Operating inside cells

Nano-surgery with laser-based scalpels and optical tweezers

Microsurgical operations, such as operations on the eyes, have been routine for years. But what about using a living cell as the field of operation? Even in miniature format, mechanical instruments could cause more harm than good. Nevertheless, research scientists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Erlangen University Hospital are working to transfer principles from conventional surgery for treatments within the cell membrane. The only part of the surgeon’s traditional toolkit left are the names, however. Nanoparticles and lasers replace the usual surgical tool for cutting, clamping and sealing incisions at subcellular level.

An interdisciplinary group has been established to conduct research into nanosurgical procedures. It draws its members from the Chair of Photonic Technologies, the Department of Oral and Cranio-Maxillofacial Surgery and the Erlangen Graduate School in Advanced Optical Technologies. Their project has been awarded €500,000 from the DFG priority program “optically generated sub-100 nm structures for bio-medical and technical applications”. It is hoped the latest molecular biology findings with regard to the cell’s interior can be implemented in practice and used therapeutically.

The Erlangen researchers will focus on laser-based scalpels and optical tweezers. “We can capture nanoparticles in a sort of ‘optical trap’ and move them with precision over a surface”, explains PD Florian Stelzle, one of the project leaders at the Department of Oral and Cranio-Maxillofacial Surgery. “If you aim a laser beam at a nanoparticle then it acts as a lens, provided the wave-length and particle size are compatible.” In a small space just behind the particle, the beam reaches a very high intensity. This transforms it into a very sharp instrument, but only at the nanometer scale.

The technique was first developed by a working group led by Ilya Alexeev, PhD., at the Chair of Photonic Technologies held by Prof. Dr. Michael Schmidt and researched on non-biological materials. This process is of particular interest for sub-cellular surgery due to the extraordinarily precise positioning and the extremely small diameter of the laser’s focus. “These contact-free nano-instruments will make it possible to make incisions in the cell membrane, penetrate the inside of the cell and carry out our operation there – just like a conventional operation on a person”, Dr. Stelzle outlines the team’s vision.

The use of optical tweezers is planned as part of the next stage. They are intended to manipulate and move individual micro and nanoparticles contact-free and channel them into cells. As the cell wall is not normally permeable to this sort of particle, the laser scalpel must first create an opening. The tweezers can move a particle into the cell through the perforated membrane. In this way, individual structures inside the cells – such as mitochondria, the “power plants” of cells – can be targeted, modified or removed. “It is now possible to envisage nano operations on an individual cell – just as if we were extracting the gall bladder or another diseased structure in order to heal a patient”, explains Stelzle.

In this way, in the future, it will be possible to research how important cellular communication paths and structures react to such operations and whether their functions are modified. In particular, further insight is expected into possibilities of using nano-surgery to manipulate the molecular mechanisms that control cell death. In this regard there is a diverse range of possible applications, particularly in the treatment of tumours, nerve regeneration and the artificial generation of tissue, known as tissue engineering.

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uni | media service | research No. 15/2012 on 17.4.2012