Abstract
Nanotechnology is
the science of designing, producing, and using structures and devices having
one or more dimensions of about 100 millionth of a millimetre (100
nanometres) or less. It is going to be a major driving force behind the
imminent technological revolution in the 21st century. Private and
public sector companies are constantly in synthesizing nanomaterial based
products. Nanotechnology has the potential of producing new materials and
products that may revolutionize all areas of life. Meanwhile, its opponents
believe that nanotechnology may cause serious health and environmental risks
and advise that the prophylactic approach should command the blooming and
distribution of such products. Nanotechnology pledges for producing novel
materials with augmented properties and potential applications (Zeng and Sun,
2008).
Nanoparticles
and nanomaterials both terms are used interchangeably in scientific
literature. However, according to British Standards Institution for the
scientific terms: “Nanomaterial is a material with any internal or external
structures on the nanoscale dimension, while Nanoparticle a is nano-object
with three external nanoscale dimensions. According to the European
Commission, nanoparticles can be defined as a natural, incidental or manufactured
material containing particles, in an unbound state or as an aggregate or as
an agglomerate with one or more external dimensions is in the size range 1 nm
– 100nm. The size of nanoparticles is comparable to the size of cell
organelles. Nanoparticles can have amorphous or crystalline form and their
surfaces can act as carriers for liquid droplets or gases. They have at least
one dimension between 1 and 100 nanometers and a narrow size distribution.
The nanometric dimensions of these materials make them ideal candidates for
surface engineering and functionalization. Due to the development of
nanotechnology in recent years, engineered nanoparticles are being used in
various fields, particularly in biomedical field.
Various
physico-chemical properties such as large surface area strength, mechanical,
optical activity and chemical reactivity make nanoparticles unique and
suitable candidates for various applications. Nanomaterials can be classified
into natural and anthropogenic categories based on their origin. Natural
sources include volcanic eruptions, forest fires, photochemical reactions,
dust storms, etc., while anthropogenic sources include human activities,
which can be of two types: Incidental nanomaterials that are generated
unintentionally as a result of industrial activities. Combustion from
vehicles, cooking, fuel petroleum and coal for power generation (Linak et
al., 2000), aeroplanes engines, welding, ore refining and smelting are
some of the incidental activities that lead to nanoparticle formation (Rogers
et al., 2005). Engineered nanomaterials are designed and created
intentionally for producing nanoparticles with specific characteristics. Due
to its unusual tunable properties, these materials are widely used in
electronics such as semiconductor chips, lighting technologies such as
light-emitting diodes (LEDs), lasers, batteries, and fuel electronics etc.
Scientists are using nanoparticles to target tumors, in drug delivery
systems, and to improve medical imaging. Emerging engineered nanomaterials
like quantum dots, nanobranches, nanocages, and nanoshells are presently
being used in advance photovoltaic cells, drug delivery nanovehicles, and
immunological sensing devices (Kahru and Dubourguier, 2010).
Nanomaterials
are also classified on the basis of morphology (rod, flower shaped, fiber,
sphere and sheet), crystalline mature (amorphous and cristaline), dimension
(0D, 1D, 2D, and 3D), and chemical nature (metal, semi-metal and non-metal).
There are more than 1800 market products containing nanomaterials, including
drugs, food products, food preservatives, clothing, sports items, cosmetics
and electronic appliances (Chou et al., 2008; Vance et al.,
2015). Nanoparticles are currently being used in biomedicine, bio-imaging,
targeted drug delivery, assisted rreproductive technologies (ART), etc.
Nanoparticle exposure to humans may be either incidental or accidental or
occupational to the natural and manmade nanomaterials. Nanoparticles enter
human bodies through inhalation, ingestion and skin, accumulate in the body
organs and cause toxic effects on the biological system. The highly activated
surfaces of nanoparticles have great potential to induce cytotoxic, genotoxic
and carcinogenic activities (Seaton et al., 2010). In-vivo studies specify
that the lung, spleen, liver, and kidney are the major distribution sites and
target organs for nanomaterial exposure (Wang et al., 2013). They
induce localized toxic effects such as cardiotoxicity, hepatotoxicity,
nephrotoxicity, etc., in related organs (Du et al., 2013; Yan et
al., 2012; Hussain et al., 2005).
