Exciting technology: detective agencies

A highly promising use of nanotechnologies is in diagnosis of disease


The key principles in diagnostic technologies are the specific recognition of a molecule linked to a disease state and detection of this recognition. Nanotechnologies offer the prospect of very sensitive recognition and very quick detection.

Early-warning test kits for disease are being developed using quantum dots and gold nanoshells. Think of gold nanoshells as Malteasers; their crunchy core is made of silica and the chocolate coating is a gold shell. Unlike quantum dots, which re-emit light energy, gold nanoshells absorb or scatter the energy.

Quick blood tests are being developed using nanoshells coupled to molecules that detect disease-associated proteins. Changes to the nanoshells’ optical properties when they bind to the target can easily be detected.

A technique called biobarcode amplification has been used to identify tiny amounts of a protein that may be an early hallmark of Alzheimer’s disease.

The future

Gold nanoshells are showing great cancer-treating potential in the lab. When the gold nanoshells are in the vicinity of a tumour, they can be heated by absorbing light at a specific wavelength. The heat produced is sufficient to kill the cancer cells close by. A longer-term plan is to produce a cocktail of different coloured quantum dots to help doctors spot early indications of cancer or identify different types of tumour.

Another plan is to use quantum dots to deliver drugs directly to cancers. Dots coated in the anticancer drug Taxol and cancer-targeting molecules have already been shown to kill tumours in mice. Dots excited by near-infrared light emit energy that breaks the bonds with Taxol, releasing the drug to attack and kill tumour cells (this process is shown in detail below). 

Many other approaches are being tested. Liposomes (artificial microscopic sacs of fluid with a phospholipid membrane) are being used to deliver DNA or RNA to cancer cells, making them more sensitive to standard chemotherapy or radiotherapy, and biodegradable nanoparticles are being used to target toxic chemicals to cancer cells, releasing their deadly cargo over a period of time.

  1. Nanoparticles (shown in yellow with blue quantum dot core) are injected into the body. They are coated in antibody (white arrow head), which is specific to a cancer protein, and taxol (pink triangle), a cancer drug.
  2. The antibody targets the nanoparticle to a cancer cell by binding to a specific cancer marker protein (green triangle) on the cell surface.
  3. Nanoparticles are taken up by the cancer cell.
  4. Infrared light is shone on the suspected site on the tumour.
  5. The quantum dot (blue) releases photons that liberate the taxol molecules bound to the nanoparticle. The taxol molecules can then destroy the tumour.

Glen McBeth

About this resource

This resource was first published in ‘Nanoscience’ in June 2005 and reviewed and updated in August 2014.

Cell biology, Immunology, Medicine
Education levels:
16–19, Continuing professional development