Staffing for cybersecurity in a tight job market. Study: Bats change flight paths to find prey hidden from echolocation. Researchers creates ultra-small accelerometer using graphene. Image credit: University of California, Irvine Nanotechnology in Medicine Medicine using nano techniques is called nanomedicine, and in a broad sense represents the application of nanoscale technology and materials to the practice of medicine.
Some of the uses of nanoparticles in biology and medicine include the following: Creating fluorescent biological labels, biological markers and molecules for diagnosis of diseases Gene delivery systems in gene therapy For biological detection of disease causing organisms and diagnosis Detection of antibodies and proteins Genetic and tissue engineering Destruction of tumors with drugs or heat Drug delivery systems Probably the most prevalent use of nanoparticles in medicine today is in drug delivery systems.
Surface Modification of Nanoparticles Used in Biomedical Applications
Some of these are: Targeted drugs may be developed. The characteristics of nanoparticles can be easily designed. Nanoparticles can control and sustain the release of the drug during the transportation as well as the location of the release.
Several routes of administration can be used, including oral, nasal, injection, intra-ocular within the eyes , etc. The number in parenthesis is the approximate size of the particle: liposomes and micelles 10 — nm used for drug delivery; dendrimers 2 — 10 nm , used for drug delivery; nanocantilivers, used for cancer detection and diagnosis; quantum dots less than 10 nm , used for sensing and detection of biomarkers, diagnosis; magnetic nanoparticles 10 — nm , used for targeted cancer drug delivery; gold nanoparticles less than 50 nm , used for attaching proteins and antibodies for biological detection; silver nanoparticles 1 — nm , used for molecular diagnostics and therapeutics.
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Reply Report! See the entire discussion on CR4, the Engineering Community. Engineering Newsletter Signup. Stay up to date on:. Helena St. Pierre and Miquelon St. I agree to receive commercial messages from Engineering including product announcements and event invitations, as well as subscriptions and other promotional notifications You may withdraw your consent at any time. You can change your email preferences at any time. Multiple nucleation proceedings can result in tiny particles aggregating to form much larger particles and typically leads to the coarsening of the size allocation of the particles This process is known as Ostwald ripening.
Chemical precipitation can be made more favourable method for producing uniform particles by better controlling nucleation, particle growth and particle interaction in a liquid medium. The schematic representation for the fabrication of nanoparticles by liquid phase technique is shown in the Fig. Chemical reduction method: Reduction is the transfer of electrons from reducing agent to oxidized metal species. It is the most often used method for the chemical synthesis of nanoparticles which deals with the reduction of metal particles to nanoparticles using chemical reducing agents such as sodium borohydride or sodium citrate.
The reducing agent can form an intermediate with the oxidized metal species without altering its oxidation state. In this situation, the reduction process can be initiated by rising the temperature, for example and it can be conducted very gradually, producing conditions that lead to the creation of highly crystalline structures of regular shape. An example of this is the formation of silver nanoparticles by chemical reduction method in which silver nitrate is taken as the metal precursor and hydrazine hydrate as a reducing agent Microwave irradiation: Microwave irradiation is one of the novel techniques developed recently for the synthesis of nanoparticles.
Microwaves are a form of electromagnetic radiations, with frequencies in the range of MHZ to GHz. The commonly used frequency in this route is 2. In the microwave method of synthesis, microwave radiations are introduced in the reaction solution. An example is the microwave-assisted synthesis of copper nanoparticles that has become popular due to its simplicity, ease of operation, rapid volumetric heating and kinetics, short reaction period and increasing yield of products compared to the conventional heating methods Solvothermal synthesis: In the solvothermal processes, the chemical reaction takes place in a sealed vessel such as bomb or autoclave, where solvents are brought to temperatures well above their boiling points.
When water is used as solvent, it is called a hydrothermal process. Singh et al.
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The effect of reaction temperature, concentration of precursor and time of growth plays vital role on the properties of fabricated nanoparticles. Electrochemical process: In this method, chemical reaction is induced in an electrolyte solution with the use of an applied voltage. Electrochemical synthesis is carried out by passing an electric current between two electrodes which are separated by an electrolyte. The synthesis of nanoparticles takes place at the electrode-electrolyte interface. This technique provides low costs, simple operation, high flexibility, easy availability of equipment instruments, less contamination pure product and environment-friendly eco-friendly process.
A wide variety of nanomaterials could be synthesized using this method. Much research work has been done on the electrochemical technique in advancing the fundamental understanding and industrial applications, but still many aspects of this technique are under study.
Arc discharge method: This is a physical method for the synthesis of nanoparticles. Two graphite electrodes acting as cathode and anode are used in this method. These electrodes are dipped in metal salt solution. An arc is struck by bringing the electrodes in contact. The synthesis of nanoparticles is carried out at an open circuit and an optimized current.
Pulsed wire discharge method: Pulsed wire discharge is a physical technique to prepare nanoparticles In this method, a metal copper wire is evaporated by a pulsed current to produce a vapor, which is then cooled by an ambient gas to form nanoparticles.
