Urea-functionalized amorphous calcium phosphate nanofertilizers: optimizing the synthetic strategy towards environmental sustainability and manufacturing costs

Phosphorus-based nanomaterials as a potential phosphate fertilizer for sustainable agricultural development

Phosphorus-based nanomaterials (PNMs) have been reported to have substantial promise for promoting plant growth, improving plant tolerance mechanisms, and increasing resistance to pathogenic organisms. Recent scientific investigation has demonstrated that utilizing PNMs can enhance plant physiological growth, photosynthetic pigments, antioxidant system, metabolism, nutrient absorption, rhizosphere secretion, and soil nutrients activation. Previous research on PNMs mostly concentrated on calcium phosphate, zeolite, and chitosan, with little systematic summarization, demanding a thorough evaluation of PNMs' broader uses. In our current review article, we address the knowledge gap by classifying PNMs according to green synthesis methods and the valence state of phosphorus while elucidating the underlying mechanisms through which these PNMs facilitate plant growth. In addition, we also targeted some strategies to improve the bioavailability of PNMs, offering valuable insights for the future design and safe implementation of PNMs in agricultural practices.

Eco-Efficient Systems Based on Nanocarriers for the Controlled Release of Fertilizers and Pesticides: Toward Smart Agriculture

The excessive application of pesticides and fertilizers has generated losses in biological diversity, environmental pollution, and harmful effects on human health. Under this context, nanotechnology constitutes an innovative tool to alleviate these problems. Notably, applying nanocarriers as controlled release systems (CRSs) for agrochemicals can overcome the limitations of conventional products. A CRS for agrochemicals is an eco-friendly strategy for the ecosystem and human health. Nanopesticides based on synthetic and natural polymers, nanoemulsions, lipid nanoparticles, and nanofibers reduce phytopathogens and plant diseases. Nanoproducts designed with an environmentally responsive, controlled release offer great potential to create formulations that respond to specific environmental stimuli. The formulation of nanofertilizers is focused on enhancing the action of nutrients and growth stimulators, which show an improved nutrient release with site-specific action using nanohydroxyapatite, nanoclays, chitosan nanoparticles, mesoporous silica nanoparticles, and amorphous calcium phosphate. However, despite the noticeable results for nanopesticides and nanofertilizers, research still needs to be improved. Here, we review the relevant antecedents in this topic and discuss limitations and future challenges.

Nanofertilizers: Types, Delivery and Advantages in Agricultural Sustainability

In an alarming tale of agricultural excess, the relentless overuse of chemical fertilizers in modern farming methods have wreaked havoc on the once-fertile soil, mercilessly depleting its vital nutrients while inflicting irreparable harm on the delicate balance of the surrounding ecosystem. The excessive use of such fertilizers leaves residue on agricultural products, pollutes the environment, upsets agrarian ecosystems, and lowers soil quality. Furthermore, a significant proportion of the nutrient content, including nitrogen, phosphorus, and potassium, is lost from the soil (50–70%) before being utilized. Nanofertilizers, on the other hand, use nanoparticles to control the release of nutrients, making them more efficient and cost-effective than traditional fertilizers. Nanofertilizers comprise one or more plant nutrients within nanoparticles where at least 50% of the particles are smaller than 100 nanometers. Carbon nanotubes, graphene, and quantum dots are some examples of the types of nanomaterials used in the production of nanofertilizers. Nanofertilizers are a new generation of fertilizers that utilize advanced nanotechnology to provide an efficient and sustainable method of fertilizing crops. They are designed to deliver plant nutrients in a controlled manner, ensuring that the nutrients are gradually released over an extended period, thus providing a steady supply of essential elements to the plants. The controlled-release system is more efficient than traditional fertilizers, as it reduces the need for frequent application and the amount of fertilizer. These nanomaterials have a high surface area-to-volume ratio, making them ideal for holding and releasing nutrients. Naturally occurring nanoparticles are found in various sources, including volcanic ash, ocean, and biological matter such as viruses and dust. However, regarding large-scale production, relying solely on naturally occurring nanoparticles may not be sufficient or practical. In agriculture, nanotechnology has been primarily used to increase crop production while minimizing losses and activating plant defense mechanisms against pests, insects, and other environmental challenges. Furthermore, nanofertilizers can reduce runoff and nutrient leaching into the environment, improving environmental sustainability. They can also improve fertilizer use efficiency, leading to higher crop yields and reducing the overall cost of fertilizer application. Nanofertilizers are especially beneficial in areas where traditional fertilizers are inefficient or ineffective. Nanofertilizers can provide a more efficient and cost-effective way to fertilize crops while reducing the environmental impact of fertilizer application. They are the product of promising new technology that can help to meet the increasing demand for food and improve agricultural sustainability. Currently, nanofertilizers face limitations, including higher costs of production and potential environmental and safety concerns due to the use of nanomaterials, while further research is needed to fully understand their long-term effects on soil health, crop growth, and the environment.

