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The nanotechnology revolution has allowed us to speculate on the possibility of hybridising nanoscale materials with live substrates, yet significant doubt still remains pertaining to the effects of nanomaterials on biological matter. In this investigation, we cultivate the ciliated protistic pond-dwelling microorganism Paramecium caudatum in the presence of excessive quantities of magnetite nanoparticles in order to deduce potential beneficial applications for this technique, as well as observe any deleterious effects on the organisms’ health. Our findings indicate that this variety of nanoparticle is well-tolerated by P. caudatum cells, who were observed to consume them in quantities exceeding 5–12% of their body volume: cultivation in the presence of magnetite nanoparticles does not alter P. caudatum cell volume, swimming speed, growth rate or peak colony density and cultures may persist in nanoparticle-contaminated media for many weeks. We demonstrate that P. caudatum cells ingest starch-coated magnetite nanoparticles which facilitates their being magnetically immobilised whilst maintaining apparently normal ciliary dynamics, thus demonstrating that nanoparticle biohybridisation is a viable alternative to conventional forms of ciliate quieting. Ingested magnetite nanoparticle deposits appear to aggregate, suggesting that (a) the process of being internalised concentrates and may therefore detoxify (i.e. render less reactive) nanomaterial suspensions in aquatic environments, and (b) P. caudatum is a candidate organism for programmable nanomaterial manipulation and delivery.
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BioNanoSci. (2018) 8:90–94
DOI 10.1007/s12668-017-0425-z
Toxicity and Applications of Internalised Magnetite
Nanoparticles Within Live Paramecium caudatum Cells
Richard Mayne1·James Whiting1·Andrew Adamatzky1
Published online: 22 June 2017
© The Author(s) 2017. This article is an open access publication
Abstract The nanotechnology revolution has allowed us
to speculate on the possibility of hybridising nanoscale
materials with live substrates, yet significant doubt still
remains pertaining to the effects of nanomaterials on bio-
logical matter. In this investigation, we cultivate the cil-
iated protistic pond-dwelling microorganism Paramecium
caudatum in the presence of excessive quantities of mag-
netite nanoparticles in order to deduce potential beneficial
applications for this technique, as well as observe any
deleterious effects on the organisms’ health. Our findings
indicate that this variety of nanoparticle is well-tolerated
by P. caudatum cells, who were observed to consume
them in quantities exceeding 5–12% of their body vol-
ume: cultivation in the presence of magnetite nanoparticles
does not alter P. caudatum cell volume, swimming speed,
growth rate or peak colony density and cultures may per-
sist in nanoparticle-contaminated media for many weeks.
We demonstrate that P. caudatum cells ingest starch-coated
magnetite nanoparticles which facilitates their being mag-
netically immobilised whilst maintaining apparently normal
ciliary dynamics, thus demonstrating that nanoparticle bio-
hybridisation is a viable alternative to conventional forms
of ciliate quieting. Ingested magnetite nanoparticle deposits
appear to aggregate, suggesting that (a) the process of being
Richard Mayne
James Whiting
Andrew Adamatzky
1Unconventional Computing Laboratory, University
of the West of England, Bristol, UK
internalised concentrates and may therefore detoxify (i.e.
render less reactive) nanomaterial suspensions in aquatic
environments, and (b) P. caudatum is a candidate organism
for programmable nanomaterial manipulation and delivery.
Keywords Nanotoxicology ·SPION ·Quieting ·
Paramecia ·Biohybridisation
1 Introduction
There are two major justifications for research into the
hybridisation of nanoscale materials with biological matter.
Firstly, despite their widespread use in recent years, signif-
icant doubt remains as to the potential deleterious effects
of nanoparticles and nanomaterials on biological matter as
even inert materials may be rendered reactive, immunogenic
or otherwise harmful to life when fabricated in nanoscale
quantities [1]. Secondly, nanomaterials may be fabricated
to exhibit highly desirable characteristics (specific electrical
properties, magnetism, high tensile strength etc.), the con-
ferral of which to live cells would potentially lead to next-
generation technologies such as bio-computer interfaces for
restorative and/or augmentative medical applications.
