Application of Inorganic Nanomaterials in Imaging Diagnosis

1
Application of Inorganic Nanomaterials in Imaging
Diagnosis
2
Introduction

• Inorganic nanomaterials are the main part of most
  contrast agents, and they can enhance the
  contrast between the patient's part and the
  surrounding tissue, which has attracted
  widespread attention from scientists in various
  fields such as biology, chemistry, physics and
  materials. There are many types of inorganic
  nanomaterials that can be used as contrast
  agents, including magnetic iron oxide materials,
  nano-gold particles, mesoporous silica materials,
  upconversion nanoparticles (UCNPs), and
  semiconductor quantum dot fluorescent materials.

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Magnetic iron oxide materials

• The magnetic iron oxide mainly includes Fe3O4 and
  ?-Fe2O3. Magnetic iron oxide nanoparticles can
  not only be biodegraded and have low toxicity,
  but also control the magnetic properties by
  adjusting the size of the particles. The bulk
  Fe3O4 is ferrimagnetic and has a multi-domain
  structure. When the size of Fe3O4 is less than
  100nm, its coercive force reaches its maximum,
  and when the size is reduced to 20nm, the
  magnetization of Fe3O4 magnetic nanoparticles is
  transformed into superparamagnetism. Fe3O4 and
  ?-Fe2O3 magnetic iron oxide nanoparticles have a
  wide range of applications in biomedicine,
  including cell tracking, biosensing, imaging
  diagnosis, and drug delivery.

4
Gold nanoparticles

• Gold nanoparticles refer to tiny particles of
  gold in three dimensions, including gold
  nanospheres and gold nanorods. Nano-gold
  particles have high electron density and have a
  strong attenuation effect on X-rays, and are
  widely used in CT angiography. Gold nanoparticles
  are widely used in molecular imaging because they
  are easy to prepare, and have the advantages of
  long in vivo circulation time, low toxicity, and
  easy binding of targeting molecules on the
  surface of materials. The most common application
  of gold nanoparticles is CT imaging. Compared to
  human tissue, gold nanoparticles have a strong
  absorption of X-rays, which is 2.7 times that of
  traditional iodine compounds, so it can greatly
  improve the contrast of CT imaging. Nano-gold
  particles are the most promising CT contrast
  agents.

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Mesoporous silica materials

• The mesoporous silicon oxide material is a
  silicon oxide with a large number of microporous
  structures inside. Mesoporous silica has good
  biocompatibility and excellent biodegradability.
  In recent years, it has attracted more and more
  attention as a drug carrier in the field of
  biomedicine such as drug transportation and
  imaging diagnosis. Compared with organic
  carriers, mesoporous silica has better thermal
  stability and chemical stability, high loading
  capacity, and shows unique advantages in drug
  delivery. With the development of nanosynthetic
  chemistry, various functionalized mesoporous
  silicas have been synthesized, and they are all
  obtained by compounding some magnetic materials
  or fluorescent materials with mesoporous silica.
  Mesoporous silica-based composite contrast
  materials are widely used in targeted MRI imaging
  and fluorescence imaging of tumors by adding
  different functional components. At present, the
  most studied mesoporous silica composite
  nano-biomaterials are mesoporous magnetic silica
  nanomaterials, which are obtained by compounding
  magnetic iron oxide nanoparticles into mesoporous
  silica. The composite of mesoporous silica and
  magnetic iron oxide nanoparticles can introduce
  magnetic properties into the mesoporous silica
  material, giving it the ability of MRI imaging
  contrast. If mesoporous silica and fluorescent
  materials are compounded together, fluorescence
  imaging can be achieved.

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Upconversion nanoparticles (UCNPs)

• Upconverted nanoparticles (UCNPs) are functional
  materials that can convert low-energy photons
  into high-energy photons, especially upconverted
  nanoparticles doped with lanthanum (Ln), which
  are currently the new generation of biological
  imaging contrast agents. A significant feature of
  upconversion luminescent materials is that the
  energy of the photons absorbed by the material is
  lower than the energy of the photons emitted by
  the material. Generally speaking, up-conversion
  nanoluminescent materials are mainly composed of
  a host matrix, a sensitizer and an activator.
  Common matrix materials include fluorides, oxides
  and chlorides. Up-conversion luminescent
  nanomaterials have excellent characteristics such
  as higher chemical stability, narrow band-gap
  emission, and good light stability. And they have
  good tissue penetrability under the excitation of
  near-infrared light without interference of
  background fluorescence, and have no damage to
  living organisms, so they have broad application
  prospects in medical imaging.

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Semiconductor quantum dots

• Semiconductor quantum dots (QD) is a nanomaterial
  composed of III-V and II-VI elements (such as
  CdTe, CdSe, ZnSe, InAs, InP, etc.). Compared with
  traditional fluorescent reagents, quantum dots,
  as fluorescent substances, have their unique
  advantages including wide band absorption,
  adjustable fluorescence emission, narrow
  fluorescence peaks, stable and long-lifetime
  fluorescence. By changing the size and
  composition of semiconductor quantum dots,
  fluorescence with a wavelength ranging from near
  ultraviolet to far infrared can be obtained.
  Modern medical research often requires multicolor
  imaging. For organic dyes, because of their wide
  emission bands, signal overlap is easy to occur,
  which affects their clinical application. The
  quantum dots have narrow and adjustable
  fluorescence emission, which makes multicolor
  imaging simple and feasible. The unique optical
  properties and mature synthesis make quantum dot
  a good fluorescent probe. As the research on
  semiconductor quantum dots continues, they will
  play an increasingly important role in imaging
  diagnosis.

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Conclusion

• For years, researchers have been exploring new
  and promising methods to improve the treatment
  efficiency of cancer and other diseases and the
  effectiveness of imaging studies. Imaging
  technology is the core driving force for the
  development of biomedical research. Advances in
  the performance of contrast materials have
  improved the clarity and resolution of imaging,
  which has enabled doctors to obtain more abundant
  medical imaging information and greatly promoted
  the development of clinical medical imaging. The
  multimodal imaging combined with different
  imaging modes and the combination of imaging and
  treatment will become the focus of future
  research on inorganic contrast materials.