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.
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.