Influence of thermal history on the structural and mechanical properties of agarose gels

Abstract

Using a multitechnique approach, two temperature domains have been identified in agarose gelation. Below 35°C, fast gelation results in strong, homogeneous and weakly turbid networks. The correlation length, evaluated from the wavelength dependence of the turbidity, is close to values of pore size reported in the literature. Above 35°C, gelation is much slower and is associated with the formation of large‐scale heterogeneities that can be monitored by a marked change in the wavelength dependence of turbidity and visualised by transmission electron microscopy. Curing agarose gels at temperatures above 35°C, and then cooling them to 20°C, produces much weaker gels than those formed directly at 20°C. Dramatic reductions in the elastic modulus and failure strain and stress are found in this case as a result of demixing during cure. An interpretation, based on the kinetic competition between osmotic forces (in favor of phase separation) and elastic forces (that prevent it) is proposed. © 2001 John Wiley & Sons, Inc. Biopolymers 59: 131–144, 2001

The effect of concentration, thermal history and cell seeding density on the initial mechanical properties of agarose hydrogels

“…Evidence for agarose possessing temperature dependant properties is available in the literature. It has been reported that fast gelation at temperatures below 35ºC can result in the formation of a stiffer, more homogenous gel compared to gels cured at temperatures above 35ºC (Aymard et al 2001). That study found that the elastic modulus, as determined from ramp compression tests, varied with the curing temperature from 12 to 82 kPa, with the highest values obtained at curing temperatures between 5 and 15ºC.…”

Polymer Gel Actuators: Fundamentals

“…Natural gels, such as agarose [26] and the calcium alginates, do seem to form ordered regions of double helix or multiple helices [27][28][29]. As a result, the mechanical properties are very dependent on the extent of structure developed during gelation [30]. The disruption of these structures during fracture could be expected to be a source of energy absorption and so increase strength and toughness.…”

Intermediate States of Aqueous Solution of Agarose on Quasi-Static Cooling

“…In fact both G' and G'' are at least three orders of magnitude lower than at conventional gel state below 30˚C. Aymard et al [20] measured G' at similar conditions but did not show this behavior probably because their instrument was not sensitive enough to detect the these orders of magnitude lower G' mentioned above. Though the cooling rate in our rhological measurements was not as low as those in light …”

“…Thus, the higher-order structure and physical properties of agarose gel depend strongly on the thermal history. While Aymard et al [20] demonstrated certain structure formation in very slow cooling or elongated curing at around 40˚C, quantitative information on the influence of cooling rate and the temperature range for this process has not been reported. In this study, we examined the structural evolution of a 1.0wt% aqueous agarose solution by a stepwise cooling with a rate less than 0.008˚C/min, and two distinct atages were obserbed before final gelation.…”

“…One of the proof of the fibrillar bundles is the large pore size that makes it an excellent material for DNA electrophoresis. The process preceding gelation of aqueous systems has also been studied mainly by differential scanning calorimetry [14], light scattering [15][16][17][18] and rheological measurements [19][20][21]. Based on the phenomena observed by temporal evolution of scattering intensities after quench either at high temperature or low concentration [14,[16][17][18] , some authors interpreted the process as a spinodal decomposition.…”