Nanosensors for Detection of Heavy Metals PDF

Nanosensors for Detection of Heavy Metals Heavy metal ions like Pb2+, Hg2+, Ag+, Cd2+, and Cu2+ from different resources have a precarious influence on human beings as well as their surroundings. Optical chemical sensors that are frequently targeted for heavy metal detection fit int...

Nanosensors for Detection of Heavy Metals Heavy metal ions like Pb2+, Hg2+, Ag+, Cd2+, and Cu2+ from different resources have a precarious influence on human beings as well as their surroundings. Optical chemical sensors that are frequently targeted for heavy metal detection fit into a cluster of chemical sensors that primarily employ electromagnetic radiation for engendering a diagnostic signal in an element known as the transduction element. The interactions between the sample and the radiation change a specific optical consideration that can be interrelated to the concentration of an analyte. Colourimetric approaches are advantageous due to their simple operation, economically feasible, transportable instrumentation, and easy-to-use applications. Several compounds are used for stabilizing nanosensors, such as polysaccharides citrates, different polymers, and proteins to improve the attributes of the nanosensors. Fluorescent quantum dots-based sensors are an efficient tool for sensing numerous metal ions. 37 Contd…. The introduction of magnetic nanomaterials (Fe3O4) into the quantum dot- based fluorescence sensors offers several additional advantages owing to their high specific surface area, special magnetic properties, magnetic operability, and low toxicity. 38 Nanomaterials for air and water pollution control The three major applications of nanotechnology in the fields of environment can be classified: 1) Remediation and purification of contaminated material 2) pollution detection (sensing and detection). 3) pollution prevention. Air pollution can be controlled with nano-adsorptive materials, nanocatalysis, and nano filters. Water pollution, nanofiltration and nano sorbents techniques are used. Nanotechnology for clean water: 1) Remediation is the process of removing, minimising or neutralising the water contaminants that can damage human health or ecosystems. 2) Remediation technologies can be divided into three categories, thermal, physicochemical and biological methods. 3) An advanced method that can be used is nanomaterials, with enhanced affinity, capacity and selectivity for heavy metals and other contaminants. 39 Contd…. The advantages of using nanomaterials in water remediation are their higher reactivity, larger surface contact and better disposal capability. Water remediation with iron nanomaterial: ✓ Zero valent Iron (ZVI) is classified into two types: (1) nanoscale ZVI (nZVI) and (2) reactive nanoscale iron product (RNIP). ✓ nZVI particles have a diameter of 100–200 nm composed of iron (Fe) with a valence of zero, whereas RNIP particles consist of 50/50 wt % Fe and Fe3O4. ✓ ZVI has high reactivity to a large number of contaminants, including Cu2+, chlorinated hydrocarbons, CrO22- and NO3-. ✓ Nano-iron could be substituted with other metals. Metals such as zinc and tin have the ability to reduce contaminants such as iron. 40 Contd…. Water remediation with ferritin: Iron stored inside protein ✓ Ferritin is an iron-containing protein that is able to control the formation of mineralized structures. Ferritin has the ability to remediate toxic metals and chlorocarbon un. ✓ The advantages of ferritin over ordinary iron catalysts are: (1) ferritin does not react under photoreduction; and visible light or solar radiation (2) it is also more stable. 41 Nanotechnology in water pollution treatment The major mechanisms used to remove contaminants from contaminated water through nanotechnology include nanofiltration and nano-sorbents. Nanofiltration: 1. Nanofiltration is a membrane process used in water pollution treatment for drinking water and wastewater. 2. Nanofiltration is a low-pressure membrane technique used to separate substances measuring 0.001-0.1 micrometre. 3. Nanofiltration is an effective method used to remove biological pollutants, turbidity, and inorganic compounds. Also, to soften hard water, remove dissolved organic materials, and trace contaminants from surface water, treatment of wastewater, and pre-treatment during the desalination of seawater. 42 Contd…. Nano Sorbents: Nano-sorbents can be used as separation techniques in the process of water purification to eradicate inorganic and organic matter from contaminated matter. Nanoparticles are effective sorbents due to their large surface area and can be enhanced with different reactor compounds to improve their affinity towards specific compounds. 