Medical Design Briefs - November 2021 - 33

The mixture of self-assembling polymers and antibiotics is cured on
human intramedullary hip implants using a handheld light source. (Credit:
Duke University)
tions to survive, which sounds horrific to me, " Segura says. " All
they really need is something to rub on the implant to stop an
infection from taking hold, because preventing an infection is
much easier than treating one. So, we came up with this coating
technology that we hope will provide a solution. "
Implant infections aren't unique to children or to cancer
patients, however. For joint replacement surgeries, for example,
infection occurs in 1 percent of primary and up to 7 percent of
revision surgeries, which requires repeated revision surgeries
and prolonged intravenous antibiotics. Treatment doesn't
always work, however, as these patients have a higher five-year
mortality risk than those diagnosed with HIV/AIDS or breast
cancer. Implant infections are estimated to cost the healthcare
system more than $8.6 billion annually in the United States
alone.
Part of the challenge of treating these infections is that bacteria
colonize the surface of the implants themselves. This means
that there are no blood vessels flowing through the bacterial
colonies to deliver the antibiotics coursing through a patient's
veins. The only recourse is often the removal of the original
implant, which is usually the best of what are only bad options.
Some doctors have taken to their own solutions, such as
using antibiotic powder when closing the surgical wound or
infusing the bone cement used to hold the implant in place
with antibiotics. Neither of these tactics have been proven to
be clinically effective. There is also the option of implant manufacturers
adding antibiotic properties to their devices. But
this would greatly reduce the product's shelf life and also
require a long and complicated process of FDA approval,
since the implants would then be in a new classification.
■ How the Antibiotic Coating Sidesteps Challenges
" We've shown that a point-of-care, antibiotic-releasing coating
protects implants from bacterial challenge and can be
quickly and safely applied in the operating room without the
need to modify existing implants, " says Christopher Hart, a
resident physician in UCLA Orthopaedic Surgery who helped
conduct the experiments.
The new antimicrobial coating is made of two polymers, one
that repels water and one that mixes well with water. Both are
combined in a solution with an antibiotic of the physician's
choosing and then applied directly to the orthopedic implant
by dipping, painting or spraying. When exposed to a bright
ultraviolet light, the two polymers couple together and selfassemble
into a grid-like structure that traps the antibiotics.
Medical Design Briefs, November 2021
Cov
ToC
After mixing self-assembling polymers with antibiotics, the infectionpreventing
coating is sprayed on to human intramedullary hip implants
with a simple perfume bottle. (Credit: Duke University)
The reaction is an example of click chemistry, which is a general
way of describing reactions that happen quickly at room temperature,
produce only a single reaction product, have an extremely
high yield, and occur within a single container.
" This study is a great example of the power of click chemistry
in biomedical applications, " says Weixian Xi, now a senior scientist
at Illumina, who was a postdoctoral researcher at UCLA
during the study. " This 'smart' and 'clickable' polymeric coating
enables protections of implants from bacterial infection
and makes a personalized approach possible. "
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Medical Design Briefs - November 2021

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