100-500 nm), non-crystalline, highly conformal,
and highly flexible (180° ASTM
D522) coating. Similarly, there can be concerns
about potential leaching from plastics
in contact with the product in the food
and beverage industry.
To prevent plastic leaching, industry
producers can coat the plastic using
plasma treatment. The two options are
a PTFE-type coating, or on the opposite
side of the spectrum, a silicone quartz
coating to create a near glass-like surface.
For example, sports water bottles
have a different interior surface, typically
due to plasma treatment or application
of a coating.
When manufacturing plastics for medical test kit packaging, plasma treatment can be used to solve difficult
challenges in the process. (Credit: PVA TePla)
Although many are simple, inexpensive
consumables, an increasing percentage
of these devices are now being surface
treated using gas plasma or have
functional coatings specifically designed
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 hydrophilic.
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.
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
14
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, untreated 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.
When polystyrene is treated with oxygen
plasma, it s very hydrophilic, so water
spreads
everywhere.
This
allows
aqueous
solutions containing biological
content to spread and deliver biomolecules
to the surface while providing
a hydrogen bonding platform to
adhere to them. Treating the surface in
this manner has many benefits, including
improved analyte wetting of wells,
greater proliferation of cells without
clumping, reduced amount of serum,
urine, or reagents required for testing,
and lower risk of overflow and crosswell
contamination.
Coating Plastics to Prevent Leaching
Using plastic labware can raise concerns
about leaching. Since plastic labware
is susceptible to leaching from plasticizers,
stabilizers, and polymerization residues,
plasma is used to coat the inside of containers
with a quartz-like barrier material.
These flexible quartz-like coatings are powww.medicaldesignbriefs.com
R&D
Assistance
If R&D assistance is required, plasma
treatment is standard enough that leading
equipment providers can modify existing,
mature tools and technology, complete
with fixturing, to deliver what are essentially
drop-in solutions. Like PVA TePla, some
providers provide access to on-site research
and development equipment and engineering
expertise.
However, for manufacturers that want
plasma-treated parts or components
without investing in in-house equipment,
the solution is to utilize a contract processor.
With this approach, the parts are
shipped, treated, and returned within a
mutually agreed time frame. For small or
infrequent batches, this can significantly
lower the price per part.
Working with a contract processor has
advantages in tapping into the years of
technical expertise applying various plasma
treatments; this can often speed R&D
efforts. As applications and production
volumes continue to evolve, collaborating
with a partner with deep plasma
treatment expertise can provide a quicker
time to market for a customer's product.
No matter which way medical device
manufacturers choose, altering the surface
properties of plastics improves the
quality of test results while increasing the
value of products.
This article was written by Ray Chen,
Sales Manager, and Ryan Blaik, Sales
Manager, PVA TePla America, Corona,
CA. For more information, visit www.
pvateplaamerica.com. Contact: 800-5275667
or e-mail sales@pvateplaamerica.
com.
Medical Design Briefs, December 2022

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Medical Design Briefs - December 2022

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