ACIDITY FLUCTUATIONS INDUCE STRUCTURAL AND FUNCTIONAL CHANGES IN COLLAGEN HYDROGEL
2Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel, Israel
The extracellular matrix (ECM) is a major part of animal tissues that provides structural support and
regulates communication between cells. Due to diseases, injury and tissue abnormalities, the chemical
conditions in the ECM may change. For example, in proximity to solid tumors the ECM acidity
increases. Increased acidity affects cancer treatment via several phenomena. Low ECM pH decreases
the cellular uptake of certain drugs and may affect drug transport towards the tumor. Furthermore,
acidity-induced structural and mechanical changes in the ECM can affect cancer cell migration,
influencing the potential for metastasis.
The ECM contains various macromolecules, the main one is type I collagen. Here, we use type I
collagen hydrogel to model the stromal ECM and study the effect of acidity on ECM structure and
function, focusing on conditions relevant to cancer. We control and manipulate the collagen pH and
characterize its structure as a function of pH, utilizing methodology ranging from the molecular scale
to the nano and micro scales. We use Fourier Transform Infra-Red spectroscopy (FTIR) to determine
the collagen secondary structure and intermolecular crosslinking. We utilize cryo Scanning Electron
Microscopy (cryo-SEM) imaging of collagen to characterize its structure as a function of pH while
still hydrated. The use of cryo-SEM allows us to observe the collagen fibers and characterize their
thickness, length, and self-arrangement. To best explore the effects of pH on collagen structure, it is
essential to study the system as closely as possible to the native form, as hydrogel drying can alter the
organization of the fibers and induce mechanical damage. Furthermore, we link collagen permeability
to pH-induced structural changes by instilling fluorescently labeled particles and examine whether
acidity-induced changes in collagen structure and permeability are reversible. A better understanding
of the connection between the ECM pH, structure, and permeability may improve drug transport and
drug uptake by cancer cells and decrease cancer cell migration from solid tumors.