Nanofertilizers: The Next Generation of Agrochemicals for Long-Term Impact on Sustainability in Farming Systems

The microflora of the soil is adversely affected by chemical fertilizers. Excessive use of chemical fertilizers has increased crop yield dramatically at the cost of soil vigor. The pH of the soil is temporarily changed by chemical fertilizers, which kill the beneficial soil microflora and can cause absorption stress on crop plants. This leads to higher dosages during the application, causing groundwater leaching and environmental toxicity. Nanofertilizers (NFs) reduce the quantity of fertilizer needed in agriculture, enhance nutrient uptake efficiency, and decrease fertilizer loss due to runoff and leaching. Moreover, NFs can be used for soil or foliar applications and have shown promising results in a variety of plant species. The main constituents of nanomaterials are micro- and macronutrient precursors and their properties at the nanoscale. Innovative approaches to their application as a growth promoter for crops, their modes of application, and the mechanism of absorption in plant tissues are reviewed in this article. In addition, the review analyzes potential shortcomings and future considerations for the commercial agricultural application of NFs.

Plant growth promoting potential of urea doped calcium phosphate nanoparticles in finger millet (Eleusine coracana (L.) Gaertn.) under drought stress

Drought is a leading threat that impinges on plant growth and productivity. Nanotechnology is considered an adequate tool for resolving various environmental issues by offering avant-garde and pragmatic solutions. Using nutrients in the nano-scale including CaP-U NPs is a novel fertilization strategy for crops. The present study was conducted to develop and utilize environment-friendly urea nanoparticles (NPs) based nano-fertilizers as a crop nutrient. The high solubility of urea molecules was controlled by integrating them with a matrix of calcium phosphate nanoparticles (CaP NPs). CaP NPs contain high phosphorous and outstanding biocompatibility. Scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD) were used to characterize the fabricated NPs. FE-SEM determined no areas of phase separation in urea and calcium phosphate, indicating the successful formation of an encapsulated nanocomposite between the two nano matrices. TEM examination confirmed a fiber-like structure of CaP-U NPs with 15 to 50 nm diameter and 100 to 200 nm length. The synthesized CaP-U NPs and bulk urea (0.0, 0.1% and 0.5%) were applied by foliar sprays at an interval of 15 days on pre-sowed VL-379 variety of finger millet (Eleusine coracana (L.) Gaertn.), under irrigated and drought conditions. The application of the CaP-U NPs significantly enhanced different plant growth attributes such as shoot length (29.4 & 41%), root length (46.4 & 51%), shoot fresh (33.6 & 55.8%) and dry weight (63 & 59.1%), and root fresh (57 & 61%) and dry weight (78 & 80.7%), improved pigment system (chlorophyll) and activated plant defense enzymes such as proline (35.4%), superoxide dismutase (47.7%), guaiacol peroxidase (30.2%), ascorbate peroxidase (70%) under both irrigated and drought conditions. Superimposition of five treatment combinations on drought suggested that CaP-U NPs at 0.5 followed by 0.1% provided the highest growth indices and defense-related enzymes, which were significantly different. Overall, our findings suggested that synthesized CaP-U NPs treatment of finger millet seeds improved plant growth and enzymatic regulation, particularly more in drought conditions providing insight into the strategy for not only finger millet but probably for other commercial cereals crops which suffer from fluctuating environmental conditions.

