Modern studies of simple protocells began to appear in the 1980s, typically in the context of origin of life research. (For a historical account of earlier work, see Hanczyc 2008). This modern research was inspired by the discovery of Bangham and co-workers in (1965) that phospholipids could not only assemble into the vesicular structures now called liposomes, but also could trap concentration gradients of ions and other solutes. From this work it immediately became apparent that the lipid bilayer was the primary permeability barrier to the free di¤usion of ions and metabolites, and that specialized proteins must be present in the bilayer in the form of channels and pumps to allow communication between the intracellular volume and the external environment.
In the 1990s, other laboratories began to investigate encapsulated systems of macromolecules. The early goals were to develop e‰cient encapsulation methods, design lipid compositions and techniques that would permit external substrates to supply encapsulated enzymes, establish conditions in which lipid vesicles could undergo growth and division, and demonstrate catalyzed synthesis of polymers such as RNA, DNA, and peptides within the liposome volume. As these goals were achieved and reported in the literature, other laboratories began to think seriously about developing a variety of further protocell systems.
Much of the theoretical research on minimal life has its intellectual origin from the ideas presented by the experimentalist Manfred Eigen back in 1971, when the notions of quasispecies and hypercycle were created ( Eigen, 1971). Cooperative structures that provide mutual support of genes, metabolism, and containers can be seen as generalizations of Eigen’s ideas. Also, Ilya Prigogine’s creation of the concept of dissipative structures in the late 1970s gripped the imagination of many theorists trying to understand the origins of life. The notion from the late 1980s of the RNA world inspired both theoretical and experimental investigations of minimal life, and even today this concept is probably still the most prevalent hypothesis about the bridge between early minimal life and contemporary life.
With the turn of the millennium, ever-increasing numbers of publications explicitly related to functional protocells began to appear. An Internet search in 2006 for the terms protocell and artificial cell produces approximately 50,000 references to each term. A similar search in the scientific literature reveals 435 citations for protocell and 1,310 citations for artificial cell. These numbers reveal exploding interest in these topics since the first modern publications about 25 years ago.
What might have given rise to this remarkable increase? First, of course, is the intrinsic interest in bridging the gap between nonliving and living matter. To truly understand what it would take to create a minimal living cell, the obvious challenge is to verify this understanding by assembling a minimal cell from its parts’ list. The first fabrication of a functioning protocell will be a major scientific breakthrough. It is also clear that protocell technology will have significant applications, particularly in the biotechnology, material science, computer and information technology, and environmental science industries. In particular we believe that the combination of computer controlled microfluidics of protocell chemistry opens up for vast applications at the IT interface.
All of these considerations in part make the PACE project timely and of real use to the increasing number of investigators who see research on protocells as their primary scientific quest. We expect that the protocell work with the context of PACE within itself will serve as a focus for such activity, calling attention to the progress that has been made so far, and identifying milestones to guide future research and development.
In an environment in which basic scientific research suffers from decreasing resources, society owes great thanks for the foresight and vision of national funding sources, such as the European Commission’s program on Future and Emerging Technologies, Department of Energy’s support for Los Alamos National Laboratory and NASA programs in Astrobiology and Exobiology, as well as for the United Kingdom’s Engineering and Physical Sciences Research Council, the Japan Society for the Promotion of Science, and the Japanese Minister of Education, Culture, Sports, Science, and Technology, all of which have provided significant financial support for protocell research well in advance of any proven applications. Without these kinds of resources, the research reported in this book would have been impossible. The eventual applications of protocell research will come through the flowering of living technology. Living technology is one of the first concrete realizations of what the U.S. National Science Foundation (NSF) and the European Commission (EC) have termed convergent technologies. Convergent technologies are the emerging syntheses of nano-bio-info-cognitive (NBIC) knowledge production, and the NSF and EC both believe that convergent technologies will have a very large socioeconomic impact in the next 25 years. We hope that this volume will help forge an international community of interested stakeholders working with protocell scientists to explore the broader global opportunities and challenges of protocell research and the emergence of living technology.