43 Nanotechnology in air pollution treatment Nanotechnology can be used to treat and remedy air pollution through strategies such as the use of nano-adsorptive materials for adsorption, degradation by nanocatalysis, and the use of nano filters to filter and separate air pollutants. Use of Nano-Adsorptive Materials to Adsorb Air Pollutants: ✓ Nano adsorbents: carbon nanostructures have high selectivity, capacity, and affinity due to their physical characteristics, including average pre-diameter, the volume of the pores, and high surface area. ✓ Nano-adsorbents have unique properties that enable effective interactions with organic compounds through non-covalent bonds, including hydrogen bonding, electrostatic forces, hydrophobic interactions, and van der Waal forces. ✓ Carbon nanotubes have been used as adsorbent materials in environmental protection because of their characteristics, including high electrical and thermal conductivity, high strength, the unique potential for adsorption, and high hardness 44 Contd…. Degradation by Nanocatalysis: ✓ Nanotechnology can be used to prevent air pollution in indoor environments in a variety of ways. Semiconducting materials photocatalytic remediation is one effective strategy used to manage indoor pollution through nanotechnology. Reaction mainly occurs on the active surface, which is the significant catalyst structure. A decrease in the size of the catalyst leads to an increase in the surface area to increase the efficiency of the reaction. ✓ Nano-catalysts are considered appropriate materials for improving air quality and reducing pollutants in the air. For instance, titanium dioxide nanoparticles have photocatalytic properties to produce self-cleaning coatings used to decontaminate environmental pollutants, including nitrogen oxides, into materials that have low toxicity levels. Carbon nanostructures, including CNTs and graphene nanosheets, have been utilized to increase titanium dioxide’s photocatalytic effectiveness by facilitating the easy movement of electrons. 45 Contd…. Use of Nano Filters for Separation and Filtration Purposes: ✓ Nano filters are structured membranes with small pores to separate several contaminants from the exhaust to control air pollution by capturing gas pollutants. ✓ Filter media coated with nanofiber is mainly used in industrial plants to remove dust and filter the inlet air for gas turbines. ✓ Silver and copper nanoparticle filters are extensively used in air filtration technology as antimicrobial agents for the removal of biological aerosols such as viruses, bacteria, and fungi that cause infections. 46 Classes of nanomaterials in the removal of organic pollutants from environment Nano-photocatalysts: The term ‘‘photocatalysis’’ refers to the processes where light is used to excite the photocatalyst and accelerate the rate of the reaction, in which the photocatalyst remains unaltered. Nano photocatalysts are photocatalysts with 1 nm and 100 nm of size, in the presence of light, can accelerate the reactions. Nano-sized metals, zero-valent forms, monometallic oxides, bimetallic oxides, semiconductors can be used for the degradation of contaminants in the wastewater such as organic dyes or heavy metal ions. 47 Contd…. Nanophotocatalysts are highly capable of enhancing the mineralization of highly toxic and complex organic substances even at 25 ℃. These nano-sized materials are highly effective in mineralizing and degrading a wide range of organic Contaminants. In mineralization, the complex organic pollutants were decomposed into simpler compounds, whereas the decomposed compounds were completely destructed in the degradation stage, resulting in the formation of much simpler compounds like H2O, CO2. 48 Contd…. Water and Air remediation using nanosize semiconductor photocatalyst: Examples of photocatalysts: 1. Titanium dioxide (TiO2) 2. Zinc oxide (ZnO) 3. Iron oxide (Fe2O3) Photocatalysts are able to oxidize organic pollutants into nontoxic materials. The advantage of using Titanium dioxide (TiO2) for water remediation: 1. low toxicity. 2. high photoconductivity. 3. high photostability. 4. Excellent chemical and biological stability. 5. easily available and inexpensive materials. The advantage of using ZnO for water remediation: ZnO photocatalysts are able to detect and remediate contaminants from water. 49 Contd…. Nano and micromotors: A typical nano-motor is a nano-scale device which is having the ability to convert energy into movement. The nano-motors are capable of generating the forces in the order of few piconewtons. The important aspects of nano and micromotors are their high operational speed, movement specificity, and ability to self-mix. Micro/nanomotors are environmentally friendly and have attractive power units. 50 Contd…. Nano-membranes: Membrane filtration with the aid of nano-materials imparts novel functional groups, better catalytic action, improved permeation and resistance to membrane fouling. These nano-materials are also playing a significant role in the degradation of organic contaminants in the Wastewater. This membrane filtration process is highly effective in the removal or separation of specific inorganic compounds and small organic molecules. Nano-membranes are highly effective in the removal of salts, desalination and heavy metal ions. Nano-sorbents: Carbon and its derivate are the most exploited adsorbents in the removal of heavy metal ions and organic dyes from the aqueous solution. Besides, the role of metal oxides such as cerium oxide, iron oxide, zinc oxide, manganese oxide, etc., finds a prominent role in the remediation process. Carbon-based nano-sorbents: Carbon nanotubes (CNTs) are tubularly structured and fabricated with carbon in nano-dimensional size with the range of 1 nm to several nm. They can be categorized as single-walled CNTs (SWCNTs), and multi-walled CNTs (MWCNTs). 