Now, silica nanobubbles for targeted drug delivery
Monday, 23 October 2006, 07:00 Hrs
Bangalore: Indian researchers at the Indian Institute of Technology (IIT), Chennai, have succeeded in entrapping antibiotics within silica nanobubbles and delivering them into cells, a major step towards drug efficacy.
The researchers have used the 'Core-shell system' that comprises a core of one material and a shell of another (inert) material.
The possibility of delivering therapeutic molecules into cells and monitoring it through fluorescence imaging has opened up new possibilities, claims Thalappil Pradeep, who led the team at IIT.
They incorporated ciprofloxacin (a known antibiotic) molecules on the gold nanoparticle surface with subsequent growth of a silica shell over that. This was followed by removal of the gold core -- using a method they have patented -- leaving behind a "nanobubble" inside which the antibiotic was trapped.
"A hollow nanobubble or nanoshell of silica (10-20 nm in diameter, 1-2 nm shell thickness) contains about 65 molecules of ciprofloxacin," Pradeep told IANS. (Human hair by comparison is 100,000 nanometres thick).
He said that they used sophisticated techniques like "fluorescence anisotropy" to show that the molecules are confined within the cage.
The advantage of such nanoscopic containers is they provide a rigid environment for the trapped molecules protecting them from unwanted chemical reactions, said Pradeep.
Though core-shell systems are known, "what is new in our work is the entrapment of antibiotics within nanoceramic shells and their delivery into cells", he said. The drug-loaded nanobubbles are stable and can be stored for extended periods.
In actual experiments, Pradeep and his colleagues incubated the shells containing the antibiotic (or a fluorescence label) with E. coli bacteria and observed the distribution of the drug inside the bacterium by fluorescence imaging technique.
In this work, the shells were not made specific to the cells, Pradeep explained. But that is possible by attaching appropriate antibodies to the nanobubbles that would allow them to 'home in' on target cells.
The work of Pradeep and fellow researchers is to appear in the prestigious journal 'Langmuir'.
"As the porosity of the shells is controllable, controlled release of drugs can be achieved," they said. "Furthermore, stability, ease of synthesis and bio-compatibility of silica shells make this system a better choice in comparison to other chemical analogues."
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