Alnus nitida and urea-doped Alnus nitida-based silver nanoparticles synthesis, characterization, their effects on the biomass and elicitation of secondary metabolites in wheat seeds under in vitro conditions

Nano-fertilizers are superior to conventional fertilizers, but their effectiveness has not yet been adequately explored in the field of agriculture. In this study, silver nanoparticles using leaves extract of an Alnus nitida plant were synthesized and further doped with urea to enhance the plant biomass and metabolic contents. The synthesized Alnus nitida silver nanoparticles (A.N-AgNPs) and urea-doped silver nanoparticles (U-AgNPs) were characterized using Scanning Electron Microscopy, Transmission Electron Microscopy, Powder X-ray Diffraction, and Energy Dispersive X-ray. The wheat seeds were grown in media under controlled conditions in the plant growth chamber. The effectiveness of nanoparticles was studied using different A.N-AgNPs and U-AgNPs concentrations (0.75 μg/ml, 1.5 μg/ml, 3 μg/ml, 6 μg/ml, and 15 μg/ml). They were compared with a control group that received no dose of nanoparticles. The plant biomass, yield parameters, and wheat quality were analyzed. The effect of silver nanoparticles and U-AgNPs were examined in developing wheat seeds and their potency in combating biotic stresses such as nematodes, herbivores, fungi, insects, weeds and bacteria; abiotic stresses such as salinity, ultraviolet radiation, heavy metals, temperature, drought, floods etc. In the seedlings, six possible phytochemicals at a spray dose of 6 μg/ml of U-AgNPs were identified such as dihydroxybenzoic acids, vanillic acid, apigenin glucosidase, p-coumaric acid, sinapic acid, and ferulic acid whereas in other treatments the number of phenolic compounds was lesser in number as well as in concentrations. Moreover, various parameters of the wheat plants, including their dry weight and fresh weight, were assessed and compared with control group. The findings of the study indicated that A.N-AgNPs and U-AgNPs act as metabolite elicitors that induced secondary metabolite production (total phenolic, flavonoid, and chlorophyll contents). In addition, U-AgNPs provided a nitrogen source and were considered a smart nitrogen fertilizer that enhanced the plant biomass, yields, and metabolite production.

Physicochemical Characteristics of Biochar from Waste Cricket Chitin (Acheta domesticus)

The properties of biochar (BC) from crustacean chitin are relatively well understood, while there are few studies on BC from insect chitin. This study presents the characterization and phytotoxic assessment of BC produced from crickets and cricket chitin. Cricket powder (BCCR) and cricket chitin (BCCH) were pyrolyzed at 500 °C and 700 °C. Physicochemical characteristics, N ad-/desorption, FTIR, were examined. SEM images were also performed. Regardless of the pyrolysis temperature, biochars were characterized by a densely "packed" solid surface/monolithic type with a non-porous structure (0.05-0.22 m²/g) and high content of N (9.4-11.8%). BCCHs showed a higher pH (12.2-12.4) compared to BCCR (8.7-10.8). Based on the XRD analysis, BCs were characterized by an amorphous carbon turbostratic structure and a randomly oriented graphitic-like micro-crystallite structure. FTIR spectra of BCs confirmed the presence of various O₂ and N-functional groups on the BC surface. BCCHs added to soil at rates from 0.5 to 1.5% significantly reduced the germination of Lepidium sativum. Stimulation of root elongation was also observed in the case of BCCR500 1.0% and BCCR700 1.5%. Thermal degradation of cricket powder and cricket chitin promotes the formation of organic N-containing heterocyclic rings, which lead to the production of N-doped carbons with potential uses in energy storage and the contaminations sorption.

