Fabrication of hydrogels with steep stiffness gradients for studying cell mechanical response.
Many fundamental cell processes, such as angiogenesis, neurogenesis and cancer metastasis, are thought to be modulated by extracellular matrix stiffness. Thus, the availability of matrix substrates having well-defined stiffness profiles can be of great importance in biophysical studies of cell-substrate interaction. Here, we present a method to fabricate biocompatible hydrogels with a well defined and linear stiffness gradient. This method, involving the photopolymerization of films by progressively uncovering an acrylamide/bis-acrylamide solution initially covered with an opaque mask, can be easily implemented with common lab equipment. It produces linear stiffness gradients of at least 115 kPa/mm, extending from ∼1 kPa to 240 kPa (in units of Young's modulus). Hydrogels with less steep gradients and narrower stiffness ranges can easily be produced. The hydrogels can be covalently functionalized with uniform coatings of proteins that promote cell adhesion. Cell spreading on these hydrogels linearly correlates with hydrogel stiffness, indicating that this technique effectively modifies the mechanical environment of living cells. This technique provides a simple approach that produces steeper gradients, wider rigidity ranges, and more accurate profiles than current methods.
Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America. raimon.sunyer@nih.gov
Raimon
R
Sunyer
Albert J
AJ
Jin
Ralph
R
Nossal
Dan L
DL
Sackett
D020106:Acrylamide / Q000737:chemistry; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D018929:Cell Culture Techniques / Q000379:methods; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D055119:Elastic Modulus / Q000528:radiation effects; D005109:Extracellular Matrix / Q000737:chemistry / Q000502:physiology*; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D020100:Hydrogels / Q000737:chemistry / Q000378:metabolism*; D055595:Mechanical Phenomena; D051379:Mice; D018625:Microscopy, Atomic Force; D041681:NIH 3T3 Cells; D015203:Reproducibility of Results; D012996:Solutions / Q000737:chemistry; D014466:Ultraviolet Rays
D001672:Biocompatible Materials; D005353:Fibronectins; D020100:Hydrogels; D012996:Solutions; D020106:Acrylamide