Application of gold nanoparticles in tumor diagnosis and treatment

1
Application of gold nanoparticles in tumor
diagnosis and treatment
2
Introduction

• In recent years, nanomaterials and nanotechnology
  have increasingly entered the clinical
  application stage. Gold nanoparticles have very
  unique physical and chemical properties. And gold
  nanoparticles are relatively safe, easy to
  prepare, and very stable. In addition to the
  small size effects, surface effects, quantum size
  effects, macro quantum tunnel effects, and
  dielectric effects of nanoparticles, gold
  nanoparticles also have unique electrical,
  optical, magnetic, catalytic effects. Therefore,
  gold nanoparticles have been widely used in the
  filed of biomedicine. In the treatment of tumors,
  gold nanoparticles have better penetrating power
  than traditional drugs, and their risks in
  diagnosis and treatment are lower than
  traditional drugs.

3
Structure and Properties of gold nanoparticles

• Gold nanoparticles exhibit unique physical and
  chemical properties due to their different shapes
  and sizes. The gold nuclei of gold nanoparticles
  are essentially inert and non-toxic. The
  synthesis of gold nanoparticles is relatively
  easy, and the diameter range is controllable,
  generally in the range of 1 to 150 nm. Gold
  nanoparticles with different properties and sizes
  can control the release of drugs in different
  parts, so it is a good drug carrier. Various
  shapes of gold nanoparticles have been developed
  to meet different therapeutic needs.Gold
  nanospheres (AuNPs) are gold nanoparticles
  produced by reduction of chloroauric acid, with
  diameters ranging from 1 to more than 100 nm, and
  they are mainly used for imaging and
  radiosensitization. Gold nanoshells (AuNSs) are
  spherical with diameters ranging from 50 to 150
  nm. The structure of the gold nanoshell includes
  a core of silicon dioxide and a thin gold shell.
  The optical properties of AuNSs can be adjusted
  by changing the diameter of the core and the
  thickness of the shell wall. Gold nanorods
  (AuNRs) are usually synthesized by the reaction
  of chloroauric acid on gold seeds using
  cetyltrimethylammonium bromide (CTAB) as a
  stabilizer. The size of AuNRs is usually 25-200
  nm. The wavelength of the absorption peaks of
  AuNRs can be changed by changing the ratio of the
  length and diameter of these particles (ie, the
  aspect ratio). There are also other forms of gold
  nanoparticles, such as nanocages and hollow gold
  nanospheres.

4
Application of gold nanoparticles in tumor
diagnosis

• One of the differences between tumor cells and
  normal tissue cells is the difference in cellular
  metabolic activity. For example, in liver cancer
  cells, breast cancer cells, or melanoma cells,
  protein kinase (PKCa) is either overexpressed or
  has abnormal activity. Protein kinases can
  phosphorylate specific substrate peptides,
  resulting in changes in the net charge carried by
  the substrate peptides. When the substrate
  peptide and nanogold are mixed, the stability of
  the nanogold colloid is affected by the net
  charge before and after the substrate peptide is
  phosphorylated. The surface charge layer of the
  nanogold is destroyed by the large net charge of
  the substrate peptide, which will cause colloid
  aggregation Therefore, the activity or expression
  of protein kinase can be indirectly determined by
  whether or not nanogold is aggregated, so that
  tumor cells and normal tissue cells can be
  distinguished. Imaging with gold nanoparticles in
  the visible spectrum can only be applied to
  cancers on the skin surface. Optical imaging of
  most solid tumors in vivo needs to be performed
  in the near infrared spectral region of 780 to
  2526 nm (especially 780 to 1100 nm). Changing the
  size, shape and composition of gold
  nanoparticles, or modifying the surface of gold
  nanoparticles can make the nanoparticles have
  high surface plasmon resonance absorption and
  scattering capabilities in the near-infrared
  spectral region. By connecting them with specific
  biological targeting molecules, gold
  nanoparticles can become a very effective imaging
  agent for tumor imaging. Studies have found that
  PEGylated gold nanoparticles, gold cages and gold
  rods all have good stability, biocompatibility,
  biodispersity, and osmotic retention effects, and
  can accumulate in large quantities at tumor
  sites. In the near-infrared spectral region,
  these types of gold nanoparticles have suitable
  local surface plasmon resonance peaks, so they
  can clearly develop tumor tissue.

5
Application of gold nanoparticles in tumor
treatment

• As a drug carrier, gold nanoparticles can improve
  the pharmacokinetics of drugs, thereby reducing
  non-specific side effects and achieving targeted
  drug delivery at higher doses. Gold nanoparticles
  can also be used in thermotherapy treatments. The
  mechanism of hyperthermia treatment involves the
  thermal stress response of cells at 42-47 C,
  which causes the activation of cells and the
  activation of degradation mechanisms inside and
  outside the cell. The negative effects of
  hyperthermia on cells include misfolding and
  aggregation of proteins, changes in signal
  transduction, cell apoptosis, changes in pH,
  reduced perfusion and tumor oxygenation, etc.
  Gold nanoparticles such as gold nanorods (AuNRs)
  or gold nanoshells (AuNSs) have obvious
  advantages in the absorption and scattering of
  near-infrared light (wavelengths from 650 to 900
  am). When exposed to electromagnetic radiation,
  especially near-infrared light, gold
  nanoparticles can generate heat through surface
  plasmon resonance effects. Because the peak of
  the absorption wave of gold nanoparticles is in
  the visible light range (450-600 nm), the
  absorption of near-infrared light by normal
  tissues is very small. Stimulating gold
  nanoparticles with near-infrared laser light can
  induce heat generation and hardly damage normal
  tissues. Therefore, gold nano-mediated
  photothermal therapy has the advantages of strong
  specificity and less trauma compared with
  traditional tumor treatment.

6
Conclusion

• Gold nanoparticles have unique physical and
  chemical properties and have been a hot spot in
  tumor diagnosis and treatment. The application of
  gold nanoparticles in the detection of tumor
  markers and the imaging of tumors is the focus of
  researchers' attention. However, more studies are
  needed on the metabolism of gold nanoparticles in
  the body and its effect on normal cell activity,
  especially on gene expression or regulation.