5 research outputs found
Polystyrene Nanofiber Materials for Visible-Light-Driven Dual Antibacterial Action via Simultaneous Photogeneration of NO and O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>)
This contribution reports on the
preparation, characterization,
and biological evaluation of electrospun polystyrene nanofiber materials
engineered with a covalently grafted NO photodonor and ionically entangled
tetracationic porphyrin and phthalocyanine photosensitizers. These
photofunctional materials exhibit an effective and simultaneous photogeneration
of two antibacterial species such as nitric oxide (NO) and singlet
oxygen, O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) under illumination
with visible light, as demonstrated by their direct detection using
amperometric and time-resolved spectroscopic techniques. Dual-mode
photoantibacterial action is demonstrated by antibacterial tests carried
out on Escherichia coli
Effect of Temperature on Photophysical Properties of Polymeric Nanofiber Materials with Porphyrin Photosensitizers
Electrospun nanofibers possess large
surface to volume ratios,
high porosity, and good mechanical properties that are necessary for
biological applications. We prepared different types of photoactive
polymeric nanofiber materials with encapsulated or externally bound
porphyrin photosensitizers. The kinetics of formation and the decay
of both singlet oxygen O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) and porphyrin triplet states that are generated by irradiation
of nanofiber materials in an air atmosphere or in an air-saturated
aqueous solution were measured and evaluated by luminescence and transient
absorption spectroscopy in the temperature range between 5 and 60
°C. We found shortening of the O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) lifetime and a significant increase in singlet oxygen-sensitized
delayed fluorescence at higher temperatures. These photophysical data
show an increase in the diffusion coefficient for O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) with temperature, and they are consistent
with a stronger antibacterial effect of the nanofiber material on Escherichia coli at higher temperature
Superhydrophilic Polystyrene Nanofiber Materials Generating O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>): Postprocessing Surface Modifications toward Efficient Antibacterial Effect
The surfaces of electrospun polystyrene
(PS) nanofiber materials
with encapsulated 1% w/w 5,10,15,20-tetraphenylporphyrin (TPP) photosensitizer
were modified through sulfonation, radio frequency (RF) oxygen plasma
treatment, and polydopamine coating. The nanofiber materials exhibited
efficient photogeneration of singlet oxygen. The postprocessing modifications
strongly increased the wettability of the pristine hydrophobic PS
nanofibers without causing damage to the nanofibers, leakage of the
photosensitizer, or any substantial change in the oxygen permeability
of the inner bulk of the polymer nanofiber. The increase in the surface
wettability yielded a significant increase in the photo-oxidation
of external polar substrates and in the antibacterial activity of
the nanofibers in aqueous surroundings. The results reveal the crucial
role played by surface hydrophilicity/wettability in achieving the
efficient photo-oxidation of a chemical substrate/biological target
at the surface of a material generating O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) with a short diffusion length
Nanoparticles with Embedded Porphyrin Photosensitizers for Photooxidation Reactions and Continuous Oxygen Sensing
We
report the synthesis and characterization of sulfonated polystyrene
nanoparticles (average diameter 30 ± 14 nm) with encapsulated
5,10,15,20-tetraphenylporphyrin or ionically entangled tetracationic
5,10,15,20-tetrakis(<i>N</i>-methylpyridinium-4-yl)porphyrin,
their photooxidation properties, and the application of singlet oxygen-sensitized
delayed fluorescence (SODF) in oxygen sensing. Both types of nanoparticles
effectively photogenerated singlet oxygen, O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>). The O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) phosphorescence, transient absorption of the porphyrin triplet
states, and SODF signals were monitored using time-resolved spectroscopic
techniques. The SODF intensity depended on the concentration of the
porphyrin photosensitizer and dissolved oxygen and on the temperature.
After an initial period (a few microseconds), the kinetics of the
SODF process can be approximated as a monoexponential function, and
the apparent SODF lifetimes can be correlated with the oxygen concentration.
The oxygen sensing based on SODF allowed measurement of the dissolved
oxygen in aqueous media in the broad range of oxygen concentrations
(0.2–38 mg L<sup>–1</sup>). The ability of both types
of nanoparticles to photooxidize external substrates was predicted
by the SODF measurements and proven by chemical tests. The relative
photooxidation efficacy was highest at a low porphyrin concentration,
as indicated by the highest fluorescence quantum yield (Φ<sub>F</sub>), and it corresponds with negligible inner filter and self-quenching
effects. The photooxidation abilities were sensitive to the influence
of temperature on the diffusion and solubility of oxygen in both polystyrene
and water media and to the rate constant of the O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) reaction with a substrate. Due to their
efficient photogeneration of cytotoxic O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) at physiological temperatures and their oxygen sensing via
SODF, both types of nanoparticles are promising candidates for biomedical
applications
Antibacterial, Antiviral, and Oxygen-Sensing Nanoparticles Prepared from Electrospun Materials
A simple
nanoprecipitation method was used for preparation of stable photoactive
polystyrene nanoparticles (NPs, diameter 30 ± 10 nm) from sulfonated
electrospun polystyrene nanofiber membranes with encapsulated 5,10,15,20-tetraphenylporphyrin
(TPP) or platinum octaethylporphyrin (Pt-OEP). The NPs prepared with
TPP have strong antibacterial and antiviral properties and can be
applied to the photooxidation of external substrates based on photogenerated
singlet oxygen. In contrast to nanofiber membranes, which have limited
photooxidation ability near the surface, NPs are able to travel toward
target species/structures. NPs with Pt-OEP were used for oxygen sensing
in aqueous media, and they presented strong linear responses to a
broad range of oxygen concentrations. The nanofiber membranes can
be applied not only as a source of NPs but also as an effective filter
for their removal from solution