Overview
How life emerged on Earth is one of the greatest open questions facing modern science. Lipid vesicles are commonly considered model systems for biological cells. This is due to their bilayer spherical structure, and to the facts that vesicles can incorporate nucleic acids and enzymes, and host biochemical reactions. In this area we are addressing the question to what extent liposomes are relevant for the origin of cellular life and the development of artificial living systems. We are pursuing two complementary lines of research to understand the fundamental design principles of living systems: (1) The building of protocells from prebiotically relevant compounds, and (2) the construction of synthetic minimal cells from contemporary biomolecules.
We apply a wide range of experimental (molecular biology, liposome preparation, cell-free transcription-translation, fluorescence microscopy/spectroscopy) and theoretical/computational methods to build and to provide a stronger logical basis for understanding the nature and requirements of cellular life.
We believe that our research has the potential to unveil a range of new fundamental structural and dynamical features on which Nature builds living systems. Moreover, we aim at exploiting the technological relevance of artificial cell research in the fields of nanomedicine, drug delivery and bioanalytics.
- Liposomes as models for synthetic cell containment and drug delivery vectors
The Emergence of Cellular Life
Life as we know it is cellular. A continuous and closed membrane separates the inside from the outside of cells. Today, the best candidates for containment are amphiphilic molecules capable of spontaneously producing micelles and vesicles. On grounds of the possible abundance of lipids and lipid-like amphiphiles in the prebiotic environment, a lipid world scenario has been suggested as an early evolutionary step in the emergence of cellular life. Several issues related to the role of lipid vesicles in early evolution have been tackled. For instance, macromolecules can readily be encapsulated within vesicles under drying and wetting cycles simulating prebiotic contitions, and lipid vesicles have been shown to be capable of autocatalytic expansion and to host complex biochemical reactions. Therefore, it’s tempting to propose that complex today life processes are an upgraded version of primitive processes based on simple vesicle systems.
We seek to provide solid experimental and theoretical bases for the construction of RNA protocell models. An important objective is to create active membrane boundaries able to perform basic functions in order to assist primitive – ribozyme-based – biochemical reactions and collaborate for the maintenance and evolution of the system.
Building a Minimal Cell
Over the past few years, a semi-synthetic approach to the construction of a minimal cell model has been employed. The term “minimal cell” has been used by Luisi and coworkers to describe molecular systems with minimal functions ensuring life. One or a few working genes are incorporated into lipid vesicles with the aim of realizing simple cell-like modules with limited and essential functionalities.
Our research aims at reconstituting essential features and distinct modules of the cell from small and physically controllable sets of molecules based on in vitro coupled transcription-translation using the PURE system. Our framework relies on DNA templates expressed by the PURE system inside liposome compartments. Specific goals towards the creation of an autonomous synthetic cell include the DNA-directed reproduction of the core machinery and of the shell compartment.
Cell-free expression of the YFP protein (green) from its gene encapsulated inside liposomes (magenta)
Liposome Nanofactory
Lipid vesicles can be used as drug delivery vectors. By decorating the vesicle surface with active cellular targeting elements, liposomes can be converted into therapeutic nanocarriers that bring drugs directly to diseased areas of the body.
Our fundamental research on the realization of complex enzymatic reactions and gene expression within liposomes offers an appealing platform technology for the development of new biosensors and therapeutic nanocontainers having further functionalities. In this context, we aim at designing liposomes with cell-like manufacturing ability and at using them as targeted drug delivery vectors, with particular interest in therapeutic RNA and brain cancer.
