Dear researchers,
We are using rat tail collagen type I as a 3D ECM matrix in our microfluidic PDMS chips. Recently, we are facing a non-linear diffusion problem through the collagen gel. We are sure that the collagen gelates, but not in a way that its structure is homogenous. As you can see from the attached image, FITC-Dextran is not diffusing linearly and the bright field image shows some cluster-like structures that we are not sure why they form. We prepare same exact recipe and materials as before however we couldn't understand why it does not diffuse linearly anymore. I would be happy to hear your comments and suggestions based on your experience or literature knowledge.
Thank you.
Funda Kus Are you preparing the collagen gel fresh every time? Re-using gels might pose such problems. Check the PDMS-chips for any uneven surface. Also try to tune the porosity of the gel to a fixed percentage.
Thank you for your response. Yes, I prepare the buffer fresh from the aliquots of NaOH, NaHCO3 and 1X&10X DMEMs and mix with collagen to start the gelation. We were having homogenous collagen months ago but we are stuck with this uneven structure for the last two months or so. Bottom layer is PDL coated glass (low contact angle) and top layer is PDMS for the collagen channel in my design. How do you think uneven surfaces might cause this problem? Collagen is in liquid form when prepared and inserted into the channel, so shouldn't it be filling homogeneously?
This is not my expertise in microfluidic PDMS chips. The main factors that could be affecting your current issue might be the collagen composition/purity or the preparation of the mixture prior to gelation. Maybe you need to do some optimisation externally before applied to the system. Best of luck!
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