Controllable nanocapsules thanks to a biovalve

Researchers at the University of Basel have succeeded in developing synthetic nanocapsules, in which enzymatic reactions can be triggered by external factors. Scientists from Basel’s Swiss Nanoscience Institute (SNI) and Department of Chemistry have integrated biovalves into the membranes of the capsules. These membranes become permeable in a reversible manner as soon as a certain pH level is reached creating the conditions necessary to switch on/off in a controlled manner an enzymatic reaction within the capsule. This innovative strategy has great potential for medical applications, catalysis, and analytical chemistry. It was recently published in the scientific journal Nano Letters.

At a neutral pH, the biovalve opens, chemical compounds can enter the capsule, and are enzymatically converted. As soon as the pH in the environment changes and becomes slightly sour, the biovalve closes. (image: Departement of Chemistry, University of Basel)

Cells of higher organisms are divided into compartments with different functions (mitochondria, peroxisome, nucleus, etc). These compartments are separated from the cytoplasm by membranes. Proteins integrated into these membranes control the active and passive passage of chemical compounds in and out of the different compartments. Often, passage is triggered by external stimuli such as pH, membrane potential, specific chemical substances, or light.

Nature as a role model
Researchers led by Professor Cornelia Palivan and Professor Wolfgang Meier from the SNI and Department of Chemistry at the University of Basel have taken nature as their role model in developing controllable compartments. First, they created robust, synthetic compartments using synthetic membranes that enclose natural enzymes. They then combined modified channel proteins with a peptide that is sensitive to pH changes in the environment, and integrated these into the polymer membranes. At a neutral pH, the biovalve opens, chemical compounds can enter the capsule, and are enzymatically converted. Afterwards, the products of the enzymatic reaction can leave the capsule again. As soon as the pH in the environment changes and becomes slightly sour, the biovalve closes. As the passage of the essential substrates is blocked, no enzymatic reaction takes place in the compartment.

Basis for numerous applications
With this innovative strategy, scientists from Basel have developed synthetic nanocapsules with reversible “gates” through which enzymatic activity is triggered by external stimuli. They have combined the advantages of the robust and variable polymer capsules with those of genetically modified natural channel proteins by attaching a stimuli-responsive peptide to the channel protein. “In comparison to other strategies, our approach is technically simple,” says Palivan. The capsules are formed by self-assembly. As the enclosed and well-protected enzymes in the capsules can be varied, and the properties of the polymer membranes can be changed according to specific needs, this strategy has great potential for applications in medicine, catalysis and analytic chemistry.

 

Original publication:

Nano Letters., 2017, 17 (9), pp 5790–5798

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b02886?src=recsys

More information:

Prof. Dr. Cornelia G. Palivan, Department Chemie, Universität Basel, email: cornelia.palivan@unibas.ch, Tel: +41 (0)61 207 38 39

Prof. Wolfgang Meier, Departement Chemie, Universität Basel, email: wolfgang.meier@unibas.ch, Tel: +41 (0)61 207 38 02