Several
reports have described the adverse effects of nanoparticles on human and
animal health, especially in context of reproductive health. The reproductive
toxicity of nanoparticles is becoming an important part of nano-science
research (Ema et al., 2010). Exposure to nanoparticles adversely
affects male reproductive system including both structural and functional
aspects. Metallic nanoparticles, generally below 30 nm, owing to their
spherical nature and diameter easily cross blood testicular barrier causing
considerable toxic changes in the testicular tissue. Hong et al.
(2015) reported decreased sperm production in testis accompanied with changes
in expression of spermatogenesis regulating genes due to exposure of metallic
nanoparticle titanium dioxide (TiO2). A sub-chronic oral exposure
of PVP-coated AgNPs to rats resulted in altered testicular histology and
sperm morphological abnormalities. In a study, testicular toxicity due to
silver nanoparticles was examined in Sprague Dawley rat. The results
indicated a significant fall in testosterone level and hike in LH levels.
Ultra structural examination revealed vaculations in Sertoli cells and
abnormalities in spermatogenic cells, sperm viability and chromatin integrity
were also affected adversely (Elsharkawy et al., 2019).
Similarly,
exposure to zinc oxide nanoparticles resulted in apoptosis in testicular
cells and structural changes in seminiferous epithelium and sperm anomalies
(Han et al., 2016). Accumulation of copper oxide nanoparticles in
testis of mouse may affect sperm morphology (Kadammattil et al.,
2018). Spherical shaped nickel nanoparticles of 90 nm size can change
motility and decrease FSH and testosterone levels in rats. At higher dose,
nickel nanoparticles induced significant structural damage to the testis
(Kong et al., 2014). Iron oxide nanoparticles of 20-80 nm size adverse
by affected the sperm and Leydig cells in mouse (Nasri et al., 2015).
Recent testicular toxicity study conducted by Verma et al. (2022)
demonstrated that low, medium and high doses (20, 40 and 80 mg kg-1) of
spherically shaped, with an average diameter of 15-20 nm, super paramagnetic
IONPs (Fe3O4) injected intra-peritoneally decreased
sperm counts and motility in spermatozoa.
With
respect to the effects due to non-metallic or semi-metallic nanoparticles
having different shapes, different outcomes have been reported. A study
conducted by Nirmal et al. (2017) on Wistar rat, exposed to 2.0 and
10.0 mg kg-1 bwt doses of OH-f MWCNTs resulted in sperm
dysfunction and degeneration in seminiferous tubules (Nirmal et al.,
2017). In another study by the same group, Wistar rat exposed to high doses
of nanoscale graphene oxide (NGO) intra-peritonially, showed reduced sperm
motility and total sperm count and increased sperm abnormalities (Nirmal et
al., 2017). It is thus apparent that nanoparticles have a considerable
negative impact on testicular tissue including damage to Leydig cells,
Sertoli cells, spermatogenesis and sperm quality. Various studies have
revealed that the testicular toxicity is caused due to combination factors.
Oxidative stress is a key factor responsible for nanoparticle mediated
damage. It becomes more harmful, especially to the testes because of high
metabolism, continuous sperm production and presence of high amount of
unsaturated fatty acids (Aitken and Roman, 2008).
With
the expansion and production of nanometerials for industrial and medical
applications, exposure chances are also increasing. Many research reports have
documented the adverse effects of nanoparticles on animals and environment.
The major concern with the widespread use of NPs is their toxicity to living
cells. Therefore, alleviating or reducing NPs toxicity remains much coveted
goal for researchers around the globe. It is the alertness and scientific
awareness which can prevent these materials from becoming bane instead of
boon for humanity.
This
editorial is written as a tribute to my beloved teacher Dr. R. C. Dalela who
has been my mentor since 1985, when I was student of M.Sc. Zoology
(1985-1987) and Ph.D (1987-1993) in D.A.V. P.G. College, Muzaffarnagar. He
has played a vital role in moulding my career, from an average post-graduate
student to the academician and a researcher I am today. I deeply cherish his
guidance, encouragement and support. It was my privilege to meet him last
November, so close to his sudden demise. The values inculcated by him
continues to inspire me in my onward journey.
I
have been associated with JEB for the past 25 years as a reviewer and an
Associate Editor. The articles published in this journal receive good
citations, which reflect the popularity of this open access journal among the
researchers of Environmental Biology and Toxicology. I must appreciate the
present editorial team headed by Professor Divakar Dalela for their efforts
in maintaining the standard of this journal. I wish all success and my
sincere co-operation for the same in the coming years.
|
|