Impacts of Metal and Metal Oxide Nanoparticle on Embryos

Review Article

Austin Endocrinol Diabetes Case Rep. 2017; 2(1): 1009.

Impacts of Metal and Metal Oxide Nanoparticle on Embryos

YK Lahir*

Department of Biophysics, University of Mumbai, India

*Corresponding author: Yogendrakumar Lahir, Department of Biophysics, University of Mumbai, Vidyanagari, Santa Cruz (E), Mumbai-400 098, MS, India

Received: June 15, 2017; Accepted: July 03, 2017; Published: July 10, 2017


In the recent past numerous studies related to nanomaterials and biological experimental models are being carried out. These are basically converging to enhance the understanding the mode, mechanism and resultant impacts on biota of the ecosystem. Extensive applications of nanotechnology are responsible for the excessive and unproportional use of nanomaterials/nanoparticles in present day life. As a result the existence of nanomaterials as discarded waste matter in ecosystem is quite obvious. This discarded bulk of nanomaterials become the prime factor that interferes in the life of biosystem. This compels to take review of such studied that are related to the detrimental effects on biosystem and redesign the research. Embryonic phase of life cycle of any metazoan biological entity exhibiting sexual reproduction is an essential, sensitive and vulnerable phase. It is very responsive to the fluctuations in the ecosystem. Embryonic phase of biosystem may be accomplished either within the body of the maternal parent or outside in open in the aquatic and/or soil aspects of ecosystem. It becomes pertinent to review the impact of nanomaterials on the biotic and abiotic components of the ecosystem specifically when nanomaterials are involved in wide varieties of products of day to day life. Nanomaterials are of diverse nature and because of their specific physicochemical properties are being exploited in biomedical, pharmaceutical, chemical, electronics, and many industrial fields. These nanomaterials are of various types like metals and metallic oxides, carbon based nanomaterials, quantum dots, polymeric nanomaterials, nanocomposites, nano-alloys and most of these are specifically functionalized for the targeted purposes. Of all these nanomaterials metals and metal oxide nanoparticles appear to be most exploited materials as a consequence are released in huge amount in the ecosystem relatively more in comparison to the rest. The metal and metal oxide nanoparticles get dispersed in air, water and soil relatively much easily and remain there either in pristine or combined forms. These features make them more detrimentally effective. In this review an effort is made to understand the intricacies involved specifically during the embryonic stage. Thus an effort is made to review the pertinent literature on the impacts of metals and metal oxide nanoparticles specifically on embryos of vertebrates.

Keywords: Nanomaterials; Metal-nanoparticles; Metal oxide nanoparticles; Placenta; Reproductive phase

Over View


The term ‘Embryo’ has its origin from Greek and Latin, (grow or get filled up); this world denotes growth at the maximum rate in most of the biosystems exhibiting sexual reproduction. Duration of embryonic phase varies with respect to the species. Embryo is the product of post fertilization process i.e., zygote is a unicellular diploid stage under goes cell proliferation resulting in blastula, gastrula and three germinal layer stage, cell differentiation, cell migration, demarcation of presumptive zones, morphometric movements, organogenesis. In these cases the embryos are relatively more protected than those developing outside their respective mother. Among mammals female individuals are provided with varied forms of placenta in different groups of mammals. The placenta is a morphological and physiological bridge between the embryo and the uterus of maternal parent which meets all requirements of developing embryo. This feto-maternal organ gets rooted within blastocyst and is delivered with the fetus at birth. The placenta ensures the implantation, interface to supply and eliminate nutrient and the metabolites, to regulate maternal recognition of pregnancy, maintains immune environment suitable for the fetus and establishes paracrine and endocrine homeostasis [1]. Among most of the invertebrates and lower vertebrates embryos are left in their natural environment (mostly outside their maternal parent) for their embryonic growth.

Mostly embryos are considered as suitable model for developmental biology and biomedical research specifically embryos of zebra fish, medake fish (Oryzias latipes), Pelophylax perezi, Xenopus, avian embryos (chick embryo) [2-4]. In case of reptilian and avian embryos the embryonic development is accomplished outside the maternal parent and morphologically the developmental stages are relatively distinct and easily manipulative for experimentation in comparison to other animals. In these experimental models the entry port for the nanomaterials is albumin, air sac; these components of the egg are likely to affect the exact concentration that reaches the tissue under study, thereby may affect the implications of the nanoparticles. The eggs and embryos of fishes and amphibians are covered with a jelly like materials made of proteoglycans, glycoproteins; this mucoidal layer is the probable protective and preventive in nature.

