Microplastic (MP) pollution—an
emerging environmental challenge
of the 21st century—refers to accumulation of environmentally
weathered polymer-based particles with potential environmental and
health risks. Because of technical and practical challenges when using
environmental MPs for risk assessment, most available data are generated
using plastic models of limited environmental relevancy (i.e., with
physicochemical characteristics inherently different from those of
environmental MPs). In this study, we assess the effect of dominant
weathering conditions—including thermal, photo-, and mechanical
degradation—on surface and bulk characteristics of polystyrene
(PS)-based single-use products. Further, we augment the environmental
relevance of model-enabled risk assessment through the design of engineered
MPs. A set of optimized laboratory-based weathering conditions demonstrated
a synergetic effect on the PS-based plastic, which was fragmented
into millions of 1–3 μm MP particles in under 16 h. The
physicochemical properties of these engineered MPs were compared to
those of their environmental counterpart and PS microbeads often used
as MP models. The engineered MPs exhibit high environmental relevance
with rough and oxidized surfaces and a heterogeneous fragmented morphology.
Our results suggest that this top-down synthesis protocol combining
major weathering mechanisms can fabricate improved, realistic, and
reproducible PS-based plastic models with high levels of control over
the particles’ properties. Through increased environmental
relevancy, our plastic model bolsters the field of risk assessment,
enabling more reliable estimations of risk associated with an emerging
pollutant of global concern.
Increasing numbers of multidrug-resistant bacteria make many antibiotics ineffective; therefore, new approaches to combat microbial infections are needed. In addition, antibiotics are not selective-they kill pathogenic organisms as well as organisms that could positively contribute to wound healing (bio flora). Approach: Here we report on selective inactivation of Pseudomonas aeruginosa and Staphylococcus epidermidis, potential pathogens involved in wound infections with pulsed electric fields (PEFs) and antibiotics (mix of penicillin, streptomycin, and nystatin). Results: Using a Taguchi experimental design in vitro, we found that, under similar electric field strengths, the pulse duration is the most important parameter for P. aeruginosa inactivation, followed by the number of pulses and pulse frequency. P. aeruginosa, a potential severe pathogen, is more sensitive than the less pathogenic S. epidermidis to PEF (alone or in combination with antibiotics). Applying 200 pulses with a duration of 60 ls at 2.8 Hz, the minimum electric fields of 308.8-28.3 and 378.4-12.9 V/mm were required to inactive P. aeruginosa and S. epidermidis, respectively. Addition of antibiotics reduced the threshold for minimum electric fields required to inactivate the bacteria. Innovation: This study provides essential information, such as critical electric field parameters for bacteria inactivation, required for developing in vivo treatment and clinical protocols for using PEF for wound healing. Conclusion: A combination of PEFs with antibiotics reduces the electric field threshold required for bacteria disinfection. Such an approach simplifies devices required to disinfect large areas of infected wounds.
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