Emerging applications of nanotechnology in context to immunology: A comprehensive review

Numerous benefits of nanotechnology are available in many scientific domains. In this sense, nanoparticles serve as the fundamental foundation of nanotechnology. Recent developments in nanotechnology have demonstrated that nanoparticles have enormous promise for use in almost every field of life sciences. Nanoscience and nanotechnology use the distinctive characteristics of tiny nanoparticles (NPs) for various purposes in electronics, fabrics, cosmetics, biopharmaceutical industries, and medicines. The exclusive physical, chemical, and biological characteristics of nanoparticles prompt different immune responses in the body. Nanoparticles are believed to have strong potential for the development of advanced adjuvants, cytokines, vaccines, drugs, immunotherapies, and theranostic applications for the treatment of targeted bacterial, fungal, viral, and allergic diseases and removal of the tumor with minimal toxicity as compared to macro and microstructures. This review highlights the medical and non-medical applications with a detailed discussion on enhanced and targeted natural and acquired immunity against pathogens provoked by nanoparticles. The immunological aspects of the nanotechnology field are beyond the scope of this Review. However, we provide updated data that will explore novel theragnostic immunological applications of nanotechnology for better and immediate treatment.

Nanoparticles: The Plant Saviour under Abiotic Stresses

Climate change significantly affects plant growth and productivity by causing different biotic and abiotic stresses to plants. Among the different abiotic stresses, at the top of the list are salinity, drought, temperature extremes, heavy metals and nutrient imbalances, which contribute to large yield losses of crops in various parts of the world, thereby leading to food insecurity issues. In the quest to improve plants' abiotic stress tolerance, many promising techniques are being investigated. These include the use of nanoparticles, which have been shown to have a positive effect on plant performance under stress conditions. Nanoparticles can be used to deliver nutrients to plants, overcome plant diseases and pathogens, and sense and monitor trace elements that are present in soil by absorbing their signals. A better understanding of the mechanisms of nanoparticles that assist plants to cope with abiotic stresses will help towards the development of more long-term strategies against these stresses. However, the intensity of the challenge also warrants more immediate approaches to mitigate these stresses and enhance crop production in the short term. Therefore, this review provides an update of the responses (physiological, biochemical and molecular) of plants affected by nanoparticles under abiotic stress, and potentially effective strategies to enhance production. Taking into consideration all aspects, this review is intended to help researchers from different fields, such as plant science and nanoscience, to better understand possible innovative approaches to deal with abiotic stresses in agriculture.

Nanofertilizers: A Smart and Sustainable Attribute to Modern Agriculture

The widespread use of fertilizers is a result of the increased global demand for food. The commonly used chemical fertilizers may increase plant growth and output, but they have deleterious effects on the soil, the environment, and even human health. Therefore, nanofertilizers are one of the most promising solutions or substitutes for conventional fertilizers. These engineered materials are composed of nanoparticles containing macro- and micronutrients that are delivered to the plant rhizosphere in a regulated manner. In nanofertilizers, the essential minerals and nutrients (such as N, P, K, Fe, and Mn) are bonded alone or in combination with nano-dimensional adsorbents. This review discusses the development of nanotechnology-based smart and efficient agriculture using nanofertilizers that have higher nutritional management, owing to their ability to increase the nutrient uptake efficiency. Additionally, the synthesis and mechanism of action of the nanofertilizers are discussed, along with the different types of fertilizers that are currently available. Furthermore, sustainable agriculture can be realised by the targeted delivery and controlled release of nutrients through the application of nanoscale active substances. This paper emphasises the successful development and safe application of nanotechnology in agriculture; however, certain basic concerns and existing gaps in research need to be addressed and resolved.

