I prepared a hydrogel which is composed of gelatin and due to nitrogen purging, it is forming full bubbled and uneven gel is forming..
how to reduce this?
Most of the time, bubbles can be eliminated by letting the solutions stand for a while in the reaction vessel without any agitation whatsoever. After a while the bubbles would subside and you can cast films on Petri dishes.
It depends on the potlife of your system (if thermoset). Usually mild evacuation, ultrasonication helps.
centrifugation works for me when im working with viscous liquid crystals
Hi Thanusha I have prepared gelatin and hyaluronic acid hydrogels and had an issue with bubbles formation in the HA system as the solns were highly viscous. You also have the issue, I assume, that gelatin is thermoreversible so I would suggest that you place your samples in a vacuum oven at 10 dC above the gelation temp for about 30 mins and see if this helps. If you have a crosslinker in your system you will need to solution cast your sample so it is reasonably thin (1 cm ht at most) - I used large petri dishes for this - before placing in a vac oven and you may also need to be careful with temp but most of the Xlinkers I'd expect you to be using should be fine at temp of < 50dC.
Hope this helps
Thanks to everyone for very nice suggestions and I will check with this..
Thanks A lott
ultrasonication is the easier and faster way to remove bubbles from viscous solutions.
Hi Irini From my experience ultrasonification can often cause polymer chain cleavage and, therefore, I would not be so sure that this is a good approach. Do you have any data to support using ultrasonification has no influence on gelatin as I would be interested in reading this. I previously have looked at viscous flow of PAA and HA solns after ultrasonication (high mwts) and perceived that degradation had occurred. Clare
All these methods help but I find with my 2-componets gels that a quick centrifugation (few seconds, high speed) after vortex mixing does the trick. Any bubble are driven to the top of the eppendorf tube, and I aspitrate the clear mixture from the bottom with a micropipette. Deon
Hi Clare, ultrasonification can be used paying attention to some important parametrs which indeed can influence the average molecular weights of the starting polymeric precursors. In particular, the time of exposure and the frequency, the higher the both the hogher the probability to breack covalent bonds. This effect can vary in extent as a function of the polymeric precursor in use. Naturally derived polymers are the most fragile and suffers reduction of the average molecular weights by ultrasonification compared to the synthetic counterparts. So it depends on the interinsic properties of the material and it can be quantified case-by-case.
Regards,
Irini
You may find convenient to use distilled water (or otherwise boiled) or to purge the water used to form the sol liquor or gel (prior to gelatin addition) by sparging N2 gas stream. Also convenient is to avoid aeration by swirling during agitation of the sol liquor, if such a step takes place prior gelation. You may also purge the liquor by sonication followed by reduced pressure before gelation.
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