Magnetite (iron II/III oxide) nanoparticles (MNPs) (a
variety of superparamagnetic iron oxide nanoparticles,
SPIONs) are one such nanomaterial possessing desirable
properties for applications involving live cells. Exhibiting
superparamagnetism and apparently low toxicity, SPIONs
are now routinely used as a contrast medium in in vivo
magnetic resonance imaging and are a proposed drug-deli-
very (or otherwise therapeutic) agent for cancer treatment
[2,3]. With regards to their effects on protists, the same
class of nanoparticle may be hybridised with the plasmo-
dium of slime mould Physarum polycephalum towards
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BioNanoSci. (2018) 8:90–94 91
enhancing its value in bio-computer interfaces and uncon-
ventional computing devices [47]. Recent evidence has
suggested that MNPs are not as biocompatible as once
thought, however, due to their potential for bioaccumula-
tion and generation of reactive oxygen species within host
cells [8,9]. Furthermore, little is known of the ecotoxi-
cological significance of SPIONs released into the envi-
ronment, but recent studies on water-dwelling eukaryotes
such as Daphnia spp. and various forms of plant life
have demonstrated that they may potentially disrupt aquatic
ecosystems [10].
This study examines the ciliated protistic pond organ-
ism Paramecium caudatum being cultivated in the presence
of excessive quantities of MNPs in order assess the poten-
tial uses of nanohybridised paramecia whilst concurrently
observing for any deleterious effects on the organisms’
health. We conclude by discussing the apparent effects of
this treatment on P. caudatum cells and the ecotoxicologi-
cal significance of these results, and present several novel
applications for hybridised P. caudatum cells containing
2 Materials and Methods
P. caudatum cultures were cultivated in Chalkley’s medium
enriched with 10 g of alfalfa (Sciento, UK) and 40 wheat
grains (Tesco, UK) per litre. Cultures were exposed to a
day/night cycle but were kept out of direct sunlight; ambient
temperatures ranged from 19–24 oC.
In experiments where P. caudatum cells were exposed
to MNPs, suspensions of 200 nm (hydrodynamic diameter)
starch matrix-coated multi-core MNPs (Chemicell GmBH,
Germany) were added to fresh culture medium at a concen-
tration of 0.25 mg ml1(approximately 2.2×1012 particles
per ml). This concentration was chosen as a comparable
quantity of nanoparticles per unit biomass to our previ-
ous studies with other single-celled organisms [5]. Stock
cultures at a concentration of approximately 1000 cells
ml1were harvested in log growth phase and added to the
nanoparticle-infused culture medium, in which they were
incubated for periods in excess of two months.
The following microscopical measurements were made
on a regular (daily) basis (n= 3 per culture per day for each):
average cell count, average swimming speed, total cell cross
sectional area and percentage of cross-sectional cell area
occupied by cytoplasmic/vesicular inclusions whose colour
was suggestive of MNP deposits. Cells were observed in
glass microscope well slides. Cells were chemically fixed
in order to record photomicrographs. Fixation was achieved
by adding 10 μl of 4% paraformaldehyde (Agar Scien-
tific, UK) in pH 7.0 phosphate buffered saline solution
(Sigma, Germany) to each slide well after swimming speed
measurements had been made.
Observations were made with a Zeiss Axiovert 200M
inverted microscope and photo/videomicrographs were cap-
tured with an Olympus SC50 digital camera via CellSens
software. Electron microscopic observations were made
with an FEI Quanta FEG-SEM in high-vacuum mode.