Nanosized Calcium Phosphates as Novel Macronutrient Nano-Fertilizers

The need for qualitatively and quantitatively enhanced food production, necessary for feeding a progressively increasing World population, requires the adoption of new and sustainable agricultural protocols. Among them, limiting the waste of fertilizers in the environment has become a global target. Nanotechnology can offer the possibility of designing and preparing novel materials alternative to conventional fertilizers, which are more readily absorbed by plant roots and, therefore, enhance nutrient use efficiency. In this context, during the last decade, great attention has been paid to calcium phosphate nanoparticles (CaP), particularly nanocrystalline apatite and amorphous calcium phosphate, as potential macronutrient nano-fertilizers with superior nutrient-use efficiency to their conventional counterparts. Their inherent content in macronutrients, like phosphorus, and gradual solubility in water have been exploited for their use as slow P-nano-fertilizers. Likewise, their large (specific) surfaces, due to their nanometric size, have been functionalized with additional macronutrient-containing species, like urea or nitrate, to generate N-nano-fertilizers with more advantageous nitrogen-releasing profiles. In this regard, several studies report encouraging results on the superior nutrient use efficiency showed by CaP nano-fertilizers in several crops than their conventional counterparts. Based on this, the advances of this topic are reviewed here and critically discussed, with special emphasis on the preparation and characterization approaches employed to synthesize/functionalize the engineered nanoparticles, as well as on their fertilization properties in different crops and in different (soil, foliar, fertigation and hydroponic) conditions. In addition, the remaining challenges in progress toward the real application of CaP as nano-fertilizers, involving several fields (i.e., agronomic or material science sectors), are identified and discussed.

Light Scattering and Turbidimetry Techniques for the Characterization of Nanoparticles and Nanostructured Networks

Light scattering and turbidimetry techniques are classical tools for characterizing the dynamics and structure of single nanoparticles or nanostructured networks. They work by analyzing, as a function of time (Dynamic Light Scattering, DLS) or angles (Static Light Scattering, SLS), the light scattered by a sample, or measuring, as a function of the wavelength, the intensity scattered over the entire solid angle when the sample is illuminated with white light (Multi Wavelength Turbidimetry, MWT). Light scattering methods probe different length scales, in the ranges of ~5−500 nm (DLS), or ~0.1−5 μm (Wide Angle SLS), or ~1−100 μm (Low Angle SLS), and some of them can be operated in a time-resolved mode, with the possibility of characterizing not only stationary, but also aggregating, polymerizing, or self-assembling samples. Thus, the combined use of these techniques represents a powerful approach for studying systems characterized by very different length scales. In this work, we will review some typical applications of these methods, ranging from the field of colloidal fractal aggregation to the polymerization of biologic networks made of randomly entangled nanosized fibers. We will also discuss the opportunity of combining together different scattering techniques, emphasizing the advantages of a global analysis with respect to single-methods data processing.

Can Nanofertilizers Mitigate Multiple Environmental Stresses for Higher Crop Productivity?

The global food production for the worldwide population mainly depends on the huge contributions of the agricultural sector. The cultivated crops of foods need various elements or nutrients to complete their growth, and these are indirectly consumed by humans. During this production, several environmental constraints or stresses may cause losses in the global agricultural production. These obstacles may include abiotic and biotic stresses, which have already been studied in both individual and combined cases. However, there are very few studies on multiple stresses. On the basis of the myriad benefits of nanotechnology in agriculture, nanofertilizers (or nanonutrients) have become promising tools for agricultural sustainability. Nanofertilizers are also the proper solution to overcoming the environmental and health problems that can result from conventional fertilizers. The role of nanofertilizers has increased, especially under different environmental stresses, which can include individual, combined, and multiple stresses. The stresses are most commonly the result of nature; however, studies are still needed on the different stress levels. Nanofertilizers can play a crucial role in supporting cultivated plants under stress and in improving the plant yield, both quantitatively and qualitatively. Similar to other biological issues, many open-ended questions still require further investigation: Is the right time and era for nanofertilizers in agriculture? Will the nanofertilizers be the dominant source of nutrients in modern agriculture? Are nanofertilizers, and particularly biological synthesized ones, the magic solution for sustainable agriculture? What are the expected damages of multiple stresses on plants?