This method has advantage of high fabrication rate and high energy efficiency. Moreover, a simple apparatus consisting of a vacuum chamber, a powder collection filter and a discharging circuit is used to prepare nanoparticles. This process is mostly useful for those metals of high electrical conductivity that are easily available in the thin wire form This technique was used by Sen for the preparation of metallic nanoparticles such as copper, silver, iron and aluminum nanoparticles with resulting nanoparticles in the range of nm while the copper nanoparticles prepared by this technique were of nm in size.
Thermal decomposition method: This method is used for the fabrication of monodisperse nanoparticles. The method is fast, simple and cost effective and provides a promising synthesis route for preparations of metal oxide and complex oxide nanoparticles. Biological synthesis: As the physical and chemical processes are costly and hazardous there arises a need for biosynthesis of nanoparticles. Therefore, scientists used microorganisms and then plant extracts for the synthesis in the search for cheaper routes for nanoparticle synthesis.
Biological agents used for the synthesis of nanoparticles consist of primarily microbes and plants Metal compounds usually reduce into their respective nanoparticles because of microbial enzymes or the plant phytochemicals with antioxidant or reducing properties.
The biological methods used for the preparation of nanoparticles include both intracellular and extracellular methods The intracellular synthesis method usually involves the use of bacteria and actinomycetes. The bacterial cell filtrate is treated with metal salt solution and kept in a shaker in dark at ambient temperature and pressure conditions For the extracellular synthesis of nanoparticles using bacteria, the bacterial culture is centrifuged at x g and the supernatant is challenged with the metal salt solution.
The biosynthesis of nanoparticles involves simple preparation protocols and a smaller amount of toxicity and includes a broad scope of applications according to their morphology. Nanosized copper particles are biosynthesised by protein-mediated process In this method, the protein solution with copper sulphate solution was reduced with sodium borohydrate. Argon gas was used as inert medium during the process to avoid oxidation.
Characterization techniques: It is very important to characterize the nanoparticles to understand the control of synthesis and their applications. There are various techniques accessible for the characterization of nanoparticles. Microscopy techniques have been commonly employed for particle size and characterization. Atomic Absorption Spectrophotometery AAS is used to check the concentration of metallic nanoparticles. Some of the most common techniques for this purpose are as follows:. The instrument has features such as an electron gun, condenser lenses and a vacuum system.
SEM is principally used to study the surface or near surface structure of bulk specimens. The principle images produced in SEM are of three types: secondary electron images, backscattered electron images and elemental X-ray maps.enter site
It is easy to interpret SEM images although the spatial resolution of SEM is approximately 15 nm, which is not as good as TEM, which can have spatial resolutions in the subnanometer range. It is also possible to image a comparatively large area of the specimen with the aid of SEM. The ability to image bulk materials and the variety of analytical modes accessible for measuring the composition and nature of the specimen makes SEM a valuable technique.
Transmission electron microscopy : Transmission Electron Microscopy TEM is one of the most common techniques employed to visualize and determines the morphology of the particles. In this technique, monochromatic beam of electrons penetrate a thin specimen, some of which are transmitted through the objective lens and then projected onto a viewing screen for example, a layer of electron fluorescent material to generate an image. Because of its high resolution, it is a valuable tool to study nanoscale properties of crystalline material.
At present, the highest resolution realised is 0. The HRTEM allows us to obtain information on the crystal planes of the particles and measure the lattice distance.
Biomedical Applications of Nanoparticles - 1st Edition
X-ray diffraction : One of the most conventional techniques that can be used to determine the structure, phases, and average size of the particles is powder X-Ray Diffraction XRD. In this technique, the structure and the lattice parameters are determined by measuring angle of diffraction when X-rays are made to incident on the powdered specimen.
The size of the particles can also be determined from the width of the X-ray peaks using the Scherrer formula The size of the particles estimated from the XRD is seldom found to be more than that from TEM studies because of the broadening of X-ray diffraction lines. The experiment is usually performed at synchrotron radiation sources, which provide intense and tunable X-ray beams. XAS data are obtained by tuning the photon energy using a crystalline monochromator to a range where core electrons can be excited 0.
There are three main regions found on a spectrum generated by XAS data. The pre-edge region is at energies lower than the rising edge. The EXAFS Extended X-ray Absorption Fine Structure region is the oscillatory structure above the main edge and corresponds to the scattering of the ejected photoelectron off neighbouring atoms.
The XANES provides information about the electronic state of the X-ray absorbing atom and the local structure around it. Finally, the EXAFS can give information on the atomic number, distance and coordination number of the atoms surrounding the element. Small angle neutron scattering: Small-Angle Neutron Scattering SANS is an experimental technique that uses elastic neutron scattering at small scattering angles to investigate the structure of various substances at a mesoscopic scale of about nm.
During a SANS experiment a beam of neutrons is directed at a sample, which can be an aqueous solution, a solid, a powder, or a crystal. The neutrons are elastically scattered by nuclear interaction with the nuclei or interaction with magnetic momentum of unpaired electrons. In X-ray scattering, photons interact with electrical cloud but in neutron scattering, neutron interacts with nuclei. The parameters which can be evaluated from SANS data includes the radius of gyration, the particle surface area, shape of the scattering particles, magnetic structure, magnetic correlation, alignment of nanoparticles as well as their response to an external magnetic field An FTIR spectrometer simultaneously collects spectral data in a wide spectral range.
Transmission spectra for the nanoparticles were obtained by forming thin, transparent KBr pellets containing the materials of interest.