For cell volume measurements, each image was anal-
ysed to extract both the cells’ cross-sectional area in squared
micrometers, but also to estimate the percentage of inter-
nalised MNPs. Each image was imported into Matlab
(Mathworks, USA) and processed in the following man-
ner: the image was converted into greyscale, and a threshold
was applied to extract all material darker than the back-
ground media. Each threshold was visually checked in order
to ascertain that only organisms were isolated in each image.
The number of pixels isolated by the threshold was then
summed to give the cells’ total cross-sectional area. This
process was also performed using a different threshold to
determine the number of pixels whose colour value corre-
sponded to dark cytoplasmic inclusions in order to identify
any internalised MNPs. As the threshold values had to be
determined visually for each image separately, this process
was performed ‘blind’, i.e. without the operator knowing
whether each image were a control or test measurement. The
number of pixels isolated by this method were then com-
pared with the cells’ total volume to give a percentage value.
Video analysis for measurement of organism swimming
speed was also performed using Matlab. RGB images were
imported from the video frame-by-frame for sequential
analysis and organism positioning. For each video set, the
organisms were isolated from the RGB image by colour,
whereupon the data for each frame was converted to a
JPEG image file for further analysis. To detect the position
of the organisms, a Laplace template of a Gaussian filter
was defined before being convolved over the image; the
size of the filter was iteratively determined by visual feed-
back of the user. After organism detection on every frame
had occurred, the positional data was passed to a bespoke
Kalman filter which accurately estimates the position of
the particle across each frame using the data from the full
time-series of particle positions to predict and confirm the
movement of each organism. From this it is possible to
measure the speed of each organism in a noisy video, cre-
ating a dataset of organism speed and momentary position.
While the script ran, frame-by-frame images were shown
on screen allowing visual validation of positional track-
ing by the authors. Average speed was calculated for each
All numerical data were subject to statistical analysis in
Matlab: two-tailed ttests and Mann-Whitney U tests were
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92 BioNanoSci. (2018) 8:90–94
3 Results & Discussion
All measurement data are shown in Table 1. The micro-
scopical appearance (morphology and swimming patterns)
Fig. 1 Photomicrographs to show appearance of P. caudatum cells
(unfixed): (a) Following exposure to MNPs. Multiple rust-coloured
deposits (arrowed) are visible in the cytoplasm. (b) Control, demon-
strating a lack of rust-coloured deposits. Scale bar 100 μm
Ta b l e 1 Table to show mean (¯x) and standard deviation (σ)values
for measurements of total cell cross-sectional area (xa,inμm2),
cell content comprising dark (including rust-coloured) objects (doc,in
percentage), swimming speed (ss,inμm s1), growth rate (μ,inh
and peak colony density (pcd, in cells ml1)(ttest and Mann-Whitney
xa ¯xxaσdoc¯xdocσss¯xssσμ¯σpcd¯xpcdσ
Control 12715.66 5994.59 7.33 1.67 132.54 42.79 0.020 0.009 309 120
Test 13381.09 4700.77 12.68* 3.16 144.94 31.64 0.021 0.009 317 123
Asterisks indicate a statistically significant difference in means to controls at p<0.0001
of P. caudatum cells treated with MNPs was not notice-
ably altered aside from the inclusion of rust-coloured
deposits and more dark objects within intracellular vesi-
cles and the cells’ cytoplasm (Fig. 1). Organisms treated
with MNPs contained approximately 5% more dark intra-
cellular inclusions (including rust-coloured inclusions) than
controls. No statistical difference was observed in total
cell volume or swimming speed between controls and test
The microscopical appearance of the rust-coloured
deposits within the organisms treated with MNPs was sim-
ilar to that of suspensions of MNPs in distilled water
(Fig. 2a). The electron microscopic appearance of the MNPs
was consistent with their description as aggregative multi-
core objects (Fig. 2b).
Furthermore, no statistical difference in growth rates or
peak colony density were observed between controls and
organisms treated with MNPs. All cultures (test and control)
persisted over the duration of the experiment (14 days).