Recent development in functional nanomaterials for sustainable and smart agricultural chemical technologies

New advances in nanotechnology are driving a wave of technology revolution impacting a broad range of areas in agricultural production. The current work reviews nanopesticides, nano-fabricated fertilizers, and nano activity-based growth promoters reported in the last several years, focusing on mechanisms revealed for preparation and functioning. It appears to us that with many fundamental concepts have been demonstrated over last two decades, new advances in this area continue to expand mainly in three directions, i.e., efficiency improvement, material sustainability and environment-specific stimulation functionalities. It is also evident that environmental and health concerns associated with nano agrochemicals are the primary motivation and focus for most recent work. Challenges and perspectives for future development of nano agrochemicals are also discussed.

Physiological and Molecular Investigation of Urea Uptake Dynamics in Cucumis sativus L. Plants Fertilized With Urea-Doped Amorphous Calcium Phosphate Nanoparticles

At present, the quest for innovative and sustainable fertilization approaches aiming to improve agricultural productivity represents one of the major challenges for research. In this context, nanoparticle-based fertilizers can indeed offer an interesting alternative with respect to traditional bulk fertilizers. Several pieces of evidence have already addressed the effectiveness of amorphous calcium phosphate-based nanoparticles as carriers for macronutrients, such as nitrogen (N), demonstrating increase in crop productivity and improvement in quality. Nevertheless, despite N being a fundamental nutrient for crop growth and productivity, very little research has been carried out to understand the physiological and molecular mechanisms underpinning N-based fertilizers supplied to plants via nanocarriers. For these reasons, this study aimed to investigate the responses of Cucumis sativus L. to amorphous calcium phosphate nanoparticles doped with urea (U-ACP). Urea uptake dynamics at root level have been investigated by monitoring both the urea acquisition rates and the modulation of urea transporter CsDUR3, whereas growth parameters, the accumulation of N in both root and shoots, and the general ionomic profile of both tissues have been determined to assess the potentiality of U-ACP as innovative fertilizers. The slow release of urea from nanoparticles and/or their chemical composition contributed to the upregulation of the urea uptake system for a longer period (up to 24 h after treatment) as compared to plants treated with bulk urea. This prolonged activation was mirrored by a higher accumulation of N in nanoparticle-treated plants (approximately threefold increase in the shoot of NP-treated plants compared to controls), even when the concentration of urea conveyed through nanoparticles was halved. In addition, besides impacting N nutrition, U-ACP also enhanced Ca and P concentration in cucumber tissues, thus having possible effects on plant growth and yield, and on the nutritional value of agricultural products.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO₄) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca²⁺ and PO₄^3- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO₄, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

Hydrogels containing water soluble conjugates of silver(I) ions with amino acids, metabolites or natural products for non infectious contact lenses

The poor handling and hygiene practices of contact lenses are the key reasons for their frequent contamination, and are responsible for developing ocular complications, such as microbial keratitis (MK). Thus there is a strong demand for the development of biomaterials of which contact lenses are made, combined with antimicrobial agents. For this purpose, the known water soluble silver(I) covalent polymers of glycine (GlyH), urea (U) and the salicylic acid (SalH₂) of formulae [Ag₃(Gly)₂NO₃]_n (AGGLY), [Ag(U)NO₃]_n (AGU), and dimeric [Ag(salH)]₂ (AGSAL) were used. Water solutions of AGGLY, AGU and AGSAL were dispersed in polymeric hydrogels using hydroxyethyl-methacrylate (HEMA) to form the biomaterials pHEMA@AGGLY-2, pHEMA@AGU-2, and pHEMA@AGSAL-2. The biomaterials were characterized by X-ray fluorescence (XRF) spectroscopy, thermogravimetric differential thermal analysis (TG-DTA), differential scanning calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR) and single crystal diffraction analysis. The antibacterial activity of AGGLY, AGU, AGSAL, pHEMA@AGGLY-2, pHEMA@AGU-2 and pHEMA@AGSAL-2 was evaluated against the Gram negative species Pseudomonas aeruginosa (P. aeruginosa) and Gram positive ones Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus), which mainly colonize in contact lenses. The in vitro toxicity of the biomaterials and their ingredients was evaluated against normal human corneal epithelial cells (HCECs) whereas the in vitro genotoxicity was evaluated by the micronucleus (MN) assay in HCECs. The Artemia salina and Allium cepa models were applied for the evaluation of in vivo toxicity and genotoxicity of the materials. Following our studies, the new biomaterials pHEMA@AGGLY-2, pHEMA@AGU-2, and pHEMA@AGSAL-2 are suggested as efficient candidates for the development of antimicrobial contact lenses.

