Scientists at Nanyang Technological University (NTU Singapore) have found a way to use sunflower pollen to develop a 3D printing ink material that can be used to make parts useful for tissue engineering, toxicity testing, and drug delivery.
This pollen-derived ink retains its shape when deposited on a surface, making it a viable alternative to inks currently used for 3D printing (also known as bioprinting) in the biomedical field. Such inks are usually soft and delicate, so when the bioprinter deposits the ink layer by layer, it is difficult to maintain the 3D shape and structure required by the final product.
To illustrate the function of their pollen-based 3D printing ink, scientists at Nanyang Technological University in Singapore printed a biological tissue “scaffold”. Laboratory studies have shown that it is suitable for cell adhesion and growth, which is essential for tissue regeneration.
The research team said that this new use of pollen was described in a scientific paper on the cover of the scientific journal Advanced Functional Materials, highlighting its potential as a sustainable alternative to current bioprinting inks.
The co-lead author of the study, Professor Cho Nam-Joon of the School of Materials Science and Engineering, NTU, said that bioprinting can be challenging because the ink material used is usually too soft, which means that the structure of the product is expected to collapse during the printing process. . Print. By adjusting the mechanical properties of sunflower pollen, we have developed a pollen-based hybrid ink that can be used to print structures with good structural integrity. The use of pollen for 3D printing is a major achievement in making pollen inks that are sustainable and affordable. Given that there are many types of pollen species with different sizes, shapes and surface characteristics, pollen microgel suspensions may be used to create a new class of environmentally friendly 3D printing materials.
The co-lead author of the study and Assistant Professor Song Juha from the School of Chemistry and Biomedical Engineering of NTU said that our research results can open new doors for customized flexible membranes that perfectly fit the contours of human skin, such as wound dressing patches or Facial mask. Such a soft and flexible film is usually made based on a flat geometry, so when applied to a large area of skin (such as the face or joints and other frequently moving areas), it will cause problems such as interlayer fracture or poor fit. Pollen-based 3D printing ink has biocompatibility, flexibility and low cost. We can make a film that fits the contours of human skin and can be bent without breaking.
The research team also includes assistant professor Jang Taesik from Chosun University in South Korea.
Professor Paul S. Weiss, Distinguished Professor of Chemistry and Biochemistry, Bioengineering, and Materials Science and Engineering at the University of California, Los Angeles (who did not participate in the study) said that pollen is a fascinating and sustainable bio-nanomaterial with countless uses. Song, Cho and their team are now adding it to an arsenal that can be built on a larger scale through additive manufacturing and 3D printing by adding it to ink.
Dr. Jeffrey S. Glenn, director of the Hepatitis and Liver Tissue Engineering Center at Stanford Medical School (who was not involved in the study), added that this is a very exciting paper that demonstrates the ability of 3D printing custom structures for manufacturing and Continuous, cheap and non-toxic materials to deliver drugs.
How to develop hybrid ink based on pollen
The most widely used bioprinting method today is extrusion-based bioprinting, in which ink is continuously dispensed from nozzles and deposited along a digitally defined path to create a 3D structure layer by layer.
One of the challenges of this approach is that it is difficult to retain the 3D structure and shape of soft and delicate materials (such as hydrogels, cells, and biopolymers) without additional support. Usually a structure called a support matrix is used, in which soft ink is deposited during the printing process. However, this causes waste because the support matrix becomes unusable after printing.
Assistant Professor Song said that previous research work focused on the development of special bio-inks for efficient deposition and printability by mixing hydrogels with fibers or particles. The main disadvantage of this hydrogel composite ink is that the nozzle is clogged, which has a higher content of such fibers or particles. In contrast, the pollen-based hybrid ink we developed has sufficient mechanical strength to Maintain its structure when clogging the printer.
The development process of this pollen-based hybrid ink began with the cultivation of tough sunflower pollen in an alkaline solution, an environmentally friendly process similar to soap making, which takes six hours to form pollen microgel particles.
Then mix the pollen microgel with a hydrogel, such as alginate (a natural polymer usually obtained from brown seaweed) or hyaluronic acid (a transparent viscous substance naturally produced by the body) to form The final pollen-hydrogel hybrid ink.
Pollen-based scaffolds for cell culture and drug delivery
As a proof of concept, the scientists printed a five-layer tissue engineering scaffold in 12 minutes, which can be used to culture cells. Collagen is then added to the scaffold to provide anchor points where cells can adhere and grow.
Then, the scientists seeded human cells on the scaffold and found that its cell seeding efficiency was as high as 96% to 97%. This is comparable to the performance of inverted colloidal crystal (ICC) hydrogels, which are widely used as 3D cell culture platforms, but they are time-consuming and labor-intensive to manufacture.
Given that pollen responds to changes in pH—when the environment becomes acidic or alkaline—the NTU team also tested the feasibility of a 3D stent as a stimulus-responsive drug delivery system. When the fluorescent red dye was dropped onto the stent, the scientists found that the pollen microgel particles gradually released the dye into the stent. The amount and rate of release increased with the addition of acid. Scientists say this suggests that pollen stents may be used as a drug delivery system with controlled release. Professor Cho said: “Pollen microgel particles have an empty shell structure, which means that they may be used to carry drugs, cells, or biomolecules in drug delivery platforms with customized 3D structures.
In view of the stimulus response properties of pollen, pollen-based stents may also be used as smart drug carriers. For example, we can further slow down the release of alginate drugs by coating a thin layer on a pollen-based stent, and stimulate the release by introducing acid.
Pollen-based support structure for soft 3D printing inks
Scientists have also discovered that soft and flexible pollen microgel particles derived from tough pollen grains may be used as a recyclable support matrix for free-form 3D printing, in which soft ink is deposited. When the ink is cured, the support matrix prevents the printed structure from collapsing.
In order to test the feasibility of their method, the scientists used pollen microgel as a support to make a 3D printed silicone rubber net for the elbow, which can maintain the shape of the elbow net during printing.
After curing the printed product in the pollen microgel at 75°C (167°F) for 24 hours, the scientists found that the printed 3D silicone rubber mesh can adapt to the curvature of the human elbow. They also found that the mechanical properties of the silicone rubber samples printed and cured in the pollen microgel support matrix were similar to those of the samples made by traditional casting methods.
The application of pollen in the field of biomedicine is based on the NTU research team reusing pollen grains (a natural renewable resource) as a variety of environmentally friendly alternative materials, from environmentally friendly paper to biodegradable sponges that can be soaked to oil pollutants .
This research is consistent with the research ambitions of Nantah in its 2025 strategic plan, which aims to transform invention and creativity into results that improve economic efficiency and quality of life.
The team is now seeking to collaborate with the industry to improve their 3D printing innovations and promote their commercial applications.
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