Our results indicate that the P. caudatum cell is highly
tolerant to being cultured in the presence of large quantities
of MNPs, as indicated by our not observing any delete-
rious effects on the health of the organisms with regards
to their size, morphology, motility, growth rate or colony
density. This indicates that, despite recent evidence sug-
gesting that this variety of nanoparticle may be harmful
to aquatic microorganisms, they do not appear to induce
any readily-observable toxicological effects in our ciliated
model organism.
Intriguingly, the observations of MNPs within the organ-
isms suggests that they were internalised in the manner of
a nutrient source, noting that the size of the individual par-
ticle cores, 10 nm, were too large to enter the cell via any
other route such as through membrane pores. This apparent
uptake of MNPs was likely a result of their starch coat-
ing. Interactions between P. caudatum and MNPs with other
coatings/no coating remain a topic for further study.
Although no measurements of MNP intracellular reac-
tivity (e.g. generation of reactive oxygen species) or the
longevity of individual cells were made, the longevity of
cultures treated with MNPs was not significantly different
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BioNanoSci. (2018) 8:90–94 93
from that of controls as both varieties were kept in culture
for periods exceeding two months (data not shown).
We propose that P. caudatum may detoxify certain
environmentally dispersed nanomaterials: that dark/rust-
coloured deposits could be easily identified in P. caudatum
cells indicates that they are aggregated in vivo into non-
nanoscale objects. This reduction in surface area to volume
ratio likely renders the deposits less reactive and therefore
less harmful.
This apparent lack of toxicological effects incident of
internalising quantities of MNPs allows us to speculate
on the potential applications of this process of biological–
artificial hybridisation. In further experiments, we exposed
10 μl droplets on glass microscope well slides contain-
ing approximately 5 P. caudatum cells treated with MNPs
to a 1.28 T 25x40x4.0 mm neodymium magnet. Holding
the magnet in close proximity to the margins of the well
caused the organisms to be drawn to the edge of the droplet
where they were held immobile (Fig. 3). By increasing the
distance between the magnet and margins of the well, the
organisms were able to move but at a significantly reduced
Fig. 2 Microscopic appearance
of MNPs. aLight micrograph
of MNP suspension in distilled
water (25 mg ml1). The
suspension is ‘rust-coloured’
and is similar in appearance to
cytoplasmic inclusions in MNP-
treated P. caudatum cells. (b)
Scanning electron micrograph of
nanoparticle suspension dried
onto a carbon tab
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94 BioNanoSci. (2018) 8:90–94
Fig. 3 Stereomicrograph showing MNP-treated P. caudatum cells
(arrowed) being attracted towards a permanent magnet (black object).
Scale bar 500 μm
4 Conclusions
Magnetic restraint of ciliates via their hybridisation with
biocompatible magnetic nanomaterials would appear to
be an attractive alternative the established methods of
microorganism immobilisation/quieting, such as: replace-
ment of media with inert viscous fluids, induction of
hypoxia through hermetically sealing the observation envi-
ronment [11,12], addition of low-concentration toxins
(e.g. aliphatic alcohols [13], anaesthetic compounds [14]),
ultraviolet light irradiation [15], establishment of fluid
pressure gradients/microfluidic compression [16] and adhe-
sion to solid surfaces via positively-charged proteins (3-
aminopropyltriethoxysilane, protamine sulphate) [17].
The advantage of magnetic restraint over these other
quieting methods is that it does not necessitate inducing
deleterious health effects on the organism, maintains the
chemical composition and hence physical characteristics of
the fluid medium (thus minimising interference with natural
ciliary beating processes) and allows for momentary adjust-
ment of the strength of attraction (i.e. by moving the magnet
or using magnets of different strengths). Although magnetic
restraint of Paramecium spp. has been previously described
via internalised magnetite (particles of ca. 3 μm diameter),
the authors did not describe the use of microparticles in
this context as being a method for fully immobilising the
organisms [18].