51 Contd…. Chitosan-derived nano-sorbents: Chitin is a natural polysaccharide that can be easily extracted from the shells of shrimp or crabs. With the process of de- acetylation, chitin can be converted into the polymer of de-acetylated-b- glucosamine called chitosan. It can be used for the removal of colloidal particles mediated by either coagulation or flocculation methods. Also, they can be used for the removal of several pollutants including toxic heavy metals, organic dyes, micro- pollutants, and hydrocarbons. Owing to the vital functional groups of amine, 1 and 2 hydroxyl moieties on the surface, chitosan-based adsorbents mediated the transfer of ionic species across the solid-liquid interfaces. 52 Chitosan as an adsorbent 53 Removal of bacterial pathogens from wastewater using nanomaterials Microorganisms are the major pollutants in water bodies as they participate in the process of removing nutrients and adding toxic metabolites in the wastewater. Nanotechnology can be used for the detection and removal of bacteria, viruses and other pathogenic microorganisms. There are several categories of nanoscale materials that remove the microbes in the wastewater. Nanoparticles can be used as biosensors for the in situ detection of waterborne microbes. Nanomaterials as: 1. Zinc oxide (ZnO) nanoparticles 2. Titanium oxide (TiO2) nanoparticles 3. Carbon nanotubes (CNT) 4. Silver nanoparticles (AgNPs) 5. Magnetic nanoparticles like iron oxide nanoparticles. These various nanomaterials were used for the removal of heavy metal and microbial pathogens from wastewater. 54 Contd…. Advantages of using nanomaterials for pathogens removal: 1. High surface area to volume ratio: enhanced interaction with the bacterial cells 2. Strong antimicrobial activity: effective at low concentration 3. Versatility: can be used in various forms like nanoparticles, membranes and coatings 4. Enhanced filtration: improved the removal efficiency for a wide range of pathogens 5. Photocatalysis activity: TiO2 can degrade organic pollutants and kill the microorganisms upon exposure to light. 6. Synergetic effect: Nanomaterials can provide multiple functionalities (e.g., antimicrobial, adsorptive, catalytic) in a single treatment step. 55 Nanotechnology in Health Care 56 Nanomaterials for Biosensors and Diagnostic Tools 57 Components of Biosensors Transducer conveys a signal that must be processed and displayed vis a signal readout and Biosensors detect targets of Converts signal via a processing system. biological importance and transducer element into a recognizes that target in a variety of measurable signal ways (e.g. affinity interaction) 58 Clinical applications of nanostructure-enabled biosensors L-cysteine assisted copper sulfide nanoparticles (Cu7.2S2) for the treatment of rheumatoid arthritis via photothermal therapy (PTT) Liposomal nanoparticles for the treatment and visualization of and photodynamic therapy (PDT). multidrug resistant bacterial pathogens with sonotheranostics. Lu et al. Adv. Healthcare Mater. 2018, 7, 1800013. Pang et al. ACS Nano 2019, 13, 2 Liposomal nanoparticle encapsulated second near-infrared (NIR-II) window A recombinant encapsulin (enc) protein nanocage surrounding magnetic lanthanide fluorophore rare earth-doped nanoparticles for embolic surgical iron oxide nanocomposites for magnetic resonance imaging (MRI)-guided navigation in the NIR-II window allowing surgeons to readily identify abnormal magneto-catalytic combination therapy for the treatment of cancer. vasculature such as tumor angiogenesis. Zhang et al. Nat. Commun. 2020, 11, 1. Li et al. Adv. Sci. 2019, 6,1902042. 59 Role of nanostructures in sensing: 1. Stabilization of biomolecules with nanoparticles: Due to large surface area and high free surface energy, nanoparticles are able to strongly absorb biomolecules to their surface and lead to their stabilization at biosensor surface. Direct adsorption of biomolecules on surface of bare bulk materials leads to denaturation and loss of biological activity of the biomolecule. This does not happen in case of nanoparticle surface due to biocompatibility of nanoparticles. Electrostatic interactions due to surface charge of nanoparticles assist in stabilization of biomolecules 2. Catalysis of reaction with nanoparticles: High surface activity of nanoparticles offer strong catalytic effects. 60  3. Improve electron transfer with nanoparticles: The active sites of redox proteins are surrounded by a thick, non-conducting protein shell, hence have no electrical connection to electrode, inhibiting electron transfer between the electrode and the active site. The conductive properties of nanoparticles (mainly, metal nanoparticles) are useful in increasing electron transfer between the electrode and the active center. 