Noninvasive assessment of collagen gel microstructure and mechanics using multiphoton microscopy

Christopher B. Raub, Vinod Suresh, Tatiana Krasieva, Julia Lyubovitsky, Justin D. Mih, Andrew J. Putnam, Bruce J. Tromberg, Steven George

Research output: Contribution to journalArticlepeer-review

287 Scopus citations


Multiphoton microscopy of collagen hydrogels produces second harmonic generation (SHG) and two-photon fluorescence (TPF) images, which can be used to noninvasively study gel microstructure at depth (∼1 mm). The microstructure is also a primary determinate of the mechanical properties of the gel; thus, we hypothesized that bulk optical properties (i.e., SHG and TPF) could be used to predict bulk mechanical properties of collagen hydrogels. We utilized polymerization temperature (4-37°C) and glutaraldehyde to manipulate collagen hydrogel fiber diameter, space-filling properties, and cross-link density. Multiphoton microscopy and scanning electron microscopy reveal that as polymerization temperature decreases (37-4°C) fiber diameter and pore size increase, whereas hydrogel storage modulus (G′, from 23 ± 3 Pa to 0.28 ± 0.16 Pa, respectively, mean ± SE) and mean SHG decrease (minimal change in TPF). In contrast, glutaraldehyde significantly increases the mean TPF signal (without impacting the SHG signal) and the storage modulus (16 ± 3.5 Pa before to 138 ± 40 Pa after cross-linking, mean ± SD). We conclude that SHG and TPF can characterize differential microscopic features of the collagen hydrogel that are strongly correlated with bulk mechanical properties. Thus, optical imaging may be a useful noninvasive tool to assess tissue mechanics.

Original languageEnglish (US)
Pages (from-to)2212-2222
Number of pages11
JournalBiophysical Journal
Issue number6
StatePublished - Jan 1 2007

ASJC Scopus subject areas

  • Biophysics


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