Finally, this ciliated model organism’s capacity for gath-
ering, internalising and concentrating nanomaterials holds
exciting possibilities for the prospect of orchestrated bio-
logical manipulation and delivery (guided by gradients of
attractants, repellents or magnetic fields) of nano and micro-
scale compounds of interest, although further research is
required in this area before practical applications can be
Acknowledgments The authors extend their thanks to Dr. David
Patton for his electron microscopy expertise.
Compliance with Ethical Standards
Conflict of Interest The authors declare no competing financial interest.
Funding This work was funded by the Leverhulme Trust (grant no.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://, which permits unrestricted
use, distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were made.
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... The results showed that the P. caudatum cell was tolerant to MNPs and had no harmful effect on the organism, regardless of the size, morphology, motility, growth rate, or colony density of the MNPs. It, therefore, suggested that MNP has no toxic effect on the ciliated model organism [137]. The toxic effect of iron oxide nanoparticles on Saccharomyces cerevisiae, Drosophila, Caenorhabditis elegans, zebrafish, and mouse models is discussed in the following sections. ...
... Utilizing hybridized nanomaterial in biological organisms may potentially reduce the effect of their toxicity [137,174]. ...
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There has been an increasing number of studies in magnetic nanoparticles with auspicious applications in medicine. Among the oxides of magnetic nanoparticles, iron oxide has emerged as an indispensable tool in nanotechnology, particularly bio-nanotechnology. This is attributed to its exceptional properties such as size, shape, magnetism, and biocompatibility. In this review, iron oxide nanoparticles were exploited in different model organisms ranging from prokaryotes to eukaryotes, elucidating their cellular functions relative to their antibacterial activity, drug delivery, and toxicity.
... Data are even more sparse regarding the effects of nanomaterials on non-human forms of life, especially at the environmental level, although the data available indicate that nanomaterials may be disproportionately more toxic to lower forms of life and have the potential for bioaccumulation. To continue the example of SPIONs, these have been found to disrupt reproduction in freshwater protists and plants 5 , although the authors' previous investigations have demonstrated that SPIONs are comparatively non-toxic in a number of model organisms including slime mould 6,7 and the ciliate Paramecium caudatum 8 . ...
... The following two varieties of particulate were chosen for use in all experiments as our previous work has demonstrated that P. caudatum will favourably ingest both whilst suffering minimal deleterious health effects in the short term (for a characterisation of these nanomaterials and their interactions, please see refs 8,9 ). ...
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As the extent to which aquatic environments are polluted with nano-scale objects is becoming known, we are presented with an urgent need to study their effects on various forms of life and to clear and/or detoxify them. A range of methods exist to these ends, but a lack of inter-study comparability arising from an absence of experimental standardisation impedes progress. Here we present experiments that demonstrate measurement of orchestrated uptake and clearance of two environmentally-relevant nano- and micromaterials by a model aquatic microoraganism, Paramecium caudatum. Experiments were based on a simple, modular, multi-chamber platform that permits standardised control of organism behaviour and measurement of variables relevant to the study of nanotoxicology, including nanomaterial chemotaxis assays, bioaccumulation and deleterious effects on cell motility systems. Uptake of internalised materials may be estimated through the addition of a low-cost fluorescence spectrometer. P. caudatum cells can clear an estimated 0.7 fg of contaminant materials (or 161 of the particles used) per cell over a 5 mm distance per 6 hour experiment, whilst suffering few short-term adverse effects, suggesting that the organism and the platform used to investigate their properties are well-suited to a range of laboratory and field-based nanotoxicological studies.
... When magnetic nanoparticles are small enough, they behave as giant paramagnetic materials (i.e., showing lack of hysteresis at room temperature), thus being designated as superparamagnetic iron oxide nanoparticles (SPIONs). SPIONs can be biocompatible particles, and some of them have already been used as contrast medium in magnetic resonance imaging and in cancer therapy [16][17][18][19]. ...
