Strategies for Drug Encapsulation and Controlled
Delivery Based on Vapor-Phase Deposited Thin Films
Alberto Perrotta, Oliver Werzer, and Anna Maria Coclite*
Vapor-phase deposition methods allow the synthesis and engineering of
organic and inorganic thin films, with high control on the chemical
composition, physical properties, and conformality. In this review, the recent
applications of vapor-phase deposition methods such as initiated chemical
vapor deposition (iCVD), plasma enhanced chemical vapor deposition
(PE-CVD), and atomic layer deposition (ALD), for the encapsulation of active
pharmaceutical drugs are reported. The strategies and emergent routes for
the application of vapor-deposited thin films on the drug controlled release
and for the engineering of advanced release nanostructured devices are
Drug therapies require the active pharmaceutical ingredients
(API) to reach the desired site of action and the success of the
treatment is governed by the time the drug requires to reach the
target, theamount of drugassembling at thetarget site as wellas its
residence time. Furthermore, considerations like administration
andstorage of drugformulations
attention as only the combination of all these allows the
achievement of successful medications ready for therapy,
marketing, and help for patients. Very often, drug molecules well
perform only when assistance from other substances is provided.
These substances (i.e., excipients) limit processing issues,
mechanical and chemical instabilities,
and poor bio-availabilityor assist for better
Hence, the development of new therapeu-
tic options is not limited to the synthesis and screening of new
APIs, but also different administration routes and alternative
dosage forms are extensively investigated. Generally, the latter is
achieved by the engineering and processing of new excipients.
Ever since medications were used, excipients are employed.
Especially, the usage of macromolecules or polymers
gliding agent, disintegration agent,orprotectivecoatingsallowthe
preparation of solid state formulations like
or powders. Develop-
ments in nanomaterial chemistry have
enabled the proliferation of different types
of drug carriers, for example, polymer–drug
conjugates, nanoparticles, nanoclusters,
micelles, dendritic polymer carriers, nano-
capsules, and nanoemulsions.
can work as scaffolds in which the drug is
loaded and preserved until delivery. The
delivery can be spatio-temporally controlled
to minimize side effects and maximize,
instead, the therapeutic efﬁcacy.
also metal-organic frameworks (MOF) (called
also coordination polymers) have shown
interesting results as drug carriers.
MOFs have very large and highly controlled porosity that can be
used for loading and releasing the drug molecules. Solutions,
dispersions, or emulsions of nanostructured materials conjugated
with drugs hardly perform without large molecular weight species
which provide, amongst others, solubility enhancement,
adjustment, and stability.
Another drawback of encapsulating
hosted, therefore multiple injections are required during a
treatment cycle to deliver an optimal dose of drug to the desired site.
Alternatively, hydrogels and more generally polymers can offer
interesting solutions that are more effective for long-term
In this perspective, natural derived products like
cellulose derivatives or gums
are well established and approved
to be used in medications.
However, with progress in polymer
chemistry, more synthetic counterparts with well-deﬁned struc-
tures, narrow molecular weight distributions, and tunable
properties are ready to be commercialized, enabling even more
In thisregard, polymers enable drug
formulation functions like protection against premature release,
and the stabilization of speciﬁc solid state forms. Furthermore,
their potential for realization of site-speciﬁc drug release and
activity are of paramount importance.
can be directly injected in a minimally invasive way, thanks to their
highmoldability, andthe ability to form tissue constructsin situ.
Particularly interesting is the use of external stimuli to trigger the
release of the drug at a speciﬁc site or speciﬁc time.
1.1. Polymers as API Carriers: Strategies and Diffusion
To date, only a limited number of products are available which
make use of a pure polymer to achieve therapeutic actions
examples of such polymer therapeutics are Copaxone
Dr. A. M. Coclite, Dr. A. Perrotta
Institute of Solid State Physics, NAWI Graz, Graz University of
Technology, 8010 Graz, Austria
Dr. O. Werzer
Institute of Pharmaceutical Science, NAWI Graz, Department of
Pharmaceutical Technology, University of Graz, 8010 Graz, Austria
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/adem.201700639.
Thin Films www.aem-journal.com
Adv. Eng. Mater. 2018, 20, 1700639 © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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