Dense collagen gels as physiologically relevant bioinks

Evolution of the tools used in Gel Aspiration-Ejection: (A) Standard syringe; (B) Angioplasty Inflation Device; (C) Single syringe pump; (D) Automated biofabrication platform with multiple syringe pumps. Figure courtesy of Dr. Gabriele Griffanti (PhD Thesis; 2019).
(From: Rapid biofabrication of printable dense collagen collagen bioinks of tunable properties. G. Griffanti, E. Rezabeigi, J. Li, M. Murshed, S.N. Nazhat. Advanced Functional Materials 30 (2020) 1903874).

This is the first demonstration of an unprecedented, robust and simple method of gel aspiration-ejection (GAE) to generate 3D, cellular, injectable and printable dense collagen gels with anisotropically aligned collagen nanofibrils. Notably, the aspiration step expels the excess fluid used in the hydrogel casting process, and the collagen meso-structure is remodelled into tissue-equivalent matrices with extracellular matrix-like features. Bioactive materials and cells can be easily incorporated at the point of fibril self-assembly. A number of instruments have been adapted to undertake GAE, including, hand-held syringes, angioplasty inflation devices, and syringe pumps. Recent breakthroughs have led to a first prototype instrument based on automated-GAE, which enabled the high-throughput biofabrication of cellular dense collagen gel bioinks.

Recent Publications:

  • Griffanti et al. Journal of Materials Research. 2021. DOI:10.1557/s43578-021-00433-w (In press)

  • Griffanti et al. Advanced Functional Materials 30;2020:1903874.

  • Muangsanit et al. Journal of Neural Engineering 17;2020:046036.

  • Kamranpour et al. Biofabrication 8;2016:015018.

  • Marelli et al. Biomaterials 37;2015:183.

Native dense collagen gels as 3D tissue models and scaffolds for tissue engineering

Schematic of the Plastic Compression Technique (From: Ultra-rapid engineering of biomimetic tissues: a plastic compression fabrication process for nano-micro structures. R.A. Brown, M. Wiseman, C.B. Chuo, U. Cheema, S.N. Nazhat. Advanced Functional Materials 15 (2005) 1762-1770).
Confocal laser scanning microscopy analysis and depth encoding of uniform seeded NIH/3T3 cell distribution during (left panel; Ghezzi PhD Thesis; 2012) and pre- and post-plastic compression (right panel). (From: Real time responses of fibroblasts to plastically compressed fibrillar collagen hydrogels. C.E. Ghezzi, N. Muja, B. Marelli, S.N. Nazhat. Biomaterials 32 (2011) 4761-4772).

This is based on the ground-breaking original research into the Plastic Compression technique that identified and characterized a simple yet revolutionary process with generic applications in tissue engineering (original publication Brown et al., Advanced Functional Materials 15;2005:1762). The technology produces dense collagen constructs with high cell-viability and tissue-like mechanical characteristics. The technology has been commercialized into a 3D in vitro tissue model (RAFTTM, Lonza Bioscience Solutions) for use in toxicology, oncology and stem cell research and screening. Its speed, simplicity and control make it ideal for large-scale or individualized bedside applications.

Recent Publications:

  • Griffanti and Nazhat. International Materials Reviews. 65;2020:502.

  • Chicatun et al. Emergent Materials 2;2019:245.

  • Ghezzi et al. Journal of Tissue Engineering and Regenerative Medicine 11; 2017:2046.

  • Chamieh et al. Scientific Reports 6;2016:38814.

  • Marelli et al. Biomaterials 54;2015:126-135.

Bioinorganic releasing soluble and bioactive glasses

(From: Bioactive glasses in wound healing: hope or hype? S. Naseri, W.C. Lepry, S.N. Nazhat. Journal of Materials Chemistry B 53 (2017) 6167-6174)
An overview of the borate glass sol-gel process; (i) mixing of precursor materials, (ii) casting and aging, (iii) gel monoliths at day 10, (iv) drying, and (v) post calcination at 400 °C (scale bars =1 cm). (iii) Demonstrates the scaling up possibilities with these gels. (From: Highly bioactive sol-gel derived borate glasses. W.C. Lepry, S.N Nazhat. Chemistry of Materials 27 (2015) 4821-4831).

