MDTmag.com 16 / September 2014
Texturing Prospective with
Drug-coated balloons may soon enter the evolutionary path for clogged artery therapies that has gone from
bypass surgery to angioplasty balloons to stents. As such, manufacturers should explore the best processes and
practices for this up and coming device. This article looks at the impact of textured drug coatings and balloons
using ultrasonic spray technology for this emerging treatment modality.
By Fielding Water, Applications Engineer,
Drug-coated balloons (DCB) emerged at the crossroads of angioplasty balloons and drug-eluting stents in
treating blood vessel obstructions. Intense research continues as medical device manufacturers compete to create better products and
processes. While the first generation of DCBs
has been released in Europe and clinical
data is being collected, DCBs are predicted
for launch in the United States by mid-2015
upon FDA approval.
Balloons for angioplasty, or the mechanical
widening of obstructed arteries, succeeded
the drastically more invasive bypass surgery.
It became the regular procedure for treating
semi-clogged arteries; however, it is often not
a long-term solution as arteries can become
clogged again or the vessel walls can become
weakened due to over-inflation.
To avoid acute relapse, stents were developed to maintain the reopening of an artery
for extended periods of time. Although stents
performed this function well, they caused
immune responses that trigger increased scar
tissue growth and reclogging of the vessel.
In 2003, the first drug-eluting stent was approved by the FDA. The use of antiprolifera-tive drugs prevented the buildup of scar tissue
in the arteries. However, the drugs can cause
blood clots or hypersensitivity, and patients
who have drug-eluting stents commonly take
blood thinning medication.
What developed from the difficulties of un-
coated balloon angioplasty and drug-eluting
stents is drug-coated balloons. The balloon is
inserted via catheter, directed to the lesion,
and inflated for 30 seconds up to a minute.
The drug on the balloon is released during
this time, and attaches to the blood vessel lining. Over the next few days, the medication
is gradually absorbed by the vessel walls into
the tissue. This results in long-lasting effects
of the drug, even with a short release period.
Texturing Within the Drug Coating
Gauging an object by the consistency of its
surface is determining its texture. Textures
can range from amorphous to crystalline, or
smooth to rough. This range can be achieved
for different balloons coated with exactly the
same amount of drug. What causes these
differences in coating is cohesion. Cohesion
is the strength of the bonds between the
various molecules in the coating. Depending
on the method of drug application, the mole-
cules experience varied cohesive forces when
applied to the balloon. This leads to different
drug molecule interactions, and ultimately,
different coating textures (Figure 1).
By reducing the surface area of the
coating, less of the bulk coating is exposed.
Lower exposure reduces compromise of
coating integrity during storage or transit
through a blood vessel. Amorphous coatings
limit drug loss. By the same token, reducing
the surface area also reduces drug delivery
upon inflation at the lesion site. On the
other hand, increasing the surface area of
the coating promotes drug delivery upon
balloon inflation. A rougher coating results in
greater contact of the coating with the vessel
wall, encouraging absorption. However, this
coating texture also increases drug transit loss
before the balloon reaches the target location,
and coating integrity can also be more easily
compromised during storage. Fine tuning of
Figure 1: Four separate balloons with identical drug deposition densities