Peptide-driven protein nanoparticle formation modulated through pH and metal ions


Technological advances in the field of bioengineering have led to the development of functional biomaterials with applications in the areas of drug delivery, diagnosis and bioenergy. Currently, computational approaches are used to guide design of proteins that form nanostructures with high accuracy at atomic levels. Alternatively, research has shown that fused protein-peptides are promising candidates for the formation of assemblies such as nanoparticles and large-cage structures with biocatalytic applications. In line with these advances, a convenient technique that allows easy control of the size of protein nanoparticles is therefore highly desirable. Recent studies have demonstrated the formation of gels by self-assembly of designed peptides by altering pH, or addition of metal ions such as calcium and potassium, and spherical protein−polymer micelles triggered by change in temperature. However, regardless of such progress, it is still difficult to control the assembled structures, in part, due to the lack of a fundamental understanding of protein self-assembly into nanomaterials.

Recently, a team of researchers at Monash University: Dr. Bhuvana K. Shanbhag (Postdoctoral fellow), Mr. Chang Liu (PhD candidate), A/Professor Victoria S. Haritos, and led by Dr. Lizhong He from the Department of Chemical Engineering explored the factors that affect protein nanoparticle formation using an enzyme−peptide system. In particular, they designed their enzyme−peptide system which incorporated bovine carbonic anhydrase (BCA) linked with a P114 peptide which could be readily produced from a single DNA construct using the bacterium Escherichia coli in high yield. Their work is currently published in the research journal, ACS Nano.

In brief, the research commenced with a detailed cross-examination of the effects of pH and specific cations and anions at varying concentrations on formation of protein nanoparticles. Next, the intermolecular protein−peptide contacts within nanoparticles were identified by cross-linking followed by mass spectrometry. The researchers then studied an alternative self-assembly trigger mechanism where magnesium ions were used as the initiators. Lastly, they tested whether the presence of other biomolecules affected assembly of protein nanoparticles and the controlled dis-assembly of the nanoparticles.

The authors observed that both pH and magnesium ion concentration could be varied independently or in combination to control nanoparticle size. In addition, they noted that the formation of protein nanoparticles did not affect the enzyme activity of proteins within the nanoparticles formed under a broad range of assembly conditions. Furthermore, the protein nanoparticles were observed to remain stable to the change in conditions once they were formed, and retained their size over long periods of storage.

In a nutshell, the study by Monash University scientists demonstrated the controlled formation of protein nanoparticles driven by a self-assembly peptide linked to the protein, in lowered pH conditions within buffered solutions or metal ion Mg2+ as two independent modulating parameters. In general, their work elucidated the key peptide−peptide and protein−peptide interactions that were affected by the two solution conditions. Altogether, the study offered vital information that enables the convenient formation and tailoring of protein nanoparticles without changing amino acid sequence.

Peptide-driven protein nanoparticle formation modulated through pH and metal ions - Advances in Engineering

About the author

Dr Bhuvana K Shanbhag

Bhuvana Shanbhag is Post-Doctoral Research fellow in Dr. He’s Lab in the department of Chemical engineering at Monash University, Australia. She completed her PhD under Dr. Lizhong He’s supervision at Monash University where she focussed on developing a novel approach to engineer enzymes with self-assembly feature to form functional enzymatic particles. In addition to her publications in Nano Letters and ACS Nano, her notable research outcomes on self-assembly of enzymes include a patent and recognition at the 2016 IChemE Global awards. Bhuvana graduated from Anna University, India with a Bachelor’s degree in Industrial Biotechnology and Masters in Industrial Biotechnology at SASTRA University, India.

She has also worked as Senior Scientist at Biocon Research Ltd., Bangalore India for 5 years on the development of downstream process for Anti-diabetic drugs. Her research interests include advanced biocatalyst development, protein self-assembly and environmental biotechnology

About the author

Mr Chang Liu

Chang Liu is a doctoral student in the Bioengineering Lab at Monash University supervised by Dr. Lizhong He with expertise in protein cross-linking chemistry. He previously has developed spray drying process for milk emulsification. His current research focusses on the development of engineered antibody fragments for analytical and diagnostic applications. He received his bachelor degree in Chemical Engineering from Monash University in 2016 and hails from Taiyuan, China. He is interested in protein engineering and aspires to apply them to cancer therapy and biomedical applications.

About the author

Associate Prof. Victoria Haritos

Associate Professor Victoria Haritos is an academic and Deputy Head of the Department of Chemical Engineering, Monash University Australia. Her research investigates the design and modification of biological systems for engineering applications especially in bioprocessing; an important area has been the development of enzymes for CO2 capture and biomass degradation. A/P Haritos holds Bachelor of Science (Hons), MAppSci and PhD degrees and has published 57 peer reviewed articles (>90% journal articles in the top 25% of the discipline including Nature Comms, ACS Nano, Nanoletters) and 7 patent applications. A/P Haritos is the recipient of awards including 2018 BHERT Award for Outstanding Collaboration in Research & Development: Industry Partnership and finalist in the 2016 IChemE Global, Biotechnology. Prior to joining Monash University in October 2014, A/Prof was a Principal/Research Scientist at the Australian national research organisation, CSIRO, where for 16 years she undertook industry-related research.

About the author

Dr. Lizhong He

Dr He completed his Bachelor of Science in Applied Chemistry and Master of Engineering in Biochemical Engineering at Tianjin University, China. He carried out his PhD research at GKSS Research Centre, Germany working on self-assembly and affinity adsorption of glycoconjugates. He then spent two years as a postdoctoral researcher at the Max-Planck-Institute for Polymer Research in Mainz where he studied functional tethered lipid membranes as biosensor. Prior to joining Monash University in 2011,

Dr. He was an AINSE Research Fellow and Deputy Director at Center for Biomolecular Engineering, Australian Institute for Bioengineering and Nanotechnology at the University of Queensland.

Dr He’s research group is focused on design and production of proteins for application ranging from therapeutical proteins and enzyme biocatalysis to environmental remediation and functional foods.


Bhuvana K. Shanbhag, Chang Liu, Victoria S. Haritos, Lizhong He. Understanding the Interplay between Self-Assembling Peptides and Solution Ions for Tunable Protein Nanoparticle Formation. ACS Nano 2018, volume 12, page 6956−6967

Go To ACS Nano

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