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destructive techniques. In the research paper published in RSC’s Biomaterials Science journal, we developed silk fibroin alginate- based 3D beads and also incorporated functional groups, which help in stem cell differentiation. These beads represent a true 3D system replicating the in vivo environment.
Human embryonic stem cells are a potentially powerful tool for therapeutic application in tissue regeneration, however, their use is ethically contentious, and thus adult stem cells such as human mesenchymal stem cells (hMSCs) have emerged as a viable alternative. These hMSCs can be obtained from healthy human adults and under proper growth conditions can form various cell types (such as bone and cartilage) in vitro (outside living organisms).
Silk fibroin is a fibre-like protein, which is glued together by sericin protein, to form silk cocoons. We use silk cocoons from Bombyx mori silkworm, the domestic
silkworm which feeds on
mulberry leaves and is found
abundantly in India. Alginate is
a polysaccharide derived from
algae and alginate beads, is one
of the extensively investigated
cell encapsulation materials.
But alginate does not interact
with cells, this results in poor
cell growth and proliferation.
Here, we formed 3D
beads by crosslinking alginate
with calcium ions and the silk
fibroin trapped in the alginate
bead slowly forms β sheets
(silk fibres) due to the aqueous
environment, resulting in a
stable silk-alginate 3D bead.
The beads were characterized
by imaging and staining with a protein stain, showing the beads were porous and in the size range of 3 mm. The silk remained physically
Ms. Smita Patil || 329
entrapped inside the beads, hence retaining their structure even after 14 days, when kept in a buffer solution. These beads are similar to water marbles, which are also hydrogels, that is, they soak up large amount of water and become many times bigger.
These alginate-silk beads supported growth and proliferation of osteoblast-like cells and hMSCs. Further, the effect of functional groups on differentiation of hMSCs in 3D microenvironment was also investigated and for this the carboxylic acid groups naturally present in alginate were utilized. Additionally, phosphate groups (PO4) were added onto alginate (Alg) by chemical crosslinking to develop alginate-PO4. We had previously shown that these groups direct hMSCs differentiation in 2D, into chondrogenic and osteogenic lineages. So in our study we formed 4 types of beads: Alg, Alg-silk, Alg- PO4, Alg- PO4 silk.
For any tissue engineering product to be successful it is extremely important that it should not cause any immune response when implanted inside human body. So we checked whether our beads were immunogenic or not by standard protocols using immune cells and found that the beads with or without stem cells were not immunogenic. It is known that hMSCs can control the immune response and they have been used for reducing immune response due to graft implantation. In our study we found that the 3D beads provided a favourable environment for growth of they secreted more factors
Bone and joint pathologies, intervertebral disc degeneration/ low back pain, tendinopathies, fractures, osteoarthritis, osteoporosis are among the largest groups of debilitating diseases today. Consequently, there is a need for further research to develop better, more effective cell-based bone tissue engineering products for clinical translation and therapeutic applications.
hMSCs and
compared to hMSCs grown in 2D.
We can deduce many things just by