Egg, zygote and early developing stages are enclosed within vitelline membrane; this membrane mostly consists of protein fibers and protein receptors that are needed for the binding of sperm, these protein receptors are species – specific in nature. As a result of signal transduction Ca+2 increase and ‘cortical reaction’ is induced, these cortical granules get added on to the Vitelline Membrane (VM) involving exocytosis and converting VM in to fertilization membrane [5]. The potential of contractibility of actomyosin can induce effective forces that plays major role in permitting the cells to sense and response to varied mechanical stimuli [6]. These developing stages are relatively smaller in size, have lower metabolic activities, potentially lower energy reserves probably due to higher growth rate and distribution limitation. Lister et al, have suggested that most of the embryos and larval stages are provided with ‘Mycosporine-Like- Amino Acids’ (MAAs), these are the gifts from their maternal parent. The levels of such amino acids may vary with respect to the type of food consumed by the maternal parents [7]. Vitelline membrane is the membranous structure which is protective and regulates the embryonic pattern. There are four major Vitelline Membrane Proteins (VMPs) having cystine. The critical cystine involves in isomerizing intermolecular disulfide bond enzymatically and facilitates assembly of egg shell [8].

Entry-ports for any toxicants are the vulnerable sites in and on the embryo that facilitate the entry; reproductive openings, pre and post fertilizational stages, larval stages in case of aquatic animals and transplacental route in case of mammals [9]. There are likely to be some deviations in the toxicological investigations when conducted in vivo and in vitro this is because within organism there is a ‘molecular crowding’ which is not there in ‘test tube’, but overall the pattern is likely to represent the derogative impacts of the toxicant under study. There are number of types of nanomaterials and their detrimental influences on biota are vast. In this presentation derogative effects due to metal and metal oxide nanoparticles pertaining to vertebrates have been elucidated.

Metal and metal oxide nanoparticles

Nanomaterials are identified and characterized because of their nanosize and specific physicochemical properties. These are fascinating materials – products of multidisciplinary nanotechnology. These have been suitably used in variety of disciplines ranging from basic and fundamental science to most of the applied branches of industries; as such these wonder particles have gained prime attention of researchers, scientists and industrialists. Nanoparticles have specific physicochemical properties that include chemical composition, size, shape, surface modification or properties, agglomerate or single nanoparticle state [10]. Nanoparticles exhibit properties that favor surface coatings, surface charge, and ‘Zeta potential’ change in shape and because of such abilities nanoparticles are functionalized to carry out targeted functions [11]. All these properties enable them to pass though almost all types of biological barriers in an organism. Sometimes these factors are likely to results in bioaccumulation and induce some biochemical, molecular and developmental defects in organism. Nanoparticles and the allied products are well known for their higher degree of interactions with biomolecules. The synthesis and engineering of nanomaterials are precisely controlled in relation to the physicochemical properties, surface modifications and other features specifically in accordance to the target specifications [12]. Parameters of nanomaterials like size, shape and core composition, purity of the metals and their precursor, surface properties, pH, ionic strength, nature of the biomolecules present in the system also affect their interactions with biomolecules [13,14]. As a result of these interactions the biomolecules are likely to undergo changes involving shift of energy within specific thermodynamics, kinetics and physicochemical limitations [15,16]. Generally greater numbers of nanoparticles are used in colloidal form at least in biomedical field and related industries. The size of nanoparticles renders them to be more towards spherical shape showing curvatures rather a particle with flat nature, this feature reflects on their assumed colloidal behavior. The colloidal behavior of nanoparticles is related to their curvature, small radii, and higher percentage of atom at their surface. These features affect their electronic structure, surface charge, behavior and reactivity; these features play a decisive role towards their dispersal or colloidal behavior. As such these nanoparticles in most probability follow “Derjguin-Landan-Overwey-Overbeek” and “Extended-Derjguin-Landan-Overwey-Overbeek” models in their behavior. This behavior of nanoparticles is related with the repulsive and attractive forces like van der Waals, electrostatic forces and double layer etc. All these forces affect the distribution of net potential energy between the nanoparticles in spite of the state of nanoparticles whether in dispersed or agglomerate state [17].

The interaction between nanomaterials and macromolecules of biosystem are likely to be either beneficial, derogative in nature or may exhibit delayed reaction, further this behavior is dose dependant [18]. Cho et al, observed that that surface charge and uptake of nanoparticles exhibit some type of correlation; negatively charged nanoparticles were found to be less adsorbed on the cell membrane surface enhance the degree of internalization of such nanoparticles was low [19]. Dose dependant histological impacts exhibit disorganization and atrophy in the hepatic tissue in case of chick embryo when treated with zinc oxide nanoparticles [20]. Biocompatibility of nanomaterials is one of the prime parameters affecting the beneficial and derogative impacts on any aspect of biosystem. This parameter plays significant role in the safety of the biosystem from the nanomaterials and appropriate application in biomedical and related fields. Any material that is intended to interface within biological system and to evaluate, treat, augment, replacement of tissue/organs and participate any functional aspect is considered to be biomaterial. Biocompatibility of such materials can be understood by following its pathways: in biosystem the biomaterial may exhibit molecular adsorption, experience mechanical, biophysical and biochemical impetus. These aspects influence structural and functional unit of biosystem and as a result it may be defensive, be a target or may interfere; when defensive there may be no effect, it is a good outcome, when a target-it can exhibit adverse effect eliciting adverse outcome, if as interferer then the response may be no interaction then it is neutral, a good outcome, if interaction occurs then response may be either poor or adverse [21]. There are many properties which contribute to the biocompatibility like physicochemical properties, surface characters, hydrophilicity and/or hydrophobicity that can enhance the suitability of biomaterial in the biomedical and related fields [22].