4. Labeling of biomolecules with nanoparticles Labeling of biomolecules such as antigens, antibodies and DNA by nanoparticles assist in development of electrochemical biosensors. Dissolution of nanoparticles (metal/semiconductor nanoparticles) and measurement of dissolved ions by voltammetry stripping offers a powerful analytical technique in measuring the effects of metals and make trace amount measurement of analytes possible. 61 Nanostructures used in Biosensing Nanorods Nanofibers 3D Nanopillars nanostructures Nanowires Nanosheets Nanoparticles Nanopore Quantum dots membrane 62 0D nanostructures in Biosensors and diagnostic tools Optical properties of gold (Au) NPs depend on their size, shape, and structure. The color changes that are observed are a direct result of localized surface plasmon resonance (LSPR). Photon absorption wavelength is a function of particle shape and size (i.e., aspect ratio), thickness of the Au shell (in nanoshells), and galvanic displacement by Au (in nanocages). C-reactive protein (CRP) antibody functionalized gold nanoparticles (AuNPs) were used for CRP detection utilizing LSPR. The binding of the pentameric CRP caused AuNP aggregation, leading to a red shift in absorbance, enabling visual CRP detection Dreaden et al. Chem. Soc. Rev. 2012, 41. Byun et al. Analyst 2013, 138,1538. 63  Magnetic NPs have been utilized within a microfluidic chip for the extraction of genomic DNA from whole blood via magnetophoresis Single microfluidic separator (a-b): a wash buffer is loaded (green), which diffuses into the wash channel (c): The test sample containing lysed whole blood and genomic DNA-bound paramagnetic NPs and output solution are then loaded (red). An elution buffer is also added to the elution well (blue). (d-e): A magnet is applied to move the DNA-bound magnetic NPs through the wash buffer yielding the extracted DNA K. Lee, A. Tripathi, Front. Genet. 2020, 11, 374. 64 1D nanostructures in Biosensors and diagnostic tools ZnO nanorod array that captures the bacteria by recognizing cell surface polysaccharides. Functionalization of ZnO nanorods FESEM images of ZnO nanorod (average diameter: 350 nm; length: 3 μm) Zheng et al. Talanta 2017, 167, 600. 65  Silicon nanowires (SiNW) in biosensing a lab-on-a-chip device containing two SiNW arrays: one for separation and one for detection. Specificity achieved using a immunoglobulin G antibody modified, roughness-controlled SiNW forest. From blood samples Troponin T (used in diagnosis of myocardial infarction) was detected rapidly and selectively, with ultralow sensitivity. immunoglobulin G antibody-modified, roughness-controlled SiNW forest. A magnetic inverted SiNW array being used to capture circulating tumor cells (CTCs). Krivitsky et al. Nano Lett. 2012, 12, 4748; Xu et al. Biomaterials 2017, 138, 69. 66  2D nanostructures in Biosensors and Diagnostic tools Nanowires in Biosensing : Tan et al. J. Am. Chem. Soc. 2015, 137, 10430. Detecting target DNA molecules with a limit of detection (LOD) of 50 pM using a single-layer 𝑇𝑎2 𝑁𝑖𝑆5 nanosheet nano-graphene oxide (nGO) nanosheets functionalized with a dye-labeled single-stranded DNA probe functionalized with DNA probes modified with that exhibits a high capacity for fluorescence quenching unlocked nucleic acids (UNAs). Specifieed for detection of target mRNA. single-step capture-anddetect method developed using a dual-targeting functionalized reduced graphene oxide (rGO) (DTFGF) nanosheet to detect hepatocelluar carcinoma circulating tumor cells (HCC- CTCs) with an LOD as low as 5 cells per mL. Robertson et al. Biosens. Bioelectron. 2017, 89, 551; Wu et al. ACS Appl. Mater. Interfaces 2019, 11, 44999. 67 3D nanostructures in Biosensors and diagnostic tools Self-assembly in order to create hybrid organic-inorganic nanoflowers that can be used in applications including biosensing. Kim et al. J. Colloid Interface Sci. 2016, 484. 68 3D nanostructures in Biosensors and Diagnostic tools A rose petal-mimicking biosensor composed of Transparent microfluidic device containing cactus- Complex hierarchical nano-functionalized surfaces for mimicking hierarchical structures coated with anti- increased capture of rare circulating tumor cells EpCAM antibodies, to enhance capture and analysis of (CTCs). rare CTCs. Dou et al. ACS Appl. Mater. Interfaces 2017, 9, 8508. Yan et al. ACS Appl. Mater. Interfaces 2016, 8, 33457. 69 Gold (Au) nanoarchitectures embedded with nano-chitosan (AuNAs@NC) for electrochemical detection of vascular endothelial growth factor (VEGF2) and MCF-7 breast cancer cells Wang et al. Appl. Surf. Sci. 2019, 481, 505 70 Point-of care (POC) tests 71 Point-of care (POC) tests Point-of-care diagnostic medical devices are in vitro diagnostics used by health care professionals to obtain results rapidly near or at the site of a patient. Point-of-care tests are simple medical tests that can be performed at any place by any person. In contrast to conventional testing, in which testing was confined to medical laboratories, entailed sending samples/specimens and waiting hours/days for results, POC tests allow easy-to-use self-testing. 72