Different methods for characterization of hydrogel scaffolds

1. Hydrogel
Characterization
Methods
By
Dhwani Jhala
School of Life Sciences
Central University Gujarat

2. Hydrogel
• Hydrogel can be defined as a crosslinked polymeric
network which has the capacity to hold water within its
porous structure.
• Amount of water varies from 10% to as high as 99.5%.
• The water holding capacity of the hydrogels arise mainly
due to the presence of hydrophilic groups, viz. amino,
carboxyl and hydroxyl groups, in the polymer chains.

3. Applications
Biomedical
applications

4. Characterization
• Physical properties
 Stress-strain
 Surface topography
 Structure
 Visco-elasticity
 Porosity
 Mechanical properties
• Chemical properties
 Solubility
 Crystallinity
 Chemical structure and composition

5. Physical characterization
• Stress - strain
Conventional techniques to mechanically characterize hydrogels: (a) strip
extensiometry; (b) ring extensiometry; (c) compression test; (d) bulge test;
(e) indentation (F = force, P = pressure).

6. • Structure of gel and surface topography
Transmission
Electron
Microscopy
•Network arrangement
•Pores distribution
•Fibre diameter and
internal structure
Scanning Electron
Microscopy
• Surface topography
• Composition
• Electrical
conductivity

7. • Visco – elastic properties
 Measures elasticity and stiffness of hydrogel
An image of the alginate
membrane under ball
indentation using the long
working distance microscope
A schematic of the hydrogel sample
holder and the loading ball

8. • Mechanical properties
and morphological
studies
• Atomic Force
Microscopy

9. • Porosity
▫ Mercury Intrusion
method
 Pore size
 Pore geometry
 Pore size distribution
 Interconnectivity
of pores
 % of void space

10. Chemical Characterization
• Chemical structure of hydrogel
▫ Infrared Spectroscopy
▫ Fourier Transform Infrared Spectroscopy (FTIR)
• It is based on the principle that the basic components of a substance,
i.e. chemical bonds, usually can be excited and absorb infrared light at
frequencies that are typical of the types of the chemical bonds. The
resulting IR absorption spectrum represents a fingerprint of measured
sample.
• Widely used to investigate the structural arrangement in hydrogel by
comparison with the starting materials

11. Ref. A. Cooper et al. / Carbohydrate Polymers 85 (2011) 149–156

12. • Quantification of the amount of free and bound
water in hydrogels
▫ Nuclear Magnetic Resonance (NMR)
▫ Proton NMR gives information about the interchange of
water molecules between free and bound states
▫ Differential Scanning Calorimetry (DSC)
▫ Thermo-analytical method
▫ Based on difference in the amount of heat required to
increase the temperature of a sample and reference
▫ Can also find out percentage of crystallinity of gel