Embed Size (px)
DESCRIPTION
Magnetic nanoparticles (MNPs), such as iron, cobalt, nickel, and metal oxides, consist of a class of nanoparticles that can be manipulated using external magnetic field. The potential use of MNPs in a variety of applications has led to extensive studies about their structural and magnetic properties. Plenty of work has been published, focusing on MNPs synthetic pathway, characterisation, and optimisation, as well as their utilisation in vivo and in vitro applications. In particular, biological and biomedical applications of MNPs are of great importance. MNPs exhibit sizes that are comparable to the size of a virus (20-500nm), a protein (5-50nm), or a gene (2nm in thickness and a length of 10-100nm), hence, they can be recruited as carriers for drug delivery. Also, MNPs’ relatively large surfaces facilitate the adhesion of organic components, whilst the exploitation of magnetic moment allows them to serve as contrast agents (in vivo MRI). Furthermore, MNPs are able to convert the absorbed energy into heat (hyperthermia), under the application of an AC magnetic field. Conclusively, the main applications of MNPs in the context of medicinal sciences can be therapeutic- and diagnostic-orientated.
Citation preview
MNPs utilisation in Biomedical Applications
Chemistry & Characterisation of Thin Films & Surfaces
Asterios Ntais
MNPs - Introduction • Fe – Co – Ni – Metal oxides • manipulation by external Magnetic Field
• size ≈ biological components (drug delivery) • surface + magnetic moment (in vivo MRI) • absorbed energy into heat (hyperthermia)
• colloidal stability | no agglomeration
• Properties depend on: magnetic anisotropy – composition – vacancies crystal structure – size – shape
atomic magnetic dipole (orbital + spin motion) magnetic order (Tc ≤)
e- arrangements
∨ magnetic behaviour
size ≤ 100nm: 1. single magnetic
domain 2. magnetisation
reversal = uniform 3. function of T
Synthesis of MNPs 1. Gas-phase methods (s-precipitates from g-phases) • CVD: volatile precursors – high T (size & growth control) • Laser pyrolysis: thermochemical decomposition • ultrapure & high quality products | low yield 2. Wet chemical methods (simple, inexpensive, better yield) • Coprecipitation: precipitation of aqueous solution + base • Massart Method: alkaline coprecipitation of ferrous & ferric salt • pH, [cations], temperature – dependent • Fe3O4, γ-Fe2O3
• uniform size distribution | nucleation & growth
i.e. iron oxides from Fe(Co)5
Synthesis of MNPs 3. Thermal decomposition (rapid process) • unstable precursors into hot-aqueous solution • organometallic & inorganic precursor, temperature, reaction time • complexes bound to iron via oxygen • surfactants (fatty acids) mediate nucleation & growth rates
4. Microemulsion • H2O nanodroplets in oil stabilised by surfactants
• A, B reagents dissolved in 2 emulsions • mixing – AB precipitation, trapped w/in H2O droplets • size and shape control • iron oxide NPs
Surface modification • need for chemical stability & functionalities - biofunctionalisation • high [protein] & [salt] environments
• H2Ophilic / H2Ophobic • ligands & coatings (organic molecules, surfactants, polymers)
Avoid: immune responses | protein synthesis failure clotting | generation of ROS (!!!)
Main goals: 1. conservation of magnetic properties 2. increased biocompatibility – decreased toxicity
Biomedical Apps of MNPs • Magnetic Hyperthermia eliminate cancer cells @ 42 - 45oC (locally) application of an AC magnetic field • Drug Delivery MNPs: drug or antibody carriers to specific organs / tissues fight w/ forces of blood flow magnetic guidance particle size: 10 – 100nm surface engineering to minimise interactions w/ phagocytic cells
Energy loss HEAT
Biomedical Apps of MNPs • Magnetic Resonance Imaging MNPs serve as contrast agents need for high chemical stability and magnetisation extensive use of maghemite (γ-Fe2O3) size ≤ 50nm: imaging of gastrointestinal, liver, spleen, lymph nodes size ≥ 50nm: diffusion imaging & brain / myocardial imaging appropriate for enzyme activity imaging (apoptosis, cancer, metastasis, inflammatory responses) functionalisation of MNPs w/ monoclonal antibodies
Characterisaton techniques • X-Ray Diffraction mapping of a material | chemical identification
• Transmission Electron µScopy structural characterisation @ atomic scale resolution
• Fourier Transform Infrared Spectroscopy “fingerprint” of a molecule MNPs: size, shape, element, phase identification
• Vibrating Sample Magnetometer Faraday’s principle (a changing magnetic field produces an electric field) delivers information about saturation magnetisation, coercivity, shape anisotropy, energy loss
Thanx Questions?