Estrogen Deficiency Induces Mitochondrial Damage Prior to Emergence of Cognitive Deficits in a Postmenopausal Mouse Model

Background: Estrogen deficiency contributes to the development of Alzheimer's disease (AD) in menopausal women. In the current study, we examined the impact of estrogen deficiency on mitochondrial function and cognition using a postmenopausal mouse model. Methods: Bilateral ovariectomy was conducted in adult females C57BL/6J. Cognitive function was examined using the Morris water maze (MWM) test at 2 weeks, 1, 2, and 3 months after ovariectomy. Neurodegeneration was assessed using an immunofluorescence assay of microtubule-associated protein 2 (MAP2) in the hippocampus and immunoblotting against postsynaptic density-95 (PSD95). Mitochondrial function in the hippocampus was assessed using immunoblotting for NDUFB8, SDHB, UQCRC2, MTCO1, and ATP5A1. Mitochondrial biogenesis was examined using immunoblotting for PGC-1α, NRF1, and mtTFA. Mitochondrion fission was assessed with immunoblotting for Drp1, whereas mitochondrion fusion was analyzed with immunoblotting for OPA1 and Mfn2. Mitophagy was examined with immunoblotting for PINK1 and LC3B. Mice receiving sham surgery were used as controls. Results: Ovariectomy resulted in significant learning and memory deficits in the MWM test at 3 months, but not at any earlier time points. At 2 weeks after ovariectomy, levels of Drp1 phosphorylated at Ser637 decreased in the hippocampus. At 1 month after ovariectomy, hippocampal levels of NDUFB8, SDHB, PGC-1α, mtTFA, OPA1, and Mfn2 were significantly reduced. At 2 months after ovariectomy, hippocampal levels of MAP2, PSD95, MTCO1, NRF1, and Pink1 were also reduced. At 3 months, levels of LC3B-II were reduced. Conclusions: The cognitive decline associated with estrogen deficiency is preceded by mitochondrial dysfunction, abnormal mitochondrial biogenesis, irregular mitochondrial dynamics, and decreased mitophagy. Thus, mitochondrial damage may contribute to cognitive impairment associated with estrogen deficiency.

The Contribution of Microglia to the Development and Maturation of the Visual System

Microglia, the resident immune cells of the central nervous system (CNS), were once considered quiescent cells that sat in readiness for reacting to disease and injury. Over the last decade, however, it has become clear that microglia play essential roles in maintaining the normal nervous system. The retina is an easily accessible part of the central nervous system and therefore much has been learned about the function of microglia from studies in the retina and visual system. Anatomically, microglia have processes that contact all synapses within the retina, as well as blood vessels in the major vascular plexuses. Microglia contribute to development of the visual system by contributing to neurogenesis, maturation of cone photoreceptors, as well as refining synaptic contacts. They can respond to neural signals and in turn release a range of cytokines and neurotrophic factors that have downstream consequences on neural function. Moreover, in light of their extensive contact with blood vessels, they are also essential for regulation of vascular development and integrity. This review article summarizes what we have learned about the role of microglia in maintaining the normal visual system and how this has helped in understanding their role in the central nervous system more broadly.