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... Paramecium are visible to the naked eye due to their rather large size (50-300 µm in length) (Van Houten et al. 2019). R. Mayne et al. (2018) showed that P. caudatum cells consumed starch, which was coated with magnetite NPs in amounts exceeding 5-12% of their body volume. This proves that P. caudatum is a candidate organism for nanomaterial manipulation and delivery. ...
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... The purpose of these organelles, which are up to 10 µm long and less than 1 µm in width, is to generate fluid currents in surrounding media. In ciliates, this serves to propel the organism as a means of motility, enhance feeding through concentrating and 'sorting' adjacent particles [1][2][3][4] and enable environmental sensing [5]. In humans, they are present in epithelial cells such as those found lining most of the respiratory surfaces (to drive the mucociliary escalator) and the fallopian tube (to aid ova transport). ...
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The aquatic unicellular organism Paramecium caudatum uses cilia to swim around its environment and to graze on food particles and bacteria. Paramecia use waves of ciliary beating for locomotion, intake of food particles and sensing. There is some evidence that Paramecia pre-sort food particles by discarding larger particles, but intake the particles matching their mouth cavity. Most prior attempts to mimic cilia-based manipulation merely mimicked the overall action rather than the beating of cilia. The majority of massive-parallel actuators are controlled by a central computer; however, a distributed control would be far more true-to-life. We propose and test a distributed parallel cilia platform where each actuating unit is autonomous, yet exchanging information with its closest neighboring units. The units are arranged in a hexagonal array. Each unit is a tileable circuit board, with a microprocessor, color-based object sensor and servo-actuated biomimetic cilia actuator. Localized synchronous communication between cilia allowed for the emergence of coordinated action, moving different colored objects together. The coordinated beating action was capable of moving objects up to 4 cm/s at its highest beating frequency; however, objects were moved at a speed proportional to the beat frequency. Using the local communication, we were able to detect the shape of objects and rotating an object using edge detection was performed; however, lateral manipulation using shape information was unsuccessful.
... Many kinds of nanoparticles being developed by researchers ranging from silica [1-5], cobalt [6-10], ZnO [11][12][13], and so forth. One of the nanoparticles that have low toxicity [14][15][16] and biocompatible [17][18][19] is magnetite so that it can be used in the biomedical field [20][21][22][23]. Practically, magnetite can be utilized as a filler material in the magnetic hydrogel to be subsequently used as actuator [24,25] or as artificial [26][27][28]. ...
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The trend of nanoparticles technology has been so advanced in several years; for instance, the bio-applications of polymer gel composites that involve micro/nanoparticles to be embedded in polymer gel have been many observed. This complex material composition can express a specific property and low toxicity so it can be used in various domain uses. Besides, the polymers material must possess certain properties to be utilized in the biomedical application (magnetic hyperthermia, cancer therapy, and food industry) such as flexible, biocompatibility, and water swallowability. Magnetite is nanoparticle with a unique property that can be utilized as a filler. The low toxicity of magnetite under the superparamagnetic condition is very useful in biomedical application. This research was succeeded to synthesize PVA/PVP polymer-based hydrogel magnetic with PEG coated magnetite with Manganese doping filler, which has good biocompatibility and stable particle. An advanced characterization using XRD has shown the crystallite size about 9-11 nm with the magnetite phase confirmed from the sample. The SAXS analysis using two-lognormal functions exhibited primary and secondary particles around 2.40 and 9.74 nm that was well proven by TEM image analysis that showed a close value of the average particles size about 9.78 nm. From the SAXS and TEM analysis, it could be observed that the samples formed clusters from primary and secondary particles
The results of the study of biocidal properties of silver, copper and silicon dioxide nanoparticles are presented. Questions about the safety of nanocomponents in connection with their unstudied impact on the environment are considered. To evaluate the biocidal effect of noble metal nanoparticles and bioelements, a unicellular eukaryotic test-system, represented by a ciliated protist microorganism Paramecium caudatum inhabiting pond water bodies, was used. It was found that solutions of noble metal nanoparticles and bioelements are not bioinert and biostimulating. Colloidal solutions of silver, copper and silicon dioxide nanoparticles have a biocidal effect and show a similar dosedependent effect if the concentration of nanoparticles in the initial colloidal solutions is the same (300 µg/ml). The colloidal silver solution is characterized by a more pronounced toxic activity in a unicellular protist biological model, since full biocidal activity against paramecium is provided by dilutions of the colloidal solution of nanoparticles to the value 1: 6 of the initial one. Compared to it, solutions of copper nanoparticles and silicon oxide have a biocidal index of 100% achieved only in values of two- or three-times dilution of the initial solution. Colloidal solutions of nanoparticles in concentrations that do not cause complete mortality of the infusoria (1: 5 of the original for copper and silicon oxide nanoparticles and 1: 7 of the original for silver nanoparticles) inhibit their reproduction intensity by approximately the same value of 55-61% (paramecium reproduction intensity index of 0.455 to 0.390 respectively).
