Magnetically recoverable noble metal nanoparticles are promising catalysts for chemical reactions. However, the chemical synthesis of these nanocatalysts generally causes environmental concern due to usage of toxic chemicals under extreme conditions. Here, Pd/Fe3O4, Au/Fe3O4 and PdAu/Fe3O4 nanocomposites are biosynthesized under ambient and physiological conditions by Shewanella oneidensis MR-1. Microbial cells firstly transform akaganeite into magnetite, which then serves as support for the further synthesis of Pd, Au and PdAu nanoparticles from respective precursor salts. Surface-bound cellular components and exopolysaccharides not only function as shape-directing agent to convert some Fe3O4 nanoparticles to nanorods, but also participate in the formation of PdAu alloy nanoparticles on magnetite. All these three kinds of magnetic nanocomposites can catalyze the reduction of 4-nitrophenol and some other nitroaromatic compounds by NaBH4. PdAu/Fe3O4 demonstrates higher catalytic activity than Pd/Fe3O4 and Au/Fe3O4. Moreover, the magnetic nanocomposites can be easily recovered through magnetic decantation after catalysis reaction. PdAu/Fe3O4 can be reused in at least eight successive cycles of 4-nitrophenol reduction. The biosynthesis approach presented here does not require harmful agents or rigorous conditions and thus provides facile and environmentally benign choice for the preparation of magnetic noble metal nanocatalysts.
A remote collection of biofluid specimens
such as blood and urine remains a great challenge due to the requirement
of continuous refrigeration. Without proper temperature regulation,
the rapid degradation of analytical targets in the specimen may compromise
the accuracy and reliability of the testing results. In this study,
we develop porous superabsorbent polymer (PSAP) beads for fast and
self-driven “microfiltration” of biofluid samples. This
treatment effectively separates small analytical targets (
e.g.
, glucose, catalase, and bacteriophage) and large undesired
components (
e.g.
, bacteria and blood cells) in the
biofluids by capturing the former inside and excluding the latter
outside the PSAP beads. We have successfully demonstrated that this
treatment can reduce sample volume, self-aliquot the liquid sample,
avoid microbial contamination, separate plasma from blood cells, stabilize
target species inside the beads, and enable long-term storage at room
temperature. Potential practical applications of this technology can
provide an alternative sample collection and storage approach for
medically underserved areas.
The
continuous emergence of infectious viral diseases has become
a major threat to public health. To quantify viruses, proper handling
of water samples is required to ensure the accuracy and reliability
of the testing results. In this study, we develop enhanced porous
superabsorbent polymer (PSAP) beads to pretreat and store water samples
for virus detection. By applying PSAP beads to collect water samples,
the viruses are captured and encapsulated inside the beads while undesired
components are excluded. We have successfully demonstrated that the
shelf life of the model virus can be effectively extended at room
temperature (22 °C) and an elevated temperature (35 °C).
Both the infectivity level and genome abundance of the viruses are
preserved even in a complex medium such as untreated wastewater. Under
the tested conditions, the viral degradation rate constant can be
reduced to more than 10 times using the PSAP beads. Therefore, the
enhanced PSAP beads provide a low-cost and efficient sample pretreatment
and storage method that is feasible and practical for large-scale
surveillance of viral pathogens in water samples.
Microalgae are emerging as next-generation
renewable resources
for production of sustainable biofuels and high-value bioproducts.
Conventional microalgae harvesting methods including centrifugation,
filtration, flocculation, and flotation are limited by intensive energy
consumption, high capital cost, long treatment time, or the requirement
of chemical addition. In this study, we design and fabricate porous
superabsorbent polymer (PSAP) beads for self-driven 3D microfiltration
of microalgal cultures. The PSAP beads can swell fast in a microalgal
suspension with high water absorption capacity. During this process,
microalgal cells are excluded outside the beads and successfully concentrated
in the residual medium. After treatment, the beads can be easily separated
from the microalgal concentrate and reused after dewatering. In one
PSAP treatment, a high concentration factor for microalgal cultures
up to 13 times can be achieved in 30 min with a harvesting efficiency
higher than 90%. Furthermore, microalgal cultures could be concentrated
from 0.2 g L–1 to higher than 120 g L–1 with minimal biomass loss through multistage PSAP treatments. Therefore,
the use of PSAP beads for microalgae harvesting is fast, effective,
and scalable. It does not require any complex instrument or chemical
addition. This technique potentially provides an efficient and feasible
alternative to obtain high concentrations of functional biomass at
a very low cost.
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