Nanotechnology to improve human tissue growth in the laboratory

Pharmaceutical industry for medicine uses is based on the production of drugs that must pass exhaustive assays that rely almost exclusively on animal models or in vitro cell culture. The first entails some ethical problems besides the difficulty to extrapolate the data to human conditions. On the other hand, in vitro cell cultures are difficult to establish and to simulate the complex cell–cell and cell–matrix interactions that are decisive in the regulation of cell performance.

Now, IBEC’s research group “Biosensors for bioengineering” lead by ICREA Research Professor Javier Ramón-Azcón, reports in the journal Nanoscale Advances an innovative scaffold, based on carbon nanotubes and cryogel technology, which allows growing tissues at the millimetre scale in the laboratory. This technology can be used as substitute for animal and in vitro cell culture models for drug discovery. Moreover, this new support will undoubtedly have a very positive impact on other fields such as organ transplantation and regeneration and disease modelling, as it will improve the “organ-on-a-chip” technology that simulates the activities, mechanics and physiological response of entire organs.

The new scaffold combines carbon nanotubes with cryogel technology

The newly developed biocomposite scaffold gets together the good tissue regeneration properties of the gelatin, the mechanical stability of the cellulose and carbon nanotubes, which improves the mechanical stability and increases the scaffold’s electrical features. The originality of this work is that researchers applied the cryogel approach technology to obtain the micropore configuration, which consists in freezing the scaffold. The microporous structure is of crucial importance because it will allow the correct nutrient diffusion between cells. During the freezing process, water forms ice crystals inside the structure that once thawed leave empty pores. Another innovative aspect is that here the directionality of freezing was forced from one single axis because skeletal muscle cells need highly aligned morphology to fuse. Skeletal muscle cells form the striated muscle tissue are responsible for the body movement trough the nervous system action.

This technique allowed generating skeletal muscle tissue by mimicking its 3D environment in a millimetre range scaffold, with high pore interconnectivity and better mechanical stability than previously used hydrogels-based scaffolds. In this case the electrical properties of the scaffold play a crutial role, as muscle cells are constantly triggered to contract in response to nerve signals electrically transmitted. By the use of carbon nanotubes, this scaffold allows the application of an electric pulse stimulus to enhance tissue development and maturation.

Growing tissues in the laboratory to study cellular responses

Tissue engineering is one of the most promising fields for the medicine of the future, and aims to fabricate, repair, and/or replace tissues and organs. It creates, for instance, micrometre sized tissues grown on a scaffold, one of the most important pillars in tissue engineering. In a nutshell, researchers put some cells on a scaffold and let them grow to form a tissue by providing the nutrients needed and applying the mechanical forces that will influence their development. The integration of 3D-functional engineered tissues with microscale biosensors is the basis of the “organs-on-a-chip” technology. It allows, for example, the detection of cellular responses to external stimuli and the monitoring of the quality of the microenvironment (e.g., metabolites, nutrients).

This new process to obtain a scaffold, which combines the anisotropic freezing of the cryogel with carbon nanotubes, will allow the production of muscle tissues at the millimetre scale for several uses, including organ-on-a-chip technology, concludes Ferran Velasco-Mallorquí, first author of the work. 

The problem is that using the scaffolds available up to date, it was not possible to overcome the micrometre scale mostly due to deficient nutrients diffusion, absence of internal structure needed to align cells and poor mechanical and electric properties, complicating the study of large tissues. The new scaffold developed by the group Dr. Ramón-Azcón, solves the main problems to grow large muscle tissue constructs by improving its electrical properties and microarchitecture pore distribution.

Reference article: New volumetric CNT-doped Gelatin-Cellulose scaffold for skeletal muscle tissue engineering. Velasco-Mallorquí, F., Fernández-Costa, J.M., Neves, L., Ramón-Azcón, J. Nanoscale Adv., 2020, Advance Article. DOI: 10.1039/D0NA00268B

Figure: General overview of the study 

  • Muscle tissue formation process 
  • Principle of cryogel technique 
  • Scheme showing the approach to force the directionality of cryogel freezing 
  • Image of a scaffold