We exploit chemo- and galvanotactic behaviour of Paramecium caudatum to design a hybrid device that allows for controlled uptake, transport and deposition of environmental micro- and nanoparticulates in an aqueous medium. Manipulation of these objects is specific, programmable and parallel. We demonstrate how device operation and output interpretation may be automated via a DIY low-cost fluorescence spectrometer, driven by a microprocessor board. The applications of the device presented range from collection and detoxification of environmental contaminants (e.g. nanoparticles), to micromixing, to natural expressions of computer logic.
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Nanotoxicology represents a new and growing research area in toxicology. It deals with the assessment of the toxicological properties of nanoparticles (NPs) with the intention of determining whether (and to what extent) they pose an environmental or societal threat. Inherent properties of NPs (including size, shape, surface area, surface charge, crystal structure, coating, and solubility/dissolution) as well as environmental factors (such as temperature, pH, ionic strength, salinity, and organic matter) collectively influence NP behavior, fate and transport, and ultimately toxicity. The mechanisms underlying the toxicity of nanomaterials (NMs) have recently been studied extensively. Reactive oxygen species (ROS) toxicity represents one such mechanism. An overproduction of ROS induces oxidative stress, resulting in inability of the cells to maintain normal physiological redox-regulated functions. In the context of this book, this chapter includes topics pertaining to chemical and physical properties of NMs and characterization for proper toxicological evaluation, exposure, and environmental fate and transport, and ecological and genotoxic effects. This chapter reviews the available research pertaining specifically to NMs in the aquatic environment (in plants, aquatic invertebrates, and fish) and their use in biomarker studies.
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Significance We identify the abundant presence in the human brain of magnetite nanoparticles that match precisely the high-temperature magnetite nanospheres, formed by combustion and/or friction-derived heating, which are prolific in urban, airborne particulate matter (PM). Because many of the airborne magnetite pollution particles are <200 nm in diameter, they can enter the brain directly through the olfactory nerve and by crossing the damaged olfactory unit. This discovery is important because nanoscale magnetite can respond to external magnetic fields, and is toxic to the brain, being implicated in production of damaging reactive oxygen species (ROS). Because enhanced ROS production is causally linked to neurodegenerative diseases such as Alzheimer’s disease, exposure to such airborne PM-derived magnetite nanoparticles might need to be examined as a possible hazard to human health.
