Rapid assembly of living micro-tissues with holographic optical tweezers; Cell 'LEGO' for regenerative medicine

The headline or sound bite for this project is 'laser-guided positioning of live cells and building of living micro-tissues - a new, cell scale manufacturing process for pharmaceutical testing and regenerative medicine'. The project showcases how scientists from seemingly unrelated backgrounds in tissue engineering and optical physics are collaborating to develop new healthcare technologies. The driver for the project is the increasing need to produce living human tissues, in the culture dish, with structures and functions that are as close as possible to those in the body and to use these in vitro tissues to more effectively test, develop and improve new and existing medicines and therapies. This approach can minimize use of animals in research and also reduce potentially costly, both health and economic, failures with new medicines.

Our ability to achieve this ambitious goal of manufacturing living micro-tissues with lasers is underpinned by an instrument called an optical tweezers. Optical tweezers, invented in the 1980s exploit a phenomenon, whereby a tightly focused beam of laser light creates a localized force at its point of focus and has the effect of attracting small particles towards it - a so called optical trap or optical trapping. Suspending the particles within fluid gives a damping force producing a single (laser) beam optical trap that is stable in three dimensions (3D) - by moving the beam of laser light, the trapped particle can be also moved and controlled in multiple directions and subsequently positioned at defined points/locations with 'laser precision'. A range of different types and sizes of particles can be trapped and moved including, 2 micron (one 500th of a millimetre) glass beads to live human cells, which are typically 10 microns (one 100th of a millimetre) in size. Importantly, the properties of the laser, in terms of its power and wavelength are such that it causes little or no damage to cells and certainly in the time taken (seconds/minutes) to trap and move them.

An evolution of this instrument is the holographic optical tweezers, where the single laser beam is split to create multiple traps, each capable of holding and moving particles. This is done using a spatial light modulator (SLM), a component typically found in an overhead and/or data projector. The SLM acts as a diffractive optical element, or hologram, and can be continuously updated via a computer program. Thus, multiple traps can be created in 3D and each trap independently controlled and positioned to create predetermined configurations and patterns. Using conventional microscope optics and a joy stick or iPad touch screen, the traps can be visualized in real time and controlled with the dexterity of a 'virtual hand'.

Here, we will use this technology to exert hitherto unattainable levels of control over the movements and positioning of live cells, with the predefined precision akin to natural processes of tissue development and formation. With dynamic, precision control at the scale of the individual cell, we will show how holographic optical tweezers can be used to manufacture definable and tuneable, 3D micro-tissues; micro-tissue components, such as cells or small (~5 micron) polymer particles containing drugs, can be assembled together within minutes in a manner similar to building with 'cell LEGO'. With inherent control over manufacturing complexity we can deliver 'simple' 3D cell aggregates with applications in drug discovery and pharmaceutical testing, each aggregate consistent with the next, assembled with an exact number of cells and drug-loaded microparticles. This will be the focus of this phase of the project.

Developing the project further we will also seek to push the boundaries for manufacture of more complex, bespoke structures that mimic specific tissues like liver, skin, heart etc and can be used to better understand disease processes and develop new therapies.

Progress and outputs from this project will be shared with the academic community via the usual methods of peer-reviewed publications and presentation (oral/poster) at research conferences and invited seminars. Significantly, the multidisciplinary nature of the project and involvement of investigators and researchers from the biological and physical sciences will ensure that our research findings will be disseminated across diverse audiences.

A key stage in the project is development and evolution of the manufacturing with (laser) light process and involves a number of technical innovations and biological observations that we fully intend to share through our demonstrated (and aspired to) publications in journals such as, Nature Biotechnology, Nature Photonics, Tissue Engineering, Journal of Controlled Release, Soft Matter, Lab-on-a-Chip, and Developmental Biology.

In terms of research conferences and workshops, we have demonstrated participation and presentations to many that are relevant to this project including, Tissue Engineering International and Regenerative Medicine Society (TERMIS), World Biomaterials Congress etc. The investigators are routinely invited to give more informal seminars, often to groups that are working directly on research relevant to the project, providing a significant opportunity to share, discuss and develop data in small focussed groups.

Recent data, training/demonstrations and 'mini-projects' in new research and techniques (e.g, holographic optical tweezers) is also currently shared with students and researchers and includes; University of Nottingham MSc Stem Cell Technology, the EPSRC Doctoral Training Centre in Regenerative Medicine, the BBSRC Doctoral Training Partnership
(http://cmswip01.nottingham.ac.uk/doctoral-training-centres/doctoral-training-centres.aspx) and the EPSRC Centre for Innovative Manufacturing in Regenerative Medicine (http://www.epsrc.ac.uk/funding/centres/innovativemanufacturing/Pages/imrcmedicine.aspx)

Engaging the wider community and the public we have active outreach programmes that includes; 'After-Schools Clubs' (e.g. the School of Pharmacy's award-winning After School Science Club for Year 5 and 6 primary school children, where we have discussed previously stem cells and tissue engineering), public lectures and exhibitions - School of Pharmacy presented an exhibit at the Royal Society's 2013 Summer Science Exhibition in London - 'Biology Builders', showcasing our research and innovation in regenerative medicine. Notably, this involved hands-on interaction with the holographic optical tweezers via a remote, iPad-controlled live interface, between the exhibit and the tweezers back Nottingham and this was extremely well received.

We also regularly participate in university 'Open Days' and 'May Fest' and give tours and interactive demonstrations of our research. Research is also publicized via university media offices (e.g www.nottingham.ac.uk/news/pressreleases/2012/march/artificial-womb-unlocks-secrets-of-early-embryo-development.aspx) and via research group websites . We shall also engage with and consult the EPSRC Press Office. The university and investigators also maintain Twitter accounts and frequently use this to communicate research outputs, conference attendance etc