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The use of atomic force microscopy for the measurement of human brain tissue elasticity

Abraham Tsitlakidis1*, Elias C. Aifantis2, Aristeidis Kritis3, Anastasia Tsingotjidou4, Panagiotis Selviaridis1 and Nicolas Foroglou1
  • 1 Aristotle University of Thessaloniki, AHEPA University Hospital, Greece
  • 2 Aristotle University of Thessaloniki, Polytechnic School, Greece
  • 3 Aristotle University of Thessaloniki, School of Medicine, Greece
  • 4 Aristotle University of Thessaloniki, School of Veterinary Medicine, Greece

Research studies focusing on the mechanical properties of brain tissue are gaining increasing interest in the last few years. Local mechanical interactions are important in the study of brain development (Budday, et al., 2015) and diseases associated with it, such as epileptic disorders (Wu, et al., 2016). They also play a crucial role in conditions where mechanical loads are applied to the brain, like traumatic brain injury, hydrocephalus, brain tumours, brain oedema and neurosurgical operations (Bilston, 2011). Possible clinical applications cover a broad range, including better understanding of the pathophysiology of epileptic disorders, prevention of traumatic brain injury, improvement of diagnostic imaging of hydrocephalus, brain tumour invasion and brain oedema, as well as design of new surgical strategies and haptics for brain tumour management. Atomic force microscopy (Binning, et al., 1986) is a form of scanning probe microscopy that can be conceived as an extension of touch, like optical microscopy can be regarded as an extension of vision. In principle, a sample moves in relation to a cantilever and the deflection of the cantilever, due to the contact with the surface of the sample, is recorded along with its position. The atomic force microscope (AFM) can be applied in air as well as in a liquid environment. The latter, in the form of an appropriate buffer, approaches better the natural environment of biological samples. As its resolution regarding forces and distances lies in the nanoscale, it has proven to be a powerful tool for the study of biological structures from macromolecules to tissues (Morris, et al., 2010). Furthermore, nanoindentation of living cells and fresh tissue slices using an AFM is an established technique (Chen, 2014; Christ, et al., 2010; Elkin, et al., 2007; Elkin, et al., 2010; Gautier, et al., 2015; Iwashita, et al., 2014). The methods for obtaining information about the elastic modulus of fresh brain tissue slices using AFM nanoindentation are described here. Specimens of fresh brain tissue are acquired from patients submitted to resective surgery for intrinsic brain tumours or epileptogenic lesions under the rules and the approval of the local bioethics committee. These specimens are transferred in constantly carbogenated ice-cold artificial cerebrospinal fluid (aCSF) from the operation theatre to the slicing facility. They are sliced with a vibratome in constantly carbogenated ice-cold aCSF, in order to obtain samples of constant thickness, suitable for study with an AFM. The slices are transported to the AFM in a portable tissue holder filled with aCSF, they are mounted onto the sample supports and they are incubated in a humidified carbogen (5% CO2/ 95% O2) atmosphere. The measurement of the mechanical properties of the tissue slices is achieved using an AFM in force mode operating in the measurement buffer solution. In specific, a mounted slice moves towards the cantilever of the AFM in the vertical axis. The force curve results from the simultaneous recording of the deflection of the cantilever, which is relative to the force applied to it, and the displacement of the sample in the vertical axis. The elastic moduli for the slices under examination can be extracted by analysing the force curves. Important factors defining the experiments are harvesting of the tissues, the preparation of the samples, the environment of their conservation, the choice of the appropriate tips and the mechanical model used for fitting of the force curves (Gautier, et al., 2015). According to the literature (Christ, et al., 2010), the brain tissue is a very soft solid material, while measurements with other tools suggest differences might be observed with disease (Xu, et al., 2007). To our knowledge, this is the first study that has successfully sliced fresh human brain tissue in order to obtain force curves with an AFM. In the future, we are expecting to finalize the details for AFM nanoindentation of brain tissue slices, to further elucidate the possible alterations of the mechanical properties of the brain in diseases where tissue specimens become available.

References

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Keywords: atomic force microscopy (AFM), brain slices, Brain Mechanics, human brain tissues, brain tumours, Epileptogenic lesions, Elasticity

Conference: SAN2016 Meeting, Corfu, Greece, 6 Oct - 9 Oct, 2016.

Presentation Type: Poster Presentation in SAN2016 Conference

Topic: Posters

Citation: Tsitlakidis A, Aifantis EC, Kritis A, Tsingotjidou A, Selviaridis P and Foroglou N (2016). The use of atomic force microscopy for the measurement of human brain tissue elasticity. Conference Abstract: SAN2016 Meeting. doi: 10.3389/conf.fnhum.2016.220.00103

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Received: 29 Jul 2016; Published Online: 01 Aug 2016.

* Correspondence: Mr. Abraham Tsitlakidis, Aristotle University of Thessaloniki, AHEPA University Hospital, Thessaloniki, Greece, abrahamtsitlakidis@yahoo.gr