Some aspects related to the interactions between metal, metal oxide nanoparticles and embryo

Concentration of nanoparticles, i.e., (nanoparticles /cm3) affects the animal tissues depending on the type of tissue and type of metal nanomaterials [10]. Lee et al found that when the embryos of zebra fish were exposed to higher concentration of silver nanoparticles it resulted in higher number of deformed embryos and higher mortality [23], similar observations were recorded in case of embryos of Oryzias latipes and Pimphales promelas when subjected to higher concentration of silver nanoparticles [24,25]. Dose dependent toxic effects were observed in case of embryos of zebra fish and chick when exposed to ZnO-nanoparticles [20,27]. Browning et al did not observe dose dependent impact on the embryos of zebra fish when exposed to higher concentration of silver nanoparticles instead accumulation of silver nanoparticles in the body of embryos was noticed [27].

Other parameter that may affect toxic effect is agglomerated state of nanoparticles because there is a change in the surface area and chemical properties; it is of common observation that most of the nanoparticles undergo agglomeration when come in contact with water, ZnO nanoparticles is good example [10]. Agglomerated ZnO nanoparticles have ability to cause relatively more toxic effects and higher degree of mortality [26]. It is of common observation that agglomerated nanoparticles get deagglomeration and after sonication these can be used; Laban et al studied the toxicity of agglomerated ZnO nanoparticles and did not observe any toxic effects with respect to the size [25]. There are some of the nanoparticles that release ions when subjected to physiological fluid; this feature plays an effective role in the respective toxicity. When embryo of zebra fish were exposed to silver nanoparticles having 10 nm size and coated with citrate 10/50nm coated with polyvinylpyrrolidone showed changed swimming behavior, delayed hatching, inflation of bladder, derogative morphological impacts and silver ions, both were investigated and mortality; Ag ions induced hyperactivity with respect to changes in light but coated nanoparticles were not very effective in this aspect [28]. Li et al observed the toxic effects of 50μm sized Ag nanoparticles and silver ions on the developing stage –in blastula of mouse that is referred as blastocyst resulted in decline in number of cells, elevated apoptosis, declined the rate of implantation, loss of weight of embryonic tissue and higher degree of resorption of Ag nanoparticles in the post implanted embryos [29]. Toxic impacts of copper nanoparticle and nickel salt on embryos of zebra fish; copper nanoparticles with 0.1mg/l concentration reduced hatching, morphologically deformed larvae and caused death of larvae at gastrula stage while lower concentration 0.01mg/l and 0.05mg/l and Cu+2 at 0.006 and 0.03mg/l appeared to be not very effective, thus indicating higher toxicity at 0.1 mg/l than Cu+2 at 0.06mg/l [30]. ZnO nanoparticles in water form aggregates, small aggregates 142.4nm and big aggregates 517.7nm, with concentration 50 and 100mg/L both appeared to be toxic as the embryos under study were killed; the concentration of 1-25mg/L retarded the growth (body length) of the larvae and rendered defective tail formation at 96 h of exposure [31]. Hydrophobicity and hydrophilicity are related to the distribution and surface feature of nanoparticles and helpful in developing predictive models of nanoparticle; Principal Component Analysis (PCA) is an effective mode for controlling many surface molecular features. It is important to identify specific features of the materials and its specific chemistry that is responsible for the biological interactions; this consequently will help in safe designing of nanoparticles [32].

Interactions between metal, metal oxide nanoparticles and vertebrates

Embryo is biologically and metabolically active and important phase in the life of a metazoan, may it be invertebrate or vertebrates. In the given ecosystem nanomaterials are available to biota and abiota because these are likely to be released either as waste or unused or discarded intentionally or accidently. Whatever the case may be most of the biological systems get affected by these materials. Embryo is metabolically active and relatively more vulnerable to the negative or derogative impacts of the nanomaterials present in ecosystem. In the current scenario the embryos are the prime target to study the effects of nanomaterials on the developmental phase of a biosystem. Nanoparticles are ubiquitous in environment and their dose and the exposure time for the organisms is changing day by day possibly causing change in the threshold toxic dose. This unnoticed slow exposure to the organisms is likely to be either fetal or injurious and/ or may result in malfunctioning or malformation in embryo and offspring.

Whenever nanomaterials either interact externally and/or internalized there is a ‘conception period’; during this period there occur molecular and cellular restructuration in biosystem; during this span of time it is very difficult to observe the response of biosystem. Nanoparticles have the ability to cross over most of the biological barriers; this feature ensures their influence on the cellular viability of the organism (Flow Chart).

Citation: Lahir YK. Impacts of Metal and Metal Oxide Nanoparticle on Embryos. Austin Endocrinol Diabetes Case Rep. 2017; 2(1): 1009.