Thermal Phase Transitions of Agarose in Various Compositions: A Fluorescence Study

Abstract

The effect of agarose content on thermal phase transitions of the agarose gels was investigated by using Steady State Fluorescence (SSF) method. Scattered light, I(sc) and fluorescence intensity, I(fl) were monitored against temperature during heating and cooling processes to investigate phase transitions. Two regions were observed during the heating and cooling processes. At the high temperature region, double helix to coil (h-c) transition took place. However, during the cooling process coil to double helix (c-h) transitions occurred at low temperature region. Transition energies were determined using the Arrhenius treatment, and found to be strongly correlated with the agarose content in the gel system. Transition temperatures were determined from the derivative of the sigmoidal transition paths and found to be increased by increasing agarose content in both cases.

Gel integration for microfluidic applications

“…Typically, the gelation temperature is 35 °C for high melting point (HMP) agarose and 25 °C for low melting point (LMP) agarose, and their melting temperatures are 80 °C and 60 °C, respectively. Kara et al 29,30 used UV-vis and fluorescence spectroscopy techniques to investigate agarose gel thermal phase transitions, which exhibit hysteresis loops. At high temperature, agarose is configured in a coiled state, and at low temperature, a state transition to a double helix occurs.…”

Gels: model systems for soft matter food physics

“…The gelation process [50] and the increase of the real part of the complex modulus at lowering of the temperature is shown in Figure 5. The hysteresis of the modulus between the cooling and the heating curve which indicates the nonequilibrium nature if the gelation process [51,52]. Indeed food systems are often far from being equilibrium physics and require in general non-equilibrium thermodynamic methods [53].…”

Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying

“…At temperatures higher than 37 °C, agarose immersed into the aqueous system remains in the sol-state and exists as a disordered ‘random coil’. Upon solution cooling, the Brownian diffusion of the polymeric chains slows down and the agarose-based hydrogel adopts an ordered double helix state [ 14 , 15 , 16 ].…”