Implementation of Optical Tweezer Microrheology Technique at the Biological Physics Laboratory of the Federal University of Viçosa

Detailed studies on the in vivo cellular environment are essential for understanding migration and aggregation processes and, consequently, related pathologies. Due to the complexity of this system, simulating this microenvironment is challenging. Investigating cellular behavior in vitro requires rheological characterization of substrates that resemble the microenvironments experienced by cells in vivo. However, traditional rheology does not allow for the identification and characterization of biocompatible viscoelastic materials at the typical cellular scale. This work aims to develop and implement a new technique capable of analyzing in detail the viscoelastic properties of substrates compatible with the environments experienced by cells in vivo. Unlike traditional rheology, optical trapping microrheology has the advantage of requiring only a small amount of biological samples. Furthermore, its implementation allows for obtaining information on local viscoelastic properties. First, the optical trapping microrheology technique was implemented at the Biological Physics Laboratory of the Federal University of Viçosa. Associated with its applicability in living organisms, this technique is pioneering in Brazil. In the second phase, the characterization of samples and the calibration of the implemented technique were carried out. In the second phase, a protocol was established to investigate the viscoelastic behavior of solutions through three experiments: free Brownian motion of a microsphere, Stokes force method (constant stress), and oscillations of an optically trapped microsphere at varying frequencies. An aqueous solution consisting of polyethylene glycol (PEG) 3000 was analyzed for evaluating and validating the technique. Solutions with different concentrations of PEG-3000 were used to investigate their behavior and obtain information about their viscoelastic properties.