The potential of nanofibers in tissue engineering – carriers mimicking human tissue architecture!

Regenerative medicine is?one of?the most dynamically developing?medical fields.?Its?main goal is?to?promote the?recovery of?diseased and?damaged human tissue.?The preparation of?tissue and?organ replacements depends on?the structure of?carriers (so?called scaffolds) providing specific conditions for?proper cell growth and?the formation of?whole tissue.

The?architecture and?the potential of?these scaffolds have undergone great development in?recent years. Scaffolds were made of?metal, collagen, polyester foams, and?hydrogel. But?by far?the best results are?achieved with?nanofibres, especially those created by?the so?called electrostatic spinning method.

What are?the advantages of?these?nanofibres?

1. They mimic the?structure of?the natural extracellular matrix in?which cells are?naturally held.
2. They feature a?small diameter that?exactly matches the?size of?the extracellular matrix,?making them ideal for?attachment, proliferation for?tissue renewal and?cell differentiation, i.e. for?the formation of?functionally and?structurally specialised cells.
3. In?addition, they can?be designed to?serve as?transport means for?bioactive factors,?i.e. to?transport growth factors and?hormones in?a controlled manner so?that the?“artificial tissue” grows properly.
4. The?scaffold components are?bioactive (allowing controlled release of?biomolecules according to?the timeframe of?tissue regeneration) and?biodegradable?(absorbed by?the surrounding tissue without the?need for?surgical removal and?without risk of?damage to?the new?tissue).

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Polymer nanofibres are?used in?many areas of?tissue engineering because they are?adaptable and?structurally diverse. For?example, for?the aforementioned electrostatic spinning, classical, coaxial or?alternating spinning methods can?be used, as?well as?the?Nanospider? free surface spinning technology.?The?modification of?the spinning nozzle allows the?formation of?fibres with unique structures and?properties. The?nanofibres can?then feature any?porosity,?depending on?the type of?material, evaporation rate, and?miscibility of?the solvents used.?This opens up?the possibility of?creating, for?example, composite fibres for?scaffolds that deliver the?relevant biomolecules to?the cells and?have the?ability to?mechanically support the?implanted cells even when the?system fails.

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Use?of nanofibres in?specific sub?fields of?tissue engineering

Although scientists are?exploring the?potential of?nanofibres in?various fields?of?tissue engineering, including growing whole organs,?the?most researched so?far are?musculature and?bones.?Regenerative medicine is?most focused on?promoting recovery of:

• Bone tissue,
• Skin,
• Musculature, and
• Cartilage.?

Interesting Fact:?It?is extremely difficult to?grow an?entire kidney or?liver. These organs represent the?highest level of?complexity. In?order to?grow a?kidney, scientists must first build a?scaffold, fill it?with stem cells, and?use complex signalling to?“invite” them to?transform into blood vessel cells.

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The potential of nanofibres in bone tissue architecture

The?design of?a carrier for?bone tissue growth is?based on?the physical properties of?bone, i.e. strength, porosity, hardness, and?overall 3D?structure.?Mesenchymal stem cells (MSCs)?are?able to?repair damaged tissue by?transforming into a?wide range of?specialised cells,?such as?chondrocytes (cartilage cells), osteocytes (bone cells), neurons, and?myocytes (muscle cells). This makes them the?rarest candidates for?use in?regenerative medicine, as?they can?be grown in?laboratories to?produce almost any?cell needed for?tissue repair.?Moreover, MCS?grow beautifully on?nanofibres,?produce abundant extracellular matrix, and?mineralise well.

Tip:?Composites based on?collagen or?gelatin nanofibres are?most commonly used because they must have adequate porosity and?morphology for?transport of?cells, nutrients, signalling molecules, gases, and?metabolic products.

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The potential of nanofibres in cartilage architecture

Cartilage tissue has?a limited capacity for?repair due?to the?reduced availability of?chondrocytes.?The?chondrocyte is?the basic cartilage cell, and?its energy potential is?unfortunately very limited.?Most of?its energy for?protein production comes from anaerobic respiration because there is?a lack of?oxygen in?the cartilage, i.e. it?is not?supplied with blood at?all. The?whole situation is?complicated by?the complete absence of?progenitor cells in?the vicinity of?the injury. This is?the baseline of?cells, from which specialised chondrocytes would have developed. Cartilage does not?contain blood vessels or?nerves, and?its nutrition is?provided by?intra?articular fluid. However, this method of?nutrition?significantly limits the?cartilage’s regenerative capacity?– damage takes a?long time to?heal and, especially in?the case of?larger defects, cartilage does not?fully recover. Therefore, one?of the?essential methods of?cartilage tissue repair is?the creation of?a?3D?nanofibrous carrier combined with chondrocytes and?progenitor cells?to?ensure proper tissue growth and?the formation of?a complete connective tissue replacement.

Tip:?The?goal of?the cell carrier is?to degrade after implantation in?parallel with the?formation of?new healthy tissue, which over time will completely replace this nanofibrous 3D?implant.

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The potential of nanofibres in skin architecture

Skin wounds normally heal with scar tissue, i.e. connective tissue lacking elasticity. Scar tissue restricts tissue movement, often causes pain, and?is aesthetically undesirable.?The?nanofibres of?the carrier allow a?“skin graft” to?be grown?and?implanted on?the wound, which then heals completely without scarring.

Tip:?Non?woven silk fibroin is?used, which is?a nanofibre created by?the well?known electrospinning method. Due?to its?high porosity when coated with type I?collagen, it?has been found to?best promote fibroblast adhesion and?the growth of?“new skin”.

Sources Cited:

1. Liu, H.,?Ding, X.,?Zhou, G.,?Li, P.,?Wei, X.,?& Fan, Y.?(2013). Electrospinning of?nanofibers for?tissue engineering applications.?Journal of?Nanomaterials.
2. Vasita, R.,?& Katti, D.?S. (2006). Nanofibers and?their applications in?tissue engineering.?International Journal of?nanomedicine,?1(1),?15.
3. Nemati, S.,?Kim, S.?J., Shin, Y.?M., & Shin, H.?(2019). Current progress in?application of?polymeric nanofibers to?tissue engineering.?Nano convergence,?6(1),?1?16.
4. Dahlin, R.?L., Kasper, F.?K., & Mikos, A.?G. (2011). Polymeric nanofibers in?tissue engineering.?Tissue Engineering Part B:?Reviews,?17(5),?349?364.
5. Ma,?Z., Kotaki, M.,?Inai, R.,?& Ramakrishna, S.?(2005). Potential of?nanofiber matrix as?tissue?engineering scaffolds.?Tissue engineering,?11(1?2), 101?109.
6. Biomedical Nanotechnology. (2017). Nanotechnology in?Tissue Engineering. P.?Gopinath. YouTube video. [6.12.2021]. Available at:?https://www.youtube.com/watch?v=4S1aqJnVaQE&t=1403s.