5 research outputs found
Substrate-Regulated Growth of Plasma-Polymerized Films on Carbide-Forming Metals
Although plasma polymerization is
traditionally considered as a
substrate-independent process, we present evidence that the propensity
of a substrate to form carbide bonds regulates the growth mechanisms
of plasma polymer (PP) films. The manner by which the first layers
of PP films grow determines the adhesion and robustness of the film.
Zirconium, titanium, and silicon substrates were used to study the
early stages of PP film formation from a mixture of acetylene, nitrogen,
and argon precursor gases. The correlation of initial growth mechanisms
with the robustness of the films was evaluated through incubation
of coated substrates in simulated body fluid (SBF) at 37° for
2 months. It was demonstrated that the excellent zirconium/titanium-PP
film adhesion is linked to the formation of metallic carbide and oxycarbide
bonds during the initial stages of film formation, where a 2D-like,
layer-by-layer (Frank–van der Merwe) manner of growth was observed.
On the contrary, the lower propensity of the silicon surface to form
carbides leads to a 3D, island-like (Volmer–Weber) growth mode
that creates a sponge-like interphase near the substrate, resulting
in inferior adhesion and poor film stability in SBF. Our findings
shed light on the growth mechanisms of the first layers of PP films
and challenge the property of substrate independence typically attributed
to plasma polymerized coatings
Temperature Activated Diffusion of Radicals through Ion Implanted Polymers
Plasma immersion ion implantation
(PIII) is a promising technique for immobilizing biomolecules on the
surface of polymers. Radicals generated in a subsurface layer by PIII
treatment diffuse throughout the substrate, forming covalent bonds
to molecules when they reach the surface. Understanding and controlling
the diffusion of radicals through this layer will enable efficient
optimization of this technique. We develop a model based on site to
site diffusion according to Fick’s second law with temperature
activation according to the Arrhenius relation. Using our model, the
Arrhenius exponential prefactor (for barrierless diffusion), <i>D</i><sub>0</sub>, and activation energy, <i>E</i><sub>A</sub>, for a radical to diffuse from one position to another
are found to be 3.11 × 10<sup>–17</sup> m<sup>2</sup> s<sup>–1</sup> and 0.31 eV, respectively. The model fits experimental
data with a high degree of accuracy and allows for accurate prediction
of radical diffusion to the surface. The model makes useful predictions
for the lifetime over which the surface is sufficiently active to
covalently immobilize biomolecules and it can be used to determine
radical fluence during biomolecule incubation for a range of storage
and incubation temperatures so facilitating selection of the most
appropriate parameters
Table S1 from A sterilizable, biocompatible, tropoelastin surface coating immobilized by energetic ion activation
The fitting parameters for the curves shown in Fig. 1B
Mechanically Robust Plasma-Activated Interfaces Optimized for Vascular Stent Applications
The long-term performance
of many medical implants is limited by the use of inherently incompatible
and bioinert materials. Metallic alloys, ceramics, and polymers commonly
used in cardiovascular devices encourage clot formation and fail to
promote the appropriate molecular signaling required for complete
implant integration. Surface coating strategies have been proposed
for these materials, but coronary stents are particularly problematic
as the large surface deformations they experience in deployment require
a mechanically robust coating interface. Here, we demonstrate a single-step
ion-assisted plasma deposition process to tailor plasma-activated
interfaces to meet current clinical demands for vascular implants.
Using a process control-feedback strategy which predicts crucial coating
growth mechanisms by adopting a suitable macroscopic plasma description
in combination with noninvasive plasma diagnostics, we describe the
optimal conditions to generate highly reproducible, industry-scalable
stent coatings. These interfaces are mechanically robust, resisting
delamination even upon plastic deformation of the underlying material,
and were developed in consideration of the need for hemocompatibility
and the capacity for biomolecule immobilization. Our optimized coating
conditions combine the best mechanical properties with strong covalent
attachment capacity and excellent blood compatibility in initial testing
with plasma and whole blood, demonstrating the potential for improved
vascular stent coatings
Plasma Synthesis of Carbon-Based Nanocarriers for Linker-Free Immobilization of Bioactive Cargo
Multifunctional
nanoparticles are increasingly employed to improve
biological efficiency in medical imaging, diagnostics, and treatment
applications. However, even the most well-established nanoparticle
platforms rely on multiple-step wet-chemistry approaches for functionalization
often with linkers, substantially increasing complexity and cost,
while limiting efficacy. Plasma dust nanoparticles are ubiquitous
in space, commonly observed in reactive plasmas, and long regarded
as detrimental to many manufacturing processes. As the bulk of research
to date has sought to eliminate plasma nanoparticles, their potential
in theranostics has been overlooked. Here we show that carbon-activated
plasma-polymerized nanoparticles (nanoP<sup>3</sup>) can be synthesized
in dusty plasmas with tailored properties, in a process that is compatible
with scale up to high throughput, low-cost commercial production.
We demonstrate that nanoP<sup>3</sup> have a long active shelf life,
containing a reservoir of long-lived radicals embedded during their
synthesis that facilitate attachment of molecules upon contact with
the nanoparticle surface. Following synthesis, nanoP<sup>3</sup> are
transferred to the bench, where simple one-step incubation in aqueous
solution, without the need for intermediate chemical linkers or purification
steps, immobilizes multiple cargo that retain biological activity.
Bare nanoP<sup>3</sup> readily enter multiple cell types and do not
inhibit cell proliferation. Following functionalization with multiple
fluorescently labeled cargo, nanoP<sup>3</sup> retain their ability
to cross the cell membrane. This paper shows the unanticipated potential
of carbonaceous plasma dust for theranostics, facilitating simultaneous
imaging and cargo delivery on an easily customizable, functionalizable,
cost-effective, and scalable nanoparticle platform