Our research program has significantly contributed to the advancement of knowledge on bioactive and soluble glasses through its research on silicate-, phosphate- and borate-based glasses. We were the first to report on highly bioactive sol-gel derived borate-based glasses. These demonstrate at least two orders of magnitude larger specific surface areas and total pore volumes compared to melt-quench equivalents, which translate to higher aqueous interaction, ion release, and mineralization rates. Depending on composition, osteogenic, angiogenic, or antimicrobial ions could be released through glass degradation. It is predicted that these glasses will have applications beyond the regeneration of mineralized tissues (e.g., bone repair and dentin hypersensitivity) and in particular in wound healing.

Recent Publications:

  • Naseri et al. Journal of the American Ceramic Society. 2021. DOI: 10.1111/jace.17802. (In press).

  • Lepry and Nazhat. Advanced NanoBiomed Research. 1;2021:2000055.

  • Lepry and Nazhat. Materials Advances 1;2020:1371.

  • Naseri et al. Journal of Non-Crystalline Solids 505;2019:438.

  • Lepry et al. Journal of Non-Crystalline Solids 500;2018:141.

  • Naseri et al. Journal of Materials Chemistry B 53;2017:6167.

  • Lepry et al. Journal of Materials Science 52;2017:8973.

  • Lepry and Nazhat. Chemistry of Materials 27:2015:4821.

  • Stähli et al. Journal of Controlled Release 200;2015:222.

  • Stähli et al. Acta Biomaterialia 19;2015:15.

Decoding the role of bioactive materials in collagen biomineralization and skeletal tissue engineering

Nanoscale evolution of intrafibrillar mineralization of single citrate-functionalized collagen fibrils fibrilized directly on transmission electron microscopy grids. (From: Multiscale structural evolution of citrate-triggered intrafibrillar and interfibrillar mineralization in dense collagen gels. W. Jiang, G. Griffanti, F. Tamimi, M.D. McKee, S.N. Nazhat. Journal of Structural Biology 212 (2020) 107592).

Both the gel aspiration-ejection and plastic compression techniques are ideal for generating hybrid hydrogels through the functionalization of the extracellular matrix-like dense collagen gels with other bioorganic molecules, e.g., citrate, silk sericin or bioinorganics e.g., bioactive glass particles. Through hybridization, the in-situ effect of these bioactive materials on the acellular intra- and inter-mineralization of collagen as well as on seeded cellular responses can be determined as a function of time in culture.

Recent Publications:

  • Park et al. Materials Science and Engineering C. 120;2021:111743.

  • Jiang et al. Journal of Structural Biology 212;2020:107592.

  • Griffanti et al. Biomaterials Science 7;2019:1064.

  • Griffanti et al. Biomedical Materials 14;2019:015006.

  • Miri et al. Biomaterials 85;2016:128.

  • Marelli et al. Biomaterials 37;2015:252.

Probing the role of dynamic physiological loading on tissue constructs

An overview of the changes induced by pulsatile (Cpulse) flow stimulation in comparison to static (Cstatic) culture and laminar (Claminar) flow on air smooth muscle cell responses when seeded within tubular dense collagen construct. (From: An airway smooth muscle cell niche under physiological pulsatile flow culture using a tubular dense collagen construct. C.E. Ghezzi, P.-A Risse, B. Marelli, N. Muja, J.E. Barralet, J.G. Martin, S.N. Nazhat. Biomaterials 34 (2013) 1954-1966).

Dense collagen constructs have tissue-like protein content and mechanical properties and provide a unique niche to investigate the effect of dynamic biomechanical stimulation in vitro on seeded cells. Physiologically relevant tensile, compressive or shear stresses and in combination with circumferential strain are translated to seeded cells, exhibiting native cellular orientation and expression of contractile phenotype and enhancing the construct mechanical properties via matrix remodelling.

Recent Publications:

  • Ghezzi et al. Biomaterials 35;2014:6236.

  • Ghezzi et al. Biomaterials 34;2013:1954.