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Posted: Oct 17, 2006
Fabricating highly mono-disperse nanospheres with biomulecules
(Nanowerk Spotlight) Controlling the shape of nanostructures is one of the challenging issues presently faced by synthetic chemists and materials engineers. Various shapes of nanomaterials, such as sphere-, rod-, wire-, triangle-, cube-, and tube-outlines have been synthesized by various approaches. However, to produce nanostructures with high monodispersity is still one of the major issues to be solved.
Most work in this area focused on inorganic or synthetically organic materials. Using pure biomolecules to produce nano- or micro-structures, without the assistance of inorganic materials, is rare. Biocompatible nanospheres have been and remain of intense interest for biosensor, drug delivery, and biomedical contrast imaging.
A new research report coming out of China now shows that highly monodispersed nanospheres of cystine (a sulfur-containing amino acid) aggregate were successfully produced by a quite simple method without the assistance of any other inorganic materials. This work could be of great significance in the production of nanomaterials, biosensors, and drug delivery.
Professor Zhanfang Ma from the Chemistry Department at Northeast Normal University in Chanchun, PR China, explains his group's recent findings to Nanowerk; "Amino acid molecules are one of the most important candidates to fabricate nanomaterials due to their stability, cost-saving, nontoxicity, and biocompatibility. Herein, we prepared multiple shapes of nano- and micro-structured cystine aggregates only by adjusting the concentration and pH value of the L-Cysteine solution under ultrasonic irradiation."
Importantly, as Ma points out, a large amount of highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained.
"To the best of our knowledge, this is the first time highly monodispersed nanospheres have been prepared using a common amino acid with small molecular weight" he says. "The reported method will promote new possibilities for future applications in biosensor, drug delivery, and medicine."
TEM images of cystine aggregates synthesized under different concentrations of L-Cysteine solution with pH = 8.0. The concentrations of L-Cysteine: (A) 0.1 mM, (B) 1 mM, (C) 10 mM, (D) 100 mM. (Reprinted with permission from IOP Publishing Ltd.)
The nanospheres of cystine aggregate are biocompatible and degradable, making them a very interesting material for drug or gene carriers in medicine as well as a good template to produce new nanomaterials.
Ma explains that the intermolecular interactions that might be responsible for the formation of nano- or micro-structured cystine aggregates mainly include hydrogen bonding and electrostatic interactions, which can be affected by changes in pH.
"Based on our experimental results we can assume that the direction of the forming network of hydrogen bonds played an important role in the formation of different shapes of nano- or micro-structured cystine aggregates " says Ma. "By varying the concentrations and pH values of the L-cysteine solution, the direction of intermolecular hydrogen bonding can be affected so that the aggregated predominance appeared in a certain direction and resulted in the formation of different cystine aggregate shapes including nanospheres, rods, spindles, dendrites, and multipods."
It can be safely said that this work will be of significance in the applications of nano- and micromaterials in biosensor, drug delivery, medicine, and the production of nanomaterials.