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Along with the development of nanotechnology, an increase in production and application of nanosized magnetite (Fe3O4) is expected. Though magnetite is considered relatively safe, information concerning potential hazards of synthetic magnetite nanoparticles with unique physico-chemical characteristics to aquatic organisms is still limited. In this study, we evaluated the toxicity of nanosized (27.2 ± 9.8 nm) and bulk (144.2 ± 67.7 nm) magnetite particles to different life stages of the aquatic crustacean Daphnia magna. In addition, phytotoxicity of the magnetite was evaluated using duckweed Lemna minor. The study did not reveal any statistically significant differences between the biological effects of nanosized and bulk magnetite particles. Both forms of magnetite induced very low toxicity (EC50 > 100 ppm) to D. magna and L. minor in the standard acute assays. However, it was demonstrated that at acutely subtoxic magnetite concentrations (10 and 100 ppm), the number of neonates hatched from D. magna ephippia was decreased. Moreover, short-term (48 h) exposure of neonate daphnids to these concentrations may significantly affect the long-term survival and reproductive potential of daphnids. These results indicate that substantial contamination of aquatic ecosystems by magnetite may disrupt the stability of cladoceran populations.
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The development of nanoparticles (NPs) for use in all facets of oncological disease detection and therapy has shown great progress over the past two decades. NPs have been tailored for use as contrast enhancement agents for imaging, drug delivery vehicles, and most recently as a therapeutic component in initiating tumor cell death in magnetic and photonic ablation therapies. Of the many possible core constituents of NPs, such as gold, silver, carbon nanotubes, fullerenes, manganese oxide, lipids, micelles, etc., iron oxide (or magnetite) based NPs have been extensively investigated due to their excellent superparamagnetic, biocompatible, and biodegradable properties. This review addresses recent applications of magnetite NPs in diagnosis, treatment, and treatment monitoring of cancer. Finally, some views will be discussed concerning the toxicity and clinical translation of iron oxide NPs and the future outlook of NP development to facilitate multiple therapies in a single formulation for cancer theranostics.
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Some researchers have described the cells of Paramecium species as " swimming sensory cells " or " swimming neurons " applicable to micro-biorobotics and biological micro-electromechanical systems (BioMEMS). Paramecium species including green paramecia (Paramecium bursaria) migrate towards the anodic electrode when exposed to an electric field. This type of cellular movement is known as galvanotaxis. Because the ideal micromachines designed for microparticle transport must have a capacity for loading certain numbers of particles, P. bursaria was chosen as a model organism. In this study, we show enhanced microparticle transport by overcoming (i) the particle size limitation for the cell-mediated transport of microspheres of up to ca. 10 µm size (doubling the size of particles ever reported) and (ii) the limit of cellular migration distance manifested by galvanotactically stimulated cells.
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Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T-1, spin-lattice relaxation and T-2, spin-spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T-1 and T-2 increases the corresponding relaxation rates, 1/T-1 and 1/T-2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T-2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T-1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.
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Physarum polycephalum is considered to be promising for the realization of unconventional computational systems. In this work, we present results of three slime mould-based systems. We have demonstrated the possibility of transporting biocompatible microparticles using attractors, repellents and a DEFLECTOR. The latter is an external tool that enables to conduct Physarum motion. We also present interactions between slime mould and conducting polymers, resulting in a variation of their colour and conductivity. Finally, incorporation of the Physarum into the organic memristive device resulted in a variation of its electrical characteristics due to the slime mould internal activity.
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The plasmodium of slime mould Physarum polycephalum has recently received significant attention for its value as a highly malleable amorphous computing substrate. In laboratory-based experiments, nanoscale artificial circuit components were introduced into the P. polycephalum plasmdodium to investigate the electrical properties and computational abilities of hybridized slime mould. It was found through a combination of imaging techniques and electrophysiological measurements that P. polycephalum is able to internalize a range of electrically active nanoparticles (NPs), assemble them in vivo and distribute them around the plasmodium. Hybridized plasmodium is able to form biomorphic mineralized networks inside the living plasmodium and the empty trails left following its migration, both of which facilitate the transmission of electricity. Hybridization also alters the bioelectrical activity of the plasmodium and likely influences its information processing capabilities. It was concluded that hybridized slime mould is a suitable substrate for producing functional unconventional computing devices.