The ElastoSens™ Bio is presented in the below short video. Take a quick tour to learn more about the basic features of the instrument.
The short video below shows step by step how simple it is to set and to run a test on the ElastoSens Bio.
Testing the bulk mechanical properties of superabsorbent polymer (SAP) gels during swelling may be challenging using traditional testing instruments. In this application note, we propose to test SAP swelling by measuring the the viscoelastic properties of SAP gels using the ElastoSens™ X3. This instrument measures the mechanical properties of materials non-destructively and with no contact using low frequency vibrations. Being very simple to use, the ElastoSens™ X3 is suitable for both R&D and QC labs.
In this study, SAP particles were weighted and dispensed into the sample holders of the ElastoSens™ X3. 6g of demineralized water were then poured into the sample holders to initiate the swelling of the SAP. The weight of SAP particles was changed in order to vary the maximum swelling ratio.
The precision of measurements was first evaluated (Fig. 1). The effect of the swelling ratio on the elasticity of SAP gel was then studied (Fig. 2). These data were processed to observe the effect of the swelling ratio on the gel elastic shear modulus after 4 minutes and the absorption time (Fig. 3 & 4). The effect of the solution’s pH on the gelation profile of SAP gels was also investigated (Fig. 5). Finally, the incremental swelling of a SAP gel (obtained by successive addition of water) was tested by measuring the evolution of the shear elastic modulus at each level of swelling ratio (Fig. 6).
Fig.1 Time evolution of the shear elastic modulus G’ (left) and tan(d) (right) of three samples of a SAP gel during the absorption of demineralized water (max. swelling ratio was 200 g/g). Repeatability of measurements of G’ at the plateau was ±2%.
Fig. 2 Time evolution of the shear elastic modulus (G’) of SAP gels during swelling as a function of the maximum swelling ratio. The swelling ratio was varied from 100 g/g to 400 g/g with increments of 50 g/g.
Fig. 5 Time evolution of the shear elastic modulus of SAP gels as a function the absorbed water solution’s pH
(max. swelling ratio: 200 g/g).
Fig. 6 Time evolution of the shear elastic modulus G’ of a SAP gel during incremental absorption of demineralized water. Water was incrementally added to get a maximum swelling ratio of 100 g/g (added at 0 min.), 200 g/g (added at 5 min.), 300 g/g (added at 13 min.) and 400 g/g (added at 19 min).
The ElastoSens™ X3 is very simple to use and is suitable to perform R&D studies as well as routine QC testings. This instrument may also be used to develop or adjust specific applications for customers (e.g.: to optimize the dosage of SAP to reach specific absorption performances).
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This study has been performed by Pr. Lerouge Lab (The Canada Research Chair in Biomaterials and Endovascular Implants) and published in the JOURNAL OF BIOMEDICAL MATERIALS RESEARCH B: APPLIED BIOMATERIAL.
Sample weighing is the most used method to characterize degradation of gels even if this technique is not directly measuring the actual state of the network that forms a degraded gel. Being able to measure the mechanical properties of a degraded gel would be an interesting way to characterize the resorption of the material.
It has been proposed here to use the ElastoSens Bio to measure during 7 days the viscoelastic changes of chitosan hydrogels when exposed to lysozyme. Tow different compositions of chitosan have been tested: 3 replicates with a high degree of deacetylation and 3 replicates with a low degree of deacetylation. For each type of chitosan, 3 control samples (not exposed to lysozyme) were monitored over the same period of time. The same testing protocol has been conducted in parallel in order to measure the changes on samples weight.
It is important to note that the same samples were mechanically tested on the ElastoSens Bio during the complete duration of the study (7 days). The gel samples were kept into the sample holders of the ElastoSens Bio during 7 days but out of the instrument between the tests. The enzymatic and control (PBS) solutions were also maintained in the sample holders on the top of the gels in order to optimize their diffusion inside the samples. The sample holders were kept into an incubator (at 37℃) between the tests and loaded into the instrument at days 1, 3, 4, 5, 6 and 7 to perform single time measurements.
The figure above shows the evolution of the shear elastic modulus (G' ) of the two chitosan formulations when they are exposed or not to enzymes. The degradation process appears clearly on the curves. The gels exposed to enzymes exhibit a clear decrease on elastic modulus (between -50% and -70%) over 7 days compared to the control samples that are mechanically stable. An interesting observation is that the two formulations exhibit different degradation rates. The chitosan formulation with a high degree of deacetylation degrades more slowly and starts degrading 3 days after the formulation with a low degree of deacetylation.
Surprisingly, the left figure above shows that the gels weight did not changed over 7 days even if the gels were exposed to enzymes. The weight of the degraded gels did not changed during the degradation process even if the visual observation of the gels (right figure above) shows clearly that the enzymes were mechanically degrading the gel networks.
The ElastoSens Bio is a suitable tool to measure the degradation of hydrogels over long periods of time. The ElastoSens Bio provides more significant statistical results thanks to its capability to non-destructively measure the mechanical properties of the same sample during a long study. The mechanical characterization of degradation processes appears to be a good way to adapt the chemical formulation of hydrogels in order to tune the degradation rates. This is especially useful for the delivery of drugs by the mean of hydrogels.
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Correlating the Release of a Model Drug with the Mechanical Properties of a Degrading Alginate/Gelatin Composite Hydrogel
Controlled release of drugs at precise locations within the body can prevent systemic toxicity and deliver accurate dosages to patients. Hydrogels have recently been used in research as drug release vehicles. One method of controlling drug delivery is by modification of the mechanical properties of hydrogels. In this note, the ElastoSens™ Bio is used to monitor the mechanical properties of a degrading gelatin/alginate composite hydrogel concurrently with a dye release study. Here, we show that the impact of melting gelatin beads on the mechanical proprieties of the composite gel can be measured using the ElastoSens™ Bio. Is is also shown that the release of the dye is correlated to the mechanical properties of the degrading composite hydrogel.
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