Evaluating the effect of pH on mechanical strength and cell compatibility of nanostructured collagen hydrogel by the plastic compression method

Document Type: Research Paper


Department of Medical Nanotechnology, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran


Objective(s): One of the main constraints of collagen hydrogel scaffolds for using in tissue engineering is mechanical weakness. Plastic compression (PC) is a physical method to overcome the mechanical limitation of collagen hydrogel.
Materials and Methods: In this study, the effects of pH on mechanical and biological properties of PC hydrogels were investigated. Collagen hydrogels were fabricated at neutral (pH=7.4) and alkaline pH (pH=8.5), and then underwent plastic compression to prepare final hydrogels. The stability, mechanical properties, morphology and cell compatibility of hydrogels were investigated.
Results: The results illustrated that increasing in polymerization pH was associated with improvement in both tensile strength and elastic modulus of hydrogels. Furthermore, cell viability assay confirmed cell survival in both hydrogels prepared at alkaline and neutral pH.
Conclusion: The results suggest that a slightly basic pH during hydrogel production is an appropriate approach to construct PC collagen hydrogels with an enhanced stability and mechanical properties as well as better handling before PC process.


1.Abou Neel EA, Cheema U, Knowles JC, Brown RA, Nazhat SN. Use of multiple unconfined compression for control of collagen gel scaffold density and mechanical properties. Soft Matter. 2006; 2(11): 986–992.

2.Salgado AJ, Coutinho OP, Reis RL. Bone tissue engineering: State of the art and future trends. Macromol Biosci. 2004; 4(8): 743–765.

3.Laurencin C, Khan Y, El-Amin SF. Bone graft substitutes. Expert Rev Med Devices. 2006; 3(1): 49–57.

4. Laurencin CT, Ambrosio AMA, Borden MD, Cooper Jr. JA. Tissue engineering: Orthopedic applications. Annu Rev Biomed Eng. 1999. p. 19–46.

5.Kneser U, Schaefer DJ, Polykandriotis E, Horch RE. Tissue engineering of bone: The reconstructive surgeon’s point of view. J Cell Mol Med. 2006; 10(1): 7–19.

6.Oakes BW. Orthopaedic tissue engineering: From laboratory to the clinic. Med J Aust. 2004; 180(5 SUPPL.): S35–38.

7. Braddock M, Houston P, Campbell C, Ashcroft P. Born again bone: Tissue engineering for bone repair. News Physiol Sci. 2001; 16(5): 208–213.

8.Novikova LN, Novikov LN, Kellerth J-O. Biopolymers and biodegradable smart implants for tissue regeneration after spinal cord injury. Curr Opin Neurol. 2003; 16(6): 711–715.

9.Rosso F, Marino G, Giordano A, Barbarisi M, Parmeggiani D, Barbarisi A. Smart materials as scaffolds for tissue engineering. J Cell Physiol. 2005; 203(3): 465–470.

10. Rosso F, Giordano A, Barbarisi M, Barbarisi A. From Cell-ECM Interactions to Tissue Engineering. J Cell Physiol. 2004; 199(2): 174–180.

11. Serpooshan V, Julien M, Nguyen O, Wang H, Li A, Muja N, Henderson JE, Nazhat SN. Reduced hydraulic permeability of three-dimensional collagen scaffolds attenuates gel contraction and promotes the growth and differentiation of mesenchymal stem cells. Acta Biomater. 2010; 6(10): 3978–3987.

12.  Charulatha V, Rajaram A. Influence of different crosslinking treatments on the physical properties of collagen membranes. Vol. 24, Biomaterials. 2003. p. 759–767.

13. Brown RA, Wiseman M, Chuo C-B, Cheema U, Nazhat SN. Ultrarapid Engineering of Biomimetic Materials and Tissues: Fabrication of Nano- and Microstructures by Plastic Compression. Adv Funct Mater. 2005; 15(11): 1762–1770.

14. Antoine EE, Vlachos PP, Rylander MN. Review of collagen i hydrogels for bioengineered tissue microenvironments: Characterization of mechanics, structure, and transport. Vol. 20, Tissue Eng Part B Rev. 2014. p. 683–696.

15. Gobeaux F, Mosser G, Anglo A, Panine P, Davidson P, Giraud-Guille M-M, Belamie E. Fibrillogenesis in Dense Collagen Solutions: A Physicochemical Study. J Mol Biol. 2008;376(5):1509–1522.

16. Yang Y-L, Motte S, Kaufman LJ. Pore size variable type I collagen gels and their interaction with glioma cells. Biomaterials. 2010; 31(21): 5678–5688.

17. Raub CB, Unruh J, Suresh V, Krasieva T, Lindmo T, Gratton E, Tromberg BJ, George SC. Image correlation spectroscopy of multiphoton images correlates with collagen mechanical properties. Biophys J. 2008; 94(6): 2361–2373.

18. Sung KE, Su G, Pehlke C, Trier SM, Eliceiri KW, Keely PJ, Friedl A, Beebe DJ. Control of 3-dimensional collagen matrix polymerization for reproducible human mammary fibroblast cell culture in microfluidic devices. Biomaterials. 2009; 30(27): 4833–4841.

19. FITCH SM, HARKNESS MLR, HARKNESS RD. Extraction of Collagen from Tissues. Nature. 1955 Jul 23; 176: 163.

20. Bitar M, Salih V, Brown RA, Nazhat SN. Effect of multiple unconfined compression on cellular dense collagen scaffolds for bone tissue engineering. J Mater Sci Mater Med. 2007;18(2): 237–244.

21. Buxton PG, Bitar M, Gellynck K, Parkar M, Brown RA, Young AM, Knowles JC, Nazhat SN. Dense collagen matrix accelerates osteogenic differentiation and rescues the apoptotic response to MMP inhibition. Bone. 2008; 43(2): 377–385.

22. Levis HJ, Brown RA, Daniels JT. Plastic compressed collagen as a biomimetic substrate for human limbal epithelial cell culture. Biomaterials. 2010; 31(30): 7726–7737.

23. Hu K, Shi H, Zhu J, Deng D, Zhou G, Zhang W, Cao Y, Liu W. Compressed collagen gel as the scaffold for skin engineering. Biomed Microdevices. 2010; 12(4): 627–635.

24. Ní Annaidh A, Bruyère K, Destrade M, Gilchrist MD, Otténio M. Characterization of the anisotropic mechanical properties of excised human skin. J Mech Behav Biomed Mater. 2012; 5(1): 139–148.

25. Varkey M, Ding J, Tredget EE. Advances in skin substitutes-potential of tissue engineered skin for facilitating anti-fibrotic healing. J Funct Biomater. 2015; 6(3): 547–563.