The research, published in the journal Angewandte Chemie, report a new class of nanostructures created from natural food grade ingredients - that could be used for food, storage, and medical technologies.
“All the components of the structures are food grade and so there is no need for additional approvals from the FDA for them, which makes food applications easier,” said Prof Alexandra Slawin, professor of chemical crystallography at the University of St Andrews.
Prof Slawin told FoodNavigator.com that the technology had “all the potential to be big move forward,” adding that in theory the methods could be used to produce safe, sustainable, nano-scale crystals for “virtually any sort of encapsulation”.
Slawin said that the beauty of the technology was its simplicity: “It’s a simple, cost effective system to make MOFs, using safe food grade ingredients.”
Effective storage
Metal-organic frameworks (MOFs) are well-ordered, lattice-like crystals that can effectively store gases and small molecules. They are usually made from petroleum-based ingredients, however the new micro-porous crystals are the first known all-natural MOF nanostructures.
The researchers, led by Sir Fraser Stoddart, professor of chemistry at Northwestern University, said the challenge in producing MOFs from natural products lies in problems with symmetry.
"Symmetry is very important in metal-organic frameworks," said Stoddart.
"The problem is that natural building blocks are generally not symmetrical, which seems to prevent them from crystallizing as highly ordered, porous frameworks."
The new findings offer a strategy to overcome this problem by using g-cyclodextrin (g-CD) - a symmetrical eight carbon sugar that is mass-produced from biorenewable starch.
Surprise finding
The researchers had initially set out to explore methods in making new molecular structures based on g-cyclodextrin.
However - much to the surprise of the scientists - their work produced crystals which upon examination were found to be metal-organic frameworks.
The researchers report combining food-grade g-CD with salt substitute (KCl) or potassium benzoate (E212), in water and Everclear grain spirit (EtOH) yields the porous edible frameworks.
The resulting crystal frameworks, arranged as cubes made from CD molecules linked by potassium ions was previously unknown.
The cubes form a porous framework with easily accessible pores, perfect for capturing gases and small molecules. The pore volume were reported to be 54 per cent of the solid body.
Far-reaching consequences
"It is both uplifting and humbling to come to terms with the fact that a piece of serendipity could have far-reaching consequences" said Stoddart.
"We achieved this level of porosity quickly and using simple ingredients," added Ronald Smaldone, postdoctoral fellow at Northwestern. "Creating metal-organic frameworks using petroleum-based materials, on the other hand, can be expensive and very time consuming."
The researchers revealed that they are so confident of the structures natural, food safe, qualities that they have already eaten some of the samples they prepared.
"They taste kind of bitter, like a Saltine cracker, starchy and bland," said Smaldone "But the beauty is that all the starting materials are nontoxic, biorenewable and widely available, offering a green approach."
The study concludes the MOFs can be synthesized using chemicals and conditions that would be“considered mild in the research laboratory setting”, but the researchers highlighted that they can also be prepared to the quality and purity suitable for food-grade applications using ingredients obtained easily and inexpensively.
Source: Angewandte Chemie
Published online ahead of print, doi: 10.1002/anie.201002343
"Metal–Organic Frameworks from Edible Natural Products"
Authors: R.A. Smaldone, R.S. Forgan, H. Furukawa, J.J. Gassensmith, A.M.Z. Slawin, O.M. Yaghi, J.F. Stoddart